Honda Cb Unicorn Engine Noise

While scrolling down below to find the              . . . you'll increase your CB750 knowledge before you get to The Buyer's Guide!. K models1969 through 1978:                                                 (1) 1969-1970         (2) 1971-1972          (3) 1973-1976         (4) 1977         (5) 1978  Note that for 1977-1978 K-models, side covers no longer expose an oil tank cap.                                          Red side cover diamond jewel = originally for 71.     Orange side cover diamond jewel = originally for 72-76. Red diamond jewel, battery side= part #87126-300-405       Orange diamond jewel, battery side= part #87126-341-405Red diamond jewel, oil tank side= part #87127-300-405      Orange diamond jewel, oil tank side= part #87127-341-405Some reproduction jewels are not exact. Example: some are missing the Hm at base of the wings.                      1969-1970           1971-1972                  1973-1976                       1977                      1978  69-70 gold-around-white-wings emblem, left side = part #87124-300-020     69-70 gold-around-white-wings emblem, right side = part #87123-300-02071-72 plastic chrome '750Four' script emblem = part #87123-300-030     73-76 white metal '750Four' on black background emblem = part #87123-341-67377 gold '750FourK' emblem = part #87123-405-000   78 gold '750Four' emblem = part #87123-405-777Insider tip: with most Honda-factory-made US-issue 1971 through 1976 no-vents 750K side covers can use either your choice of the 71-72. the 73-76'750 Four' upper emblems above the diamond jewels (the newer/bigger emblem covers the indenting used by the older emblems while most 73-76 covers still have the indenting used on the previous years);these factory-issue no-vents covers themselves should fit all K-model bikes models 1971-1976.___ ___ ___ ___ ___Honda 750 Super Sport. part numbers:Left, 1975-1976 83700-392-000 (can be followed by a color code)Left, 1977-1978 83700-410-000 (can be followed by a color code)Right, 1975-1978 83700-392-000 (can be followed by a color code) <75-77F      78F> US Honda 750F Super Sport side cover.       1969 to 1970, they were smooth and available in colors to match side covers. Somewhat brittle and prone to cracking.1971 to 1978, a stronger ribbed-surface version was used, available only in black.Beginning for 1973, air intake was restricted using baffling to reduce intake roar! Tip: the top half of the assembly is known as the air filter.   3. An example of year-to-just-very-next-year US visual changes 1970 >   < 1971 Different: 1. tank emblem colors, 2. side cover shapes, 3. side cover emblems, and 4. air filter housing design & colors. There were 3 types: factory original, factory recall, and aftermarket.               Regular thumb latch                                                      'Recall' safety latch 17550-377-315Blame it on the recall.These defect notices were sent out:TIP: any 750 Honda ignition key will open the recall safety latch.Almost 40 years later, many dealerships still install it.However, most 69-76 Honda 750K buyers prefer the original latch.1977-1978 K-models placed the entire gas cap under a locking lid.All F-models and A-models placed the entire gas cap under a locking lid.Least common is the aftermarket locking gas cap.   Sold in the mid-1970s, it used a hollow-center hex-shaped key. 1.       2.      3.       4.  1. Black letters onto tank color, 1969-1970       2. White letters onto tank color, 1971-1972 3. White letters onto black tank panel decal, 1973-1976       4. Gold letters onto tank color, 1977-1978 Gas tank emblems, 69-78 Honda US 750 K-models 1.              2.    3.             4.  1. 69-70K tank emblem, black letters with polished edges on its own small black background = 87124-300-020       2. 71-72K tank emblem, white letters on its own small black background = 87123-300-020 3. 73-76K tank emblems, white letters on its own black background = right 87121-341-700, left 87122-341-700 4. 77-78K tank emblem, gold letters on its own black background = 87122-405-000 Insider tip: use the correct-color (black) mounting screws. Use a black Sharpie marker pen to touch-up a scratch on a black screw. Insider tip: on some models, left and right tank-side emblems are the same; on some, they are different. On some models, later one of the 'side' emblems was discontinued, causing later use of the only remaining choice to be used on both sides. Usually not noticeable. Emblems are a soft bendable metal as to follow curves of either side of tank. through the years!                                                        69-71: on frame    72-76: on grab rail     77-78: under a longer grab rail.                                  8. Correct standard spark plugs and spark plug caps US 69-78 750K.                                    .    9. Most often, which general-style gas valve ('petcock') do the US 750 K-model gas tanks use? 1969-1974 >            < 1975-1978 Seated, is by your right leg                Seated, is by your left leg. Note: height from bottom of tank to bottom of petcock, additional minor variations and/or changes may have occurred within some shown or listed types. Photo above/right shows white nylon screening used on newer model petcock. Older model uses this brass screen, found above removable lower bowl (crud always there):.    10. Which US K-model ignition switch to use? Check the wiring harness plug.             Round plug, under tank: 1969, some 1970/1971. Square plug, under tank: some 1970/1971, 1972-1976. Up between gauges, block plug behind headlight, has the fork lock built into it: 1977-1978. rear Note: 1976 F-models use a 'peppier' one-tooth-smaller front sprocket than same year K-models. Note: 1977-1978 F-models use 'peppier' both front & rear sprockets than same year K-models. - - - - - - - - - -. front / 48 rear           1977-78  #630 chain, 15 front / 42 rear Note: 1976 A-models use a 'peppier' one-tooth-smaller front rear sprocket than same year K-models. Insider tip: Some past owners of 69-76 530-equipped sprockets and chain havepurposely changed them 'up-size' to the bigger but less-popular 630 replacement kits.    14. Standard chains used, all US Honda 750 models 1969-1978    1. Standard chains used, US 750 K-models 69-78:                                    1969-76:  #530 chain, 100 links         1977-78:  #. models 75-78:                                    1975-76:  #530 chain, 102 links        1977-78:  #. 30 o-ring chain, 88 links    3. Standard chains used, US 750 A Automatic models 76-78:                                    1976:  #530 chain, 104 links        1977-78:  #.    15. Honda 750 K-model general warning light types US 1969-1978                                      1969-1971                             1972-1976           1977-1978.    Only 2 main Honda 750 K-model US turn signal lens types:          1969-1974                            1975-1978 It's small and tall!            It's wide and almost flat!. 1969-1974 turn signal lens: 33402-268-672         1975-1978 turn signal lens: 33402-377-671 1969-1974 needs two lens cross screws: 93700-030250B         1975-1978 needs two lens pan screws: 93500-040250A 1969-1974 lens gasket: 33443-268-671         1975-1978 lens gasket: 33406-377-671 The tiny letters on lenses can reveal some origin & other information. Insider tip: often overlooked- on all models, when installing the new long clear battery vent/overflow hose, make sure it is inserted in/through all proper guides top to bottom; if not, you will lose paint or chrome due to battery acid fumes or acid spittle. Insider tip: acid spittle can also ruin chains. Below decal is from 1976 K-model inner fender:.    The two US 1969-1978 Honda 750 tail light shapes:                 1969-1971                                       1972-1978 gasket &                                         gasket & 2 screws                                          4 screws. Red, with clear at bottom to illuminate license plate; some replacements had amber portions on sides. Very small letters & numbers on the lenses can reveal some origin information.                                             Calipers were silver 1969-1970, were black 1971-1976, and new-style 1977-1978 caliper was black. Part numbers for US K-model. You need to drain the dirty oil at 3 spots: the oil tank, its bolt (92800-12000) and washer (94109-12000) peeking from under a plastic side cover; the oil filter housing at the front of the engine, bolt (15420-300-020); and from the crankcase oilpan drain plug (92800-12000) and washer (94109-12000) at the bottom of the engine.                            Oil Filter (internal paper cartridge with 2 seals: large seal for filter housing to engine case, small seal for filter bolt):   Honda 15410-426-010     K&N KN-401     Fram CH6009                     Insider tip: The original oil filter bolt uses a small 1.    The 3 different US K-model original grip styles used 1969-1978!           . 1969-1971                      1972-1976                       1977-1978. Left (clutch-lever side): 1969-71  95011-14200; 1972-76  53166-342-670; 1977-78  53166-390-780.Right (throttle side): 1969-71  95011-14100; 1972-76  53165-342-670; 1977-78  53165-390-780.                  Cover: 30370-300-020             Screws: 93700-06032             Gasket: 30372-300-300. Sometimes also called an 'alternator' cover or an 'AC generator' cover. cover: 11631-300-040    gasket: 11397-300-040    the 3 center face (to field coil inside) screws: 93500-06020     the 3 center face washers: 90425-300-000 Note: 1977-1978 F-model SuperSports used a black cover:.                                       1969-1971 pod            1972-1976 bracket            1977-1978 pod. (older-to-newer from left-to-right)                                      Top lefts above: chrome-cover type, all 1969-1976 K&F models.     Top rights above: flat silver, 1977-1978 K & A models. Bottom row photos above:. The 2 carb choke-activation types, Honda 750 K-models 1969-1978                     . 1969-1976: metal lift-up lever, below gas tank, lever pivots on outer carb left (clutch lever) side. 1977-1978: cable 17950-404-670 to new-style carbs, pull-knob is up next to speedometer. Insider tip: the mount under the choke cable pull-knob for all 1977-1978 models is often found broke off at its mounting bolt, leaving the choke cable found swinging loose. This mount is known as 'Stay, Choke Cable', and is part #17951-404-670. Fits all US models of Honda 750 1977-1978: K,F, and A.    Choke.              1969 through 1976 do. Upper portions of these bars use bar-bottom oval holes to fish switch wiring through the bars and out the lower center bigger oval and then into the rear opening of headlight case. Correct bars for 69-76 also have a small hole near each upper oval, used for switch internal locator pins to lock switches from turning. Warning: the wiring holes can slice and short wiring if any have sharp edges. : K-models 1969-1971 Watch for different lengths, hardware, metal stiffener collars under bolt/washers, collared washers, and a metal stiffener near underside center. Possible different mounting types on the 69-71 K-models on a year-by-year basis so be sure that separation measurements between all mounting bolt holes on the replacement chain guard are same as those of mounts on bike.      Black. : K-models 1972-1976 Watch for different lengths. Will not directly replace 69-71 plastic as different mounting tabs separation. Black metal: K-models 1977-1978 Watch for different lengths. Chrome metal: none came from Honda on 69-78. I do appraisals for factory-stock condition; ratings, assessments, and evaluations only for 1969-1978 Honda 750s: models A, F, and K. 300 = generally, this part began or was modified to during 750 K-model years 1969 to 1971  323 = generally, this part began or was modified to during 500 K-model year 1973 341 = generally, this part began or was modified to during 750 K-model years 1972 to 1976  392 = generally, this part began or was modified to during 750 F-model years 1975 to 1976 393 = generally, this part began or was modified to during 750 A-model years 1976 to 1978 405 = generally, this part began or was modified to during 750 K-model years 1977 to 1978 410 = generally, this part began or was modified to during 750 F-model years 1977 to 1978 Insider tip: 'model year' often starts many months before 'calendar year' starts. Insider tip: In some states, on the ownership titles of many Honda 750s, the. QUESTION: "After right-side crash damage, I replaced the brake pedal with a used one. I now find it doesn't have the horizontal piece used for the pedal adjustment/stop-screw. Weren't all-year K brake pedals the same as my US 1974 Honda 750K?" ANSWER: No- your replacement is lacking the tab pointing most-upward in this photo: (the tab points horizontally inward toward the bike when pedal is installed; see actual tab wear-spot from adjuster stop-bolt on this photo looking down from above it). Stop-bolt and locknut is seen in background. All years had a vertical (upright when on bike) piece with a hole for the pedal return spring. But until into the K-1 model towards K-2, there was no brake pedal adjuster or stop screw, so no horizontal tab. Summary: there were three different types 69 through 78. 1977-1978 pedals were different in multiple ways.         1969-1971  46500-341-000             1972-1976  46500-341-670             1977-1978   46500-405-010 Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types. 35. Of the 16 paint color choices, which was the most-often available paint color choice for US Honda 750 K-models 1969-1978 when they were new?.   36. Only two different swingarm grease fittings/nipple types and locations were used on Honda 1969-1978 US 750 K-models . . . and that helps eliminate.                  Above/Left: 1969-1975 US K swingarms used. 4.5 grease fittings, one at the each end of the swingarm pivot bolt ends (see above left, to rear of rear brake light foot switch). Some choose to instead thread the holes and then use automotive fittings. No grease fitting was actually on the black swingarm itself.   A push-in grease fitting is 96201-30001. Above/Right: 1976-1978 US K swingarms used. grease fitting, threaded into the bottom side center of the swingarm (see above right). This threaded bent-angle grease fitting is 96201-. 1969-1972: 50530-294-000 (was superseded by 50530-341-670, the 73-74 750 kickstand)     1973-1974: 50530-341-670 (kickstand below in red block)           (Based on part numbers and supercede numbers, it appears that one kickstand, 50530-341-670, can be used by Honda 750 K-models 1969-1974). 1975-1976: 50540-341-670 has a rubber kick-up extension      1977-1978: 50540-405-010 also has rubber kick-up extension (kickstand below in block) The 'rubber kick-up block' used 1975-1978 is the same part-number each of those years: 50548-356-700.     Even better, the same kickstand ('sidestand') 10mm x 1.25 pivot shoulder bolt and its 10mm-thread nut can be used the entire series:            kickstand (side-stand) 'screw' (kickstand pivot bolt): 90108-283-000, and its side-stand nut: 94031-10000 or 94031-110000. Springs: 1969 through 1978 used at least 4 different K-model kickstand (sidestand). 38. Follow the history of the 5 main different mirror models used on US K-model 750s 1969-1978! Almost any set, original or a 10mm x 1.25 -threads upstalk aftermarket, will work for almost any 750K year (except for the first 302 K0 models, which used 11mm). Year by year, watch for changes to length of stems (7", 8", etc) and to diameter of round portions (4", 4 1/2", etc). Some look like the mirror glass is glued in, others look like a rubber lipseal is holding in the mirror glass. Watch for frozen pivot areas. But for collectors and restorers, here is a good general guide. #1. The 69-70 750K 'acorn-nut clamp' model, AKA: 'the first design', or     the 'K-0 type'. 1969-1970. 0-300-000 The smallest mirror glass diameter. Watch for different words, logos and other by acorn nut on backside of original mirrors. Several changes. Watch for replicas. Watch for different upstalk lengths and glass diameters. Soon later, Honda stopped offering the 69-70. 39. Watch when buying used front sprockets: there were two completely different methods used to retain Honda US 750K front sprockets to the shaft; 530 sprockets from 1969-1976 sprockets use one way, 630 sprockets from 1977-1978 use the other. 1969-1976 530 front sprocket type   Honda 750 (above and below photos chosen for ease of showing sprocket-trapping comparison only, as 1969-1975   models also had some automatic chain-oiling hardware similar to this above at/in this end of shaft) 1977-1978 630 front sprocket type      Honda 750 1969-1976 front sprockets were trapped on the shaft by a retainer known as a 'fixing plate' using two 6mm hex bolts. The fixing plate matched a grove on the shaft; then slightly turned like a key; the two 6mm hex bolts into the sprocket locked it in place. This same front sprocket retainer, 23811-292-000, was used on many other older Honda street & dirt bikes. However,. 41. Looking at some used stock exhaust pipes for a US Honda 750K somewhere between 1969 and 1978? Knowing these three Honda exhaust code numbers will help eliminate some wrong choices. 1.           2.          3.   1. 300 series, Honda 750K 1969-1971 --Clamps. at engine-- Some of the earlier ones had removable baffles and no 300 marking Said to have the best chroming Said to be less restrictive than 341 series Said to need carb rejetting if used to replace 341s Heat shields on upper pipes 300s are rarest and most valuable to collectors Can use a full set of 341s instead on 69-71 but will lower value to a sharp collector Other minor variations A transition year 2. 341 series, Honda 750K 1972-1976 --Clamps. at engine-- Quieter than the 300 series Reproductions available Said to be more restrictive than 300 series Said to need carb rejetting if used to replace 300s Watch for clogged drain holes and rusted areas Heat shields on upper pipes Various baffle changes 3. 405 series, Honda 750K 1977-1978 --Clamps.   46. "I'm trying to buy a used original-paint gas tank or side covers on the Internet, but instead of telling the colors, some only show 'color code' letters after the part number. What are the.   47. US year model is identified by a metal tag on the frame head in front of the gas tank on the right side. Top-right corner of tag on examples below has the month & year of manufacture.        Note: in some states, state ownership titles used the year of sale as the bike's year model. So, for example, some 1972 Honda 750 ownership papers list it as a 1973 model. Note: involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types. -030B.However, many used '300' parts for sale used on the Internet are really '341' parts-- the sellers sometimes used quick or weak research to help list their parts for sale, sometimes using wrong part numbers. Here is a general list of air filter housing. :(known as 'covers')K0 1969-1970 year models, housing is often the same color as gas tank and side covers, through frame #10444649 which is the last K0 frame: 17231-300-020-(color code here).K1 1971 year model, black only, beginning with frame 1044650 which is the first K1 frame: 17231-300-030B.K2-K6 1972-1976 year models, black only: 17231-341-010.K7-K8 1977-1978 year models, black only: 17231-392-000. Insider tip: the baffling in your own air-filter case bottom can be modified.Bafflingcan be removed (back to old intake roar) or have holes drilled in baffling (a little more intake roar).Sound is more noticeable on bikes with fairings or windshields, or when opening the throttle wide.Insider tip: drilling at the wrong place will allow water in.For convenience, here is a general list of air filter housing cases (. :K0 1969-1970 year models, housing is same color as gas tank and side covers, through frame #10444649 which is the last K0 frame: 17214-300-040-(color code here).17214-300-040AZ: Candy Blue Green 17214-300-040CM: Candy Red 17214-300-040CQ: Candy GoldK1 1971 year model, black only, beginning with frame 1044650 which is the first K1 frame: 17212-300-030B.K2-K6 1972-1976 year models, black only: 17212-341-000.K7 1977 year model, through frame 2731019, black only: 17240-405-305.K7 1977 year model, beginning frame 2731020, black only: 17240-405-315.K7-K8 1977-1978 year models, black only: 17240-405-315.More air filter information at Quick Tips 2 and 114!Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   49. There was chrome plastic trim/molding along the bottom edge of the gas tank of every 750 K-model 1969-1978. They are NOT all the same. Below are the three main differences. 1969-1970: chrome plastic trim, all silver chrome (no stripe) Trim part number R 17521-300-000 / Trim part number L 17522-300-000 Uses no clips. 1971-1976 K: chrome plastic trim, silver chrome with a full-length black horizontal stripe Trim part number R 17521-300 (and 341)-010 / Trim part number L 17522-300 (and 341)-010 Uses no clips. 1977-1978 K: chrome plastic trim, all silver chrome (no stripe) Trim part number R 17541-405-000 / Trim part number L 17542-405-000 Uses clips 17544-323-000 and 17545-323-010. Usually, original and reproduction tank trim are both available. A-model 750 Automatics also used bottom-edge chrome trim on their gas tanks. But F-model 750 SuperSports did NOT use bottom-edge chrome trim on their gas tanks. Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types. silver finish with black (see examples below):   This dull 69/70 part was superseded by the 71-76 polished part 18315-300-0.   (This is a question we often receive)   51. "I bought an old US 750K and the rubber fuel lines from the petcock to the carbs are destroyed. My local auto parts store had hose sizes and clips that didn't feel right. What do I need?" Using the wrong parts looks bad and can cause trouble. All correct parts are available. There have been two sizes of fuel line during 1969-1978 US K-models. SIZE 1, original small fuel line, 5mm, all 69-70 K0 models, and also for about the first third of the K1 1971 year-model: The 1969/1970 'K-0" model, and also about a third into the K1 1971 year model production, used a smaller 5mm size fuel line, used until frame #1071335 (which was about 1/3 through the K1 model year). Examples of this smaller fuel line are 95001-50160 and 95001-50280. A smaller (5mm) retaining clip was used, 'Fuel Tube Clip 5mm' #95002-250000. : There were about 77,000 750 K-1 models made. The first K1 (1971 year model) was frame #1044650. The smaller 5mm fuel line was continued to be used through frame #1071335, which means it was used on the first almost 27,000 K1s. The following next almost 50,000 K1s used the bigger 5.5 fuel line and clips instead-- but the same petcock was used both before and after the change. SIZE 2, improved larger fuel line, used for the last two-thirds of the 71 K1 year-models through to the end of 1978 model: Fuel line: Not the SAE similar-sizes at the auto parts store.     95001-5500160M For US Honda 750 models since frame 1071336 (one-third through the K1-model year), used the 5.5mm. D 95001-5500160M black fuel line, fresh and pliable, available online and at Honda dealerships in bulk or by the foot or in pieces. 5.5mm is correct for the 750's brass ports. for the factory clips. --Not 'clear' fuel line that will quickly harden and split. --Not wrong size fuel line that might leak, split, slip off, or collapse at a bend. --Not 'vacuum' line that isn't fuel-resistant. --Not hose unrated for heat. Clips: All 71-78 US K-models since 1971 frame 1071336 (one-third through the K-1 model year) use clip #9500202100 at the hose piece ends.      Known as 'Tube Clip B10". They work with the catch-rises on the petcock andwith the catch-rises on the other connection points.Get a few extra clips as they are easy to lose during installation.Don't use hose clamps! Tee: 1975 and 1976 US 750 Ks use an under-tank fuel-line 'tee' splitter in between their single-hose petcock and the two carburetor feeds. Honda calls this tee a 'fuel joint': its part number is 16235-657-000. Be sure to replace all 3 hoses connected to this tee. This tee was also used on some older Honda cars. Insider tip: Slit the end inch of old hardened hose at the petcock end before pulling the hose off. Otherwise you might accidentally pull out a pressed-in brass port from the petcock body. Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   53. Often a cause of poor performance is intake air leaks. Now no longer sealing 'air-tight', leaking are the old cracked & hardened carburetor 'insulator' rubber boots which originally were also meant to keep carburetors cool and reduce vibrations from the engine.Equivalent to an intake manifold on a car, but rubber instead of metal, and four instead of one.         For US K-models 1969-1978, there have been 3 versions of the rubber carburetor insulators.1969-1970 year K-models (K0)Insulator A, needs two: 16211-300-305Insulator B, needs two: 16212-300-305Metal insulator band: 17255-300-000Insulator band's 4X22 cross-screw: 93500-040220AUsed these parts above through engine #1044805,which was the last K0 1970 model year engine.1971-1976 year K-models (K1-K6)Insulator A, needs two: 16211-300-030Insulator B, needs two: 16212-300-030Metal insulator band: 17255-300-010Insulator band's 4X22 cross-screw: 93500-040220AUsed these parts above beginning with engine #1044806,which was the first K1 1971 model year engine.1977-1978 year K-models (K7-K8)Insulator 1: 16211-405-000Insulator 2: 16212-405-000Insulator 3: 16213-405-000Insulator 4: 16214-405-000Metal insulator band: 17255-405-000Insulator band's 4X22 cross-screw: 93500-040220A69-70>        71-76>         77-78> Insider Tip: don't use hoseclamps. Use the correct bands.For US Super Sport F-models 1975-1978, there have been 2 versions of the rubber carburetor insulators.1975-1976 Super Sport:Insulator A- 16211-300-030 (same as K-model of same years)Insulator B- 16212-300-030 (same as K-model of same years)1977-1978 Super Sport:Insulator 1- 16211-410-000Insulator 2- 16212-410-000Insulator 3- 16213-410-000Insulator 4- 16214-410-000For US Hondamatic A-models 1976-1978, there have been 2 versions of the rubber carburetor insulators.1976 Hondamatic:Insulator A- 16211-393-000, uses two.Insulator B- 16212-393-000, uses two.1977-1978 Hondamatic:Insulator 1- 16211-393-020Insulator 2- 16212-393-020Insulator 3- 16213-393-010Insulator 4- 16214-393-010These are the least-available of all US 750 insulators.77-77A insulators are smaller diameter than K/F insulators due to the A's smaller carburetors. Their curves/shapes are different too.Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   (This is a question we occasionally receive) 54. "I have a K-0 model Honda 750. I believe that makes it a valuable 'sandcast' engine model. How can I verify this?" 'Sandcast'-molded engine cases have a rough surface, like sandpaper. Used only for the first 7414 Honda 750 engines made, then a stronger (and smoother) casting system replaced it. Not all K-0 Honda 750s had engines that used the 'sandcast' engine cases. Easiest way to verify is with your engine number. Sandcast engine cases were #1000001 through #1007414. The last 750 engine that used sandcast cases was #1007414. If numerically yours is higher than 1007414, then not sandcast. Original sandcast engines used this smooth oil filter case, but many were later replaced with the newer 'finned' oil filter case. Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   55. Salvage-yard and Internet searchers: Looking to replace a cracked top bridge? There were 3 main different top bridge styles used on US K-model 750s 1969-1978!The 3 top fork bridge differences US Honda 750 K-models 1969-1978: 1>   2>   3> 1. US K0-K2 Nicknamed 'unicorn' style. Uses chrome 'meter bracket bands' around gauges. Do not install top bridge without two special notched D-shaped spacer-washers 53235-300-000 , one each, at center in each center gap area, or top bridge can crack when tightening around fork tubes. Top fork bridge part number: up to frame #1003433 (sandcast 1 to 3433), 53230-300-010, superseded by 53230-300-315; after frame #1003434 (sandcast 3434 to 7414), 53230-300-020, superceded by 53230-300-673, later superseded by 53230-300-315. After sandcasts, 53230-300-315 through end of K2. (NOTE: it has been reported that in Europe and some other countries outside of the US, the 'unicorn' style was used through the 1975 K model) Insider Tip: measure the width of the 'tip of the unicorn horn' if you are buying a used part-- that was one difference. 2. US K3-K6 Uses a small black meter bracket to connect gauges. Do not install top bridge without two special notched D-shaped spacer-washers 53235-300-000 , one each, at center in each center gap area, or top bridge can crack when tightening around fork tubes. Top fork bridge part number: 53230-341-305 3. US K7-K8 Uses a small black meter bracket to connect gauges. Has a mount for choke cable pull knob. Top fork bridge part number: 53230-405-000 Insider Tip: each fork tube top is tightened to with a bolt in the fork bridge. 1969 through 1975 used an 8mm bolt, but 1976 through 1978 used a thinner 7mm bolt. 1969-1975: 90155-369-000. 1976-1978: 92101-805-60B. Here's what the three fork bridges look like installed and with gauges etc on them:                 Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   56. Salvage-yard and Internet searchers: Looking to replace a damaged 750K headlight holder? Some call them Honda 750 headlight 'brackets' or 'ears'; Honda calls them 'fork covers'. This visual guide section shows the 4 general designs used by Honda 750 US K-models K0 to K8.    K0-K1    K0-K1     K2    K2     K3-K6     K3-K6    K7-K8    K7-K8   K0-K1 Fork CoversPainted same color as gas tank and side covers.On bottom-half of vertical portion are threads for a small reflector.On horizontal portion, one hole at its end for a turn signal stalk to go through and then into headlight shell.Part number, right: 51602-300-672-(color code letters here)Part number, left:51606-300-672-(color code letters here)K2 Fork CoversChrome.On bottom-half of vertical portion are threads for a large reflector.On horizontal portion, one hole is at its end for a turn signal stalk to go through and then into headlight shell.Looks like K0-K1 shape, but in chrome and with bigger reflector.Part number, right: 51602-341-670XWPart number, left: 51606-341-670XWK3-K6 Fork CoversChrome.On bottom-half of vertical portion are threads for a large reflector.On horizontal portion, one hole is at its end for a headlight shell bolt,and one hole inward of that for a turn signal mount.Left fork cover has a square mounting hole for turn signal buzzer.Part number, right: 51602-341-701XWPart number, left: 51606-341-701XWK7-K8 Fork CoversChrome.Low on vertical portion is a built-in mount for a large turn signal.On horizontal portion, one hole is at end for a headlight shell bolt.Part number, right: 51602-405-000Part number, left: 51606-405-000Note: there can be variation, transition and cross-over issues with the earliest models of these. Bring old part to compare.Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   57. Keep just five threaded oil tank lines in stock, and you can replace any one used on any US Honda 750 K-models 1969-1978! The oil tanks on these Honda 750 K-models all have two oil lines thread-connectored to the bottom of the oil tank.Honda calls the hose with an. threaded metal fitting (see photo above at right) at the tank end is 'Oil Hose B'. It threads on to the front half of the oil tank, next to the tank drain bolt.Both hoses have angled bolt-on fittings at their engine ends.Hose A>               Hose B> 1969-1972 Hose A: part number 15510-300-0071969-1972 Hose B: part number 15520-300-0071973-1978 Hose A: part number 15510-300-0171973-1976 Hose B: part number 15520-300-0071977-1978 Hose B: part number 15520-392-020Some early-model hoses were gray instead of black. Not to be confused with aftermarket hoses that used stainless-steel braiding.On sandcast engines, the earliest type hoses were smooth fabric, not webbed, and the metal ferrule was not crimped. The next hoses used were webbed fabric, but still used smooth metal ferrules. Ultimately, all 750 hoses became webbed fabric with crimped metal ferrules.   Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   58. After a few early front disk brake rotor improvements, US Honda 750 K-models used 3 different part numbers for the factory rotors. (Part numbers below for A-model and F-model rotors too!) <1969       <19761.       2.        3. 1.  1969-1971 K-models   disk brake rotor 45120-300-0402.  1972-1975 K-models   disk brake rotor 45120-341-0003.  1976-1978 K-models   disk brake rotor 45120-392-000Note: K-model disk rotors were 295mm.Some disk-to-hub. differences:All K-model disks used 6 nuts and bolts. But 1969 through 1975 also used 3 flat lockstrips called 'tongued washers' that connected acrosstwo bolts each; each flat strip had 'fingers' that were bent up to prevent the 8mm hex nuts 94001-080000S from vibrating loose/off.   The tongued washer (lockstrips) used were 90522-300-010 from 1969-1973, later superseded to 94108-18000.1974-1975 K-models used tongued washer (lockstrips) 94108-18000.1976 through 1978 K-models did not use the flat lockstrips; instead they used 8mm 'flanged' nuts 90309-357-000 for vibration security.F-model SuperSport rotors:1975-1976  front disk brake rotor 45120-392-0001977-1978  front disk brake rotor 45251-410-000, superceded by 45251-410-3051975-1978  rear disk brake rotor 43120-371-000A-model Hondamatic rotors:1976-1977  front disk brake rotor 45120-392-0001978  front disk brake rotor 45120-393-780Note: Involves transition models. Additional minor variations, different part numbers, changes and/or crossovers may have occurred within some shown or listed types.   61. Salvage-yard and Internet searchers: there were several variations of front brake master cylinders used on US K-model 750s 1969-1978!      Bring your old master cylinder, and.   Salvage-yard and Internet searchers: There were 5 different battery boxes used on 1969-1978 Honda 750 US K-models.        Each year is similar but with different mount holes, etc. Mount holes were used for various brackets, flashers, solenoids,     starter safety switches, various charging items, and fuses. Commonly referred to as a battery 'cage', the box itself is rubber cushion-mounted. Inside the box, the battery is surrounded by bottom & side anti-vibration rubber cushioning. : under the bottom of the battery, 1969 through 1976 used a large rubber pad 'Battery Rubber 50329-300-010', whereas 1977-1978 instead used two round rubber pieces 'Battery Rubber B 50327-300-000' under the battery instead.   Salvage-yard and Internet searchers: 4 different US 750 K-model chrome grab-bar 'Rear Bumpers' 1969 through 1978!                                               K0-K1: on left-side only    K2-K6: full grab rail     K7-K8: longer full grab rail.   68. Is your gas tank no longer firmly secured while being cushioned? All US Honda 750 models used gas tank rubber mounts at both ends of the fuel tank. 40 year old rubber mounts harden, tear, shrink, stiffen, disintegrate and/or fall out. Honda used these same rubber front cushion mounts for all model years-- and for all models K, F, and A: Honda 750 1969 through 1978,.   73. Salvage-yard searchers, bring the old one to compare: There were 4 different oil tanks that came with US Honda 750 K-models 1969-1978! K0 1969-1970    55100-300-050B K1-K5 1971-1975        55100-300-060B K6 1976    55100-341-000 K7-K8 1977-1978     55100-392-000    K1-K6 has 4 large 'dimples' on its outer side. K0-K6 polished dipstick cap is exposed even when side cover in place. K7-K8 dipstick is hidden by side cover. Watch for.   74. Forgotten, yet they help protect your bike every mile: the rubber dampers inside the rear wheel hub. It's probably time to replace them!Honda 750 US K-models 1969-1978 hard-cushion damper part numbers below.K0: R (small, not shown here) 41241-300-030, L (big) 41242-300-010K1 through K5, and early K6:     R (small) 41241-300-040, L (big) 41242-300-020late K6 through K8: 41241-300-050 (two pieces are instead now a joined single piece)K6 up to frame 2560085 uses the K1 through early K6.   76. Salvage-yard and Internet searchers: Only two different speedometer drives were used on K-model 750s 1969-1978! Honda calls this part a 'Meter Gear Box'                       Honda 750 K-model speedometer drive part numbers K0 speedometer drive: 44800-300-0. can usually be used on any model? 32401-300-010, the oldest cable. Look at 32401-300-010 as 3 attached wires: --the thick main cable, and --extra lead A (round bullet connector at top in photo), and --extra lead B (flat spade connector at left in photo). All models use the thick main cable portion. K0-K2 also uses extra lead A.   85. Right-side    handlebar switches US Honda 750 K-models had 6 different right-side switches 1969-1978. All have a starter button and honda cb unicorn engine noise a kill switch, some have headlight functions. Also known as 'starter/kill switches' or as 'throttle-side switches'. Sun can fade/discolor the entire unit and also deteriorate the kill switch knob. Some can use a spring-loaded throttle-drag adjustment at bottom. K0-K6 uses bar-.    97. Salvage-yard and Internet searchers: Which ignition coils are correctfor US 750 K-models 1969-1978?The two coils are mounted on the frame, under the gas tank.The left coil fires sparkplugs 1 and 4, the outer two cylinders.The right coil (photo above) fires sparkplugs 2 and 3, the inner two cylinders.Usually, the right coil (1&4) has a yellow wire.Usually, the left coil (2&3) has a blue wire.The sparkplug wires are permanently attached to the coils.Coil part numbersright coil: 30501-300-013, superseded by 30501-300-003left coil: 30502-300-013, superseded by 30502-300-003Insider Tip: the coil for the outside cylinders has the longer sparkplug wires. At the ends of these coils, there should be the correct standard spark caps for US 69-78 750K:                                    . part numbers.K0-K5 were available from Honda only as parts(arm 28300-300-000, joint 28241-300-010, etc),not available as complete assemblies, but appear to use the same as K6 models.K6: 28240-300-000.K7-K8: 28240-392-000.All list the replacement rubber as part 28311-329-000.Did you know:Honda 750A Hondamatic models have nokickstarter visible; kept strapped under seat, emergency kickstart lever 28240-393-000 or 28240-393-770 is stored, used on.    (This is a question we often receive) 109. "I see old Honda 750 K-models listed for sale that tell of.    114. Air cleaner cases, US Honda 750 models('cases' are the upper half of the assembly; the bottom half is known as the air filter. :K0 1969-1970 year models, housing is often same color as gas tank and side covers, through frame #10444649 which is the last K0 frame: 17214-300-040-(color code here).17214-300-040AZ: Candy Blue Green 17214-300-040CM: Candy Red 17214-300-040CQ: Candy GoldK1 1971 year model, black only, beginning with frame 1044650 which is the first K1 frame: 17212-300-030B.K2-K6 1972-1976 year models, black only: 17212-341-000.K7 1977 year model, through frame 2731019, black only, with top hose port: 17240-405-305.K7 1977 year model, beginning frame 2731020, black only, with top hose port: 17240-405-315.K7-K8 1977-1978 year models, black only, with top hose port: 17240-405-315.Need to replace the rubber gasket between the upper and lower halves?Part #17221-341-000 for K1 through K6.This gasket is known as 'Packing, air cleaner'.Insider Tip: replacing this gasket where it was missing often eliminates some poor running.Note: there was an emissions change (an intake port added) for 1977-1978 K,F, and A models, as well as on 1976 A models. For convenience, here is also a general list of air filter housing 'covers' (. (or a tire with both a red and a yellow dot)--red dot is lightest part of this tire, goes at wheel valve stem.    118. Some part numbers for warning/service decals and labels, US Honda 750 K-modelsInsider Tip: some clear-background decals had 'variants', almost like a 'reversal image'; clear letters on black backgrounds, or black letters on clear backgrounds, or clear using white.Also, some were in different languages and/or in multiple languages.Originals and reproductions are available for most. wheels are the same, their front wheels use different disk rotors (see Quick Tip 58).  <front      rear>   Center hub areas, 1978 Honda 750 F SuperSport Comstar wheels The black plastic  rivet covers Front and rear Comstar wheel rivet covers look very similar but they are different and they will not interchange. They are known by Honda as 'Spoke Plate Marks'. On their inner side, each has two small nipples that insert into these holes on the wheel in between the rivets. Front: 4.    126. "Mystery switch button!In a box of supposedly Honda 750 handlebar switches, I found a really odd left-side one. Besides the turn-signal switch and the horn button, it's got a mystery extra button added.    127. Chain adjusters, for all US 1969-1978 Honda 750 K-modelsUsed to adjust the angle of the rear axle/wheel and to adjust the slack of the drive chain.Two main types. K0 through K6 were the same; the K7-K8 adjusters were different.The one obvious difference on the sides helps to spot the correct set to use!<K0-K6 <K7-K8Both had a round hole on the sides of the body, for the axle.K0-K6 also had an oblong 'window' hole on the sides of the body.K7-K8 did not have that second hole.Chain adjuster 'body',. wheel axles, for all US 1969-1978 Honda 750 K-modelsK0-K6 front axle: 44301-300-000, superceded by 44301-425-870K7-K8 front axle: 44301-393-870, superceded by 44301-425-870(part numbers are for bare axles only-- no spacers or nuts)K0-K6 front axle.    133. Rear foot peg differences for all US 1969-1978 Honda 750 K-modelsAlso known as passenger foot pegs, there were three different rear foot-peg styles.Honda refers to these as 'pillion (passenger seat) steps'.K0-K4: a. -shapeUses replacement rubber 50710-405-000|Note: Some model-year metal peg mounting brackets were straight, some were angled.And for the K5-K6 model years, the metal left-sideand right-side peg. 30 o-ring chain 77-78new: exposed fork tubes 77-78new: gas cap hidden under a lid 77-78new: ignition key up near gauges 77-78new: choke now a cable, up by gauges 77-78new: no heatshields on new upper exhausts 77-78new: no chrome covers on rear shocks 77-78new: handlebar wiring now outside of the bars 77-78new: oil tank cap no longer exposed 77-78new: side cover shape 77-78 new: front fender has no forward hoop new:. 1977 Honda 750 F2 Super Sport  25,000 made November 1976 to May 1977 America colors: Black NH1 and Candy Presto Red R8CS new: ComStar wheels 77-78 new: dual front disc brakes 77-78 new: black engine 77-78 new: fork legs are black 77-78 new: emblem on side covers new: stiffer clutch springs 77-78 new: dual horns 77-78 new: choke now a cable, up by gauges 77-78 new: calipers now behind forks 77-78 new: rear disc brake 77-78 new: accelerator pump on carb set 77-78 new: electrical connections in headlight shell 77-78 new: sprockets 15/43 77-78 new: 88-link.