Engine modifications K0 - F3
Engine Modifications from K0 to F3, mainly based on Reinhard Hopp's book "Honda CB 750 - Die Geschichte einer Legende":
| Engine # | |
| CB750E-1000001 | K0 |
| CB750E-1000140 | Bolt at the final drive changed from M8x80 to M10x82 |
| CB750E-1000220 | new lower case, engine case only available as set |
| CB750E-1000425 | Transmission changed for better shifting |
| CB750E-1001081 | new crankshaft |
| CB750E-1001760 | 7 instead of 8 clutch disks |
| CB750E-1003528 | new final drive shaft and sprocket |
| CB750E-1005307 | fixed right bearing of main tranny shaft |
| CB750E-1007220 | new lower case, deeper oil pan |
| CB750E-1007415 | introduced circular opening in lower case |
| CB750E-1007500 | End of sandcast engines |
| CB750E-1009554 | finned oil filter casing |
| CB750E-1010336 | cam holders with additional oil passages, new rocker shafts and valve cover |
| CB750E-1014996 | new exhaust valve guides, new valve guide seals |
| CB750E-1026144 | new cylinder head, cylinder block: new central M6 bolt, cyl. block w/8 rubbers i/o 12. Case with guard to prevent damages from broken drive chains. New sprocket cover, new shift mechanism w/11 parts i/o 7 |
| CB750E-1042806 | weaker clutch springs |
| CB750E-1044813 | K1 |
| CB750E-1044805 | new case, final drive 18/48 i/o 16/45 or 17/45, chain oiler |
| CB750E-1044812 | carbs w/links i/o individual cables |
| CB750E-1044968 | improved neutral position |
| CB750E-1056080 | new clutch basket |
| CB750E-1064903 | introduced special washerless bolts |
| CB750E-1068376 | cramp for scavange hoses |
| CB750E-1071336 | fuel hoses 5.5mm dia. i/o 5.0mm |
| CB750E-1113723 | grooves in gear shift drum changed from 0.5mm to 1mm for 4th and 5th gear |
| CB750E-1114461 | new head gasket |
| CB750E-2000001 | K2 |
| CB750E-2061311 | shorter oil hose w/white mark. Main jets 110, smaller cutouts in air filter case |
| CB750E-2200001 | K3 |
| CB750E-2200001 | new cylinder head, new valve guide seals, improved oil passages to camshaft, new piston rings (three part oil scavenge rings), new cam chain guide, larger piston pin circlips, new final drive shaft, new sprocket cover |
| CB750E-2228679 | new cylinder head, new valve guides, new valve guide seals, no more rubbers between fins |
| CB750E-2300001 | K4 |
| CB750E-2304501 | new cylinder block, smaller cam chain tunnel |
| CB750E-2352923 | new cylinder block |
| CB750E-2348093 | crankcase mission cover now has gear indicator |
| CB750E-2372115 | K5 |
| CB750E-2428762 | K6 |
| CB750E-2470427 | clutch almost indentical to F1: new clutch basket, new clutch cover and chrome cover |
| CB750E-2434657 to CB750E-2439607 | new gear shift drum, new center shift fork for improved shifting. New gears on countershaft w/bronce bushings, new case |
| CB750E-2700001 | K7 |
| carbs w/accelerator pump, shorter intake rubbers, new final drive shaft, sprocket w/center bolt, wider chain line (as F2), final drive 15/41, new clutch, new camshaft (as F1), new pistons (as F), compression ratio 9.2/1. New transmission: 4th gear 1.133 i/o 1.087. Final drive gear 50 teeth i/o 56 (as F1), primary drive 1.985 i/o 1.708 | |
| CB750E-2719530 | new valve guides |
| CB750E-2719997 | new cam carriers (as F2) |
| CB750E-3000001 | K8 |
| new intake and exhaust valves, new valve spring retainers and cotters | |
| CB750E-3021913 | new cylinder block w/larger cam chain tunnel |
| CB750FE-2500004 | F1 |
| new camshaft, carbs w/additional idle air. New pistons, compression ratio 9.2/1. New case w/o primary chain oiler. Final drive gear ratio 43/50 i/o 48/50. 4th gear on main shaft 31 i/o 30, 5th gear on countershaft 31 i/o 32 | |
| CB750E-2600014 and CB750GE-1000014 | F2 |
| new cylinder head with bigger valves (34/31mm i/o 32/28mm), larger combustion chamber, larger carb mount rubbers, stronger cam chain, new camshaft, stronger valve springs, new retainers, cotters, new pistons compression ratio 9/1. New rod bigend bolts and bearings, stronger clutch springs, additional fins on crankcase, larger fins on oil pan, "oil cooler" - finned plate between oil filter case and engine. Final drive 15/43 or 14/43. | |
| CB750E-3100001 | F3 |