The Evolution of the CB750 Power Plant

This table of CB750 engine modifications was compiled by Axl Griessman at, and is based on Reinhard Hopp's book, "Honda CB 750 - Die Geschichte einer Legende".

Engine # Changes
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 & 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