SOHC.co.uk Forums > CB750

F2 Engines

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UK Pete:
I have just got an 1978 f2 minus engine, and stripped it down, and am in the process of ordering up all the bits needed for rebuild/restoration, up until today i have been really excited about it almost obsessed, i have just dropped off the frame and swing arm off at the powder coaters, and i have managed to track down an engine of the same year, so you would think all was good, well no it is not i have read up and discovered that every body seems to slate the f2 off with its comstars and apparently crap engine i am really peed off to find out the engine in the f2 is no good, before i totally loose interest and shelve the project, possibly sell it on, is there any body hear that has a good thing to say about the f2 especially the engine or is there anything i can do to the engine to make it better as i will be taking it apart and rebuilding it anyway, as you can probably tell i am a bit down hearted now maybee i should have joined the forum before getting this model.
Pete

dave400:
Sell it and buy a 400/4  ;D
I'm sure you can fix that F2 engine up or use the F1 engine if it's a better choice.

Cheers

Dave

Spitfire:
The F2 was a big improvement on all the CB750's that went before, it had the most powerfull engine of them all with a beefed up bottom end, new cylinder head and carbs with injectors. The brakes were the best ever fitted to a CB750, the Comstars are a matter of taste, I like them. The frame is the same as the F1 and certainly handles a lot better than the previous CB750's.
So you have good handling, good brakes, a powerfull engine with one weak spot which can be cured by fitting another motor from any SOHC CB750.
The engines  weakness is in the valve guide department, expect problems at 30k miles, it can be fixed but it is expensive.
The great news is that the F1 engine will fit perfectly and if you paint it black only the carbs will give it away.
The F1 engine is solid and restored power levels back up to the early CB750 standards, I don't know what my F2 engine is like as I have never heard it run, but if it is no good I will fit an F1 motor.

Cheers

Den

mick:
Hi Pete, i wouldn't get to down hearted about the bike, like Den says the problems can be sorted & if you dont want to go that route the F1 motor slots straight in, ive owned loads of bikes over the years & some of them have had some really crap write ups in the mags but ive found the bikes to be ok with no issues, keep going with your resto and you will enjoy the bike for what it is  ;) cheers Mick. 

Bryanj:
As an ex dealer mechanic of the period the only thing that goes wrong with the F2 engine is the exhaust valve guides, fit new ones and you are OK for about 30,000 (more if you get the later super hard replacements but be advised you WILL NOT be able to fit them yourself!!)

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