Topic: 1975 cb750 top end gasket and seal renewal

[Cobalt Kid 60]

Hello to everyone on this forum.
I have been reading many posts of partial to complete tear downs of the cb750 . I am intrigued with the vast knowledge that is given so freely to anyone who requires help or just assurance as to what they are trying to accomplish is good and on track. Cheers to everyone! So  here goes my dilemma . I acquired a 1975 cb750 with 26000 on the clock. I am replacing the head gasket as it is leaking. I have the complete set of gaskets and o-rings to do everything from the base gasket up. I have taken everything apart down to the cases and will reassemble .  Everything looks good, valves, pistons bore, camshaft, rocker arms, etc . I am going to clean up the valves and valve seats, mostly carbon deposits and will lap them some to just ensure a proper seal . So my question is this. Is 26000 a lot of mileage  for this bike. Am I best off just to put things back together with new gaskets and seals ? Or should I lightly hone the cylinders and put in new rings? Also what about the cam chain? Has it stretched enough in the 26000 miles to be replaced, the tensioner and guides seem hardly wore? The bike did not smoke or burn oil, just the leaky head gasket hence the tear down.

Any help would be appreciated.

Cobalt Kid

[lafindufondu]

26k is not high miles for CB750.  However, it really depends on how it was ridden and if the previous owners kept up with maintenance, which often times they did not.  You will want to hone the cylinders, it is possible that they need to be bored out if out of spec.  I would replace the cam chain tensioner rollers and cam chain, since you're in there.

[Old Scrambler]

After getting the bores spec'ed and honed, new rings are a must since your already in there. Be sure to get the 'pucks' well sealed because they tend to leak at high rpm's.