Topic: CB350F: two failed top end rebuilds, stock bore and 393cc

[maxheadflow]

That spec for CB750 say 0.025-0.055mm
0 0015" =  0.0381mm
Service limit 0.25mm!

My 836 cylinder ran @ 0.2mm  clearance without smoking.
(83whp)
That is rebored to 849cc, clearance agreed around 0.03mm. I have not measured to verify.

Well a service limit of 0.25mm pretty much means you hone a .02 mm out and stuff in the next oversized piston..    Probably won't get it the cylinder round tho.  We used to recommend boring if the cylinder clearance was more then about 0.004" (about 0.1mm) at at that clearance the pistons will rattle a bit.   This is in Socal where temps can be on the warm side. 

 0.03mm almost 0.0015"   

The stuff I posted came right out of the service manual.

Here is a pic out of the MC service spec manual.   Maybe it's due to a fact that there is a typo? 

Other pistons (CB500/550) that are smaller state  new clearances as 0.01mm to 0.04mm, (0.0004-0.0016) as new bore fit.   I would think that 0.001 to 0.0012 is good for a CB350F (the spec book don't list piston clearance for the cb350F) It could be fit to 0.0004" but the tune would need to be spot on. 

[PeWe]

CB750 shop manual has also that small clearance mentioned where describing the procedures with pic 3-60.
 0.01mm to 0.04mm, (0.0004-0.0016)
That must be acceptable clearance piston to bore wall, not total, right? Total should in that case be double up as I see it.

[maxheadflow]

CB750 shop manual has also that small clearance mentioned where describing the procedures with pic 3-60.
 0.01mm to 0.04mm, (0.0004-0.0016)
That must be acceptable clearance piston to bore wall, not total, right? Total should in that case be double up as I see it.

I found the fit location in the manual here and in my own CB manual.   Thanks.   If you are thinking double because of 2 sides, that would be wrong, it's total clearance.  The low side is tight IMO.