Topic: 73 Cb500-4 piston fit?

[XC204]

I'm in the process of putting cylinders on newly ringed original pistons. The pistons have been thoroughly cleaned and new rings installed. I honed the cylinders. This is the first time in 69 years that I have been this deep into an engine. So my question is how snug should the pistons be in the bore ? Oh and they are going in their original cylinders. This is my build thread.
http://forums.sohc4.net/index.php/topic,101767.0.html

[HondaMan]

Generally (like, 99% of the time), new rings will not seat into worn bores. This is due to the way these bores wear when new: they are slightly egg-shaped now from overcooling, toward the 2 o'clock position on #4 and 10 o'clock position on #1 cylinders. The metals were not cured when made, which caused this warp: it happens on 100% of these engines. Now the metal IS cured and won't warp again unless you bore more than 2.0 mm, which is about how thick the cured layer is now.

I'd really suggest that you bore the cylinders at least one step (0.25mm  or 0.5mm oversize, contact CruisinImage for a nice set of pistons and rings for under $150) and make the clearance 0.0006"-0.0010" (yes, that tight) for an 500/550 that will last 80k miles.

[XC204]

Thanks Hondaman ! didn't want to have to do that but since I bought the rings about 9 years ago my budget spread pretty wide. So do I get the replacement pistons first to measure then add .6 to 1thousand th to that to th bore siz?
Gary

Oh my daughter lives in Denver so I know the roads you talked about in one of your posts about texting a bike out  285 maybe

[HondaMan]

Thanks Hondaman ! didn't want to have to do that but since I bought the rings about 9 years ago my budget spread pretty wide. So do I get the replacement pistons first to measure then add .6 to 1thousand th to that to th bore siz?
Gary

Oh my daughter lives in Denver so I know the roads you talked about in one of your posts about texting a bike out  285 maybe

Yep, you've got it: take the pistons to a machine shop that does [small] engines, and INSIST that you want it that toght, as they may not want to bore that tight. If  so, find another shop: sadly I get a LOT of these engines where machine shops have overbored them to be like car engines (0.002"+ clearance), which is nearly worn out to start with.

I just bought a CB500 set from CruizinImage for $160 delivered, so it's not terribly expensive for the parts. The machine shops vary everywhere, but around here this would be about $140 for the bore work.