replacing rings

Ok, I know that I don't have as much compression as I could on my puch maxi, and I'm looking to do as much as I can to make it run faster. I want to put new rings on it, but Im new to all this stuff. I've heard from about half the people that I talk to that you have to sand the cylander to make them expand properly, and the other half say you don't. So what's the answer? Also, I heard from someone that you can do it by hand with sandpaper, and I'd rather do that than bring it into a shop, because the one near me is known for screwing everybody's stuff up.

Re: replacing rings

The cylinders on most mopeds are REALLY hard,like madeout of chrome.

But I still like to lightly cross-hatch hone them before installing new rings. Check the piston and bore to make sure they're`in spec' also. You can insert a new ring about 1/2" into the bore and check the ring's `end gap'. The specs will be listed in the manual as to what is acceptable, but I have always found I have more leeway than what they state(same's true with automotive applications).

E.G.: If they state .011 gap maximum allowed, you can probably get by with .016" for NON-RACING applications. don-ohio (:^)

Re: replacing rings

Allen Murphy /

In fact, Don--you're exactly right, it is chrome!

I remember seeing a Porsche cylinder that was all aluminum with a industrial hard chrome plate lining--one tough cylinder, to say the least.

I've cross-hatched with a ball hone, and I've been told you can do it with a flap wheel if you're careful.

Al Murphy

Re: replacing rings

ok, that's good info, and thanks, but is it necessisary to hone it, and how can I do it with like sand paper instead of a hone?

Re: replacing rings

Actually I don't think any older mopeds are chrome, your puch engine definitly isn't chrome. It is a cast iorn liner in the aluminum cylinder.

use a course sandpaper around 100 grit and lighlty sand up and down in a circular motion to scratch diagnol lines criss crossing in the bore. It isn't necessary to do it much.

Re: replacing rings

Rings can be "lapped" in useing an old aircraft trick. This seriosly reduces break-in time. Useing an junk piston, not the one you intend for the final build, with the rings you intend to use, slather with a fine valve grinding compund or similar abrasive, put the piston ring assembly in the cylinder and give it 50-100 strokes or until the ring surface shows a nice even grey all the way around. clean all this real good and install those rings on your good piston and into the cyl.

Re: replacing rings

I don't know,Paul..........I'm pretty sure that the old Puchs,circa 1976 up had a chrome-like substance lining the bore..........but I defer to the Puch experts here. don-ohio

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