Topic: Oversize piston rings in a standard bore?

[lordwhimsey]

My piston rings are shot but I just happen to have a set of .50 oversize rings that are fairly fresh. Can I just file of the ends and put them on my standard pistons or is this a big no no?

[Alan F.]

I'd say its probably a no, if your rings are shot your bore may be out of round also making a rebore more likely.
Oversize rings probably need oversize pistons I'd think, but I'm not familliar enough to say.
Members with more experience in this area will be along shortly to give their recommendations.
What bike is it and how many miles does it have?   (before they ask...)

-Alan

[lordwhimsey]

Thanks for the input. It's a 550, the original engine lost one of the big ends so I scavanged a crank, cylinders and pistons from an old engine with cracked cases.

I've no idea on the mileage on this engine but there are some burnt oil deposits down the side of the pistons so I thought new rings would be in order.

I'm on a very tight budget so a rebore is out of the question. I'm trying to get it back on the road with the minimum of expenditure but I'm keen not to risk death or serious injury! I'll probably go for a rebore when/if my finances pick up but for the moment I'll settle for it not exploding!

[HondaMan]

If you do that, they will never seat, at least not in the life of that engine (it takes about 30,000 miles of wear to seat them in that situation). And, it will burn oil.

Piston rings are cast so that when the gap is closed, they are perfectly round. It's a very precision thing...when you file off the ends of the rings to make them fit a smaller bore than the one for which they were designed, it creates gaps in the area around the ring gap itself.

Check on eBay with mrsuperdeals (it might be mrssuperdeals) for some MC rings. They will cost about $20, and are good rings. Get stock size. If the pistons are burned (pictures?) you must replace them. If they are just dirty from blowby, they can (must) be cleaned with Scotchbrite (rub vertically, not horizontally) before reusing.

[lordwhimsey]

If the pistons are burned (pictures?) you must replace them. If they are just dirty from blowby, they can (must) be cleaned with Scotchbrite (rub vertically, not horizontally) before reusing.

Hi, thanks for the help. Are these burnt or just dirty?

[754]

did you swap entire crank into your case.. if you did, was every bearing pastiguaged?
 If you did not, you may soon be in for another case-splitting adventure...

[Flying J]

i looked up mrsuperdeals on ebay and he has no listings. I emailed him to find out if he still sells piston rings.

[lordwhimsey]

did you swap entire crank into your case.. if you did, was every bearing pastiguaged?
 If you did not, you may soon be in for another case-splitting adventure...

Yes, I used the whole crank but don't worry, I plastigauged the lot; they were all fine. Brilliant invention; much cheaper than a bore gauge and a micrometer! Although I now have a life time supply of plastigauge!

[lone*X]

[/quote]

Hi, thanks for the help. Are these burnt or just dirty?


[/quote]

Those should clean up just fine. 

[HondaMan]

Hi, thanks for the help. Are these burnt or just dirty?


[/quote]

Those should clean up just fine. 
[/quote]

What he said... 
Those are fine, be thorough in your cleaning, and make sure you clean the oil holes under the 3rd ring, and the piston pin (wristpin) oiling holes, too. Use small drill bits, as if they were tiny files, to pull the carbon out of those holes.

[lordwhimsey]

So, just a new set of rings! Thanks for the help Guys.