well i have been doing a top end rebuild on my MC28
and everything was going nice.
until i went to put the new rings on my second piston.

got the bottom one on fine put the top one on and woo it grabbed it like its life depended on it. could not get it to slip around or move freely. and in the end i F'd the ring up trying to get it off.

so ordered a new set of rings which arrived today.
cleaned up the piston and started again.
exactly the same thing happened. the top grove appears to have shrunk ? impossible i know.
it wont even except the original rings and its not like its just tight in one place its tight the whole way round.

never seen anything like it.

so new piston it is and i have to wait a bit longer to get my bike out on the road. ho hum

Hi
You might have a bit of carbon in the ring grove , you could clean it out using a part of the old ring and carefully scraping it arround the grove.

The top and bottom rings are different.The bottom ring wont fit in the top grove.
It goes in but wont fit flush in the grove and is a bugger to get out.
Have you tried fitting the ring from the bottom grove into the top one???

If you have and its still the same you might have got all the rings mixed up, if you got all 4 rings out from their boxes at the same time.
You might have fitted both the top rings into the other piston.
Not that Ive ever done that
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Harley Davidson is the worlds most efficient way to turn petrol into noise without the harmful side effect of horsepower.

Do a search for "Keystone"...

http://www.nsr250.net/forums/viewtopic.php?t=1894
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Andy.
NSR-WORLD.COM

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gutted.
unfortunately this info has come to late to save my piston.

now i have been told it is easy to see.
hindsight is such a wonderful thing.

Dont be so hard on yourself.
Were not all HRC trained.
As it says in the topic Andy pulled up,It is hard to see the keystone but you can see it, BUT why would you be looking if you dont know they are different.
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Harley Davidson is the worlds most efficient way to turn petrol into noise without the harmful side effect of horsepower.

Because you didn't know they were the same??
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Please do not PM me technical questions, if you can't find it on the Forum start a thread