Hi all my rear cylinder is having a low compression, think the rings are about to go or something! What to do and what to order would be helpful. front cylinder is running strong and with a good compression. Should i change it also?
Had a complet topend done 3000km ago, it had a problem with oil pump after the rebuild so i believe the rear seized up two times(kicked over once it was cooled), it happened during low speeds, and now the rear cylinder is knocking also.
A week ago had a look at the plugs and the rear was running way too rich although both cylinders have the same set up with the AS 1-1/2 out. The next day rear cylinder fouled on start up. Guess low compression can cause fouling also... pressure vs temp.
so again what to do to make sure what to order is what i am asking, thank you!
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feel the wind

hi there,well my bike seized up 3 weeks ago and i didnt start mine up after it had cooled,but if it seized up topend you would be best to take barrels off and cheack it,i got topend rebuild kit for mine and it was around 180 pounds,best to do both barrels,
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NSR250 MC18

Two cylinders of my MC16 have being replated during the last topend rebuild so which rebuild kit should i buy? or is there no telling till i take the cylinders off? had a shop do it last time so have no idea what the specs are.
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feel the wind

By the sound of it I'd guess the rear piston has enough damage to reduce compression (i.e. at least one of the rings isn't free anymore) but not enough to stop it running.

Get the barrel off and have a look, get the front off too if you can (it's the easiest one anyway) but at just 3000k's old I wouldn't bother replacing anything that's not damaged. If the rings are free and there's no sign of seizing.

If the barrels have been plated you need to measure the clearance, the letter on the barrel now means nothing.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Thanks. i will take look at it with the chambers off. will i need a new set of gaskets for the chambers?
i dont understand the idea of free rings, is it good to have free rings? whats a free ring and whats a not free ring?
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feel the wind

Make sure the rings are free (can expand) and not stuck in the ring groves.
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If I have to take the carbs off once more...

Ok. will take the chambers off and have a look for the above.
Ring moving free, and if any damage to the cylinder or the piston,
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feel the wind