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Some photos of my Top End

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Took the top end apart on my 97 Rm250 this afternoon, thought it would be good to order a new Wiseco kit since I just got this bike so I wasn't sure on the history of it.. So far the bike is solid, the guy obviously took care of it.. The top end looked alright, i do have a couple concerns though.

Here's some photos of the cylinder, it's hard taking photos of cylinders because of the glare.. it looked pretty good, no bad scoring marks or gouges.

cyl3.jpg

cyl1.jpg

Checking the Bore - seems fine to me, within spec

cylMic.jpg

boreMic.jpg

The Piston that was in it.. It's an ART piston and you can see marks from where it was slighty rubbing the power valves. If you run your finger over the marks you can't really feel much. This is one of my concerns, can I adjust the powervalve depth in the cylinder on this by turning the 2 dials on the cylinder? Never worked on a RM before..

piston.jpg

Here's something else I noticed.. the crank looks like it has a hot spot.. not sure if this is factory from assembly or not.. nothing is bound up, the engine ran good before I took it apart.. There is no play in the connecting rod at all..

crank.jpg

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That mark on the crank is from the factory.

The cylinder looks worn through from the pics

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well If you look at the Mic you'll see it measures within the limit.

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If it is stock bore, it may be a good idea to pull the power valve out and lightly file/sand the area that is hitting the piston. If it was an overbore it is more likely to need this to give clearance. But if it was mine, I would take a small amount off the edge of the power valve. Less chance of the rings getting caught on it too which would cause major problems. Crank blue looks like factory.

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I cleaned up the power valves with my Dremel/Flex shaft assembly.. Turned out perfect.. I have plenty of clearance to the piston and the valves move freely.

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hi, just curious, how did everything work out for you? I too have a 97 rm250 and i am curious as to what else you did. and why is your crank blue? is it heated for a press fit at the factory? thanks

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If the cylinder is in spec deglaze/hone it to get the crosshatching back and slap it back together, wondering why it looks like your bottom end is so dry, does not appear to be any residual oil down there

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Your piston is probably out of spec, rocking in the bore, and rubbing the pv. The crank appears to be rebuilt. Side thrust washers look fairly new, and are different than what Zook used. Put 'er back together and ride it

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yes i agree.. i've been into bikes/ engines all my life 37years and I have yet to have any trouble with wiseco pistons. I worked in a engine shop and we used Wiseco on all the 2 stroke engines as well as some circle track or drag race engine.. You just have to make sure your piston to wall clearance is right and your ring end gaps.. In this case my piston to wall in the tightest spot was .003 and I file fit the rings to have a .015 gap.. It's failproof this way..

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