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Old 01-27-2004, 04:41 PM
gear graphic's Avatar
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Default Cr Exhaust valve cleaning question..

02 cr 125
Doing my top end... Actually I'm down to the frame and bottom end, but - First time for me with the exhaust valve... Not as complicated as I thought, and I'm read up on them, but just a couple of questions for you guys..
1. How critical should I be with cleaning the valve, oven cleaner got 1/2 off, but i need to resort to mechanical efforts. Is the clearance on the machined part of the valve extremely critical... should I try not to scratch it up at all ? How do you guys usually clean 'em.
2. How about the bearing in the case for the shaft..... after the oven cleaner, it felt real dry... I got some oil in it and feels better, but what's the best way to lube it.... it looks like a sealed bearing (maybe not now after the cleaner)..... What kid of heat does this bearing see. I guess i could just replae it... but I'm getting tired of waiting for parts...

Oh, another thing... I'm not new to workin on bikes, but it's been quite a few years... my last bike was an 84...
so, I'm Putting a new piston in.... about 50 hours on the top end.... yeah, i feel guilty for letting go.... but any how,
The rings were shot, .018 end gap, but the piston itself isn't scared at all... I was a little surprised. Thought it'd be scratched to hell. Didn't measure the piston or bore yet. The cylinder looks perfect. So my question is... Does the nikasil help with piston wear, or is it that i did a really god job keeping the air filter clean?

I have the bike down to nothing and I'm going over everything (susp. bearings and such)... and i changed the fork seals..... That was a treat.... Not so bad now that I know whats in there...
So any other thoughts for this Old Goat that has recently got back into racing.... Fire away.
Thanks....
steve
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Old 01-27-2004, 04:48 PM
gear graphic's Avatar
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Default Re: Cr Exhaust valve cleaning question..

I just read the power valve thread started by jackal... mat and YP pretyy much answered my questions.....
Should have listened before I spoke.... Sorry
Feel free to fire any other thoughts though.....
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Old 01-27-2004, 05:05 PM
Faded's Avatar
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Default Re: Cr Exhaust valve cleaning question..

Did you check your manual for the spec on the rings? On my 250 new was @ 0.012" and shot was 0.026", quite a difference! When I replaced mine @ 40hrs they measured 0.016".

The Nikasil plating serves a dual purpose roll. It is extremely hard in order to protect the cylinder bore and to stand up to the extreme punishment that would wear a standard cylinder out in no time. It also helps with heat transfer. When trying to extract 30-some-odd hp out of 125ccs of diplacement things are going to get hot and the Nikasil helps to dissapate the heat.
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Old 01-27-2004, 05:15 PM
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Default Re: Cr Exhaust valve cleaning question..

Faded,my manual also lists 0.026" for the service limit on the rings. When I did my topend my Ringend gap was at 0.018".
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Old 01-27-2004, 05:15 PM
gear graphic's Avatar
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Default Re: Cr Exhaust valve cleaning question..

Thanks for the insight Faded.... No I didn't check the spec... just assumed the old rule of thumb... .004 for every inch of bore = .008. I only have my owners manual... didn't get a shop manual yet. But i thoght i would have more wear at this point.. Your wear at 40 hours sounds similar.
Maybe I'm not riding as hard as I thought LOL.
So I just bought a new piston and rings before i tore it apart.....
Oh and while I have you... i wanted to say thanks... i've been reading this forum for a bout six months now, and I've gotten tons of useful tips and insight from you, as well as many others here. ATM rocks... I'm oficially addicted.
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Old 01-27-2004, 05:29 PM
gear graphic's Avatar
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Default Re: Cr Exhaust valve cleaning question..

I guess sometimes I'm Dumber than I look...
I just measured the new ring and it's .012, I don't know where i got the .008 from.
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Old 01-27-2004, 07:31 PM
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Default Re: Cr Exhaust valve cleaning question..

Gear Graphic.....we all have brain farts every now and then
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