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Javipop

 
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Thu Feb 08, 2018 6:48 pm » Post: #1 » Download Post

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Last edited by Javipop on Tue Oct 05, 2021 12:11 pm; edited 1 time in total
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tleighbell

 
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mc21 crank seals

Thu Feb 08, 2018 7:00 pm » Post: #2 » Download Post

I am no expert but Andy has posted pictures showing badly deteriorated center seals. It may be a common problem so there is a good chance your center seal needs to be replaced. If i have the crank out of the motor there is no way i would put it back in without rebuilding the whole thing unless I could be sure all components are in top condition. I would think the centre seal is important for all engine operation as it prevents leakage between cylinders which would be just as bad as leakage outside the crankcase.
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Mr. Z

 
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Fri Feb 09, 2018 6:34 pm » Post: #3 » Download Post

If you're going to replace the outer seals, I would just go ahead and change the center seal as well. Chances are very good it's gone bad or will soon. At least that was the case with my MC21 that had the same hard cold starting symptoms as yours.
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Javipop

 
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Fri Feb 09, 2018 9:18 pm » Post: #4 » Download Post

Ok thank you , I will changue the three seals is the best
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Andy
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Sun Feb 18, 2018 3:14 am » Post: #5 » Download Post

Please note:

The centre seal on all 1989-1997 NSR250s is integral to the centre bearing. The O-ring around the outside of the centre bearing IS NOT the main centre seal on these cranks.

The crankshaft on ALL YEARS must be split to replace the [main] centre seal.

A bad centre seal can indeed, and almost certainly will, cause poor starting.
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Javipop

 
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Wed Feb 21, 2018 4:12 pm » Post: #6 » Download Post

thank you for your help . The o-ring number 9 in the photo where is it exactly ? I have dismount the engine and crankshaft but I don,t see this o-ring
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Andy
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Thu Feb 22, 2018 11:44 pm » Post: #7 » Download Post

That O-ring should be located in the narrow (1mm) groove in the centre main bearing. (89~97 models)
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Javipop

 
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Fri Feb 23, 2018 8:06 am » Post: #8 » Download Post

thak you Andy
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