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  #21  
Old 06-08-2011, 01:53 PM
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Being an air cooled engine, the valve guides are usually set up a little looser than most typical water cooled models. Because of this, the valve stem seals need to be in good condition. The xr400 uses high quality positive PC type seals that do an excellent job in controlling oil seepage past the guides. If the engine is smoking a lot, my guess would be the problem is in the cylinder. When you get the top end apart, take the jug and piston to a machinist who can accurately measure the cylinder and piston for wear. If it doesn’t fall within the recommended clearances, have it bored to the smallest possible overbore size. Then have the machine shop preform a vacuum test on the head and if it fails, have them grind the valves and cut the seats. Then put it together with new gaskets (including new valve stem seals), new timing set (I think some CRF chains will interchange and are cheaper and stronger), and a new cam chain tensioner (I prefer a manually adjusted tensioner). After all of that you would have spent around 400ish dollars but your bike would be ready to run for a long, long time.

Good Luck

Andy
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  #22  
Old 06-08-2011, 02:04 PM
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id like to do that, but i dont have 400$ to spend on it... so im just going to re-ring it and do new valve guide seals for right now
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  #23  
Old 06-08-2011, 02:14 PM
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Originally Posted by supercr125 View Post
id like to do that, but i dont have 400$ to spend on it... so im just going to re-ring it and do new valve guide seals for right now
At least make sure you just run a hone through the bore.... otherwise the rings will never seat properly.

Thanks
Scott
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  #24  
Old 06-08-2011, 02:18 PM
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Before you go into the top end please order the factory shop manual. You can get one from a dealer or order it from the Honda website. This is a really thorough manual that will get you through most anything you attempt.

Best of luck with diagnosing the problem and read Mainjet's PM's carefully. He knows his stuff on these bikes.

Bill

Last edited by Florida 393; 06-09-2011 at 07:18 AM.
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  #25  
Old 06-08-2011, 03:20 PM
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yea if i do the rings i am deffinatly going to hone it!! is the cylinder plated? nikasil plated? and i do read his pms VERY carefully, also i will be buying a workshop manual soon to
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  #26  
Old 06-08-2011, 03:26 PM
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yea if i do the rings i am deffinatly going to hone it!! is the cylinder plated? nikasil plated? and i do read his pms VERY carefully, also i will be buying a workshop manual soon to
Don't know on the newer ones but the older ones were all steel sleeves. Whoever you have run the hone through it should be able to tell.

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Scott
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  #27  
Old 06-08-2011, 03:27 PM
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alright cool
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