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2000 xr650l smoking on decel

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Hey guys...

So I ride a 2000 xr650l has 4300 miles on it.  I got it with 2000 miles on it. The bike had sat since 2005 and after tearing down the carb 4 or 5 times, changing the oil, and adding a few other parts my buddy and I brought her bike to life.  The bike always smoked a little on decel especially if the hill was steep but lately he's telling me it's smoking like a two stroke when going down steep hills.  Never under acceleration or normal riding. I've changed the oil 4 times since I got her and check the oil after each ride.  I'm thinking probably the rings but I'm taking her to Honda for a leak down test.  Any ideas?

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On 6/10/2017 at 5:06 PM, BillsXr said:

... it's smoking like a two stroke when going down steep hills.  Never under acceleration or normal riding...Any ideas?

It is caused by a worn cylinder or oil control ring problem.  

During deceleration, when the throttle plate is closed and a high vacuum in the combustion chamber is developed, oil is drawn up from the bottom end, past the rings, and burned.  You will see the oil smoke begin to slowly appear as the RPMs begin to drop and it will increase the longer engine braking is allowed to happen until the throttle plate is opened or load decreases (pulling in the clutch, stopping, etc.) and vacuum is lowered.  

You will see the smoke go away instantly if you just slightly crack the throttle or pull the clutch in to decrease engine braking.

The valve seals and stem seals could also be contributing but, unless they are in terrible shape and the guide heavily worn, they won't supply enough oil to see the type of smoke yours is throwing out.  The typical puff or two on startup is all that will be visible from the valve seal issue.

Edited by Hollerhead
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On ‎6‎/‎24‎/‎2017 at 7:47 PM, Hollerhead said:

It is caused by a worn cylinder or oil control ring problem.  

During deceleration, when the throttle plate is closed and a high vacuum in the combustion chamber is developed, oil is drawn up from the bottom end, past the rings, and burned.  You will see the oil smoke begin to slowly appear as the RPMs begin to drop and it will increase the longer engine braking is allowed to happen until the throttle plate is opened or load decreases (pulling in the clutch, stopping, etc.) and vacuum is lowered.  

You will see the smoke go away instantly if you just slightly crack the throttle or pull the clutch in to decrease engine braking.

The valve seals and stem seals could also be contributing but, unless they are in terrible shape and the guide heavily worn, they won't supply enough oil to see the type of smoke yours is throwing out.  The typical puff or two on startup is all that will be visible from the valve seal issue.

So basically time to rebuild the top end.  Thanks  I appreciate the input.

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20 hours ago, BillsXr said:

So basically time to rebuild the top end.  Thanks  I appreciate the input.

Ha!  Yep, in a nutshell.  Don't cut any corners or she'll smoke when rebuilt too.  Ask me how I know.    

If you don't have the stuff to bore and hone yourself don't take it to a guy that "thinks he can handle it" because he does machine work on "all kinds of engines".  Let someone with a good reputation on the bike stuff do it for you.  Shipping is cheap.  On the left coast you can't beat Engine Dynamics.

Side note, it'll run that way forever if you don't mind the little puff every now and then and it isn't using as much oil as you think.  It embarrassed me pretty bad though so I couldn't ride mine that way. :ride:

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