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Discussion Starter · #1 ·
I've got a 2003 450 that started smoking this morning. It seems to have good compression & is running okay, just smoking extensively. I changed the plug & within 30 seconds, lots more smoke. The end of the plug is wet from oil. Valve stem seal maybe? Any ideas would be appreciated.

Thanks!
 

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yes maybe your valve stem seals or your your piston rings, or valve guides, or cylinder. theres really no way fo knowing unless you tear it down to find out. make sure it is oil and not gas smoke.
 

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That's a bad habit for your atv to start. I would start it on the patch asap.
The sooner the better. It will go through withdrawls, so be aware.
 

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Was it sunk? Water/mud/sand in the cylinder to cause the damage?
 

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OHHH!! That kind of smokin'.
 
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Discussion Starter · #7 ·
It was sunk in water about 2 months ago. It has been riden since then with no problems. I had been riding it this morning for about an hour & a half before the smoking started.
 

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Sometimes sand can get trapped in the cylinder and wear into the piston rings or cylinder walls causing premature failure. You may get lucky and be able to put new rings on and hone the cylinder. If not you can have the cylyder bored and have a larger piston put in.
 

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HondaMechanic is right, but I would also like to add that by not cleaning out the intake after you knock dirt off the air filter when cleaning doesn't help your motor either. Before you tear your motor apart, do a compression and leak down test to help you diagnose your problem. Any thing over 10% leakdown and you need to listen and find out where the air is leaking from (valves or rings).
 

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We just rebuilt a 450 & the oil rings were wore due to sinking the bike. We started it up, & let it run for about 10 min. It still smokes. I know it should just be the oil in the cyclinder that we put in there for the rebuild. How long should it smoke?
 

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When we do a motor job on a bike that was smoking bad we take it for a drive after the motor job is done .. The exhaust is usually coated inside with wet oil and the bike will smoke for several miles .. I think if you take it for a drive and get the exhaust hot it will soon stop smoking . .

Don't forget to clean & oil the air filter good with air filter oil ..
and check the crankcase breather ..
 
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