piston or valves ? - Honda TRX Forums: Honda TRX 450R Forum
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post #1 of 5 (permalink) Old 08-12-2019, 12:00 AM Thread Starter
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piston or valves ?

so my 2005 450r is burning oil but i dont know if its coming from the valve seats or rings. any easy way to tell which on before i tare into the motor ?
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post #2 of 5 (permalink) Old 08-13-2019, 10:16 AM
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Have you tested compression with a gauge? Does it smoke only on start up or the whole time it’s being ridden? You could test rings by pouring a teaspoon of oil in spark plug hole and see if compression jumps back into the normal psi range.. their may be some other threads on this
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post #3 of 5 (permalink) Old 08-13-2019, 11:58 AM Thread Starter
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It only really smokes when I give it throttle. I don’t notice it doing it at idle
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post #4 of 5 (permalink) Old 08-13-2019, 12:39 PM
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Are you sure it’s oil? How much oil does it use after several hours of riding? How long has it been since the engine has been freshened up? If it’s never been touched it wouldn’t be a bad idea to replace the piston/rings and have the head gone through.
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post #5 of 5 (permalink) Old 08-13-2019, 10:50 PM
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Doing a compression test won't do much for you on the Honda 450R's since the exhaust valves hang opened just a tiny bit due to the centrifugal decompression wing that is on the Cam Shaft.... you only get full compression when the engine is running. I'm betting it's the Piston rings for sure, especially if it smokes when you give it throttle.

Now If it was the Valve Guide Seals it would smoke only when the engine is cold (first initial start up) for a minute or so then goes away when it warms up, especially in colder Clements.

I would put my money on piston rings for sure. If you decide to rebuild it I'd get a Piston, Piston Rings (Or a just decent quality aftermarket piston kit) top end Gasket Kit, Valve Guide Seals (usually valve Seals come with good top end kits), get the Cylinder Ball honed (or buy a ball hone along with all the parts if you know how to do it), check the valves while the head is off. I usually recommend replacing the piston when ever doing a top end rebuild since it is a fast moving part.

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