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slowxr

XR650. Tightening valves/UniFilter?

8 posts in this topic

Took my 650 to Precision Concepts for a top end. I've got 13K dirt miles on it. Still runs strong, starts easily and runs smooth.....but my intake valves kept tightening up.

So PC opened up the top end and recommended valves, piston, springs etc.

They believe that the valve damage is due to the UNI Filter passing dirt and highly recommended switching back to the OEM filter.

Anyone heard of this?

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I would think that as long as you have a good seal around the mating surface of the filter that the UNI filter would be superior in keeping dirt out of the engine. Flows more air too. And all mx bikes come with a foam filter these days for that very reason.

I think there may be a bit of speculating going on here.

Which xr650 are we talking about? There are differences in the air filter system between the bikes.

Is the air box drilled and what conditions are you riding in?

I have read that for desert type riding your better off not drilling the air box, the slight gain achieved, is not worth the added sand/silt/dirt that your filter is asked to deal with.

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It is not uncommon for the problem of the intakes tightening up to occur. The Honda OEM intake valves tend to develop valve seat wear and sink into the head and thus cause the clearance to diminish. This is the probable cause of the valve problem in my estimation. Is the piston damaged or prematurely worn?

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Mine is an XR650r. I do ride desert but I don't ride in the dust and often lead. I don't have my sidepanel cut.

I had heard the same thing about the OEM valves. I'm not sure about the piston. I got the feeling I'd already paid for the labor, so I might aswell replace the piston while they were in there.

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OEM valves have a hard outer surface but once worn through they tend to wear quickly, not to metion that the seats usually show heavy chatter from the factory machining. So I would have to say that the wear on your valves is normal wear n tear and to replace your stockers with some after market stainless valves.

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When replacement is needed, Kibblewhite valves and R&D valve springs are a good choice.

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Took my 650 to Precision Concepts for a top end. I've got 13K dirt miles on it. Still runs strong, starts easily and runs smooth.....but my intake valves kept tightening up.

So PC opened up the top end and recommended valves, piston, springs etc.

They believe that the valve damage is due to the UNI Filter passing dirt and highly recommended switching back to the OEM filter.

Anyone heard of this?

They tell everyone this on every bike if you are not running the oe filter.

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They tell everyone this on every bike if you are not running the oe filter.

That pretty much sums it up, for Hondas anyways. I'm going on 20K and have never used any filter but OEM. Right intake tightens a bit and bike still runs strong.

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