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Dirty Carb ??

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Just finishing up the top end on my 2004 crf450. Roughly 150 hours plus

( 2nd set of intakes). the last set of valves only lasted maybe 20 hrs before I had to start to shim, my mechanic kept saying your sucking dirt in and killin your valves :thumbsup: . My air box is always clean,and Im anal on my filter changes, although I always seen a little dirt on the carb slid, Piston and cylinder were in unbelievable good condition, with all the hours, never even touched the cylinder, just through in a new pist&rings (old rings were still in spec) If I was pulling any large amounts of dirt in the piston and cyl should have been a mess.

Pulled the carb apart and its just full of dust and dirt, its ugly. Any thoughts ? or is it just build up from so long ?

I still believe the vent lines pull in dirt.

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Just finishing up the top end on my 2004 crf450. Roughly 150 hours plus

( 2nd set of intakes). the last set of valves only lasted maybe 20 hrs before I had to start to shim, my mechanic kept saying your sucking dirt in and killin your valves :thumbsup: . My air box is always clean,and Im anal on my filter changes, although I always seen a little dirt on the carb slid, Piston and cylinder were in unbelievable good condition, with all the hours, never even touched the cylinder, just through in a new pist&rings (old rings were still in spec) If I was pulling any large amounts of dirt in the piston and cyl should have been a mess.

Pulled the carb apart and its just full of dust and dirt, its ugly. Any thoughts ? or is it just build up from so long ?

I still believe the vent lines pull in dirt.

When you clean and reinstall your air filter, you might try greasing the seal lip ( where the filter seals to the airbox). Also, run a small bead of white grease just inside the airboot where it meets the filter. This can tell you whether your filter is a)oiled properly and b)sealed properly.

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When you clean and reinstall your air filter, you might try greasing the seal lip ( where the filter seals to the airbox). Also, run a small bead of white grease just inside the airboot where it meets the filter. This can tell you whether your filter is a)oiled properly and b)sealed properly.
I've used both rim grease and white grease since new and the only time I've found dirt in the top of my carb was when one of my vent line filters malfunctioned. When the vent filter is functioning, no dirt in the carb. BTW, I've never found dust on the white grease inside the airboot, so it didn't appear to be coming through the filter or filter seal......

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Ok, don't know what might help you now. Sorry! I've never had that issue with my CRF450X or my buddies that have the 450R.

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the last set of valves only lasted maybe 20 hrs before I had to start to shim
What did you do to the seats and guides when you replaced the valves?

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when you did the first valve job were the seats cut also or did you just drop new valves in?

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Seats were cut, at my local dealer, he sounded confident that he could do them. But they didnt last long :thumbsup:

I sent the head to the pro's this time. :applause:

Before I even rode the bike, I pulled the airboot apart and sealed it.

Maybe I didnt get the filter on straight one time :ride: but Id like to think it was the vents.

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Did you replace the valve springs - if the valve floats due to worn springs, they will wear very quickly. If the seats were cut and the installed height of the springs not checked, there sould be insufficient tension which will also allow float. RHC is a stickler for detail on valve assembly - perhaps you should PM him.

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If the seats were cut and the installed height of the springs not checked, there sould be insufficient tension which will also allow float.
:thumbsup:

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