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Impeller grinding on headcover casing - WHY?

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Have a 2005 EXC. I think it is on its original piston judging from the previous owner he just trail rode with his kids- I have only had it a year and have not put too many miles on it - just 5 enduros and a dozen days out trail riding.

After a while the bike got so that the engine produced a loud hiss/whine. No one really could put there finger on it from the outside, and it ran well - but when I stood on my pegs the engine was loud enough that I started wearing ear plugs (it was louder standing up because the loud came from in front of the tank). I always suspected the water pump as it came from the top front of the engine. So today I finally took the top off and sure enough the fan had wore a 1mm groove in the housing.



The bearings all feel good - could the impeller/rocker shaft have drifted inwards driving the impeller against the housing??

Any thoughts?

Various symptoms the bikes is showing (no idea of hours so could be anything)

-more vibrations coming from engine

-more backfiring and popping despite setting valves

-Engine seems to be running hotter the last few times

-no hot spots found in combustion chamber or head - all looked normal

-the pump seals were going, some weeping happened when I started the bike in February in the cold

-today will not start at all (hence ripping it open) NEVER done that before

|I do not have a good history of diagnosing bike problems so I need your help!

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just a SWAG but the impeller is connected to the cam...i wud be inspecting the valvetrain...bet it's a bearing.

i wudn't ride it until u figured it out. :confused:


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can't ride it anyways as it won't start!

I am thinking bearing at the moment. I went out and had a good look at them and there is some side to side slop in the bearings - maybe .3mm not as much as the groove the impeller had made but I will get that dealt with first. I am hoping a sloppy valve train is the root of everything.

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If the bearings are good and the lock-ring set, there is no endplay. Was the camshaft pin properly seated to the plastic impeller?

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So I pulled off the bearing and once in my hand I could feel some slop - not much. Picked up some new ones - they weren't perfect, had a little movement but easily half what the used ones had. I measured about .003 inches of play in the direction of the lobes - meaning there could have been +/-.003" in the tappet contact on the valves - is this my popping hard/starting problem?

I also pulled off the valves tonight and they were worn pretty good.

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