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Excess valve clearance

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It was kind of strange. I was working on my electrical system starting and stopping my bike. All the sudden there was a lot of valve noise. Now I have about 3mm of clearance on my left side exhaust valve. It's the side away from the cam chain.

Bike seems to run fine.

I can only think of two things that woudl cause an increase of clearance. One would be a loose adjuster. No such luck. The other is fried cam or rocker arm aka cam follower. There is not a lot of view through the valve adjuster holes, but the surface of the cam seems fine. The lifting surface is nice and smooth.

I really don't want to take the valve cover off, but I'm thinking I had better.

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Well took the cover off and the rockers look fine. Took a quick look and no unusual wear to them or the cam.

I'll go look a little closer, but it sure looks good.

I just can't think of anything other than the adjuster loosened up on it's own. Seems tight though. If there was a piece of crud stuck under the valve the engine wouldn't run well and it runs just fine. That's about the only thing that I can think of that would cause excess clearance. OK other than one thing. The valve seat came loose and it moved. However, the last time I had that happen the engine lost compression and ran like crap.

Guess I'll find out on tomorrow's ride...

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Hope it survives,,as you say I can't think of anything that'd cause that to happen,,The bloke with the Tensioner pin problem could do with your explanation of head cover removal without engine removal if you feel like it..,though he's a 600 and I think you're 650L,,any difference in procedure I don't know,,

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Well took the cover off and the rockers look fine. Took a quick look and no unusual wear to them or the cam.

I'll go look a little closer, but it sure looks good.

I just can't think of anything other than the adjuster loosened up on it's own. Seems tight though. If there was a piece of crud stuck under the valve the engine wouldn't run well and it runs just fine. That's about the only thing that I can think of that would cause excess clearance. OK other than one thing. The valve seat came loose and it moved. However, the last time I had that happen the engine lost compression and ran like crap.

Guess I'll find out on tomorrow's ride...

Valve seat is falling out..

B

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Valve seat is falling out..

B

If it has started to come out and is stuck partway out of the head, yeah, you'd have a whole bunch extra clearance.

Dave

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Well now I'm about 99.9% sure. I only got about 20 miles of riding in last weekend before it told me that the it was time to stop. The seat must have fallen back in because all the sudden I lost power and the engine quit as soon as I let off the throttle. The valve was open. A little bit of wrenching and I had clearance again. From there it was a slow ride to the dirt road and then back to the truck.

Back at the truck it was beer drinking time.

If I can get a little time this weekend I'll take off the head and see what it looks like.

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Well now I'm about 99.9% sure. I only got about 20 miles of riding in last weekend before it told me that the it was time to stop. The seat must have fallen back in because all the sudden I lost power and the engine quit as soon as I let off the throttle. The valve was open. A little bit of wrenching and I had clearance again. From there it was a slow ride to the dirt road and then back to the truck.

Back at the truck it was beer drinking time.

If I can get a little time this weekend I'll take off the head and see what it looks like.

Well if you had beer than what are you complaining about:smirk::lol::smirk:

Post pics when you get it apart..

B

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Years ago I was working on the ligths of very nice 87 xr 600 I use to have , it was summer it was very hot and I gess I spend too much time with the engine idling and not moving / cooling when I was done stoped the engine minutes after I restarted; and guess what ...... valve noise; the reason one of the ex valve seats drop down few mm . The solution remove the cilynder head and repair or replace the valve seat . Regards Flavio

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