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Intake Camshaft Binding

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Hey, I have a 2009 YZ250F that I noticed had its intake cam binding after I would snug down the camshaft cover (not even torqued). The guy that worked on the head told me there might be some galling on the cam covers, and I should sand it off. I didn't see or feel anything on the contacting surfaces , but sanded it some with really fine sandpaper. Didn't help I wouldn't even get it past 5 ft. lbs. and I wouldn't be able to turn the cam by hand on the bench.

 

Anyone seen this before or have any idea what this is or what I could do?

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What's the history of the bike?

Are you torquing it in a criss cross pattern and in to stages?

I bought the bike with a locked up crank and pretty much fully rebuilt the engine. I didn't replace the camshafts though. The cylinder head was sent off to have the seats recut and valves replaced. The shop also polished the cam journals, I can't remember that that changed anything though. I was bench shimming it when I decided to look into why it was binding. The shop I sent the head to said the binding could cause overheating. That may have already happened before though.

Yeah I did it in two stages but couldn't even get to 5 ft. lbs. without it binding. I was using the pattern in my manual which says to torque from the outside in. Is that right?

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Did you oil the journals and cam before assembly?

 

I would call the shop that did the head and raise hell. If you run it, it will destroy itself. The journal is a bearing surface. You just can't polish out gouges and expect it to be ok. The proper way to fix it is mill down the mating surfaces of the cap and re-bore the journal.

 

 

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Did you oil the journals and cam before assembly?

 

I would call the shop that did the head and raise hell. If you run it, it will destroy itself. The journal is a bearing surface. You just can't polish out gouges and expect it to be ok. The proper way to fix it is mill down the mating surfaces of the cap and re-bore the journal.

 

 

Oh dang, not what I wanted to hear, but thanks for letting me know man. Would re-boring the journal have to be done by a machine shop or is it something me or a local mechanic could do?

 

Yeah, I oiled the camshaft and cylinder head surface.

 

 

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Oh dang, not what I wanted to hear, but thanks for letting me know man. Would re-boring the journal have to be done by a machine shop or is it something me or a local mechanic could do?
 
Yeah, I oiled the camshaft and cylinder head surface.
 
 

It's something that an machine shop experienced in MX /ATV work should handle. I would call one up and tell them what happened, what's been done and the issue you have now. I've heard a shop named Fast heads does good work on here but I personally don't have any experience with them.

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It's something that an machine shop experienced in MX /ATV work should handle. I would call one up and tell them what happened, what's been done and the issue you have now. I've heard a shop named Fast heads does good work on here but I personally don't have any experience with them.

Okay thanks, so you really don't think sandpaper or emory cloth could take out whatever binding it up then?

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As long as the cams aren't binding on the buckets, you can use sand paper!

 I have done it several times

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The correct fix is to disassemble the head, mill a few thou off the caps, line bore or hone the head get the bore straight and even), check with plasitgage. Clean the head, assemble, redo the shimming of course.

Sandpaper is what you do to a 2X4 when your cut is poor......

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The correct fix is to disassemble the head, mill a few thou off the caps, line bore or hone the head get the bore straight and even), check with plasitgage. Clean the head, assemble, redo the shimming of course.
Sandpaper is what you do to a 2X4 when your cut is poor......

I took it to a local mechanic and he thought my camshaft was warped. I'm gonna start with replacing the camshaft, if it still binds I might have it honed out.

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The correct fix is to disassemble the head, mill a few thou off the caps, line bore or hone the head get the bore straight and even), check with plasitgage. Clean the head, assemble, redo the shimming of course.
Sandpaper is what you do to a 2X4 when your cut is poor......

Would I have to get an oversized cam if I have to go that route?

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1 hour ago, William1 said:

The correct fix is to disassemble the head, mill a few thou off the caps, line bore or hone the head get the bore straight and even), check with plasitgage. Clean the head, assemble, redo the shimming of course.

Sandpaper is what you do to a 2X4 when your cut is poor......

Agree until you said plastigage. That is what hack rednecks use in dirt track car 350s because they don't know how to use micrometers. 

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Just now, DeAndrae Loewen said:


Any idea how much they charge?

First check your shims or pull them out and check it for binding. 

I cant remember but it's very reasonable and they specialize in doing cam caps. Call them up and ask. 

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First check your shims or pull them out and check it for binding. 
I cant remember but it's very reasonable and they specialize in doing cam caps. Call them up and ask. 

They'll be closed now, but I'll check into that.

The valves are in spec, at least with the warped camshaft. I'm going to change it out first.

If that isn't the only problem I might be forced to maybe send it off or risk it myself.

Thanks for recommendation, man
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