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01 yz250f intake cam won't spin freely

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I've got a 01 yz250f and I pulled the valve cover to make sure the bike was still timed. I took off the intake cam to Check for wear, but everything looked fine. I put it back together and took a more kicks than normal to get it going. Went for a little spin and drove 100 yards when I It just died. Brought  it into the shop and pulled the valve cover and took the chain off, and the intake valve would not spin freely like it should. It is possible that I had it out of time by one tooth, or that The cam cap didn't sit down properly? Any thoughts?

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Could have been out of time.  Your timing marks should line up exactly; check em.

Your statements in the post indicate the most likely problem though....

"I put it back together and took a more kicks than normal to get it going. Went for a little spin and drove 100 yards when I It just died."

Dollars to doughnuts you over torqued the cam caps.  They are only 6mm bolts...~ 7.5 inch lbs.

Cams should spin freely even when the caps are torqued down... properly.

 

Edited by ronbuell
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The cam cap is aluminum and can get tweaked easily.  You need to have the cap fully and correctly seated when you start to run the bolts down.  You also need to gradually sneak up on the torque spec.  I had the same thing happen to a WR450 intake cam.  It would not spin with the cap on.  I ran it anyway and destroyed the bearing surface along with the cam.  It must turn freely after torqueing. If not, do not start the engine.  Also, ensure that you slather the cam with heavy oil before you set the cap on place.  I use chain saw bar oil as assembly lube.

When I say spin freely I mean you can move it with light to moderate finger force. 

Edited by L. Euler
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Torqued all the Bolts to 7.2 ft lb and still doesnt spin freely. The cap went on nicely and slowly tightened in a cross cross pattern to torque specs.

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If it still will not spin freely, there is something still not right.  You need to pull it and check to see if some aluminum galled to the cam bearing surface.  If it did, you should be able to clean the cam and have it free up.  I'm talking about the plain bearing side, not the roller bearing side.  Check the roller bearing and make sure they spin freely before you bolt it back up this time.

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The bearings spin free and I have checked all of the contact surfaces and they are smooth. The first time when I opened  it after it wouldn't start , the surface that the cam rolls on Wasn't totally smooth but I sanded them out. They too were quite minor but probably still affected but didn't solve the problem. Any advice  is appreciated!!

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It worked good before I went to check the cams and timing. I'm pretty sure I checked to see if the cams spun freely after I put them back on the first time and they were same as before.

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 I suspect the bearing cap is fouled. Will the cam turn with less bolt torque?  Personally, I would consider trying to run it with reduced torque as it appears the damage has been done.   Or at least kick it through several revolutions while gradually increasing bolt torque to see if it will run itself back in. 

Edited by L. Euler

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Yes L.Euler, if I just press the cap down, it will spin freely but once I add pressure it will seize. Do you mean have the bolts slightly on and kick it over and slowly add torque to specs?

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10 hours ago, Matias said:

Yes L.Euler, if I just press the cap down, it will spin freely but once I add pressure it will seize. Do you mean have the bolts slightly on and kick it over and slowly add torque to specs?

Yes. And make sure you have lube on the bearing surfaces.  Unfortunately, I think you may have some damage to address.  I found a head with cam caps on EBay for my WR450 when I messed up the cap.  My symptoms were exactly as you have described. 

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L.Euler, wouldn't just cam caps to the job or would I be better off buying the head at the same time? stevethe, I didn't touch the valve shims and it isn't binding on the valves.

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It is my understanding that the cam journal is line bored with the caps attached to the head, which means the caps are matched with the head.  So, I bought a whole assembly just to be sure.  Of course you can try just the cap, but do a bit of research first.  I just looked at the OEM parts breakout for a 2001 yz250F head and the bearing caps are not listed as separately available.

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Ok thanks guys! If you guys find a cheap good head, let me know. I am looking for one but they all seem quite expensive 

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Also one thing I forgot to mention is that when I'm was handling the engine, couple of the wires on the neutral safety that bolts into the bottom of the engine broke. I read the you don't really need it, so I just didn't connect the connectors. Is that true that I can just leave them disconnected without it affecting anything?

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Update guys! I put the cap bolts on loosely and kicked it over and slowly tightened them to torque. Cleaned the carb and put it together and it started in 2 kicks! Works like a charm now! Thanks for all the help!

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