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PLEASE HELP - NEED YZ426 Cylinder Head Cap

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I am just worried because people have told me that when you out another cap on your head that didn't come with your head, the clearences might not be the same causing problems. Do know anything about that?

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I not sure what side it is, I would have to talk to the dealer. But now I am being told by my dealer that they may cause problems to put on another cylinder cap other than the one that came with the head, because it could create problems if the clearences are different. Do you know anything about this.

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The cap is bolted to the head and then the cam bore is machined. Putting a different cap on is probably going to make the cam bore out of tolerance. What is wrong with the original? If it is scored but not broken it can probably be repaired by a competent machinist. If you have to change caps the bore can also be resized by a good machinist. I would shy from a dealer doing the work as few of them have the equipment or knowhow to do that kind of precise machine work.

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Thanks for the help, I believe one side of the cam cap is cracked. Dealer is telling me I have to buy a new head to match the new caps, is this true?

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Thanks for the help, I believe one side of the cam cap is cracked. Dealer is telling me I have to buy a new head to match the new caps, is this true?

Re-read tc66nova's reply...

The cap is bolted to the head and then the cam bore is machined. Putting a different cap on is probably going to make the cam bore out of tolerance. What is wrong with the original? If it is scored but not broken it can probably be repaired by a competent machinist. If you have to change caps the bore can also be resized by a good machinist. I would shy from a dealer doing the work as few of them have the equipment or knowhow to do that kind of precise machine work.

Yes - if you get another cap you will need to have a qualified machinist verify/machine the clearances. How about contacting someone who does 4-stroke heads like Eric Gorr (http://www.eric-gorr.com/)?

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Dealers are great... I love my local yamaha dealers...

Why did they have your bike in the first place - what was wrong with it? I would ask for all of my parts back, order a new cam cap, or find one used, and then take the parts and your yamaha service manual to a machine shop. They should be able to match the new cam cap to the manual's specs.

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Automotive aluminum heads are commonly welded and repaired. I do not know anything about the companies named in other posts but check you area phone book for a race engine shop and call them and I will bet that unless it is really screwed up they could weld it and remachine it so that you can hardly tell it was hurt. I would at least chek it out before I spent big$ on a new head casting. And before you listen to the nay sayers that don't think that it will work just consider that most heads and blocks on Top Fuel nitro cars have weld in them and most pro stock heads do also, and they work and hold up well.

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