Center intake valve clearance ?


Today I talked with few guys working in yamaha services. They've told me that I have to set valve clearance a little difrent then the manual says.

They said that center intake valve should have 0.2-0.22 not the 0.1-0,15 in 01 yzf 426. They say that the same thing is in yzf 250 any year. They say that that's because the center inatke cam lob is engaged 15 deg ealier.... is this true and good to set this clearance at 0.2??

Another question is?

Cam I put 450 cam chain into 426? I know that it is shorter but that's not my problem because I can get tsubaki chains in any lenght. As I found there is only diference in lenght and sidle plate shape. Am I right?

First question: NO. The cam lobe for the center intake is set at a different angle because the center intake valve is set at a different angle. Under no circumstances should you set the center intake to anything other than .10-.15mm. Are you sure these guys worked there, are were they hanging around the back with a beer?

Second question: NO. The tooth profile of the 450 cam chain is different. This was a big issue that people were worried about during the early experiments with the 450 exhaust cam in a 426 engine. The 426 chain would not sit down into the sprocket teeth as the 426 chain does, and many felt this would prevent the swap from working. Because it is close to the same, and because the cam sprocket is relatively large, and because the chain passes over only a quarter of it, the conversion turned out to be OK.

However, we are talking about a crank sprocket. The chain must cover half the sprocket correctly, and the chain runs over it twice as fast, and over each tooth twice as often. Because of that, I would not run anything other than the correct one.

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