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vet250f

Replacing lifters when installing new cam?

11 posts in this topic

Thats the standard when changing cams in most automobile engines (rollercams excepted), how about in a YZF?

I would not like to have to read a lot about -03 cams going bad in -01/-02 engines just because no one replaced the lifters when changing cam.

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First one would need to put lifters in the YZ. Cam pushes directly on the valve stem (with a pesky little shim and shim bucket between them). No push rods, tappets, lifters, etc. But you knew that already. eh?

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Well, the "shim bucket" is called a lifter on the fishes.

The cam does NOT push directly on the valve stem, of course there is a lifter (and "pad") in between!

The manual says: reinstall valve lifters (and pads) in their original place.

That means the old exhaust lifters goes the same place as the old cam...

I´m not asking a question here, I´m telling people to replace the lifters when installing their "wery-hard-to-get-2003-camshafts", just in case!

"I ride with my rims on the dirt, its just a piece of rubber between" :)

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Yeh I hear ya vet, thats been my experience as well.

The manual replaces the cam by itself. When it talks about checking the lifters (4-39), and yes their called lifters in the manual, for scratches/damage, they indicate to replace the lifters and head together.

Kinda odd, but I guess the lifters are matched to the head casting. The fact that they wear with the cam is secondary to them (yamaha).

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Ok, I guess the lifters and cam is not cast-iron as in a Chevy. :)

So if the lifters are matched to the head, I have the answer to why there are different color-coded lifters in the fishes.

Thanks

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That's a very good point, vet250F. I was in automotive rebuilding industry in a past life. Functionally the bucket is like a hydraulic lifter, so the comparison is good.

The reason lifters (buckets) are replaced is that they get worn concave on the face with high mileage. This lifter mates with the old cam, because they wear to match. When you put in a new cam the face of the lobe is nice and square (picture the cross section).

When you run a new cam on worn buckets, the edges of the lobe are taking all the force, and they may break down. The key word is "worn". Dirt bikes have pretty low mileage relative to cars. If your bike has low mileage and you don't see wear, you should be OK. Also, I wouldn't be suprised if the factory makes either the cam section or the bucket crown slightly convex in the first place. This would insure the edges don't contact because slight "off square" conditions due to tolerances.

-Toby

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I meant no attitude with my post. I was thinking of lifters in the traditional valve train sense of the word. I did not realize that the shim bucket would be called a lifter.

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YZ250F_Rider wrote:

Kinda odd, but I guess the lifters are matched to the head casting. The fact that they wear with the cam is secondary to them (yamaha).

Vet250F wrote:

Ok, I guess the lifters and cam is not cast-iron as in a Chevy.

So if the lifters are matched to the head, I have the answer to why there are different color-coded lifters in the fishes.

I think your question has already been answered. They are coded like Yamaha pistons. The tolerances vary so Yamaha color codes them for the best fit. Fit being the lifter bore in the head. That's my take on it anyway.

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I looked for the lifters on Parts fish and Yamaha of Troys websites and couldn't find them. I wonder what the part number and price is?

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