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Intake valve is too lose, yz250f '05

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When the bike was new the left valve intake gap was 0.1-0.12, after a couple hundreds miles the gap was more like 0.15, 3000 miles later it seams that it gets down to 0.1. I preferred to replace the original 182 shim with 175, the gap was again around 0.15. After 500 miles the gap became around 0.3-0.35.

After 700 miles more, today, I replaced the 175 shim with 186 (the biggest I have), the gap is now 0.25.

I’m planning to order a 195 shim, but I’m wondering how come the gap was getting bigger, not smaller like for anybody else?

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either the base circle of the cam is wearing, the bucket is wearing, the valve stem is mushrooming, carbon on the valve face that keeps it open, the shim is in wrong or you are magical.

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When the bike was new the left valve intake gap was 0.1-0.12, after a couple hundreds miles the gap was more like 0.15, 3000 miles later it seams that it gets down to 0.1. I preferred to replace the original 182 shim with 175, the gap was again around 0.15. After 500 miles the gap became around 0.3-0.35.

After 700 miles more, today, I replaced the 175 shim with 186 (the biggest I have), the gap is now 0.25.

I’m planning to order a 195 shim, but I’m wondering how come the gap was getting bigger, not smaller like for anybody else?

WOW! I've never seen the gaps get bigger, they ALWAYS get smaller. I'd be worried enough about that if it was mine that I'd remove the head & pull the valves out for a look. But that's just me.....

The only things I can think of (that's not silly like the valve shrinking) is there is something building up between the valve & the seat. That will move the valve downwards & increase the gap. Or maybe the bucket is wearing out on the top where the cam hits it, and it's getting thinner. Or maybe when you shimmed it last time you didn't get the shim in there correctly and it was slightly cocked. Once the cam presses on it it pushes it back where it belongs & the gap gets bigger. But you've done this a couple of times so it's probably not that. Any one else have any ideas for this?

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This may not be directly related, but of all the posts I've read on valve adjustment problems no one has mentioned this. When checking intake clearance,always check outer valves at the same time. This means two sets of feeler guages. If checking just one outer at a time the slight "Rocking" motion of the cam will give you incorrect readings. Hope this helps.

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In fact I checked bought, the left and the right one, and reshimmed bought, the right one was also around 0.09-0.12. The original shim was 186, I replaced it with 180, the gap which immediately after was around 0.15 after awhile was around 0.2. Now I shimmed all 3 intake valves, the gaps are 0.25, around 0.12, around 0.12, from left to right.

After installing the shims I checked the shim that is level with the spring retainer and that it turns inside the retainer. The shims are correct, I measured it with a digital caliper.

I don’t know about carbon build up…I suppose that it is the reason I have different readings +/- 0.02-0.04, every time (20 hours) I’m checking the gaps, but a 0.1-0.15 build up to last that much and no sounds of open valve in the intake tract…?

Could the 0.3 gap be responsible for wearing the bucket or the cam? ( there are no signs of wear on bucket or cam and the stem isn’t mushrooming )

Thank you for your suggestions

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If you think checking outer valve clearance at the same time is "Bogus", mount a Dial Indicator to measure cam next time you check valves.You will see it affects clearance.

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