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Yz426f issue....backfire hot valve clearance

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Just recently got a 2000 yz426f. Hot cam auto decompression installed. Went through it and discovered the valves needs adjustment. Intakes were at .13 for the left and middle and .15 for the right. Exhaust was .23 and .25 after adjusting the bike starts with the throttle a little open but backfires heavily does having the hot can require a different size shim than stock? Timing is correct. If anyone has any info on recommended valve clearance for the hot can that would help greatly!

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"cam"

Hot Cams use the same clearances as the factory spec's.  .10-.15, and .20-.25mm (.004-.006 and .008-.010").  Cold engine.

Exhaust backfire is caused by either an air leak at either end of the header, or by an excessively lean idle.  Note that a small amount of it is a sign of a healthy and correctly adjusted idle circuit on YZF's; don't try to get rid of every last trace, or yoiu'll end up with a rich idle that will make it harder to start and cause stalling.

Having to open the throttle slightly to start is a sign that it may be set for too slow an idle speed, or be slightly rich at idle.  Adjust the fuel screw per the manual for the idle speed drop, and see how it runs in general after that.

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I know. I know. Stupid auto correct

 

thank you so much. Its been driving me crazy because I've been hearing the hot cam requires a different clearance. Yet I couldn't find anything on it. I'll mess around with it Saturday and see what I come up with. Thanks again!

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You have a point, or at least, you very well might.  The 2000 model was built with stainless steel valves.  The specs I quoted are for all titanium 5 valve models, '01 through '09.  Assume that this 2000 is still steel valve equipped and us the specs quoted above instead.

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i'll dick around with my timing some more. Verify everything's in spec. See how it runs then if not I'll take it back to where I had it. Thank you for the information though!!!

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Well the bike started beautifully after dicking around with the timing ( in my haste I had it 180 degrees off....go me!) But now the spark wire seems finicky. Moving it around in certain places it produces a beautiful blue spark. Moving around more produce weak or no spark. Has anyone ever replaced the wire on these or am I S.O.L. and need to replace the whole coil/ wire assembly?

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15 hours ago, Yzrider426 said:

in my haste I had it 180 degrees off....

No you didn't.  It's not technically possible on most modern thumpers, and if it was off more than two teeth, it would not have run in the first place.

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I must've misspoke. The lobes I noticed were facing each other instead of opposite. It ran perfect after that. Now if I can get this stupid coil working....

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