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YzEdge

06 yz450f wont even try to start

13 posts in this topic

I replced the intake valves, set the valve clearence and timing I got fire and fuel but it wont fire, cough, sputter, back fire or nothing. is possible to be 180 deg out of time?

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I replced the intake valves, set the valve clearence and timing I got fire and fuel but it wont fire, cough, sputter, back fire or nothing. is possible to be 180 deg out of time?

Double check the valve timing. Then check it again. You bet it can be out of time.

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No. Ignition takes place at each TDC, so it makes no difference which one you use. They're all the same until the cams are timed, as it's the cams that make one TDC the top of the compression stroke, and the other the top of the exhaust.

It IS possible to have the flywheel mis-indexed so that the spark occurs at the wrong crank position, by pushing the key out of place as you assemble it. If that were the case, and the cams were timed in accordance with a mis-positioned flywheel, they would also be wrong. Verify TDC by using a screwdriver through the spark plug hole.

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No. Ignition takes place at each TDC, so it makes no difference which one you use.

At the risk of sounding stupid... I thought a 4 stroke fired the plug every other TDC...

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A four-stroke has a ignition/power stroke event on once every second revolution, but the ignition gets its trigger signal from the flywheel, not from the cams, and produces a spark before TDC on every revolution. This means there's a "wasted" spark at the top of the exhaust stroke, too, and also that there is no difference between one TDC and any other until the cams say there is.

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A four-stroke has a ignition/power stroke event on once every second revolution, but the ignition gets its trigger signal from the flywheel, not from the cams, and produces a spark before TDC on every revolution. This means there's a "wasted" spark at the top of the exhaust stroke, too, and also that there is no difference between one TDC and any other until the cams say there is.

I stand under now. :ride:

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i checked the piston and its on top, i also replaced the timing chain and adjuster, my intake valve clearence seems a little lower then normal 1.30, 1.45, 1.35 i figured it was because of the new valves. i also cleaned the carb, still nothing?

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my intake valve clearence seems a little lower then normal 1.30, 1.45, 1.35 i figured it was because of the new valves.
That's not your valve clearance (at least you had better hope it isn't). That's your shim sizes, and yes, they all are smaller than normal. It indicates that quite a lot of material was removed from your valve seats. If your clearance and timing are good, that in itself should not be an issue for now.

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more problems developing, it seem to be cranking over a little tight so i decided to check the timing for the 20th time and it looks right so i checked the intake valve clearence again and i couldnt get a feeler gage in so i lowered the shims to 1.20, 1.35 and 1.25 put it back together and i still cant get a feller gage in???

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It lives, my intake cam was spun on the gear, my friend brought over his extra cam and the lobes were in different places relevant to the timing marks. Thanks for all the info. What a brain teaser

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is it possible to twist the gear on the cam?

Yes, but then your previous statement regarding the timing marks and the cam lobes both being in the right place would be inoperative.

How did you spin a cam sprocket without damaging the head?

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Sorry I didnt get back to you sooner. It jumped time and broke the valve guides and springs and bent all 3 intake valves, I had the head looked at and it was fine, I should have changed my timing chain sooner because it was stretched out, costly mistake

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