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08 yz450f backfiring after valve adjustment

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hello everyone, I bought a yz450f a few months back and it ran good but it was hard to start. I checked the valves and they were all .1 or .2 below the limit except for 1 valve. I changed all the shims they were indented and now Im within spec for all the valves. I did take the carb out of the boot and did take the silencer off.

Now the bike backfires like crazy runs better when the choke is on it also gets super hot now. Im wondering if adjusting the valves requires a rejet or if its a possible air leak. I re-sealed the pipe with high temp gasket and it still does this. The clamp on the carb is full tight.

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36 minutes ago, sangheraent said:

i didnt know there was a silencer gasket? theres no clamp either its an FMF slip on pipe

Ok, wasn't sure if factory. ..

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7 hours ago, Gray4ACause said:

Sounds like timing might be off.

you think theres a chance im a tooth or so off? I lined up the dots and marked my cams when i put it in I hope its not off.

 

its popping and backfiring like crazy there is a chance i got some crud in the carb I guess, Ill try to clean the carb out and if that doesnt work back to the drawing board.

 

my personal feeling is that its carb or airleak because it runs noticebly better when the choke is on. so that typically means pilot circuit is lean>> fuel air screw adjustment jet too small or jet clogged.

 

starts first kick now though no issues like before

Edited by sangheraent

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If it ever ran well before, then  it's not the jetting.

If you removed the carb, you probably damaged the plastic hot start nut, and now the plunger is no longer seating, and it is leaking air.

If you let it sit a long while with fuel in the carb, then the carb will need cleaning, and possibly soaking.

Remove the float bowl cover and see if there is scum or green corrosion.

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When you checked the clerance, you had the cam cover off.  When doing that, you may have pulled the hot start cable out of its socket at the carb, or you may have broken the plastic nut that anchors the cable to the carb.

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so grayracer513 hit it right on the head the hot start cable boot was way up there and cable might have been hung up put those back in place and she runs great again!! thank goodness because jetting is a pain in the ass.

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