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New Top End,Smokes, Pops,

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I just got done installing a new head,piston, rings, and timing chain in my 05 crf450r. The valves are all in spec and its timed right(have checked it several times). I have checked and lubed the hot start on the carb and installed an adjustable fuel screw on it as well..

However , the bike is smoking very slightly on hard revs. Sometimes its almost impossible to see, other times you can make it out pretty easily. By no means is it smoking badly, and it only does it on a hard rev.

The bike is also popping on these hard revs...When i was trying to jet my 2006 yfz450 i was told by several peope that you really have to test a bike under load, and that reving a bike on a stand is not a good indicator of what needs to be done... Thsi held true for my yfz...same situation here??

Can anyone help me out?? With the experience i have and the info i have gotten off the forums here, i am running out of possibilities with this bike...

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Did it have these problems before the make over?

Check the ground wire that bolts on with the ignition coil.

Make sure the intake boot is tight on the head and carburetor.

Is spark at the plug tracking down the porcelain on hard acceleration?

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Did it have these problems before the make over?

Check the ground wire that bolts on with the ignition coil.

Make sure the intake boot is tight on the head and carburetor.

Is spark at the plug tracking down the porcelain on hard acceleration?

reason for the rebuild was that the bike wouldnt kick start. Appearantly there was damage to 2 of the valve seats preventing it from building enough compression to start. So i bought a new head and threw in a piston,rings,and cam chain.

What would i be looking for with the ground wire connecting with the ignition coil? Just to make sure its tight?

Also, how would i know if spark is tracking down the porcelain on hard acceleration? I have never heard of this before.

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How did you do the break-in. Easy or hard. Did you hone or at least scotch brite the cylinder?

cylinder was cleaned with a scotch brite pad. It looked brand new when the piston came out if it and the walls were very smooth. No grooves or nicks at all..

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My 2007 has some slight smoke on hard free rev. I think its perfectly normal. I would be easy on it and let it break in. If it is popping you either have an air leak at the header or at the mid pipe. Did you install a new exhaust gasket at the head when you reassembled. Break it in easy first and then put a few hard runs on it and check the plug to see if it is rich or lean.

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Yea, I did replace the gasket. Whats the proper break in procedure?

depends on who you talk to. do a search on wet vs. dry rebuild and you can read for hours the differing opinions about how to put your top end back together. I did the top end on my '05 and not knowing any better, I put a nice coat of oil on everything and it smoked just like yours is. If yours is doing it for the same reason then it may be because your rings didn't seat during your break in and now some oil is squeezing past them. Take your bike out and run it to the top of 2nd gear and then let the engine braking slow the bike down on its own without you applying the brakes. do this a handful of times and this will put enough pressure on your rings to maybe fix the problem. It did the trick for my bike, good luck!

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If it continues to smoke, take the top end off again and buy a new ring. The piston is fine, but the ring didn't seat, so it'll need a new one. But this time, get the cylinder honed. Dont worry, you wont "hog out" the bore by honing it, but you need to break the glaze in the cylinder to seat the ring.

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If it continues to smoke, take the top end off again and buy a new ring. The piston is fine, but the ring didn't seat, so it'll need a new one. But this time, get the cylinder honed. Dont worry, you wont "hog out" the bore by honing it, but you need to break the glaze in the cylinder to seat the ring.

alright, ill give it a try. Where can i get it honed?? How much does it typically cost? Thanks.

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