Idle impaired WR400 !!! Help wanted !!

Ok guys here is my story.... My bike is not idleling anymore since I`ve changed by stock pipe/header for a WB Hi-boy Header and pro-meg shorty(8 discs) and I have gone to YZ timing. Before doing these modifications the bike was ideling perfectly. Prior to the modifications the jetting was stock and.... all remained stock except for my main jet which I brought up to 172 (from 168) but that won`t change anything as fas as idleling is concerned.

I read a recent post on a bike that didn`t idle or hard to start and in there they mentioned that this problem could be caused by the throttle slide plate being upside down... I checked it last night and I had installed it correctly. My pilot screw is set at ~ 1.25 - 1.5 turns out and when I turn it out more the mixture is rich and there is an untolerable bog with black smoke so I`m figuring that I`m ok as far as the pilot cct but I could be wrong. I`ve also tried to fidle around with the idle screw but to no avail.....

So far I haven`t really done a test ride I`ve only tested on the bench... should I go out and ride it for 1/2 an hr to make sure it`s all warmed up and then chk the idleling ?? Aside from idleling, when I went through the throttle range it felt crisp and good thorughout the range. Another thing I noticed is that when I manually hold the choke 1/4 to 1/2 open it seems to be better.... Maybe I though that I brought the motor to operating temperature but I didn`t....

Any advise will be greatly appreciated.

thanks guys.


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