coughing and chirping?? ?

[f4istunna]

Just wanted to see if you guys could possibly help me figure this problem out on my old ladies 400.

Im assuming it has to do w/ jetting but ive messed w/ it a few times and still cant get it.

Uni foam filter w/ lid & snorkel on, fmf slipon w/ stock header.

Now it has a k155 main and a 40 pilot, stock needle clip in middle (3rd down i think) i cant remember how many turns out the screw is but... i tried it from 1/2 out to almost 4 out and didnt make much diff. The plug is black when i check it and the coughing and chirping is making me think rich also. But the black plug could be from the rings because it smokes a bit also and needs a topend rebuild over winter.

It also pops and backfires on heavy decel Thats what got me confused. It wont stay idling for more than a few seconds. At full throttle seems to run good even half to 3/4 throttle is good. Just idle has the cough and so does up to about 1/4. the cough usually makes it stall.

I Had the stock 38 pilot in over summer and it still did the same thing :confused:

Hopefully someone w/ similar mods cant point me in the right direction as to where i should be w/ jetting.

Any help is much appreciated.

[416exfreak]

Maybe its just getting to much oil on the plug.

Rebuild it and see if it still happens.:ermm:

[CSR400EX]

even if its smoking, i think for just a slip-on, its a little too rich. my full curtis sparks took a 155 keihin main. my old 400 needed the top end rebuilt, and it smoked worse than a 2 stroke, and it didnt run bad at all.

[f4istunna]

ya when i first bought it awhile back it needed rings bad. It smoked like a chimney but ran real good. Also had an aluminum airbox w/ k&n then. and 160 main. I put the stock box on and a uni since we run Xc style riding w/ it.

Even if i take the lid off it still coughs. Ill go get a 148, 150,and 152 and see how she does. The 40 pilot will be fine right?

[CSR400EX]

yea it should be fine unless you add a full exhaust in the future