XR 400 Cam Problem

[Blackguywithouta400]

I just finished installing my xr400 cam yesterday and now I have a real bad stumble at low rpm or 1/4 throttle when I whack it wide open from idle it stumbles and then starts to pull. My mods so far are: Carb minus choke with a 42 Pilot jet, needle raised 1 clip, Main 170 this is with a DMC full system K&N Filter, open air box. Any suggestions? Other than that the motor is stock still. Thanks.:mad:

[Stunz]

Have you tried a smaller main jet, like 162 or 165?

[MR. HONDA EX'S]

Check your plug. It sounds like it could be running to rich, and flooding out. Change the main or lean out your air/fuel screw. Turn in your screw well lean it out. If you didn't know that. Try this.

[RAPTORAZ]

Sounds to me like it's lean. If it were rich it would bog, not stumble. I'd try a 45 pilot. Since off idle is where it stumbles.

[DISHO1]

make sure your accelerator pump works

[Leo]

assuming your talking factory jets here, a 170 sound's like it would be pretty fat to me..

mine has a very bad bog/stumble on hard acceleration (like out of a corner) when the MJ is fat..

w/o the lid, and running the T4 open it likes a 162.. w/ spark arrestor in the pipe it's just a touch fat.. if I put the quiet core in (pretty restrictive) I get a terrible stumble out of corners unless I drop down to a 155...

I think I'd be trying something in the 162 -165 range (depending on what your dealer has on hand ;))

I went round and round trying to get it cleared up, before I dropped the MJ.. remember that at wide open throttle you are running on the main-jet, regardless of engine RPMs.. my thinking is a rich main jet + the squirt from the accelerator pump when you hammer it wide open overloads the motor with fuel for a second or two giving you the spit/sputter/bog....

Leo

[Wheelie]

Your needle and pj settings sound correct, but your main circuit is too rich. Try a 158 or 160 main jet, one of those two should hit your engines 'sweet spot'.

[Blackguywithouta400]

Well i went back to the 160 Main jet. I loaded up and went down to the local business park ( see we have to do that when u live in Seattle) and let her rip OMG what a difference :D the bike has power everywhere TONS of bottom end 1,2,3,4th will wheelie just fine now, it even lifts the front on WO shifts, also it will pull the rev limiter in 3rd & 4th so i guess the 416 kit will really make it fun.
THanks all for your help with the jets:D