Yesterday I adjusted the accelerator pump screw. While following the instructions in the Tech Articles, I am getting an occasional backfire out of the carb.

My carb settings: Baron's BAK, 170 mikuni, stock pilot, needle 4th clip, PMS 2.5 turns out, Bub Big Willy's pipes.

Everything runs great, however for some time, I have gotten a bit of a cough while declerating if I hit the throttle (not blipping) for example as approaching a turn, slow down, off the throttle, as I go through the turn, I hit the throttle and SOMETIMES get a bit of a cough. So I attempt to Adjust the Accelerator Screw.

I remove the BAK, run the bike, and turn the screw. It was out almost all the way. It seems now that at any position of the screw, when I blip the throttle (as per the instructions) I get an occasional backfire, maybe once every 4 or 5 blips. I also get a cough, again not on every blip, but there was no setting of the screw that did not backfire or cough. This was all while sitting in the garage. Didn't get to road test due to rain.

Am I missing something, or should I just see how it handles under road conditions?

My bike is all stock and acts the same way........anyone know the fix?

Howdy fellas. You might try opening you PMS an eighth of a turn at a time and test it in between adjustments. That got rid of my backfire on decel anyway. RATL.

mine not a backfire through the exhaust...it like a couogh or backfire through the carb slowing to a stop and takin off again is when it happens

Fire ResQ wrote:
This was all while sitting in the garage. Didn't get to road test due to rain.

Road test .... you can't fine tune it sitting in the garage blipping the throttle

Coughing through the carb usually signifies a lean condition.

Doc

Yep, like Doc said, and cold weather will make it even more lean......

I had this problem for 14K miles, since new. Although turning off the accelerator pump would make it run better.... it was not the cure at all. In my case, and only consider this. It was a mysteriously leaking intake, dealer put on 4 and then switched to a Ben Herr Intake and that fixed it. The intake leak in this case did not respond to normal diagnostics of squirting choice fluids around intake. Only showed up with emissions diagnostics. Just keep this in mind. If nothing else works or it don't run right after you try em, have a shop probe the exhaust and get a reading. One cyl. will show really lean, other will be full of carbon. (Visible if you take exhaust off.) It pops back because it's not got enough vacuum due to the leak to suck air and gas correctly. Trust me, it drove me nuts.

After it was fixed Accelerator pump was returned to normal setting and it won't pop back no matter what. Owner of dealership told me it should run without messing with the accelerator pump. In the end he was absolutely right. It was driving him nuts too, he was doing all the work for free under warranty.

You had a good dealer, MS1700, I hope you put him in our directory.........

where can you buy a ben herr intake manifold?

I adjusted my accelerator to the min setting long time back now and have had no problems,it may just need a little more pump as you open the throttle,after about a 1/4 throttle it shoudnt need to pump any fuel,with my manifold I covered it with silastic and that stoped it leaking through all the cracks,I now use about 6 liters per 100km, over 300km per tank