Hi All. I've done a lot of reading and quite a bit of tinkering so, this is me looking for some insight.

I bought an 89 Sportster 1200, with a Screamin' Eagle big bore kit, about two months ago. From the beginning, the Engine intermittently runs rough.

It has an S&S Shorty "G" Carb.

I changed the plugs, which helped a bit. I increased the middle jet by one size. I cleaned the carb thoroughly. At one point, fuel was pouring from the overflow, so I took the carb apart and found that the float needle had come unseated. I put it back together and it it started running again.

I increased the middle jet size because I thought it was undersized for a big bore. I don't have any of the documentation of the big bore upgrade, because the guy I bought it from said he didn't keep it. I have his word to go on, and I'm basically choosing to believe that he's on the up and up. He says the shop that did it is closed in Atlanta, and he didn't keep any docs.

After I cleaned the carb, I sprayed starting fluid around the carb and intake and found a leak. It seemed to be around the manifold, so i ordered gaskets and replaced them yesterday.

When I did so, I discovered that the right side (hex) bolts were finger loose. I had to order that special wrench to do this. After replacing the gaskets and getting everything properly tightened, it sounds smoother, but there's still the popping, sputtering and coughing.

It happens throughout the RPM range, from low to high. I've adjusted the idle adjuster according to the S&S website, and I've also adjusted the accelerator pump.

It ran pretty well, even with the bad intake gaskets for a while. But a few days ago, it suddenly got much worse.

I run only hi-test gasoline. Fuel flow seems to be good. There's no rust in the tank.

I don't know much about the electrical system on this bike, but i'm starting to suspect that the problem might lie there.

Any help GREATLY appreciated.

 

Sounds like it could be the Crank Position Sensor (CPS).

 

Thanks, off to Google.