Hi folks, I've got a 1990 Sportster 1200 (4 speed) which is not running well and I've been trying to get it going for a couple of months now with no success. I suspect its a carb issue, but I'm rubbish with carbs, so would appreciate any help before I give up and set fire to the thing!

The bike has the following bits fitted:

Screaming Eagle pipes
Screaming Eagle air filter
Screaming Eagle ignition module & coil
Mikuni HS40 carb
Ramjet manifold

When I got the bike, it ran OK for a month or so then it started dumping fuel out of the overflow so I bought an overhaul kit for the carb and replaced the needle jet and seat and checked the float level. This didn't fix the fuel overflow and eventually I traced it to the float catching on the float bowl slightly. After filing a couple of raised seams on the float, it now only sticks if the bowl is emptied - once full it seem OK now.

Anyway, now the bike will start and idle OK but it hesitates under acceleration and backfires through the carb. I have removed the manifold and replaced with new gaskets, so I'm pretty sure there isn't an air leak.

Is there anything I've missed?

Could this be related to the VOES switch or ignition rather than the carb?

I'm pretty much out of ideas now other than buying a new carb which is way more money than I want to spend.