Lean missfire? Harley Engine Discuss Lean missfire? in the Harley Tech & Harley How-to forums; '02 Sportster 1200, K&N air filter, Screaming Eagle II pipes, otherwise bone stock. Ran great all summer, noticed slight popping out the exhaust on decel. This morning it started popping ...

[Whopper]

'02 Sportster 1200, K&N air filter, Screaming Eagle II pipes, otherwise bone stock. Ran great all summer, noticed slight popping out the exhaust on decel. This morning it started popping out the carb under steady cruise. Runs strong under acceleration, idles smoothly at 1000 RPM. Cruise at any speed with light throttle and there is an intermittent pop from the carb and the attending miss. I tried the "choke" but that made no difference. Any ideas before I start tearing into it?

[Wrightturn]

Hey Whopper,

Sounds like you are too lean. If the carb has not been rejetted you should. The stock low speed is usualy a 42 and should go up to a 45. For decel pops the the most effective thing I have found is to change the needle to the 1988 Sportster 27094-88. Surprised the choke didn`t make a difference. You will need to uncover the mixture screw by drilling a small hole in the plug and pulling the plug. Gently bottom out the screw and turn out 2.5 turns.

Only other possible is an air leak at the carb or manifold.

[evoKENevo]

If I'm reading you right,it sounds like you had the slight decel popping all summer..not just recently.

If that's the case I'd say you've been running just a bit on the lean side all along..and that with temps dropping the denser air these days has more oxygen in it causing you to be running even leaner,now.

Meanwhile you may have developed an intake air leak,too. So check that first. Then even if you do (or don't) find an air leak..go thru your carb and make sure it's set up exactly as Wright advised..including the needle recommended that most guys seem to wrongly omit "bothering" with..noting that a 180 main jet seems to be just about right for an otherwise stock sportster with the kind of exh. and air filter set-up you've described,too.

[street bob]

Whopper... follow the thread under the Sportster and Buel heading titled
"why does my 1200 spit......"
You'll be glad you did... Trust me!