Just picked a bike up a few days ago (99 sportster 1200) and noticed that it backfires a good amount on decel and also pops through the carb from time to time while holding the same speed.

The bike has unknown HD straight pipes and a kuryakyn "pro" hypercharger. I pulled the plugs and they look pretty good (will post pics if need be), I figured that it needs re-jetted, carb clean and I should be good to go. I then looked up underneath at the bottom of the carb and the plug for the mixture screw is MIA, leading me to think that the carb was already re-jetted so now I am lost...

I have no issue what so ever taking the carb. off, cleaning it and re-jetting it, it's just I don't know if I should go order jets or is the issue something else. I loathe doing things twice if they don't need to be, I would like some insight on what else might be causing this problem.

Thanks in advance...

p.s. I know that without any baffles I will tend to get backfires but I cant see baffles making this big of a difference for how much it backfires at the moment...

 

There's a lot of information on the forum on tuning your carb. Your problems are very, very common. Check some other posts for answers too.

Also, buy a can of Seafoam and run some through your system, then see if you even need to adjust.

Welcome,

John

 

John, I understand that but from what I can tell is that it has already been done. Just curious as to if there is anything else outside of the carb that would cause this.. Thanks

 

Check for leaks at the intake. That will make it run lean and carb fart. Adjust the a/f screw yourself you might make it better. Just because the carb was rejetted doesnt mean its correct. Drop the bowl check the main and slow jet size. 170 main 42 slow a/f screw 2.5 turns out from seated is a good place to start.

 

If plugs look good check for intake leak. Since the a/f cap is off someone has obviously tried to tune it and like said doesnt mean they did it right lol

 

you can open it up and change carbs in under an hour