Hello there, I apologise.... I'm new to this forum type thing. I have a 1996 1200 Sportster Sport, which I believe that when I bought it in 1999, it had already had engine work, K&N filter, Screaming Eagle cams and ignition. I have fitted 2" straight thru exhausts and a belmouth intake with a fine stainless mesh. She is popping thru the carb and backfiring on the over run. Is the mixture to weak? I have looked at the jets and this is where I am getting confused; the main jet is marked 210 and the other is marked 3.4
I am not good with computers, but everything I can find suggests that the 'normal' main jet sizes go up to 190. I can only assume that the jets have already been increased. Can (should) I go larger? Also, the other jet (marked 3.4) doesn't seem to match anything I can find.
If I can improve the jet sizes, would it be just a case of removing existing and fitting new, or are there other procedures I need to carry out?
Any help on this subject would be very gratefully accepted. Thank you for reading. Zippy13

 

Hi Zippie. What type of carb is it? @ inch strait pipes are the worse choice in pipes you could use. They have no back pressure and cause more issues the 2 girl friends and a wife. The stock CV carb has a 42 pilot jet, and around a 165 main jet. 210 seems way too big. I would use a 46 180 combination, and 1 3/4 pipes for better performance. Good luck.

 

Fixing the carb for correct mixture is the least of your problems. With that intake system you're gonna trash the engine in a very short time, assuming you're street riding and not building a competition only bike.

 

thanx for your input guys, I think I will just revert to a more appropriate 'filter', even tho the bellmouth looks LUSH! I've been running the 2" staright thrus 9 or 10 years now with no problems before vanity gripped me with this 'trumpet'! Have no problems with pillion as she is a solo seated bobber. I got a Ural combo and a Honda VTR1000 if the wife wants a spin