Carby Tuning

[trev29]

Hello. First ever post. Loving this site!!  I have just spent the best part of a day n a bit, cleaning and rebuilding the carbys on my fj1200 (1988). I have hand drilled the mains the next drill bit size up, set the floats to 23mm, installed a 4psi fuel pump and a efi fuel filter (mainly to keep everything clean because the amount of tank debris in the float boals was astonshing). Set the needles on the third mark, have uni pods, a 4 to 2 exaust.... and OMG!! what a difference!  Feels like i been riding a 250 around compared to now haha. There is however some minor backfiring on decerlleration. Any pointers would be appriciated. Oh and mixture is at 2.75. Cheers.

[Travis398]

I have hand drilled the mains the next drill bit size up......................
There is however some minor backfiring on decerlleration. Any pointers would be appriciated.

[andyb]

Don't drill jets unless it's just to get a rough size so you can order the proper ones.  At the very least, file off the markings so you don't confuse them with the size stamped on them later on.

If you've got a relatively open exhaust (i.e., any 4-1/4-2-1 or pretty loud slipons), some decel pops are pretty much par for the course.  If it's excessive, look at the pilot and mix areas.

[oldktmdude]

   Check your headers for leaks; cracked pipes, loose nuts or leaking gaskets. Air gets sucked into the exhaust system on decel and unburnt fuel ignites in the headers. Andy has also made some good points.    Pete.

[trev29]

Thanks andy and pete. Already took the stamped numbers off. The bike runs and rides great, so the minor pops on decel dont bother me so much. Thanks guys.