Jetting Thoughts... (Non-Valk)

[CajunRider]

This would be a Triumph Thunderbird Sport (885 cc triple - Kheihin Carbs).

Had to replace pipes... went with cheapest I could find.  Of course, they are LOUD and I had to re-jet.     I went up one size on both the idle and main jets... turned mixture screws out to 2 1/2 turns. 

When starting cold, full choke for about 10 seconds, then back off the choke till I see about 1500 rpm.  Leave it there for about 5 to 10 minutes... it will NOT take throttle without choke until COMPLETELY warm!!

Once it's finally warm, remove choke and it'll take throttle off of idle... but starts backfiring on decel... a LOT.  I have to hold just a smidgen of throttle to stop the backfire while decelerating... but then it takes forever to slow down.     Or... keep a smidgen of choke on and it won't backfire... but idles about 700 rpm too high.

Engine doesn't really wake up till 4000 rpm... but above that it runs harder and harder until the rev limiter kicks in.  (I'm thinkin it'll pull up to 12 grand if that wasn't a good way to blow it up.)

So the question is what of the following 3 to try??

- Bump the idle jet up another notch and put mixture screw back to about 1 1/2 to 2 turns.
- Bump the main jet up another notch (maybe 2).
- Shim the needle so it gets a smidgen of fuel off the main much earlier.

What say the carb gurus??
Thanks in advance!!

[JaysGone]

Easiest to try is bumping the PMS to 3 turns.
My carb experience is with single carb and V-Twin.
Bigger pipes?? Might have air/fuel ratio leaned out??

[98valk]

idle mixture screws can be opened upto 4 turns out, after that a larger pilot jet is required.
shim or raise the needles for 1/4 to 3/4 throttle opening. always tune for the main jet first and then downward to the idle mixture.