Triumphrat

Jimbo · 06-01-2007

Hey All;
I've got a minor irritation on my 06 790. I've NARKed it, Staintune peashooters, and rejetted to 130's. Bike pulls great (especially in midrange) and seems to outrun my friend's stock Scrambler quite handily.

My only issue is that it gets this little muffled backfire on idle (not popping, it's always done that like crazy on decel). I'll be riding it reasonably hard, and pull up at a light or a freeway offramp and fmmmpph (and no it's not the rider or the passenger)! I live at near 7000 feet and ride daily down to around 2000. It farts at both elevations.

I haven't adjusted the idle screws a bit, didn't want to mess with needles or shims (at least not till I've got access to a dynomometer and can make sense of the fine tuning). It goes in for it's 12000 mile service in a week or so. Any suggestions? Thanks!
:-g

Geoff · 06-01-2007

If you removed the AI, and it still does it, my guess (since you havent touched the mixture) is that it is lean.
You could install the thrux needle and / or adjust the idle mixture a tad richer. I have had good luck with jenks tuning guide, he says 790 stock needle, your jetting is good, but needs 1 or 2 shims on the needle and 2.5 turns out on the pilot screw.
If you put the thrux needle in, go 135 mains, 1 shim and 3 turns out on the screws. good luck
G

[ This message was edited by: Geoff on 2007-06-01 06:09 ]

PaleForce · 06-01-2007

Hey fella...

I had that problem when my bike was bone stock. Syncing the carbs and adjusting the idle mixture took care of it.

pabonne · 06-01-2007

I was getting the occasional carb fart too after cutting down the airbox, putting on K&N's and rejetting. I'm also running 130 mains. I backed the mixture screws out another half turn and bumped the idle rpms up slightly and it hasn't happened since.

[ This message was edited by: pabonne on 2007-06-01 19:55 ]