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Newbie Question: Backfire on startup with TORs (Scrambler)

2679 Views 10 Replies 7 Participants Last post by  barfito
Picked up an 06 Scrambler two weeks ago. Had the TORs and the block off kit installed before I even picked the bike up...turned out to be a bad decision because the mechanics at the dealership determined that they did not need to rejet, leaving me with a very peaky bike that turned plugs white in a hurry.

Anyway, I rejetted with the help of the Jenks Bolts guide posted elsewhere on the forum (what a godsend, thanks for that tip) and the bike is now VERY well behaved with 115 mains and single shims.

The only thing is that when I go out to start it in the morning (and this only happens after the bike has been sitting) I turn the gas on, pull out the choke, hit the start button and it roars to life after emitting a huge backfire. Anyone experienced this or have any ideas? My neighbors thank you.

Great forum, BTW
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You're not using the throttle, are you?
Nope. I pull the clutch in out of habit, but that's it. When I press the button, it INSTANTLY backfires and comes alive. Can't complain about that kind of response, but again, the neighbors can. I get up pretty early to go to work, and I feel kind of guilty. Plus, living in Washington, DC, you want to do as few things that simulate the sound of gunfire as possible, dig?

Mine used to do this some when I had the pilot screws too rich. It hasn't done it with the pilot circuitry adjusted properly.

I thought Mare had hit the bulls eye on that one,.....By loud backfire it is an explosion in the exhaust. Do you rev the engine before shutting it off? My bike is well broke in and I run 120 mains, one shim @ 3.400 ft. above sea level. That is with TORS, air box snorkel and baffle removed. 115 with TORS only, sounds in the ballpark. Check for a float level problem. Check your plugs,...this may indicate which carb is having issues. Check your oil level. Hopefully it isn't increasing. Try less choke. Did you adjust or change the pilots?
Anyone out there with a scrambler experiencing something similar? If you shut it down hot, your pipes should be clear of any gas fumes when you start cold. With AI in place and too rich a mix,...BANG!

[ This message was edited by: Jimi_X on 2007-02-09 19:42 ]
Running too rich? Aren't backfires the result of left-over fuel in the carb float bowl from the "previous" ride?
I have the TORs on my Scrambler, and it "barks" when I start it in the morning (sorry, neighbors!) if I pull the choke out all the way. I pull it out half way and the bike starts normal. Haven't re-jetted yet, so I can't say if that makes a difference. Try a partial choke for your cold starts and see if that helps.

To support what Redbird said, I had my bike dyno'd recently and it showed up very rich pilots, my mistake. After adjustment to the correct A/F ratio with the gas analyser, the startup bangs on choke stopped.

I thought they removed the chokes on all the Florida models. :-D :-D

Good one, Larry!
Thanks alot, everybody. I'm going to start off by trying the half-choke thing, and I'll throw the bike on the gas analyzer tomorrow. I'm not sure I have the pilots exactly where they should be. When I got the bike the mixture screws were turned out pretty much all the way...after I rejetted the mains, I returned the screws to the baseline then wound up screwing them out another turn after hearing the idle "seeking."

Thanks again!
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