Bonneville America Forums Forums Technical Forums Performance Mods Slight backfires, intermittent idle & stalling???

On my ride home from work today I noticed a bit of slight backfiring at idle when I was at stop lights, idle intermittently falters at a stop and a tendency for the bike to stall as I start out when the light changed. I'm thinking it may be running a bit rich and getting way too much fuel(flooding) when I pull the throttle back to set out.

Stock mains & pilots, K&N filter w/ full air box & snorkle (not modified). Any thoughts, comments, suggestions would be welcomed. BTW...the Black Beauty runs like a dream otherwise at any speed.

Stuck float? That's an easy check, run a piece of clear fuel tubing up from the hose barb on the bottom of the carb, and open the bottom screw. Your looking for the fuel level to register to the lower/upper seam of the float bowl/top half or slightly above. Also, the level to be the same on both carbs. If one side is high, voila, float problem.

Check rubber caps on carb if they're dryrotted. My bike was doing the same exact thing...changed them, runs perfect now.

My America backfires,on slowing down. been doing it since I got her 10 years ago. Have gotten use to it.

mine only backfires on startup and only the first time in the day, not sure whats up with that.

If you aren't sure it is over fueling, I'd check for running lean first by doing what Paul suggested, check for a vacuum leak at the squirrel condomns and also check the intake rubbers that hold the carbs to see if they aren't cracked. Too much air at idle will cause this but not really affect your top end.

If the float is stuck, you should see fuel coming out of a carb vent or even fill up your crankcase.

Okay...vacuum caps on the carbs are OK (at least visually), float levels check out fine @ about 2mm above the float bowl seams on both carbs. What if one of the float needles were bunged/worn? Seems to me that would also let more fuel into the float bowls and be evident when I checked the levels on em'. What about carb sync....if one carbs was outta sync I think that would also affect idling a bit??? Or if the trottle cables were slightly out of adjustment? The cables seem to be correct re: freeplay & response. Any additional thoughts????

Intake rubbers are OK too & no fuel spills from the vents or in the case. But dang me for being so blind. At idle the mill was barely taching @1K. A little turn on the idle adjuster to a hair above the 1K rpm and whoeeeee! FIXED!

Ocham's razor strikes again, or Murphy's law whichever you prefer.

I'm guessing that vibration may have backed off the idle adjustment just enough to present itself as a fuel lean problem as Gregger mentioned. Anyone ever have the same experience..is this common?

Adjusting the idle and or mixture screws is normal. Your carbs might be due for a sync also.

I'm Still getting a bit of a stall when starting out from a stop from a warm idle. I found a fuel pump tester/vacuum guage @ harbor freight for $9.99. The vacuum guage reads up to 28" Hg (inches of mercury) I figure it's $20.00 for a pair of em & well spent if they will work in syncing the carbs.

dump some seafoam into the tank every other fill up for a while worked for me!

You'll find that balancing those carbs will improve the response and power.

Huh! I got a Polaris Bell Mouth from Zmilin in the mail today & installed it. I hadn't noticed before but the K&N filter is not wet with fuel, but definately reeks of gas and the base was a little wet (fuel).

So I have come to conclusion that Black Beauty is running rich at idle/stops. So, now I'm wondering....float levels are okay.....not a crack or age damage visible on/in any of the squirrle rubbers, manifold tubes or airbox....idle adjustment was a temporary fix at best and may have made the real issue more prominant???

I haven't synced the carbs yet..but that's next on my list. What if the advance/return throttle cable(s) were out of adjustment? I haven't touched em since I bought the BA so it doesn't seem likely....


All of the collective advice is appreciated....this is a real bugger of a troubleshooting issue for me & not resolved yet either!

I would do what Oldroadie and Gurdy suggest,the smell of fuel in your airbox is normal,that beeing said,if you got an inch of gas laying in there you got troubles.My bike also faulters at a red light,not always once it's good and hot it seems to smartin up.Let us know what you find.

Well, I dropped about 2oz of Seafoam in the tank and cleaned the K&N filter thoroghly (although it didn't appear to need it) and rode out and about for an hour or so. Later this afternoon I took er out again and WHOEEE, what a change!

Talk about a real difference! No stalling, Idles smooth as a baby's arse, and acceleration/performance is right back to what I had before all the trouble began. I'm thinkin cleaning the K&N helped, but adding the seafoam really helped the most.

end of problem....

I have a. 2007 America that has 30k on it and has run perfect til this week. It acts fine except once in awhile it quits then revs up with extra fuel. Is there a screen in the tank or fuel filter? The dealer has done all the service until now. Just wondered if junk can get in peacock. I notice some paint off where you put in gas nossle so maybe chips are floating around in gas. Any thoughts. I thought I may drain tank tomorrow.

Remove the little hidden filter/screen, an exploded view on BikeBandit will show you where it's at. Buy an inline filter from Fast Eddy and install. Run some Seafoam in your gas too. It's looking like gasoline quality is only getting worse, just wait until E-15 is mandated, we will have to put 2 cycle oil in our tanks and who knows what else.