Backfires when starting

[BBChopper]

I love that shit scares the shit out of the cagers!!!!! :2thumbs:
:roll: :roll: :roll: :roll:

 

[stig]

Ive got mean mother pipes and mine backfires on startup also about 80% of the time when it is hot. For some reason only right after i gas up. I've leanred to live with it. It wakes everybody up at the gas pumps.

mine has also done this since the mean mothers were installed,i have no leaks. but it only happens once in a while....when you dont want it to.......

 

[LamboV12]

God – don’t let me get started on this problem! But it was able to fix it.

First, to be technically correct the condition is an afterfire, not backfire. Afterfire is in the pipes, backfire is in the carb. Had to be either fuel or ignition.

Did everything to the carb, including aux vent removal. Some said float because the carb is on the right and the bike leans left on the kickstand, that after you ride and put it on the stand leaning left, fuel drips down the hot intake and pipes and Ka-Boom. Well that did not work either.

Next ignition. For BDM that’s controlled by ECH – but that was changed 2 or 3 times and always had the problem.

Mine was really bad and I have it on video – In the dark you could see a flame shoot out of the pope at the same.

Hate to say it but the remedy ain’t cheap but guarantee to work.

I pulled all my wiring and direct wired the whole bike. I’m one if the first to dump the ECH. I also changed to a Mukuni carb. That was about 6 months ago and the bike has NEVER done it again – Never.

Was it the carb or elimination of the EHC? Don’t know but it worked.

An afterthought that came to me is this – When I did the conversion I went to a Crane ignition which requires a cam sensory. Dogs use a crank sensor instead. I blocked the crank sensor and had to get a new cam cover case that has a sensor for the cam, instead of the crank – so that could be part of the problem. Maybe carb is OK, ECH is OK but it’s getting a false signal from the crank sensor..

My direct wire was elaborate changing everything BDM, speedo, controls, etc over to standard HD stuff.

You may check out bdmridgeback - he has a conversion kit that allows you to dump the ECH and still keep the stock controls, speedo, etc. However, I think his set up still uses the original crank senssor.

 

[djwilpers]

Well I snugged up my exhaust flanges...got about 1/2 turn on each of the 4. I think it's a little better; but, it still backfires outside the exhaust after a gas stop. Maybe not as bad or as often though!

 

[djwilpers]

Still got the "afterfire"... Any more ideas?

 

[bruce]

I also have a 06 K9 and mine backfires at the same time sometimes but use to do it every time, most of my problem was in the carb. with dialing in the carb. jetting, and adjusting the idle mixture screw I have been able to cut it almost totally.

 

[phatchopper300]

Anybody still having trouble with start up backfire. Does it mean carb. is running rich. Thanks for any advise.

 

[JDog]

I am not a BD owner, but have messed with bikes for a while.

Check the float level on the carb.

Try closing the fuel petcock before you are pulling into the gas station to drop the fuel level in the bowl a bit. After you restart, turn the fuel back on. If it is a carb heat issue this should help.

Don't be a noob and forget to turn the fuel back on. Been there, done that.

I do this also, I think it helps but if not, enjoy the looks when Dog wakes up!

 

[oldmutt]

My bike did when it was stock and with the BR pipes and jets it does it less. I was getting gas on Sunday and two harley guys were there. When one of them started his bike he got the same bang. I kind of like it!

 

[ALDog]

Mine does it too and has since I bought it but it is louder with the V&H pipes on it. I do think Vegas hit the nail on the head though. I think when the bikes are hot, some fuel leaks into the cylinder and there you have it. I wouldn't worry about it unless someone around you has a gun and thinks you shot at them

Mine does it too. My guess is fuel percolation due to heat. I've noticed on my Holley on my car that fuel will dribble out of the squirter after it's heated up and sits to cool. I would imagine the super g does the same thing. A small amount of raw fuel gets into the cylinder and is pushed out into the exhaust pipe upon cranking. First time that cylinder fires and fire shoots out the exhaust port it ignites the fuel in the pipe. I'd just ride it.

 

[phatchopper300]

Mine does it too and has since I bought it but it is louder with the V&H pipes on it. I do think Vegas hit the nail on the head though. I think when the bikes are hot, some fuel leaks into the cylinder and there you have it. I wouldn't worry about it unless someone around you has a gun and thinks you shot at them

Yea its not a big deal and it only happens every so often. I do love when everyone ducks at the gas station or at the resturant when it fires up.

 

[stinger1]

Turn your air mixture screw out fraction of a turn, maybe a little more. This will solve the problem and will make no difference to the running of the bike. after a while engines settle in and wear slightly, at first it needs less air but after wearing slightly it needs a little more.

 

[Rally]

On my 05 Chopper with Hooker Widetails I too get an occasional "bang" when starting a warm engine.
Don't give it any gas after she warms up when starting up again.

So far I get a kick out of it since I've had FI bikes and this never happened.

The looks after the "bang" are priceless as I can't help but laugh to myself as I pull away. :roll::roll::roll:

 

[Iahcon]

I'm going to re-awaken this thread, I just got my '07 Mastiff and am experiencing the backfire or afterfire or whatever you want to call it.
The sound is a little embarrassing if anything, when your buddies are shaking their heads and laughing about it...
My question - is the backfire causing any damage to the engine? That would be my only real concern with this little issue.

 

[scubaman15]

no damage ...just tell them you can't hear them laugh ...cause there so far back ! Mine still does it once in a while . Happened this week at a stop and most if not all were startled ...I just had a chuckle ...kinda wish I could do it on demand ...

 

[phatchopper300]

I believe it also has to do with the air mixture screw. I replaced mine and it did it a few time and have adjusted the screw and it has quit the afterfire. Just my experience and
.02

 

[francoblay1]

Mine does it too. I am still using the stock pipes but no baffles in them. I just love it

 

[MadMarx]

I also have a 06 K9 and mine backfires at the same time sometimes but use to do it every time, most of my problem was in the carb. with dialing in the carb. jetting, and adjusting the idle mixture screw I have been able to cut it almost totally.

Same here on my 06 Mastiff w/ Mean Mothers.
I also replaced my exhaust gaskets with the copper (compression) gaskets.

 

[reloaderbmg]

mine dose it too! "its a dog" let it bark!!!

 

[Slick-Dog]

As MARV already stated......... Tighten up your exhaust flanges or replace the gaskets. You have an exhasut leak! Some pipes cause the flanges to not tighten down hard enough so I use two flat exhaust gaskets to ensure I get a tight seal. Check them weekly.

And keep your throttle closed while starting.

:flag:

hehehe I had the same thing happen with the Rienhearts I have...Dam good advice to check when riding all the time! :2thumbs: