[steveusmc]

Sometimes, not always, my 1995 Wideglide will backfire like a dang shotgun when I sart ut up later after riding for awhile. You never know for sure when it will do it...sometimes not at all. I have an EV-3 cam, screaming eagle ignition, rejetted carb, V&H Propipe, and Kuryakyn hypercharger. A few of us were parked outside a local place a few weeks ago and we were about 10 or 15 feet from the closest group of folks eating on this outside patio area. I was thinking of warning them just in case but didn't. When I hit the starter this sumbitch went Kapow!!! like you've never heard. I thougth I was gonna have to go do the Heimlich Maneuver on some of those people....and I think all the war veterans hit the deck.

Anyway, sorry for going on but is it just vapors sitting in the exhaust pipe or carb or what? Sometimes it will do it when I start the bike back up after getting gas or as sometimes when the bike has sat for a couple of hours. There sure are a LOT of louvers in the inside of this Propipe but I don't know if that contributes to it or not. There is NO discoloration of the pipe and the bike runs great otherwise. Any thoughts on this and should I even worry about it? I just don't like scaring the shiite out of people when they aren't expecting it. When I'm with my friends I always yell..."Fire in the hole" when I get ready to crank.

Semper Fi,
Steve....Pensacola
USMC 1972 - 2003

 

[LittleBear]

Only thing I can think of is to check your float level on the carb. If the bike stops with the piston up and an Exhaust valve open, a little gas from the carb leaking into the head and down into the pipe could cause this.
Also, it could also be a bad needle and seat for the float which would act like a missadjusted float.
I know the RK had vacuum petcocks in 95, not sure about the wide glides. If so, there is no overflow vent line on the float bowl of the carb. Only place gas has to go is into the heads.
These are just my guesses, maybe somebody else will have another idea.

 

[Ed Y]

Steve,

Exactly what procedure do you use to start the bike:

when cold?
when hot?

LittleBear has some good ideas too.

 

[Fourcats]

I'd say your timing is advanced a bit more than needed.

 

[heritage43]

I don't have the same engine as yours (mine is a TC88) but I have the same mods as you do and mine would do the exact same thing! a nasty cough on hotstart only on first crank then a start on second try. Perfect in every way otherwise. My manual says that on hot starts us an 1/8 to 1/4 throttle ( that wasn't working without backfire) . I also tried using the choke to prevent back fire on start to no benefit. I now do about 1/2 throttle then hit start and be ready to jump right off the throttle at start up. It works for me with no cough or nasty spit back. Nothing hurt to try. Good luck.

 

[steveusmc]

Ed,
First start of day: Full out choke. If pretty cold outside, a couple of half rolls on the throttle. It starts right up, no backfires. If fairly warm outside, maybe a half roll of throttle..starts right up..no backfire.

After it's up to operating temp and it has sat for 10 minutes or 2 hours. No throttle (unless it's pretty cold out). As soon as the engine fires I roll on the throttle. If she's gonna BLOW, she does it as soon as she gets fire. That's why I lean toward the vapors or residual fuel.

The bike starts great, just likes to BARK once in awhile.

Thanks.

Semper Fi,
Steve....Pensacola
USMC 1972 - 2003

 

[Ed Y]

Steve,

Sounds like you've got it right. I've found with a good tuned CV carb and a hot or warm engine, you shouldn't really need to blip the throttle before starting. And it really only takes a very small turn to get a little gas from the accellerator pump. Are you running maybe a little rich which would go along with your residual fuel idea? As mentioned above, probably also wouldn't hurt to check the timing.

Next time you're in the situation when you think it normally does it, put the bike in gear and roll it a little, then start it.

 

[Jams]

Some backfire problems are from an air leak at the exhaust mount. Unburnt fuel mixes with fresh air in pipe and ignites from a hot carbon cinder in the pipe.

 

[ohiomotoxer]

Adjust the fuel screw !!

It is under the carb between the float bowl and the intake manifold, some are plugged with an aluminum washer so you can't adjust it, thanks EPA.

Read #4 on how to remove the fuel screw plug:
http://www.dynojet.com/pdf/8101.pdf
Adjust the fuel screw (while the machine is running and up to temperature) to get the highest smoothest idle.
Once you burn your hands trying to adjust the damn fuel screw get one of these to make life MUCH easier:
http://www.dragspecialties.com/fatbook/prod_detail.asp?productID=69989

This way when the temperature changes you can adjust the FS and no more popping on decell OR backfire through the carb.

 

[rickr01]

SteveUsMC

My 1998 carburated Dyna does exactly the same thing. Fill up at gas pumps everthings running fine when shut down to gas up, then hit the starter and KA POW! old folks scowling at me , a few with loads in their pants. Bike runs like a top other then this maledy. I've checked timing, intake leaks, float level, jetting, you name it. The only thing I noticed is that the cross over tube on the exhaust, (I am running stock head pipes with cycle shack mufflers), is leaking ever so slightly. There is a tiny donut gasket between the bell shapes of the cross over tube. Can't stop it from leaking a tiny bit. I am not pulling it apart again. Nature of the idle vibration. Other then that I have no idea whats causing it.

 

[Otto]

I noticed se ignition so it dual fire wasted spark like stock, motor slightly warmed over ok basicly there is a full charge waiting so what happen is ignition firing both plugs and exhaust is open in overlap and bang also the ignition will spark just turning on or off nature of the beast

 

[steveusmc]

Thanks for the responses.
Otto, I assume this won't ever hurt the motor?
Steve

 

[Otto]

its mostly just annoying it can be hard on exhaust and head gaskets you could change to a quality single fire ignition like the crane HI4 race or daytona twintech

 

[steveusmc]

Otto..and either one of those will work well with my engine set up? Aslo, while you're in here. My plug wires have the little ground wire. I have seen plug wire sets on the internet that say, "no grd wire required". Do you have a top quality set of plug wires to recommend...that I can still use with my SE ignition if I don't change it right away? With or without the grd wires.
Thanks,
Steve...Pensacola

 

[rickr01]

Otto,
I run the stock ignition and on my 98 evo, it's definately the wasted spark scenario. Are you saying this is the issue with dual spark ignitions? If so why do some of my Bro's with similar set ups, dual fire, not experience this?

Not disputing your assessment, just trying to see where the differences may cause the problem.

That explosion is not at all good for head gaskets!

Rick

 

[Geezerdog]

Steve

I've got a similar problem with my injected TC. Probably not as severe as what is being discussed here. A much lesser backfire when I start, hot or cold on the very first plug fire when I crank (every time). 99% of the time the engine catches and runs just fine. (05 WG) w/stock head pipes and SE slip-ons. :dunno:

 

[rickr01]

Steve

I've got a similar problem with my injected TC. Probably not as severe as what is being discussed here. A much lesser backfire when I start, hot or cold on the very first plug fire when I crank (every time). 99% of the time the engine catches and runs just fine. (05 WG) w/stock head pipes and SE slip-ons. :dunno:

G-Dog,

Mine as well as others that do this start easy run a fine and do not backfire until it's hot and you stop to get gas or just turn off the engine and restart soon after. It is not consistant either. My never does it with a cooled off engine.

 

[Otto]

injected bikes have a different thing going they are single fire already with a injected motor some of it has to do with injector blead down and reduced overlaps lets not go there now. sutle differences between motors can affect this, all pipe, jetting, ignition timing, milage, manufacture date on ignition, idle speed, voes setting, you have to remember no 2 engines are the exactly the same the big thing here it to use the sytem that goes in the cone not a box that plugs in to your harness the cone versions know with cyl to fire while the box type fire both on first spark.and don't forget the coilhere i where i prefer the dyna i'll pull some part # later at the shop. on plug wires i dont use stainless wrapped wires ever!

 

[steveusmc]

Otto...I have the stainless braided plug wired....but they are very flexible. Should I get rid of them and get a high quality performance wire? Recommendation would be appreciated....and please comment about the requirement for the ground wire on the plugs wires.
Thanks,
Steve

 

[Otto]

well the coil is a dyna twinfire 2 fits under stock covers works great. twin tech model 1005 module . as for wires the ground wire is to ground out voltage leak and suppress noise which could cause timing variations, wire suggestions I personally like ultima {midwest} crane 300+,dyna race wires, some of the se stuff aint bad either and if you are running those chrome head bolt covers that slide on the spark plug GET THEM OFF they have tendence to cause misfires.