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Bike keeps backfiring and sputtering

69K views 51 replies 17 participants last post by  Thunder~Struck 
#1 ·
I just bought my first bike the other day, 2005 Super Glide Custom. The previous owner (who is the GM from the dealership I bought it from) did some custom work to it, but I don't know exactly what he did. I'm a newbie....

The other day, I was riding up a fairly steep hill. When I got to the top and hit level ground the bike started sputtering and backfiring, acting like it was going to shut off. Luckily, I wasn't too far from home, and was able to milk her back to the garage.

Tonight, I decide to ride to the gas station and fill it up. The whole way there, and back, it kept doing the same thing. The only time it didn't sputter and backfire, was when I was going up hill (25-30MPH in 2nd gear.

Does anyone have any idea what would cause my bike to act like this? I'd appreciate any help/advice you guys could give me.
 
#3 ·
2005, Should be a carbed bike. Sounds like it just needs some fresh fuel and maybe some sea foam run through it. Did this just start? How long have you had it? How much runming before this.started? May also be a fuel filter trying to clog up. Could be a faulty tank vent, creating a vacuum in the tank starving it of fuel. Did it set a while before you got it? If so then maube the carb needs rebuilt.

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#7 ·
The bike had been sitting for about 2 months when I bought it. I just filled it up with 90 octane, which is the highest available in town. The bike ran great for the first couple of days. After about a total of 3-4 hours of riding, that's when she started acting up. When I picked the bike up from the barge company, the battery was dead, and there was no fuel in it. The bike has a little over 14K miles on it.

I'll check the spark plugs and sediment bowl after work, and dump some sea foam in the tank.

I appreciate all the info. I'll keep you guys posted.
 
#8 ·
The thing is with the high octane fuel, you need to buy it from a station that sells a lot of it.... never know how long the fuel has been sitting in their tanks absorbing water.


If your bike doesn't have a high compression motor that actually needs the octane, you'll be better off buying mid grade or regular, as they will cycle through that stuff quicker than the premium.
 
#9 ·
The gas station that I got the fuel from is a self service fuel station, that not too many people use. Should a drain out all of the fuel and replace it, or will dumping a can of Heet or Sea foam in be ok? Is the sputtering and backfiring going to cause any other problems until the fuel system clears?
 
#25 ·
Some dry-gas (heat) may tell you if it is water in the gas but if it were my bike, I would drain the tank and replace the fuel with fresh fuel with a bit of dry gas added, don't over do it with the dry gas. Most fuels today have a fuel dryer in them but the addition of a bit more may clean out any residual moisture left in the carb or tank.
Always try to get fuel from a station that you know moves the fuel as opposed to a station that doesn't do much business, moisture will accumulate in their tanks when it sits.

If you drain the tank, dump the fuel into a clean white bucket and let it settle a while. If there is any water in the tank you will see it puddle in the bottom of the bucket . Put something under one side of the bucket to tilt it so it's easier to see.

Make one fix at a time and ride the bike rather than doing multiple things and not knowing what the problem was. The backfiring can sometimes do damage to other parts. Also don't overlook the filter screen in the petcock as the source of the problem.
 
#19 ·
I have a similar issue. 96 superglide. Sat for a while before I bought it. For 7 years they only rode it around the neighborhood once a month. I bought it a year ago and seemed to ride well with occasional sputtering, cold start. I ride it at least 1x per week or more. Use non eth gas. Recently had stater and coil replaced, carb rebuilt, 10k service plus, plugs and wires replaced etc. I rode one day to work and after work that day the bike would not stay running. This is when the majority of the above work was completed. After 1 month got the bike back, ran fine for a week, then one day it sputtered, backfired, shoots fire thru pipe. About 3-4 minutes of riding it was fine. After work, started bike and it did a half start and died, started up (hesitantly) 2ND time. warmed it up, rode 5 mins backfiring, spitting fire etc. Pulled over, called for a ride. Bought new plugs. When we pulled the plugs the gapping was wrong. Replaced the plugs, bike rode fine for 3 days and now back to spitting fire and back firing. It's very frustrating. Why would I keep blowing my plugs? I'm not extremely mechanically inclined but I understand enough and am willing to try figure it out. Any suggestions? I'm overy $1k spent trying to fix it already.
 
#20 ·
I have a similar issue. 96 superglide. Sat for a while before I bought it. For 7 years they only rode it around the neighborhood once a month. I bought it a year ago and seemed to ride well with occasional sputtering, cold start. I ride it at least 1x per week or more. Use non eth gas. Recently had stater and coil replaced, carb rebuilt, 10k service plus, plugs and wires replaced etc. I rode one day to work and after work that day the bike would not stay running. This is when the majority of the above work was completed. After 1 month got the bike back, ran fine for a week, then one day it sputtered, backfired, shoots fire thru pipe. About 3-4 minutes of riding it was fine. After work, started bike and it did a half start and died, started up (hesitantly) 2ND time. warmed it up, rode 5 mins backfiring, spitting fire etc. Pulled over, called for a ride. Bought new plugs. When we pulled the plugs the gapping was wrong. Replaced the plugs, bike rode fine for 3 days and now back to spitting fire and back firing. It's very frustrating. Why would I keep blowing my plugs? I'm not extremely mechanically inclined but I understand enough and am willing to try figure it out. Any suggestions? I'm overy $1k spent trying to fix it already.
this is a 3 year old thread.....

It sounds like the manifold seals are bad.
Get a repair manual if you plan on working on it.
this might help Ronnie's Harley-Davidson's 1996 Harley Davidson Street Bike FXD SUPER GLIDE® (GH) Sections

Now go to the New to the Community section ..... introduce yourself and post a picture of your bike.
 
#22 ·
Make sure it's not electrical like maybe a loose plug wire , hot wire to the coil, or loose grounds-possible lack of electric. If that all checks good run some dry gas through it with some good 93 octane. Still an issue clean the carb. Ask previous owner if it always had a pop or backfire to it if so the diaphragm in the top of the carb could be torn causing a lean condition. Make sure the jets are correct for the bike , oh and be sure it can breathe good (air filter ). Good Luck Mate.
 
#33 ·
I said OK. It's a good thing when a new member comes into the forum and uses the SEARCH function !
I was just pointing out that this new member has been here as long as I have and has 2 posts and is dragging up old threads !
The new old threads don't have markers on them for the members that posted to them like the old format had. I look at a thread that's a couple years old and I don't see the marker that shows I already posted to it like the old format did. OR I'm missing something ...
 
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