wrscomncents

I'm in Oklahoma

Thanks I will look into that.

snyper I will look into those CDs. I do have the mixture screws out. I have tried to set them on that carb withut much luck. If I turn the screw all the way in the backfire stops. Obviously shutting off the fuel. It will start to backfire as I turn the screw out at about 3/4 of a turn and get worse as I continue out. All of the others are set right around two turns out.

Cleaned the carb body with carb cleaner and a brush. The kit I bought included the float bowl o-ring, float needle and valve assembly and o-rings. It did not include the idle jets. I have had them off twice now and only have had a problem with number 4 cylinder. Since it looks like I will be pulling them off again maybe I should get new jets? So frustrating. I have had this bike down to engine and frame and now I have one cylinder holding me up. If nothing else I am learning a ton about the bike. I was a little over whelmed when I first got it. Sooner or later I'll get it running to perfection.

Okay will do.

Actually pretty good. It will pop every now and then at cruise but accelerates well and runs pretty smooth. I will get a little popping when I decelerate but the loud backfire starts again at idle.

Okay duh. Thanks

Yes it is a LOUD backfire not just a popping. And it does it at an idle and as soon as the bike starts. Really not much time for the exhaust to get hot. I'm not sure how you go about load testing the coils. I have had a spark tester on each wire and the spark does jump a considerable distance. Well past one. The needle valve and seat are both new and appeared to be working properly. At the risk of sounding stupid I'm not sure what the enricher is. Once again appreciate all your time and input.

BlueSky Checked compression with all plugs out and throttle full. Engine cold. Like I said I had to check with a compression tester that had to be held in the plug hole so it may not be exactly accurate but should be close enough.

Sylvester I will check that out. Were you getting a backfire. I have lightly blown air into the carb to check the slide movement and all appeared to be working fine but it can't hurt to check.

Yeah I know. It's like when someone asks you why their car is making that funny noise. I'm just trying to pick everyone's brain here because I have run out of ideas.

Patch I agree with you. I'm definitely going to do the fogging. I'm just not sure if the backfire is related to the leak in the exhaust or a problem with the carb. Could it be that the carb is okay and the problem is the exhaust leak?

T The leak is right in the area where the metal bracket connects from the shield to the pipe but I cannot see it.

Yeah I can try to.

snyper I have changed the exhaust gaskets on both pipes and when I hold a lighter by them I show no signs of a leak. There is a spot where the chrome shield is welded to the pipe that actually blows out the lighter. I have felt that area while the bike is cold and I cannot feel a hole or a crack so not sure how big it is. Its also very hard to see that area. Don't know if that would be enough to cause this backfire.

Okay thanks for checking over again. I guess you're right that I should go ahead and do the fogging since I am going to have to pull the carbs again. The problem I have now is I'm not sure what else to do with that carb once I have it off. I have already cleaned it twice and replaced the needle and seat. The float is set exactly as all of the others which are working fine. I feel like I am pulling it just to pull it. Is there anything else that could be causing the problem such as the main jet?

Patch I really appreciate your response and your time, along with all the others who have responded. That being said, respectfully, I'm not sure exactly what you are referring to as far as the number 2 cylinder being the problem with the backfire on the number 4 cylinder. I can certainly understand the concern with the number 3 cylinder being at only 150psi but number two is at 200psi. I have thought all along that this bike sat for a long time and I intended to perform the fogging on it after reading your post, as soon as the riding season ends. I had never heard of fogging before reading your post. So I'm not sure how that relates to the backfire. It appears that the problem revolves around the number 4 carb and it looks like I will be pulling the carbs off again. I had a problem with this cylinder after the first time I rebuilt the carbs with number 4 not firing at all. When I pulled the carbs off for the second time I replaced the needle and seat thinking that the first one may be faulty. So I found that if I close the fuel mixture valve on that carb (#4) the backfire stops. If I open it slowly the backfire will start after about 3/4 of a turn. I may be missing what you are referring to and if so please let me know. I am trying to learn as much as possible and I appreciate your thoughts. Another question as far as carbon on the valves. I can see how the fogging procedure will clear the rings but I'm not sure how the valves would be cleaned since they are above the cylinder. Am I missing something?

XV1100SE Yes I have synced them. I have not tried running a higher octane fuel but the problem is only occurring in the number 4 cylinder so I don't believe it is a fuel grade problem. Appreciate the response though. Looking for anything that may help. By the way I had a 1979 XS1100 for many years. Loved that bike.

Patch Thanks for the response. The only reason I only posted that cylinder is because it seems to be the only cylinder that is having a problem. All of the other three have been running fine. So here is the compression on the other three. #1 210 #2 200 #3 150 #4 190. I know that number three is below normal but at the same time I get the lowest drop in RPM when I pull the plug off of that cylinder. Also I am using a compression gauge that has to be held down on the spark plug hole to get a reading so I'm not sure how accurate those reading are. All of the valve readings are pretty much the same. All intake valves are at .15mm except #1 and #2 outside valves are at .13mm. All exhaust valves are at .16mm. All plug wires have been checked and all are getting good spark. The backfire occurs as soon as I start the bike. I have had it on the road and it will back fire once every so often at cruise but very little. It does not seem to increase much when decelerating, only a little. It seems to occur mostly at idle and as I said it is a very loud popping type of backfire out the exhaust. Hope that is helpful.

Ok. Thanks

Okay that makes sense. Looks like I may have to pull the carbs again. I'll try banging on it a bit first. I think I may have a problem with that particular carb. I rebuilt all of them and only this one has been giving me problems. I didn't even realize it at first the bike was running so well on just three cylinders and this is the first Venture that I have had. I noticed that it was just a little sluggish when I accelerated at high speed and I decided to check the cylinders. It was then that I discovered that the number 4 cylinder was cold and not firing. At least now I know it is firing. If there is anything specific that you can think of that I should look for when I open them back up please let me know. Thanks for your help.

sldunker Thanks for the response. I will check the choke again. I did check them all before reinstalling the carbs but I will check again. I have had the carbs off twice now so I may have to pull them again. I just don't want to do that unless I have to. What would be the main cause of the back fire if it were carb related. I'm just trying to wrap my head around the problem. For instance I can understand why the cylinder was not firing before if the carb was dirty and no fuel was getting to the cylinder but what would cause the back fire? Too much fuel? I did not see any fuel leaking from the overflow tube but I will definitely check that again. Appreciate any ideas.

BlueSky Thanks for the response. It is a very loud popping backfire. I have had a spark tester attached to the wire and I am getting a very strong and steady spark. Have also tested using the spark plug attached to the wire and same results. It did not appear to be intermittent. Any suggestions on other ways of checking would be helpful. Thanks again.

I need some help. I have a backfire that is coming from the number 4 cylinder. It occurs when at an idle mostly although it will also occur at times when riding. It is a very LOUD backfire that occurs about every five to ten seconds while at an idle. I know it is the number four cylinder because when I pull the plug wire on that cylinder it stops. I had a problem earlier with that cylinder not firing at all. I removed the carbs and re-cleaned and rechecked the floats then reinstalled them. Now the cylinder is firing but I have this terrible backfire problem. I did a compression test on all cylinders and number 4 is 190 psi. I recently checked and reset all the valves. On number 4 the intake valve is currently at .006 which is the outer limit (.004-.006) recommend and the exhaust is also at .006 which is the inner limit (.006-.008) recommended. I have used a lighter to try to find any leaks in the exhaust and the only thing I have found is an area where the chrome cover piece is welded to the pipe will blow out the lighter when I pass by it. Would that be enough to cause this type of problem? It is before the Y connection to the number three cylinder pipe. I am getting great spark to all cylinders. I have tried adjusting the fuel/air mixture screw out from two turns to three and a half with no change. Any ideas would be greatly appreciated. This is driving me crazy, one because I can't find the problem and two because I can't ride.

Steven, great post. I may try this after the season is over. I bought an older bike (1999) that I believe sat quite a bit. Thanks for the info.