1978 yamaha xs1100

[MORGZILLA]

I have a 1978 Yamaha XS1100 that normally runs great, a few months ago after I leaned out of a turn the bike stumbled and backfired and ran as if were running on two cylinders. The bike still does not run very well backfiring a little when letting off the gas. Had carbs professionally cleaned and adjusted. What do you think is my problem? Is it starving for fuel? Is one of the coils missing? Is the angle cut off censor going bad? Any help would be appreciated as I love to ride the old beast all the time,Morgzilla

[natemoen]

First off, I would suggest checking you pickup coil wires.

http://www.xs11.com/forum/showthread.php?t=543

[jetmechmarty]

Had carbs professionally cleaned and adjusted.

That's a red flag for me. That's something that goes under the heading, If you want it done right, you have to do it yourself. That's a tedious, time consuming job if it's done right. If you paid say $200, it may have been done quickly. There are exceptions, but likely you'll have to do it again.

Certainly, look for the easy electrical problem first and eliminate that before you make a mess.

[natemoen]

That's a red flag for me. That's something that goes under the heading, If you want it done right, you have to do it yourself. That's a tedious, time consuming job if it's done right. If you paid say $200, it may have been done quickly. There are exceptions, but likely you'll have to do it again.

Certainly, look for the easy electrical problem first and eliminate that before you make a mess.

Thought the same but figured I would leave it alone for now.

[MORGZILLA]

Carbs cleaned

I normally do it myself but I had a good friend of mine that has been a mechanic for 20+ years and he has helped me over many years and I trust him. He just bought a new supersonic machine that cleans carbs. A couple of years ago we both replace the inside of all four carbs and adjusted the float bowls. I rode to work this morning and I almost did not make it to work the bike was running so bad. I let it sit for a few hours and I just drove it home and it was running fine. I am confused why all of a sudden it starts running bad.

[jetmechmarty]

I let it sit for a few hours and I just drove it home and it was running fine.

I don't think it's a fuel issue unless maybe your fuel tank is not venting properly. That will make it run out of fuel, then be OK after it sits for a while.

[DGXSER]

That could very easily be a pick up coil wire. They can be intermitent in their behavior. Not to hard or costly to replace the wires on them. Be a good starting point.

Another way to tell is now that it is running so much better, take the ignition cover off, with the bike running, use a pair of needle nose or similar to pull and tug on the wires to the pickup coils and see if the engine starts acting up again. That will let you know quick if it is the issue.

Also, once it starts running poorly again, as it probably will, run it for a few miles then check the temps on the headers. That will let you know which cylinders are running poorly. That can help alot in figuring out if it is electrical or fuel. Easy way to check temp is spray the headers with a squirt bottle of water.

[MORGZILLA]

78 xs1100

When I first started having the problem with the bike running rough it was after I leaned into a right hand corner, and when the bike came up straight it started running rough. Do you think it might be the angle sensor cut-off switch? I will try looking at the coil pick up wires and try the exhaust like you said to see what side it is. I will also make sure the tank is venting.

[natemoen]

The tipover switch is an all or nothing, so I doubt that is the problem. If you want to be sure you can just unplug it and see if it helps. It is right above the iggy coils and is the little box that has an arrow on it pointing up.

With the pickups, don't just look, be forceful when checking those wires.

[xs11lover]

That's a red flag for me. That's something that goes under the heading, If you want it done right, you have to do it yourself. That's a tedious, time consuming job if it's done right. If you paid say $200, it may have been done quickly. There are exceptions, but likely you'll have to do it again.

Certainly, look for the easy electrical problem first and eliminate that before you make a mess.

But I think it was running bad before he had his carbs "fixed"
I'd vote for the pickup coil wires, I had a 79 that crapped out the same way, and the field bomb does it here and there now. It's an easy fix.

[MORGZILLA]

78 xs1100

Thanks for everyones help, hope I can find the fix. When you mean pick up coil wires are you talking about the spark plug wires or the wires that lead into the coils?

[Tat2demon]

http://www.xs11.com/forum/showthread.php?t=543

[skids]

Well, you got a lot of comments here, but the truth is IMHO if you are getting minor "afterfiring" with aftermarket carbs/pipes during deceleration, this may be nothing to worry about. The OEM carbs, airbox, filter, and pipes were well-engineered by the Japanese engineers. You mess with any of these components and you will see some less-than-perfect results, depending on your goals. For example, personally, I can live with the sputtering/"put, put", on deceleration (nothing too loud), and the drop off of torque above 95 mph with one of my systems, but that is a personal acceptance with the system that I am using. If you alter the OEM system, you might gain somewhere in the throttle positions, but lose in others.

[MORGZILLA]

1978 xs1100

The bike I bought from Bob Jones and between me and my buddie(mechanic for 20+ yrs) the bike has been running great for 11 years with over 20k miles put on her since I purchased the bike from Bob. The bike just started acting up like I said a few months ago when I went into a right hand turn leaned over. When the bike straighted up it was burbling and running like it was only on 2 cylinders and than within a few minutes would be back to normal. However the small backfiring was there on decelleration. The bike will run ok and then all of a sudden will start acting up. I will check the pick up coils and go from there, thanks Morgzilla

[DGXSER]

Theonly other thign that makes snese bsed upon your diagnosis that the leaning of the bike started the issue is if you disturbed some crud in the tank that got to your carbs and now is causing some plugging of jets.