79 sputtering/backfiring/bogging

[MadAdventures]

Hello everyone!

I've been riding my 79' XS1100 as a daily for a few months
and it's been great, until about 2 weeks ago when it started having an issue with not idling, coupled with sputtering at low rpms and backfiring through the spectrum. It also doesn't get much acceleration power into higher rpms. This started happening after a repaired a wire in the pickup coil.

Any idea what else could cause this? The backfire is definitely coming from the right exhaust.

[Prisoner6]

Hello everyone!

I've been riding my 79' XS1100 as a daily for a few months
and it's been great, until about 2 weeks ago when it started having an issue with not idling, coupled with sputtering at low rpms and backfiring through the spectrum. It also doesn't get much acceleration power into higher rpms. This started happening after a repaired a wire in the pickup coil.

Any idea what else could cause this? The backfire is definitely coming from the right exhaust.

Hello, and welcome!

First thing I'd do is check those pick-up coil wires again ...

What you're describing sounds like it could very well be a broken pick-up coil wire. Maybe the repair wasn't complete, or maybe you have another broken wire.

Have a look at this:

Pick-up Coil Wire Repair

When checking the pick-up wires, don't be afraid to give those wires a reasonably firm tug from each end of each wire.

It could be something else simple, such as vapor lock/fuel starvation due to the fuel tank not venting properly ... but do the simple check on the pick-up wires first.

[BA80]

This started happening after a repaired a wire in the pickup coil.

You answered your own question.

[DiverRay]

Make SURE you didn't mix any wires in the repair process! Also, check the fuel lines and make sure they are not kinked and look at the right side carbs and check for gas flowing or a vacuum cap popped off.

[MadAdventures]

I appreciate the swift and informative replies! I will be working on it this afternoon, and I will reply with what I find out! This is a great community, and I'm proud to be a part of it!

[skids]

Hello everyone!

Any idea what else could cause this? The backfire is definitely coming from the right exhaust.

Rotted-out the baffles in the mufflers?

[MadAdventures]

It's been raining all day today here in South Louisiana, so I didn't get an opportunity to uncover her. Hopefully I'll be able to get this thing solved tomorrow. Thanks for all the feedback!

[MadAdventures]

Alright, so I checked all the wires well, repaired a couple, but it made no change. Now, on full choke, it will start, and only idle if I'm holding the throttle open, and it bogs at 1000rpms. Can't increase it passed that. Any ideas?

[Dbshea]

Alright, so I checked all the wires well, repaired a couple, but it made no change. Now, on full choke, it will start, and only idle if I'm holding the throttle open, and it bogs at 1000rpms. Can't increase it passed that. Any ideas?

Not insulting your intelligence here, just spitballing. Did you verify you've got a big blue spark on both coils?

[MadAdventures]

No offense taken. If I knew what to look for, I wouldn't be seeking your help.
I did check the sparks last week before it got worse, but I'll check again!

[Dbshea]

No offense taken. If I knew what to look for, I wouldn't be seeking your help.
I did check the sparks last week before it got worse, but I'll check again!

If you are certain those ignition wires are correct and well connected then you need to take the big step back and look at major systems. Check the primary and secondary resistance on both coils. Pull the plugs and clean them up, perhaps when the wire went south you did a number on the plugs and they're covered in filth? Is your vac advance hooked up properly?

When I diagnosed my broken pick up wires, I verified the failure with the engine running. Obviously keep your digits a safe distance from the moving parts, but by tugging the wires while running I was able to verify the issue as well as the repair.

It COULD be carb related, but I would stick to electrical at this point.

[MadAdventures]

I just discovered that one of the coils is arcing to the engine. Would that alone cause all of the issues? And where should I buy new spark plug wires?

[MadAdventures]

I may be calling it the wrong thing, as I keep seeing it called the sparkplug cap.

[Dbshea]

I just discovered that one of the coils is arcing to the engine. Would that alone cause all of the issues? And where should I buy new spark plug wires?

It is not helping you at all. Electricity is following the easiest path. Where is it arcing from? Unfortunately these coils aren't "easily" rebuildable tho it can be done. If its arcing from the end near the cap, unscrew the cap (counterclockwise) from the plug wire. Trim 1/8" off the end and screw the plug cap back on (there is a threaded post inside the cap) if it's on the length of wire, for the time being insulate the hole with a few good layers of electrical tape.

[TopCatGr58]

Don't forget to check the resistance of the cap while it's off with an ohmeter. The internal resistor can corrode, and greatly increase resistance, so that the power can't get thru it to the plug, and perhaps another reason why it's arcing to the engine??

The cap can be taken apart IF you find the resistance way above the usual 5K ohms. There's a straight screwdriver slot in the PLUG end, loosen it, take out the resistor cylinder, spring, and clean/and recheck resistance of resistor. If still way above 5K after cleaning, then get a new cap. You can put a thick piece of solid wire, or longer spring thick gauge spring in there to still use the cap....just no resistance which isn't a problem as long as you're not using an AM radio!

T.C.