XS11 Special. No power

[nitsuj]

Hi guys, I hope you can help, I'm at wits end. I've fixing a 1980 XS1100 Special for a friend. I'm having a problem that I know I'm going to have trouble describing. Bike starts right up and runs and idles fine. Throttle responds normally. When riding, it seems to be running fine, then for no reason, it seems to lose power. All 4 cylinders are still firing, and it doesn't want to stall. It's not like just one cylinder stops firing. All 4 do it. It just loses power and sounds like someone just stick a rag in all the intakes. It sounds choked off for lack of a better word. Not by actually pulling the choke, but like it's just been suffocated. If you stop during this behavior, the bike doesn't try to stall or sputter. It just won't make power. Seems like the warmer it gets, the more it does it. When it's cold, it will run well for a while, then act up. Just for giggles, I ran it with the fuel door open to make sure it wasn't a clogged tank breather, made no difference. Still did it.

I used the propane method to check for a vacuum leak, couldn't find one.

The carbs have been removed and cleaned and re-cleaned. I'm positive it's not a clogged jet. The XS uses that goofy vacuum fuel pump thing on top of the carbs, I'm not familiar with that set-up. Is there a common problem to look for there? Any input would be appreciated. Thanks.

[tarzan]

It sounds like it could be fuel starvation.Lines kinked,octy could have a bad diaphragm (the thingy on top of carbs.lol),or crap in tank plugging screens on petcocks.
I would check that stuff as it is simple to do
Rick

[DGXSER]

Other item it might be is the pick up coil wires. A bad connection there could be getting opened up as the timing gets advanced and loosing power, intermitent lose of spark basically.

[TopCatGr58]

Hey there Justin,

Sounds like what the others have said, fuel starvation, not enough to kill it, just enough to prevent it from giving full power. The Octopus on the top of the carbs can go bad, the fuel valve sticks, or the vacuum hose going to it gets cracked/leaks and won't open properly or fully.

Test is to turn the petcocks to PRIME, and run the bike that way, or wait until it wants to loose power, and THEN turn to Prime, wait a minute or so and then try to ride it. IF the power returns, then you need to work on the OCTY. IF it still has no power, then it's not a fuel flow issue, and you'll need to trouble shoot the ignition.
T.C.

[nitsuj]

Thanks for all the advice guys. I'm in the garage now (aint technology great?) and I'm looking it over. The octopus seems ok, not sure. I can't take it apart, the diaphram is stuck to both sides, tearing it apart will ruin it. I can tell you it seemed to run the same on all petcock setting including prime, but then again, I may not have waited long enough for it to clear up. The vacuum line to the octo seemed a little short and maybe kinked, so I replaced it. No other fuel lines looked kinked. Pulled the petcocks out of the tank, they seem good. I'll try a test ride, if it's not fixed, maybe I'll look at electrical things tomorrow. Keep the suggestions coming.

[nitsuj]

Ok just noticed an odd condition, not sure if it's the problem but at this point, who knows. I just noticed that fuel flows from both petcocks when switched to on or reserve with the engine not running. If it's a vacuum operated system, wouldn't they only flow with the motor running? Prime works as it should on both sides.

[soccer4m]

same problem

I vote for checking the pickup wires under the left cover. I had the same exact symptoms on an 89 Midnite. After going over and over numerous things, cleaning carbs numerous times, plugs, synching, etc. It was the pickup wires. Easy to check, just check the forum. The short check is to pull the left cover, feel the wires and if either one feels like it stretched or narrow, start the bike, twist the wire in that area and if it runs wierd when pulling, or twisting each wire, that is the problem. Easy to splice in new wires if needed, again check the repair section. Let us know,,,,Mike in S.D.

[nitsuj]

Ok, I'll check the pick up coil wires tomorrow. I'm out of garage mode and in to Captain and Coke mode now.

Thanks for the advice. I'll keep you guys updated.

[psycoreefer]

Hey one more thing to keep in mind is the electronic ignition box up under the seat. If the pickup wires seem to check out I'd look there. Mine did exactally what your describing except it was linked to bumps, I'd hit a bump and loose power, hit a bump and it would come back. Ended up being a bad connection on one of the plugs that goes into that box. I found it by running it with the seat off and wiggling the plugs. All I had to do was pop the connectors out of the plug one by one and pinch em closed a little with a pair of pliers then put them back.

[nitsuj]

Thank you all so much for the advice. The ones who guessed it was the pickup coil wires were dead on. I opened it this morning and found 2 broken wires, one was broken in several spots. Spliced them and it runs like a beast now.

Thanks for all the help, the guys on this forum are a class act!

[DGXSER]

Glad you got it fingered out and fixed. Just in time to go for a ride on a beautiful holiday weekend!

[nitsuj]

Well, it still needs inspected, and since it's not mine, I won't be riding the XS this weekend. But I will be riding. There's a pretty red Ducati calling my name in the garage, I think I'll give in and take my Italian mistress out on the town. ;-)

Hope you guys have a good one too. And thanks again for all the help.