Strange miss

[XS1100 Newbie]

Plugs are firing ok. Just have to be able to close and open the valves right.

[Barnfresh]

just sayin... the plug was firing through the porcelin insulator, then accross the gap.. miss would come and go. Took me forever to find since the plugs were new..

[XS1100 Newbie]

Some news, but no solution yet. I received my shims, and done the valve adjust. Checked the timing marks again, and they were right on. Before installing my cam cover, i thought i would fire it and see what i had. The bike started great, and ran smooth, but number one was still cold. I took another compression check on number one, it was at 100 lbs cold, and improvement of 40 lbs from before the shims were done. I still have to wonder about fuel. As stated before, i had just done my carbs a few days before. It just seems with all that i have checked, that is the only thing left. If i somehow got my jets pluged on number one, then it would not be getting fuel, but the fuel enrichment circuit should still be working. I have two of the things needed to fire, i have compression, fire, but i don't know about fuel. There is fuel in the bowl, i checked that. I thought about the coil, but if it was bad, number 4 would not fire either. How could the fuel be blocked from getting to the cylinder?

[DGXSER]

Once you have narrowed it down to fuel, which it sounds like you have, then it becomes a matter of stoichiometry. Not just fuel, but the right fuel mixture. Now two things can be happening, you could be getting to little fuel, or to much. To much has one source, the carbs. To little fuel can also be to much air, as in a vacuum leak. Get the bike running, and use a propane torch, unlit. Point it around your carbs, the boots at the head, and such. If the engine speed picks up, you have a vacuum leak giving you to much air.

When I was at XSEast last spring my bike suddenly started running like crap. Bad miss on one cylinder. It was right after a fuel stop, so I thought sure it was bad gas. Instead, it wound up being a missing mixture screw. It had loosened up enough it bounced out or leaned the mixture so much it backfired out the carb and spit it out.

[XS1100 Newbie]

I think it would have to be not enough fuel. The plug was dry as a bone. I will check for a vacumn leak. That seems possible because of how things happened. Will report on the next test.

[Barnfresh]

swap the plugs in different holes... or try another plug... humor me... I've chased that rabbit before...

[XS1100 Newbie]

Swapped plugs from a firing hole. No difference.

[XS1100 Newbie]

OK, i put things back together, and it is a little better, but still doesn't burn until i bring the rpm's up. Seems to start responding at about 2000 rpm's. You can definately feel the imbalance. Checked for vacumn leaks with propane, and found none. I am back to thinking it is carb. May ride it today for a bit and see how it runs out. Will adjust mixture and see if that helps.

[motoman]

OK, i put things back together, and it is a little better, but still doesn't burn until i bring the rpm's up. Seems to start responding at about 2000 rpm's. You can definately feel the imbalance. Checked for vacumn leaks with propane, and found none. I am back to thinking it is carb. May ride it today for a bit and see how it runs out. Will adjust mixture and see if that helps.

Again Newbie, you have a primary ignition voltage problem. To prove this out, remove your seat/tank and using an anolog meter, with key on check voltage at either of the red wires at the coil plug-ins..........bettin you won't have 12V but report back with actual voltage and that will pretty much pin-point the issue of where to go to remedy the issue.

[XS1100 Newbie]

I will do that for you, but please explain how i can have half a coil bad. Low voltage, or any coil problem should affect two cylinders, not one. Number 4 is firing fine. Not trying to argue, just need an explanation.

[DGXSER]

Read THIS thread and see if it sounds familiar to you.

[motoman]

I will do that for you, but please explain how i can have half a coil bad. Low voltage, or any coil problem should affect two cylinders, not one. Number 4 is firing fine. Not trying to argue, just need an explanation.

Your correct. Do that test anyways, then with ignition switch back on, check voltage at the regulator's brown wire. Should be 12V there and 12V at the brown wire on the fuse panel. Tis kinda the backwards way of tracing voltage loss, but will work either way.

[motoman]

Importantly I forgot to add to check batt. voltage with key on first since tail lite and any marker lites drop that voltage some. That will be the baseline for what the rest of check points should be.

[XS1100 Newbie]

That thread would sound like my problem except that i know that it is in number one cylinder, and appears to go away with higher rpm's. The bike seems to rev fine with no load. I was going to take it for a spin this morning, but my garage door was broke, and i can't get it open. Have to replace springs. If i had the money, i would put coils on just to have better coils, whether it was a problem or not. I will pull a vacumn test on the cylinders again, and see if there is something there.

[thumperjsa]

Just curious as I had a similar issue to this. Turned out to be a idle mixture screw tip broken off and blocking the hole if I recall correctly. At least I think that is the one if I recall closest to the cylinder. Because the problem seems to exist before you get to higher RPM and the plug is dry, seems to be a problem with fuel flow to me. But I am not an expert on these engines either. Just thought I would throw this in for you to check to make sure that hole isn't blocked.