misfire

[ridingagn]

JAT---- picup coil wires? This drove me nearly insane (a short drive) when I got my XS.

It did nearly the same thing.

And later on after I had repaired them, I was having an intermittent problem on acceleration because of a P/U wire that had rubbed through the insulation and was grounding out on a screw head when the vacuum advance pulled the breaker plate back.

I'm leaning toward that too. I will pull the pick-ups off and see what I can find. Although I had the cover off through all this, and could not make it do any better or worse moving the wires around when it was running.
Martin

[XSokieSPECIAL]

I'm leaning toward that too. I will pull the pick-ups off and see what I can find. Although I had the cover off through all this, and could not make it do any better or worse moving the wires around when it was running.
Martin

Be certain the air gaps are correct on the pickups.

[bikerphil]

If you remove and plug the vacuum line going to the advance unit, then rev the motor and see if it misfires. This way, the pickup coil wires aren't flexing due to movement of the vac advance. If it improves, PU coil wires need repair.

[ridingagn]

If you remove and plug the vacuum line going to the advance unit, then rev the motor and see if it misfires. This way, the pickup coil wires aren't flexing due to movement of the vac advance. If it improves, PU coil wires need repair.

I disconnected the vacuum to the advance, plugged the port at the carb and let the bike warm up. Idles perfectly, but as soon as rpm increases above 1200 or so the random popping out the exhaust starts and continues as rpm increases. Back down to idle and it goes away and idles smooth as silk.
So sorry...... I wish that had been the problem, but no dice.

I will continue to work it out and will certainly post what ever I find as the solution.
Martin

[XSokieSPECIAL]

I disconnected the vacuum to the advance, plugged the port at the carb and let the bike warm up. Idles perfectly, but as soon as rpm increases above 1200 or so the random popping out the exhaust starts and continues as rpm increases. Back down to idle and it goes away and idles smooth as silk.
So sorry...... I wish that had been the problem, but no dice.

I will continue to work it out and will certainly post what ever I find as the solution.
Martin

Back to the carbs. JAT. Sorry.

I really want to know what this is!

IMHO Try changing the carbs and see what happens. More work but nothing else seems to make any diff. Out of ideas.

[Rasputin]

Thoughts

I have a couple of thoughts here.
First is what jets are in the carbs both pilot and mains? With both pods and a 4 into1 on it that can make a huge difference. Tuning without a colortune will not show you the flame color, you could be tuning it to the best it can be with those jets but still not be quite right.
Second what year carbs are we working with (sounds like 80 or newer), can you read a number on the carb bodies? There are differences and that may help someone come up with a sound solution. You have said you have an older set of carbs with the big screw on top which would be the ones my 79 came with.
Third, have you checked the slide diaphragms for pinholes or tried a leak down type test? No mention has been made of their condition.
Fourth, is there any way you can video it or something so we can hear what it is doing. I find it so much easier to diagnose things when I can see, feel, or hear the issue.
It sounds like many things have changed with what you have done and I just think more info may trigger some ideas from the guys. I too am confused and sitting on the edge of my chair waiting to hear the solution. Just thinking out loud mostly.

[randy]

We may have gotten a bit off track here, the problem followed the float....

The puff back has moved to #3 cylinder.
That means the puff problem followed the float, but not the cold header temp or the rough idle.???? @#$%*&.

So for those of you who like a challenge.....
why would the puff follow the float? (remember it runs super smooth and at proper temp otherwise)

Why? Maybe the float is sticking on the side of the bowl, or on the pin? Or that float just don't float like it should, as Tod stated that is a rare thing if the float is plastic, but anything is possible. If you have them out, compare how they all float in water? JAT

[dbeardslee]

I disconnected the vacuum to the advance, plugged the port at the carb

With a '79 you still have the mechanical advance, so it's still going to move even with the vacuum plugged. If you suspect pickup coils you might try a DMM on the four pin connector at the tci. Hold the slots so they are horizontal and put a probe in the two 'top' slots, followed by the two 'bottom'. Readings should be 720 ohms plus or minus 20%. If you jiggle the wires down by the pickups while you're testing, and the readings start jumping around, or the readings are out of spec, suspect the wires. If the readings are within spec I'd go with Randy's suggestion. My $.02

[trbig]

I agree with checking the slide diaphragm in the top of the carb for holes. While you have the carbs off.. again... you can set them up on the bench and mount them somehow so they are level like sitting in the bike. Hook a fuel line with fuel up to them like it was on the bike, then check and make sure the fuel isn't leaking and the flaot valves are doing their job.

You can check the slides on the bike if you have a small mirror. Am I correct in that the bike has pod filters? Anyway... as you give the bike gas, you can watch the other slides and see if they are rising the same, or one is staying down. If the air box is still on, you can disregard this part.. lol.


Tod

[Montreux_Blue]

I like to use a colortune. Works well for me. This thread will show you how if you do not have a colortune
http://www.xs11.com/forum/showthread.php?t=13124

Me and John have tried to use Colortune several times to no avail. Now Carbtune REALLY works though.

[XSokieSPECIAL]

With a '79 you still have the mechanical advance, so it's still going to move even with the vacuum plugged.

Yes your right about still having mechanical advance, however, the mechanical advance is BELOW the breaker plate and moves the lobes on the shaft itself rather than the breaker plate with the pickup coils and wires mounted on it. So the pickups and wires would remain stationary with the vacuum hose disconnected.

[dbeardslee]

XS - You're right - my bad.

[cloerts]

geniusloerts,

Forgive me, but I don't recall the story on the Frankinbike...

Is it a mix of years & parts? Hence the name?

The bike has a 1980g frame serial number, a 1981 Engine serial number, and a mix of other years and models on the body parts. Electrical and carbs are anyone's guess. The Frankenbike moniker is partly that, and partly that it was ugly and dead when I got it.

[ridingagn]

With a '79 you still have the mechanical advance, so it's still going to move even with the vacuum plugged. If you suspect pickup coils you might try a DMM on the four pin connector at the tci. Hold the slots so they are horizontal and put a probe in the two 'top' slots, followed by the two 'bottom'. Readings should be 720 ohms plus or minus 20%. If you jiggle the wires down by the pickups while you're testing, and the readings start jumping around, or the readings are out of spec, suspect the wires. If the readings are within spec I'd go with Randy's suggestion. My $.02

Back to the carbs. JAT. Sorry.

I really want to know what this is!

IMHO Try changing the carbs and see what happens. More work but nothing else seems to make any diff. Out of ideas.

Sorry for not posting the past few days. Wanted to wait until I had something to report.
I found the infamous broken pick up coil wires. Not one, not two, but three.
The right blue, the left red, and the white wire all had breaks where they flex at the bottom before passing through the case. I repaired the wires following the suggestions listed elsewhere here in the forum. The bike idles more perfect than before, and is very smooth. But there is still a random "pop" out the tail pipe. It's not a pronounced backfire like there was before, but more of a soft "blat" like some unburned fuel vapor is igniting in the horn.

I'll try to address some of the other suggestions that have been posted here. All slides are bench measured equal, clean, unblemished and respond immediately when bike is running and throttle applied. All mixture screws are at about 2 turns out. Carbs have been synced, mixture screws re-adjusted, and carbs re-synced. (lather-rinse-repeat) I examined the diaphrams when I had the carbs off and could find no pin holes. I added a "dampner" from a Ford vacuum system to the vacuum advance line. This does a great job of stopping the dance, but it causes the advance to keep the rpm's up when I let off the throttle, so I took it off. The pick up coil to lobes were at .020. I reset them to .010. I pulled the connector to the pick up coils. Measures 733ohm and 737ohms.

I have not traded out the carb bank yet.
Martin

[XSokieSPECIAL]

Sorry for not posting the past few days. Wanted to wait until I had something to report.
I found the infamous broken pick up coil wires. Not one, not two, but three.
The right blue, the left red, and the white wire all had breaks where they flex at the bottom before passing through the case. I repaired the wires following the suggestions listed elsewhere here in the forum. The bike idles more perfect than before, and is very smooth. But there is still a random "pop" out the tail pipe. It's not a pronounced backfire like there was before, but more of a soft "blat" like some unburned fuel vapor is igniting in the horn.

I'll try to address some of the other suggestions that have been posted here. All slides are bench measured equal, clean, unblemished and respond immediately when bike is running and throttle applied. All mixture screws are at about 2 turns out. Carbs have been synced, mixture screws re-adjusted, and carbs re-synced. (lather-rinse-repeat) I examined the diaphrams when I had the carbs off and could find no pin holes. I added a "dampner" from a Ford vacuum system to the vacuum advance line. This does a great job of stopping the dance, but it causes the advance to keep the rpm's up when I let off the throttle, so I took it off. The pick up coil to lobes were at .020. I reset them to .010. I pulled the connector to the pick up coils. Measures 733ohm and 737ohms.

I have not traded out the carb bank yet.
Martin

AHA! I knew it!!!!

Great man, now it sounds like the carbs. If you have another bank of carbs you could swap them out just to see if it makes a difference. Personally I would take the best looking rack and get some kits and do a complete overhaul. I'm running 79 carbs on my 80 special and I had trouble with running rich until I reset the floats to lowest setting within specs, actually just a little lower. Mine are set at 24.5 mm. I think it has to do with the brass floats and the difference in todays fuels.

Watch out for the broken off tips stuck in the carbs from the idle mixture screws also. I had to remove broken tips from all 4 of mine.