Bad running. Any ideas?

[tlbranth]

Decided to cobble something together to see fuel levels in the carbs. I hooked it up to #2 and to #4 for comparison. It's a tad difficult to read heights accurately but #2 looks to be about 2mm higher than #4. I thought they both looked higher than they ought to be to I fussed around with some fuel in a spare bowl and a float held up at its pivot with a bit of baling wire and by measuring this and that and going with the 21mm spec for setting float height it looks like the fuel level is supposed to be about at the bottom of the carb body (where you measure float height from). #4 is about there but #2 is, like I said, about 2mm higher.
Here's what I'm thinking:
The rain squall thing is a red herring. The popping is because the fuel level in #2 is too high. That level caused the plug to foul and give up the ghost.
Here's another thought:
The float height spec was set in a day when we could buy actual gasoline. I'm wondering if the ethanol lowers the specific gravity of the fuel so the float rides lower in the fuel making the level higher when you set it by measuring float height at fuel valve closure. This might explain why the whole thing is running a tad rich. But then I tend to make things up.
Some of you might find my fuel level tool handy. It's not real hard to make from a spare bowl drain screw.

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[jdvorchak]

fuel level should never be at or above the carb body on any motorcycle carb I've seen. Ethanol changes the specific gravity of the fuel? I doubt it. If it does I doubt it would be a significant change. I'm betting the shock absorb-er pin is stuck on #2 float needle allowing the fuel level to come up. In any event you're pulling the carb rack and carefully determining the problem.

[CYBORG]

I noticed what looks like spark plug wire numbering in the photo, and it looks like 1 and 4 are on the same side. I know you know better,....but what am I missing?

[jdvorchak]

I noticed what looks like spark plug wire numbering in the photo, and it looks like 1 and 4 are on the same side. I know you know better,....but what am I missing?

Good catch! I was looking at the plastic tubing.

FYI on the KZ and GS forums they all say that using the plastic tubing is the correct way to check level. The FSM for both shows the measurements for initial setting the float level and then the final check using a plastic tube with measurements. Those measurements are always from 1 to 4mm below the carb body as I remember.

[tlbranth]

I noticed what looks like spark plug wire numbering in the photo, and it looks like 1 and 4 are on the same side. I know you know better,....but what am I missing?

I switched 1 & 2 to see if the popping would change sides

[CYBORG]

Don't 1 and 2 come off of the same coil? So, the wasted spark just becomes the primary spark, and visa versa?

[tlbranth]

Don't 1 and 2 come off of the same coil? So, the wasted spark just becomes the primary spark, and visa versa?

Yes. Hott suggested I might have a leaking high tension wire on #2 that would cause popping. So I switched 1&2 but the popping stayed on the left side.

[CYBORG]

Oh, I get it now......popping is hard to track down. Compression test? (could be a burnt or leaking valve )

[JSBail]

The float height spec was set in a day when we could buy actual gasoline. I'm wondering if the ethanol lowers the specific gravity of the fuel so the float rides lower in the fuel making the level higher when you set it by measuring float height at fuel valve closure.

I think you have it the other way around, ethanol has a heavier specific grav than gasoline. The specific grav of the gas we can get at our local gas stations varies a bunch depending on what web site you use as reference, who makes it, what octane and so on but generally speaking ethanol blended gas tends to have a heavier specific grav than its pure gas counterpart but I agree with jdvorchak in that I doubt it's significant assuming the octane of the e10 is the same octane of the pure gas you used to initially set float height. Even if it was significant and you initially set your float height with pure gas then that fuel level would be showing lower now with e10 rather than higher.

[tlbranth]

The float height spec was set in a day when we could buy actual gasoline. I'm wondering if the ethanol lowers the specific gravity of the fuel so the float rides lower in the fuel making the level higher when you set it by measuring float height at fuel valve closure.

I think you have it the other way around, ethanol has a heavier specific grav than gasoline. The specific grav of the gas we can get at our local gas stations varies a bunch depending on what web site you use as reference, who makes it, what octane and so on but generally speaking ethanol blended gas tends to have a heavier specific grav than its pure gas counterpart but I agree with jdvorchak in that I doubt it's significant assuming the octane of the e10 is the same octane of the pure gas you used to initially set float height. Even if it was significant and you initially set your float height with pure gas then that fuel level would be showing lower now with e10 rather than higher.

Well, like I said, I tend to make things up.

[JSBail]

Well, like I said, I tend to make things up.

Nothing wrong with that, sometimes you have to think outside the box before the answer presents itself. Keep us informed in what you find out.

[jdvorchak]

One other thought. I've never seen anyone try to use a plastic tube while the carbs are mounted on the bike. Always on the bench, after your carb work, and prior to installation. Roady did a really nice write up, in Shop Talk, about how to set float level on an 1100. Basically you adjust the float level with the floats just touching the float needle. So you are rotating the rack until your arms are tired, checking and making small changes to the float tang, to achieve the proper measurement.

[HOTT]

....Hott suggested I might have a leaking high tension wire on #2 that would cause popping. So I switched 1&2 but the popping stayed on the left side.

I think that was Eric...but I'da took credit if it worked

HOTT

[tlbranth]

....Hott suggested I might have a leaking high tension wire on #2 that would cause popping. So I switched 1&2 but the popping stayed on the left side.

I think that was Eric...but I'da took credit if it worked

HOTT

Oops. But hey, when you're old as I am you can say dumb stuff and get away with it.

[tlbranth]

One other thought. I've never seen anyone try to use a plastic tube while the carbs are mounted on the bike. Always on the bench, after your carb work, and prior to installation. Roady did a really nice write up, in Shop Talk, about how to set float level on an 1100. Basically you adjust the float level with the floats just touching the float needle. So you are rotating the rack until your arms are tired, checking and making small changes to the float tang, to achieve the proper measurement.

Yep. That's how I did it. Next time, I'm using the tube and set each float on the bench. That's how I do my CB750.