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Nothing at idle on #4 carb

  • Thread starter Thread starter ChicagoRob
  • Start date Start date
C

ChicagoRob

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Howdy.

Just rebuilt a rack off an '82 1100GL that had been sitting wrecked in a guy's garage since '86. Had 5k on it when someone crossed the double-yellow which resulted in a 90mph head on. Ouch. Spent 7 months in the hospital but is still riding today. Bought was was left of the bike from him for $300. (Engine, carbs, rear-wheel, swingarm & coils/ignitors) Now for the carbs.

Anyway, I rebuilt them and I'm not getting anything out of #4 at idle. The plug is getting spark and the gap is good but when I turn the air screw or pull the plug wire it doesn't make any difference to the bike's idle. The other three react the way that you'd expect.

Both float height and sync are good. I checked the hole under the air screw and it's clear.

Any ideas?

Thanks,

Rob
 
Clean out the pilot jet and make sure you can see a pin of light through it.
 
hampshirehog said:
Have you tried swapping the plugs?
Click to expand...

No, didn't. Too late, already pulled and drained them.

I just did throw on the known working rack, though and it reacts as expected so it's gotta be something with the other carb.

Maybe something is still plugged?

Rob
 
chef1366 said:
Clean out the pilot jet and make sure you can see a pin of light through it.
Click to expand...

Pulled it and it looked squeaky clean. Could see light through the tiny opening at the end. Ran a wire through it again anyway. Shot some air down the tube while it and the air screw were out and got good flow.

I should probably mention that I had a heck of a time getting the pilot screws out. It took an extended soak and some heat to free them. They had some black gunk on them that had completely clogged them. The carb dip dissolved it pretty good, though.
 
If you blow carb cleaner in the pilot air jet it should come out the pilot jet.
 
Does the #4 cylinder fire with the slightest throttle move ment or if you turn the idle up?
 
hjfisk said:
Does the #4 cylinder fire with the slightest throttle move ment or if you turn the idle up?
Click to expand...

Yeah, it was firing when I was synching at 3k. (Well, that header got really hot, so I'm guessing that it was firing.)
 
I'm going to disassemble and dip/clean the whole carb again 'cause something ain't right. Can't hurt.

I'll update tomorrow.

Rob
 
ChicagoRob said:
Yeah, it was firing when I was synching at 3k. (Well, that header got really hot, so I'm guessing that it was firing.)
Click to expand...
So if it fires with a slight throttle adjustment , then I would tend to have to think that the throttle plate is closing to much on that cylinder, if all else is good and clean, which would mean the syn is off a little.
 
hjfisk said:
You were syncing them with a set of gauges correct
Click to expand...

Yep, a Morgan CarbTune Pro (The 4 tube model). 1 & 4 slightly higher than 2 & 3. Takes me a few tries because I still haven't mastered tightening down the nut without turning the screw a little.
 
Last edited:
Ok, finally got back to it. Yesterday was so nice, the wife and I took a drive in the country.

The dip worked! Musta been a clogged tube because I have a smooth idle now. But...

During the test ride, any cruising with the throttle cracked (think 25mph cruising at 3k) it feels like one cylinder isn't firing. It's jerky and kinda sputtering in the 2.5k to 4k range with small throttle. Full on throttle is strong and smooth all the way to 9k (Well, the first attempt stumbled a little over 8k but the second and third attempts didn't). Highway cruising at 4 to 5k is smooth. I'm also getting a lot of decel pops especially in the 4 to 6k to throttle off range.

I should mention at this point that it's stock carbs, finally a stock air box with full snorkel (the old one was cutoff very low) and a recently repacked V&H 4to1. The airbox is sealed well with new foam all around and a clean/oiled K&N filter.

Runs like crap cold and gets better with heat. Sync is still good and all of the valves are between 5 and 9.

What's the thoughts on the low throttle stumbles and the decel pops?

Thanks,

Rob
 
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