[FieroGT42]

I got a bike with a torn diaphragm that was running super rich. The idle screw was also set so low that it wouldn't idle, cold or hot. The bike did run if you held the throttle, just very poorly and super rich.

I replaced both diaphragms since one was completely torn and cleaned the carbs. I also rejetted to 140/40 front and 142/40 rear per recommendations here because I coastered and shaved the ears. I know, too many variables at once isn't good but I didn't want to redo the carbs.

Now the bike just cranks and cranks. When I'm cranking, fuel dribbles out of the T on the carb vent lines. From what I read this is supposed to go to tank but I don't see anywhere to attach it. It's an 86 and I read that it may not have that from the factory. Pretty sure gas shouldn't come out of there though.

Is this the carbs flooding? I drained them both and got a normal looking amount from each.

Help would be much appreciated. I'm supposed to bring this bike to a safety course on the 12th. Thanks.

Jason


Edit:
Checked that the A/F screws were at 1 1/2 turns. Started up for a few seconds on both cylinders at 1200 RPM and dropped slowly until it died. I can get it to run sometimes for a few seconds at half throttle but not idle. Both carbs are spitting fuel and wetting the filters. They're 140/40 and 142/40 jets, brand new genuine Keihin.

 

[FieroGT42]

No junk in the carbs. Float is airtight. Spring in the needle is springy and moves freely. Float needle rubber looks good. Pilot needle looks good.

I'm trying to find how to check/set the float level because I'm really at a loss as to what else to do. Is there any way to check them without putting them back on the bike and taknig them back off for every adjustment?? That's ridiculous...


Edit:

The only way I can find is with the carbs on the bike and RUNNING, which I can't do because it won't run. I'm kind of stuck here.

 

[wmsonta]

The manual has a very good procedure to check the fuel level in the carb bowl w/o removal. I recommend it. The manual is a free download here and worth the time.

edit-the bike need not run to check fuel level.

 

[slimvulcanrider]

y different jets front and rear?

do you have a service manual?

 

[wmsonta]

Oh, hey I get it. Yes you can check them on the bench. I have done it, although I do not remember now. Somebody here can probably tell you or I can find it given time. You can test needle and seat on the bench also. Virtually anything to do w/carbs can be done on the bench.

 

[WilliamTech]

Place a clear 5/16" (or is it 3/16" ?) hose on the carb drain nipple. Hold unattached hose end up --hose will be looped like a J.
Open up drain nipple, open up petcock.
Observe fuel level in clear tubing....evaluate to float chamber.

hope this helps
:smiley_th

 

[FieroGT42]

The only off-bike float procedure I found in the manual was tipping them upside down to check the point at which the needle seats. That doesn't check the actual fuel level though. Everything looks perfect to me, but then why is this carb flooding?

Larger jet on the rear due to coastering and intake modification. The rear runs hotter especially with the modifications. Larger jet there is supposed to help according to consensus of the mod/jetting people here. The cross-sectional difference is very small, and it shouldn't flood the bowl.

Yes, I ahve the PDF manual and it says how to check them on the bike with a special tool, which would be a PITA even if I rig up my own clear tubing for it.

Checked every parts store and hardware store around here. No clear fuel line anywhere! I guess I"ll order some online...

 

[wmsonta]

but then why is this carb flooding?

That is easy, Needle and seat or holy float. On a gravity system there is no other answer. I check N&S w/mityvac.

Checked every parts store and hardware store around here. No clear fuel line anywhere! I guess I"ll order some online...

Farm supply stores. Farmers use more clear hose than anybody. I bought 15 ft of 5/16" (fits mityvac nipples) for $0.29 a ft.

HTH

 

[WilliamTech]

Checked every parts store and hardware store around here. No clear fuel line anywhere! I guess I"ll order some online...

I am shocked a hardware Store doesn't carry clear line. Maybe Walmart Pet dept. (Fish Aquarium supplies) would carry the proper size.

:smiley_th

 

[slimvulcanrider]

The only off-bike float procedure I found in the manual was tipping them upside down to check the point at which the needle seats. That doesn't check the actual fuel level though. Everything looks perfect to me, but then why is this carb flooding?

Larger jet on the rear due to coastering and intake modification. The rear runs hotter especially with the modifications. Larger jet there is supposed to help according to consensus of the mod/jetting people here. The cross-sectional difference is very small, and it shouldn't flood the bowl.

Yes, I ahve the PDF manual and it says how to check them on the bike with a special tool, which would be a PITA even if I rig up my own clear tubing for it.

Checked every parts store and hardware store around here. No clear fuel line anywhere! I guess I"ll order some online...

hmmm. how do rhese so called pro's measure heat difference between front and rear carb? a thermal laser? i have the exact same set of mods done running 142/40's on both carbs, and only 2 degrees difference in temp between the two cylinders. for the people that are haveing problems which are fixed by running two different size of jets, somthing is wrong in the compression of one of the cylinders.

your problem however sounds to be faulty float needles. take a Q-Tip with rubbing alcohol and clean the needles and the orifices. Then hold the carbs up side down and try to blow through the fuel inlet nipple.. you shouldn't be able to. if you can, keep adjusting the spring tension by bending the little tab until you can not blow through carbs.

 

[FieroGT42]

I did that twice, after I put in a new one. I was surprised at how little it took for me to be unable to blow through them. Same problem. Second new needle fixed it. I guess I shouldn't assumed a new part was good.

Front is still running rich with visible smoke at open throttle. The rear cylinder isn't. I don't see any smoke at idle. I"m going to proceed to setting the pilot screws, idle speed and balancing.

Thanks everyone

 

[slimvulcanrider]

You might drop down to 140/40 jets in the front

Sent from Motorcycle.com Free App

 

[FieroGT42]

It's already 140/40 on the front and richer than 142/40 on the rear. I may need smaller jets but I don't know how to calculate that myself without buying several sets and spending forever trying them. It's my understanding that the rear cylinder is supposed to get a bit more gas from the factory which is why the front/rear have different needles.

So now I have 2 problems left (besides being rich. THe bike, not me. Wish it was the other way around).

1: Trouble getting the idle set.
My next problem is that the idle doesn't want to be between 900 and 1300. You know, right where it's supposed to be. I drop the idle down to about 1300, then the slightest hair's width lower and it chugs down to 900. I don't think that's good for the oil pressure.

2. The pilot screws don't seem to do anything at all.
I backed out to 2 1/2 turns. I set idle to as close as I can, then turn in the screws one at a time. The idle should drop off and I'd back off the screws to smooth the idle again. It doesn't drop. It really feels like I can seat one of the pilot screws and the RPM never changes. This is leaning them as they go in, correct? So is it just running so rich that it doesn't change anything?

BTW I'm on stock exhaust, ear shave with UNI PK-92 pods, coastered, and 140/40 front jets 142/40 rear jets at 600-800 ft elevation.

 

[VN750Rider/Jerry]

Going back to the original post, if gas is coming out through the carb vent lines, then either the float needle valves are leaking, the floats are sticking, or the float levels are set to high. Gas should never come out of the vent lines.

 

[FieroGT42]

Yep, that's fixed. It was a poor sealing float needle, and a brand new replacement that also leaked. I didn't know what else it could be because I was using a new part. 2nd one did the trick.

 

[wmsonta]

Fiero, I would not expect the mixture screws to change idle rpm. When going to a larger pilot jet, it is not unusual to turn the mixture screws in. The range of adjustment is 1-3 1/2 turns from the bottom. If it idles best outside this range, you have other issues or the wrong pilot jet.

 

[FieroGT42]

Really? I was told to set them by tightening them down until RPM dropped a bit (lean), then out just until it stabilized. I also read that in a few threads on here as well.

I'm ordering 135 and 138s. Vulcans aren't the only bike that run more fuel on the rear cylinder. This should give me one of each from 132-142 so I can fit any size with +1 on the rear.

BTW, cheapest place i've found to order just a few genuine jets at a time is power-barn. Carbjetkits is the absolute cheapest I've seen but they're generic.