Bike won't run, fuel from carb vent line - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 17 (permalink) Old 07-31-2013, 07:01 PM Thread Starter
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Bike won't run, fuel from carb vent line

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.

Last edited by FieroGT42; 07-31-2013 at 07:33 PM.
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post #2 of 17 (permalink) Old 07-31-2013, 09:25 PM Thread Starter
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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.

Last edited by FieroGT42; 07-31-2013 at 09:33 PM.
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post #3 of 17 (permalink) Old 07-31-2013, 10:06 PM
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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.

Last edited by wmsonta; 07-31-2013 at 10:10 PM.
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post #4 of 17 (permalink) Old 07-31-2013, 10:17 PM
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y different jets front and rear?

do you have a service manual?
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post #5 of 17 (permalink) Old 07-31-2013, 10:29 PM
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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.
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post #6 of 17 (permalink) Old 08-01-2013, 08:10 AM
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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

'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!

Last edited by WilliamTech; 08-01-2013 at 08:24 AM.
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post #7 of 17 (permalink) Old 08-01-2013, 11:08 AM Thread Starter
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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...
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post #8 of 17 (permalink) Old 08-01-2013, 11:52 AM
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Quote:
Originally Posted by FieroGT42 View Post
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.

Quote:
Originally Posted by FieroGT42 View Post

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
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post #9 of 17 (permalink) Old 08-01-2013, 01:58 PM
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Quote:
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.


'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!
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post #10 of 17 (permalink) Old 08-01-2013, 02:35 PM
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Quote:
Originally Posted by FieroGT42 View Post
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.
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