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Carbs and Fuel System
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post #1 of 5 (permalink) Old 08-28-2009, 02:17 PM Thread Starter
 
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Not a 750/but I trust the guru's on this forum.

96 Vulcan 1500 Classic - Carb CVK40.

Been a week and 5 days of problem free riding since I put the carb back on the bike and the same ole' problem I had last month resurfaced this morning. Felt her stumble at 20mph going through town and she smoothed out on the back road at speed. Pulled into the lot, shut her down and pulled the right side aircover. Fuel bubbling from the air intake jets and in front of the butterfly flooding.

What I've done in the last three weeks since this problem started.

Brokedown carb, fully cleaned three times
Float replaced
Needle replaced
Fuel level set at 1mm below mating surface/using service fuel level tube
All diaphrams inspected/no holes or cracks/good seals
Tank cleaned
New fuel filter
Petcock inspected and screens cleaned
Every vent/vacuum/fuel line replaced
Tank vents inspected and operational/no pressure build in the tank (hissing/whistling or pressure when I pop the cap)

Its like some pressure is pushing the fuel level up/it seeps out the air intake and venturi vents past the butterfly into the cylinder. It will do this for about 15 minutes after the bike shuts off then stops (when engine cools down).

I'm considering a fuel pump bypass just to see if that may be the issue.

Also noticed some oily junk in the air switch where the crank vent hoses run. When I manually acticated the diaphram, oily gunk spit out of the tube where the carb plugs in. If that switch is bad, is it possible that it could create vacuum where it t's into the top of the carb which is "pulling" fuel up????

Grabbing for straws here.....I'm determined to track and fix this problem.
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post #2 of 5 (permalink) Old 08-28-2009, 02:20 PM Thread Starter
 
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P.S. I have posted the same on the VROC main site. Just looking for additional recommendations....
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post #3 of 5 (permalink) Old 08-28-2009, 02:59 PM
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Someone on VROC had this exact same problem a month or so ago. Don't know if I can find it but I'll look and try to point you to it... (was it you?)

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart
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post #4 of 5 (permalink) Old 08-28-2009, 03:08 PM
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Never mind, it was you... Sorry. I was hoping you had this fixed by now. I don't know enough about the older 1500's to be of any help. But the VROC group has a bunch of guru's on that carb. someone will eventually help ya.

Could it be that your float bowl level is set too high, allowing the expansion from heat to bubble over? I know you said 1mm setting, but maybe it should be a little lower???

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart
SEAFOAM JUNKIE!



Last edited by fergy; 08-28-2009 at 03:11 PM.
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post #5 of 5 (permalink) Old 08-28-2009, 03:40 PM Thread Starter
 
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It was likely me Fergy. It started about a month back and I posted a couple of questions on the VROC site then. Thought I had the issue knocked out but its just haunting me now.

I started with the float level at the mating surface per the book on the first time. Ran good for two days then started again. Last time I took it down to 1mm below and it was fine for a week (rode 80 miles daily for the week on the commute). I can take it down to 2mm below and still be within the book specs.

Last edited by Cassack; 08-28-2009 at 03:45 PM.
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