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Carbs and Fuel System
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post #1 of 16 (permalink) Old 04-23-2010, 11:30 PM Thread Starter
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Performance Help

Someone please point me in the right direction.
One time, my Vulcan goes up to 6,500 and sputters, the next time it
fair up to 7000 and then it acts like it has a turbo and hits hard and fast up to the redline+(yes, the 750 Vulcan will wind up to 10,500).
I have K&N's in the pods and Cobra Slash cuts.

Thanks in advance.


1992 Vulcan 750
Bought May 2008 Mileage 12,499


Current Mileage 20,600
R/R Replaced/Relocated
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post #2 of 16 (permalink) Old 04-23-2010, 11:55 PM
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Sounds like carbs. Have you tried adding 1/2 a can of Sea Foam to a tank of fresh gas?

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post #3 of 16 (permalink) Old 04-24-2010, 01:53 AM
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Quote:
Originally Posted by delenew View Post
Someone please point me in the right direction.
One time, my Vulcan goes up to 6,500 and sputters, the next time it
fair up to 7000 and then it acts like it has a turbo and hits hard and fast up to the redline+(yes, the 750 Vulcan will wind up to 10,500).
I have K&N's in the pods and Cobra Slash cuts.

Thanks in advance.
Check your air filter media, sounds like clogged mains or vacuum piston assy. or air restriction or just bad gas. Pick one!! LOL


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post #4 of 16 (permalink) Old 04-24-2010, 06:55 AM
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Check the hose that "t" s off of the carbs. Some times it will get air bown directly into it and it will cause the carbs to flucuate. Push hose up under the fuel tank away from direct air flow.

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post #5 of 16 (permalink) Old 04-24-2010, 11:07 AM Thread Starter
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This has been an ongoing problem for around 10 tahks of gas.
Brand of gas or octane rating does not matter(even tried race gas).
I use about 2 ounces of Seafoam in every other tank of gas.
Should I use more than that.

The vent hose is in the air stream, I will change that after it stops raining and check the results.


Thanks for all suggestions.


1992 Vulcan 750
Bought May 2008 Mileage 12,499


Current Mileage 20,600
R/R Replaced/Relocated
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post #6 of 16 (permalink) Old 04-24-2010, 01:04 PM
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Quote:
Originally Posted by delenew View Post
and then it acts like it has a turbo and hits hard and fast up to the redline
DAMN! now my mad scientist side is awake...

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post #7 of 16 (permalink) Old 04-24-2010, 04:15 PM
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The amount of Sea Foam sounds right for maintaining the carbs. I was thinking you might have gunked up carbs, which isn't likely with your regular use of Sea Foam. The hose in the wind may very well be the source of your problems.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
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1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #8 of 16 (permalink) Old 04-26-2010, 11:27 PM Thread Starter
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I moved the hose out of the air and it now runs consistant.
Thanks again.


1992 Vulcan 750
Bought May 2008 Mileage 12,499


Current Mileage 20,600
R/R Replaced/Relocated
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post #9 of 16 (permalink) Old 04-27-2010, 05:44 PM
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You have an intermittent fuel delivery problem.

Fubar the Seafoam crapola, get to the problem.

Most likely there are one of two causes...

1) IF, and that's a BIG IF, you have not jerked around with the carbs and you've got a bike with a few years (regardless of miles) there could either be a float problem or a needle valve problem. Most likely, needle valve. Small part, $8.00 at Kawasaki, but a full teardown of the carbs required. How to determine??? You need to proceed to the next step first.

2) Next step...air cutoff valve...no, it doesn't cut off air, but from the front cyl there is a vacuum line running up to the fuel petcock. First, disconnect that vacuum line and apply some vacuum (suck baby suck). Is there a positive seal or do you just get an airry gas taste in your mouth while the vacuum goes away(you can also do this with a manometer and a vacuum pump and avoid the lovely taste of fuel, but why would you ask me for such insight?)?
3) IF there is an obvious lack of suction/vacuum, please don't talk to any females about the problem. Do try the test again with a NEW pc of vacuum hose.
4) New vacuum hose, no seal on the tongue?? The air cutoff-valve is FUBAR. Temp fix, get some solid core gasket material from any auto parts store and cut a gasket to seal off the petcock. Five minutes tops, but keep the holes for the screws really really tight on clearance or you'll wind up with a leak...and then fire...and then an insurance claim... and loss of stuff that us guys like to have handy for those meaningful meets.

Now, if you got past part two and all is well, then you're screwed. The needle valves are bonkers. Pull the tank, etc and rebuild the carbs. Sorry bout that, but it's the only true explanation.

How do I know? 84,700 miles on an 86 and over one million documented miles on two wheels.

Go Fish.
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post #10 of 16 (permalink) Old 04-27-2010, 06:00 PM
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Quote:
Originally Posted by AlwaysOnTwo View Post
You have an intermittent fuel delivery problem.

Fubar the Seafoam crapola, get to the problem.

Most likely there are one of two causes...

1) IF, and that's a BIG IF, you have not jerked around with the carbs and you've got a bike with a few years (regardless of miles) there could either be a float problem or a needle valve problem. Most likely, needle valve. Small part, $8.00 at Kawasaki, but a full teardown of the carbs required. How to determine??? You need to proceed to the next step first.

2) Next step...air cutoff valve...no, it doesn't cut off air, but from the front cyl there is a vacuum line running up to the fuel petcock. First, disconnect that vacuum line and apply some vacuum (suck baby suck). Is there a positive seal or do you just get an airry gas taste in your mouth while the vacuum goes away(you can also do this with a manometer and a vacuum pump and avoid the lovely taste of fuel, but why would you ask me for such insight?)?
3) IF there is an obvious lack of suction/vacuum, please don't talk to any females about the problem. Do try the test again with a NEW pc of vacuum hose.
4) New vacuum hose, no seal on the tongue?? The air cutoff-valve is FUBAR. Temp fix, get some solid core gasket material from any auto parts store and cut a gasket to seal off the petcock. Five minutes tops, but keep the holes for the screws really really tight on clearance or you'll wind up with a leak...and then fire...and then an insurance claim... and loss of stuff that us guys like to have handy for those meaningful meets.

Now, if you got past part two and all is well, then you're screwed. The needle valves are bonkers. Pull the tank, etc and rebuild the carbs. Sorry bout that, but it's the only true explanation.

How do I know? 84,700 miles on an 86 and over one million documented miles on two wheels.

Go Fish.
you do not need to be insulting we are only relaying what has worked in our cases i cannot diagnose or repair a car or motorcycle that is not in front of me neither can you. how far you have ridden is of no consequence there are others here like jerry that have prob ridden further.


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