Probably Carb issue (long) - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 12-15-2010, 11:04 PM Thread Starter
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Probably Carb issue (long)

I have a new-to-me 1994 750 with 13K miles on it. I assume that means it spent a lot of time sitting. When I first got it, it ran ok but was very hard to start, even on mild California mornings. In addition the idle was not consistent. So I put new plugs in it (copper NGKs). You can set the idle at the stop sign but its going to be different the next time you stop. This is getting much worse, to the point that I have to set the idle at 3,000 RPM just to ensure it doesn't die if it decides to lower itself.

So today I was riding around and felt one cylinder stop firing (the tell-tale jerking). I pulled off and pulled each plug wire one-by-one. When I pulled the front wires, neither affected the idle. However, I was feeling the spark through my dearskin gloves. I grabbed an old plug and verified spark when connected to either plug wire against the cylinder. I then pulled the plugs out. They were wet but when I plugged them into the plug wire and held them against the cylinder after a field cleaning they did spark. In addition I could see the adjacent plug firing through the plug hole (it was dark).

I then started the bike up again. For some reason I have to use a flood start procedure to hot start it (fuel valve off, full throttle). I noticed that the exhaust front cylinder was not hot (of course), but when I gave it throttle it would "kick in" and the exhaust would get hot (after cleaning the plugs).

So, at this point, I don't think I have an ignition problem. I haven't tried a compression check but the exhaust pressure is similar enough that I don't see the compression being low enough to off-line a cylinder. It really feels as though the front carb just isn't idling (probably too rich is my guess). The other day I put Sea Foam in it and it had sat for about 48 hours when this happened. So I'm thinking I should do one of the following...

1) Let the carb sit longer with the Sea Foam and hope it clears something out.
2) Pull the carb and clean it on the bench.
3) Adjust the carbs (I really don't know much about this)
4) Assume I've been idling too much doing all this testing and take it out on the freeway (and risk breaking down on the side).
5) Something else.

I'm curious what the group thinks.

-Robert
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post #2 of 12 (permalink) Old 12-15-2010, 11:30 PM
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Clean the carbs. That is my vote.

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post #3 of 12 (permalink) Old 12-15-2010, 11:36 PM
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I 2nd the vote for the carb cleaning. Make sure to get the pilot jet clean, just be sure to not jam anything hard up inside the jet, doing that can cause damage to the inside of the jet.

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post #4 of 12 (permalink) Old 12-16-2010, 12:41 AM
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If your plugs are wet, it's possible your float might be stuck and dumping fuel & flooding the cylinder. Try pulling out the drain screws from the float bowls and spraying some carb cleaner in there 1st and tapping on the float bowls with the plastic end of a screwdriver. It's worth a try before going through pulling the carbs. This sounds a lot like what I went through last year.

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post #5 of 12 (permalink) Old 12-27-2010, 04:57 PM Thread Starter
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Quote:
Originally Posted by shark88 View Post
If your plugs are wet, it's possible your float might be stuck and dumping fuel & flooding the cylinder. Try pulling out the drain screws from the float bowls and spraying some carb cleaner in there 1st and tapping on the float bowls with the plastic end of a screwdriver. It's worth a try before going through pulling the carbs. This sounds a lot like what I went through last year.
I do I identify the float bowl drain screw?

-Robert
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post #6 of 12 (permalink) Old 12-27-2010, 06:33 PM
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Similar problem with my VN750. The ethanol in the gas tends to screw up your carbs if the bike sits for any length of time. The dealer told me don't let the bike sit for more than three weeks to avoid getting your jets clogged. I let my bike sit too long and no amount of carb cleaner or Seafoam could solve the problem. Now I won't even let it sit for three weeks.

Clean your carbs. Any problems after that and you can begin to look at your electrical system. In my case the RR was bad, also.

Butch

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post #7 of 12 (permalink) Old 12-27-2010, 07:04 PM Thread Starter
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This is a '94 with 13K miles on it. I think that speaks for itself. Plus, there is nothing quite like California gas to destroy anything.


-Robert



Quote:
Originally Posted by hctublerub View Post
Similar problem with my VN750. The ethanol in the gas tends to screw up your carbs if the bike sits for any length of time. The dealer told me don't let the bike sit for more than three weeks to avoid getting your jets clogged. I let my bike sit too long and no amount of carb cleaner or Seafoam could solve the problem. Now I won't even let it sit for three weeks.

Clean your carbs. Any problems after that and you can begin to look at your electrical system. In my case the RR was bad, also.

Butch
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post #8 of 12 (permalink) Old 12-27-2010, 09:06 PM
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Quote:
Originally Posted by RobertGary1 View Post
(How) do I identify the float bowl drain screw?

-Robert
https://www.vn750.com/photopost/showp...o=2587&cat=670
This photo shows the distinctive shaped jet cover that is found on the bottom of each carb.
There is a drain screw and nipple on the reverse side.

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post #9 of 12 (permalink) Old 12-27-2010, 09:11 PM
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I had a problem with the Cal. emissions junk on my 06, but being in Tenn. I fixed it...
Not sayin thats your problem, just mentioning it as a possability...
Have a good one...Old Dog...

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post #10 of 12 (permalink) Old 12-28-2010, 04:17 PM Thread Starter
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My bike must not have been originally sold in California because it does not have the recirc fuel tank. The tank has vents on the rear that are just open. The California bikes recirc the fuel tank vapors back into the intake.

-Robert


Quote:
Originally Posted by Old Dog View Post
I had a problem with the Cal. emissions junk on my 06, but being in Tenn. I fixed it...
Not sayin thats your problem, just mentioning it as a possability...
Have a good one...Old Dog...
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