Couple questions - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 06-08-2018, 09:45 PM Thread Starter
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Couple questions

I'm trying to help a friend with his 03 750 vulcan. It hasn't been run in a couple years. So first thing I did was remove the carbs and cleaned them. Cleaned the jets, checked needles and seats. Replaced plugs with irdium plugs, have spark on all cylinders. Removed mouse nests from both air pods, there is no foam prefilter anymore.

Got it started, seems to start hard. It will not idle. 2500 rpm on up seems fine. Below that seems like I lose a cylinder and dies. Checked plugs, frt are fine, rear and black and soiled.

Questions: how important and the foam prefilters to it running?
Seems like a carb sync problem potential, agree?
Anything I'm missing?

Never got into a vulcan before so any insight would be greatly appreciated.
Thanks for the help
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post #2 of 10 (permalink) Old 06-08-2018, 10:22 PM
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Rear carb flooding? Stuck float valve (1st guess). Possibly float height too high, easy to check with a piece of clear tubing. Sometimes you can whack the sides of the carb to jiggle the float loose.

Dropping off at idle and coming alive at 2500rpm sounds like a clogged pilot jet, but you have to stop the flooding first to see if it goes away.

I forget what stock filters are supposed to look like, but just losing the pre-filter shouldn't matter.

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post #3 of 10 (permalink) Old 06-08-2018, 10:54 PM Thread Starter
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I agree that it sounds like a pilot jet issue not idling. I cleaned them both very well. All the holes in the jets. Checked that floats were working before I put them back in. Hooked up to my parts washer. Not to say that sediment from tank or lines couldnt have obstructed something again.

Float height, didnt mess with either of there heights. You mention a clear tube?
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post #4 of 10 (permalink) Old 06-08-2018, 11:27 PM
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Originally Posted by Deyo21 View Post
I agree that it sounds like a pilot jet issue not idling. I cleaned them both very well. All the holes in the jets. Checked that floats were working before I put them back in. Hooked up to my parts washer. Not to say that sediment from tank or lines couldnt have obstructed something again.

Float height, didnt mess with either of there heights. You mention a clear tube?
I've had a lot of floats/valves hang after a rebuild. So much that I'll give them a shot of wd40 before buttoning them up. First thing I do if they're stuck, is whack the carb with something that won't leave a mark or cave it in. It's worse if the carb is going to sit for a while before it gets used.

Doubt it's float height, but that's checked with a clear hose from the drain port. Best to see the pic in the manual, but I posted the pic here somewhere. You hold the hose up even with the line on the carb body and open the drain valve screw, the gas in the hose rises to the level in the bowl, which is supposed to be at the parting line on the crab body..

I would guess dirt from the tank if the pilot is clogged again. But it can all be from flooding.

Always a good idea to shake the float when it's removed from the carb, to see if there's gas in it. Plastic floats don't usually leak like soldered brass can, but they can be broken. If the float sinks, it never closes, carb floods.
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post #5 of 10 (permalink) Old 06-08-2018, 11:32 PM
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Did you strip both carbs and clean all the parts together, or did you keep the carbs and parts separated?

Slide needles are different front-rear. How much difference it would make, I'm not sure. Seems like it would make the rear carb leaner/front richer, but I can't say for sure.
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__________________________________________________ ____________
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post #6 of 10 (permalink) Old 06-09-2018, 12:43 AM Thread Starter
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The floats both worked properly when bench tested. I'll check them tomorrow. I kept all the parts separate for frt and rear carbs.
Sounds like I might just take them back out again and recheck everything.
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post #7 of 10 (permalink) Old 06-09-2018, 08:12 AM
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Sounds like your idle circuit is messed up. Did you remove the plugs covering the idle screws, pull them, and get some carb cleaner in there? Here's a link that has a little more detail. . . .

https://www.vn750.com/forum/22-carbs-...ml#post1262722

My bike has foam air-cleaner elements only. There is no paper element. . . . I doubt mine would run right without the foam.

Good luck!

GDI

Last edited by GDI; 06-09-2018 at 08:15 AM. Reason: added comments about air-cleaner
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post #8 of 10 (permalink) Old 06-11-2018, 04:16 PM Thread Starter
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Update, pulled carbs today. Sure enough rear float is stuck open! Any trick to prevent this??
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post #9 of 10 (permalink) Old 06-11-2018, 05:50 PM
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Update, pulled carbs today. Sure enough rear float is stuck open! Any trick to prevent this??
I usually give the needle valve a shot of spray lube, and hold the carb upside down to put the bowl back on. Then I try to get gas in it as soon as possible.

Was the float itself stuck on something or the needle valve was hung up? If the float drops too low during assembly, the valve can tilt over sideways.

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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #10 of 10 (permalink) Old 06-12-2018, 10:10 AM
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