Stalling above 5000 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 17 (permalink) Old 09-08-2010, 09:12 PM Thread Starter
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Stalling above 5000

So I just finished putting a new stator in. Works great. But now the bike wont idle or start unless I am giving it just a little bit of throttle. Then once I get it started it idles rough and if I try to accelerate it seems to accelerate just fine until about 5000rpm and then the rpms just drop off completely until I let off the gas. I trying to figure out if I need to pull the carbs or I am missing something obvious. Ive used some seafoam and screwed the mixture screws 2.5 turns out. It has cobra pipes ive just put on but that shouldnt matter I dont think. Hope you guys can help.
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post #2 of 17 (permalink) Old 09-09-2010, 11:45 PM Thread Starter
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So it seems that nobody has any ideas maybe this will give some help. I pulled off the gas tank just to verify everything connected correctly etc etc. Seemed okay. So just because, I decided to start the bike with just the carb fuel lines hanging there, no gastank, and see what happened. The bike ran just perfectly normal. Idled fine, reved up, no issues. Put the gas tank back on. Back to hard starts and holding the throttle to run. Does this sound like something in the petcock or gastank? The gas tank is full right now with a half can of seafoam.
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post #3 of 17 (permalink) Old 09-10-2010, 12:30 AM
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If you changed pipes it usually means you have to re-jet as well. I'm no expert on this bike yet, but I think the carb mixture screws only affect the idle mixture and not the high rpm mixture. I don't know what to make of the effect of pulling the tank off. Maybe it's set too rich and the lower fuel pressure is offsetting the change you made with the mixture screws?

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post #4 of 17 (permalink) Old 09-10-2010, 12:33 AM
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From what you're describing, it's possible the petcock may be clogged or gummed up. When the tank is near empty, look inside to see if there is any rust in it.

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post #5 of 17 (permalink) Old 09-10-2010, 09:27 AM Thread Starter
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There is definetely a little rust in it that i planned on getting out in the near future. Is there a way to clean the petcock if i remove it?
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post #6 of 17 (permalink) Old 09-10-2010, 10:14 AM
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I would clean the tank first, so you don't have bits of rust in the fuel. There are many ways to clean a tank. I used The Works toilet bowl cleaner, which is about 20% hydrochloric acid. Otheres use a muriatic acid, which is twice as strong. You can google the complete instructions. I believe one guy recommended drying the tank with acetone. DON'T! Just one drop on the outside of the tank and the paint is gone! Use WD-40 after rinsing the tank to prevent flash rust.

If the filter on the petcock is gummed up, soaking it in Sea Foam and using a very soft bristle tooth brush (if needed) should clear it. Just be sure not to tear the screen; it's not real substantial. If crud has some how gotten into the guts of the petcock, you need to disassemble and clean. If the diaphragm is torn it should be replaced. They sell petcock rebuild kits on ebay for around $26.

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post #7 of 17 (permalink) Old 09-10-2010, 05:08 PM
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Are the hoses all connected propperly? The carb vent hose has to go the the right ear, and make sure that it does not bottom out. Better yet cut the end at a ninety degree angle. This keeps it from cutting off the air flow.

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post #8 of 17 (permalink) Old 09-10-2010, 09:56 PM Thread Starter
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I'm keep hearing about the vent hose but am not sure which one it is? Where is it located on the carb? Currently there is no hose going to the right airfilter. I'll be checking the petcock and tank over the weekend.
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post #9 of 17 (permalink) Old 09-10-2010, 10:06 PM Thread Starter
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Well I found the vent hoses in the pictures so I'll see where that's going later.
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post #10 of 17 (permalink) Old 09-10-2010, 10:13 PM
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also see if the petcock will hold vacuum on the bottom fitting if not you will be starving for fuel with a vacuum leak. you do not need to rejet for pipes on these bikes. you only need to rejet for the earshave


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