New Vulcan owner - getting it running - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 6 (permalink) Old 04-12-2013, 11:53 AM Thread Starter
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New Vulcan owner - getting it running

Hi Team,

I thought I would pull this thread from the newbie section and continue it here. I got the bike home and finally got a chance to play with it, I pulled the tank and hooked up an auxiliary tank with a T fitting and got the same poor running -starts on choke but dies with any throttle opening or choke disengaged-. I applied vacuum to the petcock and fuel flowed well. After this I moved to another project for a while.

I did a number of trouble shooting tricks but wasn’t really keeping track, but here is the sequence I think I did.

I started it again with the aux tank on and this time plugged the vacuum line and it revved up like it should! WTF?? I put the tank back on and tried again, started it with the petcock on reserve with the vacuum line and it went back to original poor running condition. I pulled the vacuum line and as soon as I did it started running well again.

The problem is, now it started pouring fuel from somewhere on one of the crabs. I cut it off, dried the gas and for some reason decided to blow into the petcock vacuum line. I tried it again and it seems the fuel leak has stopped, but it still runs poorly if I attach the vacuum line on the petcock or don’t plug the vacuum line if it is unplugged.

It also started rattling from the rear cylinder at high RPM, I decided now might be a good time to add fresh oil and filter. As I feared, I think there was gas in the oil so it's definitely a good time to change the oil. I now know that it has a mechanical time chain tensioner as opposed to hydraulic so thinned out oil wouldn’t cause tensioner failure. I found the Grambo Trick write up and the Carb Blowback write-up.

My plan it to add fresh oil and filter, double check for vacuum leaks and do both of the tricks above. If the problems aren’t fixed by that, I will probably pull the carbs... I will also keep better track of my steps.

The tips I already received are appreciated and any more advice or tips are also appreciated

Cheers!
S

Quote:
Originally Posted by Betteron2wheels View Post
Hi Team,

I'm picking up new-to-me '94 today. The previous owner(PO) did a lot of the fixes such as using the correct grease on the DS splines and a few electrical system mods. I checked it out last week, got it to start with the choke on but it dies if the choke is cut or any throttle is applied. He says he cleaned the carbs but the problem persisted. My 1st step will be to wrestle the carbs off, take them apart and ensure all of the parts are there, give them a complete cleaning including a sonic bath and hope that does the trick. Other than that it's pretty clean, the tank is rust free on the inside but has a couple of dings, it has a wind screen and saddle bags and he gave me an inch+ thick folder with new part receipts and maintenance history.

I haven’t had a chance to get through this forum to discover all of the easy mods but it already seems like there’s plenty. Looks like it’s going to be a fun bike, it might be just the right size for the fiancé.

Cheers,
S

Quote:
Originally Posted by Wolfie View Post
Welcome to the forum !
As for your issue...check the idle screws on each carb. The might be turned in too much. Also check for vacuum leaks. The petcock is vacuum actuated, and may not be allowing enough fuel to flow...heck...check the flow first....disconnect the center thin hose from the carb (vacuum liine)..attach a longer one of same diam...remove the fuel lines one at a time and suck on the hose (you wont get gas in yer mouth)...this will show you the fuel flow. If its fine, search for a vacuum leak.
Also, there is a black, knurled plastic knob on the left side by the carb. Thats an idle speed adjustment.

2004 Dr 400
2004 VFR800
1983 Virago 750 “under construction”
1994 VN750 - Purchased Feb ‘13, Doesn’t run, in project “queue” to fix
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post #2 of 6 (permalink) Old 04-12-2013, 12:02 PM
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This is just a shot, but one thing to check:

I'm wondering if the petcock could be leaking fuel into the vacuum line? You could start it once, then check right away to see if the inside end of the vac line is wet.

On the fuel overflow, sounds like a float was stuck and you were able to free it.
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post #3 of 6 (permalink) Old 04-12-2013, 02:50 PM Thread Starter
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Spockster,

Good idea, while drafting my last post, it occurred to that the petcock could be faulty. I'll take your suggestion and check the line; It could be a stuck float, but I didn't do anything to cause it to free up. I hope it's a simple fix because I really don't feel like doing a carb service. I'm going to try to spend time on it tonight.

Cheers!

2004 Dr 400
2004 VFR800
1983 Virago 750 “under construction”
1994 VN750 - Purchased Feb ‘13, Doesn’t run, in project “queue” to fix
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post #4 of 6 (permalink) Old 04-15-2013, 01:27 PM Thread Starter
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Team,

I went ahead and ran the bike then checked the vacuum line; it did have gas in it. When I sucked on it I could pull air through it. I set the idle-air screws to 2.5 turns out, did the carb blowback and the Gambro trick which fixed the rattling cam chain!

I decided to drain the fuel and take the petcock out; at 1st I tried to drain it through the petcock and discovered that the flow was not consistent.

I would apply vacuum and fuel would come out the rear outlet and had bubbles (indicating an air leak in the petcock or the hose) and required constant-additional vacuum. Another time it would flow from the front with no bubbles and require no additional vacuum such that I could plug it with my thumb and it would still flow. It would switch when I released vacuum. Either way it was slow going so I siphoned the rest from the top.

I stripped the valve and cleaned it, added a diaphragm from an ’83 Virago, lubed the o-rings and reassembled it. Now it has positive-stop on the vacuum inlet, meaning I can hear the plunger move and not pull any more through it.

Here’s where I get confused (again); after putting the petcock back on the tank and running it, it runs poorly and backfires and still leaks fuel. I pulled the vacuum line and there was gas in it again. Hmm, I started it again with the vacuum line of and fuel leaked out of the carb vacuum outlet. This is when I got frustrated and called it a night.

I noticed in the Carb photos and label post that each carb has a vacuum inlet as well. I’m going to check that tonight and see what’s attached to it and try to blow-back the carbs again.

---Is there a vacuum diagram available on this site?---

Cheers!

2004 Dr 400
2004 VFR800
1983 Virago 750 “under construction”
1994 VN750 - Purchased Feb ‘13, Doesn’t run, in project “queue” to fix
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post #5 of 6 (permalink) Old 04-15-2013, 05:51 PM
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Sounds like the float is stuck on the carb with gas flowing out of the vacuum port. Possibly some very judicious tapping with a wood or plastic hammer or screwdriver handle might un-stick it. Hard enough to shake it real good, light enough to not break the carb or intake rubber. Sometimes carbs will do this after being drained, but usually don't stick again unless there's trash in there.

The vac line on the rear carb goes back to the valve for the air injection/emissions plumbing. The line off the front carb goes to the petcock.
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post #6 of 6 (permalink) Old 04-17-2013, 09:41 AM Thread Starter
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Tapping the float didn't help, I went ahead and did what I should have done from the beginning which is pulling the carbs and giving them a good clean. I've cleaned many carbs and these were the biggest PITA to remove. How Kawasaki could make it harder than removing V-4 carbs I don't know, I suppose part of it is the non-conventional float setup. Anyway, I got them off, stripped them and gave them some time in the sonic cleaner (If you clean more than 1 set of carbs a year I highly recommend getting one) and reinstalled. It fired right up more easily than ever; but, it's back firing and blowing a lot of smoke. I don't have the intakes or the vent hoses hooked up to the air box yet and I need to make sure the air-idle screw is set correctly before I worry about it--hopefully tonight.

More to come, Cheers!

2004 Dr 400
2004 VFR800
1983 Virago 750 “under construction”
1994 VN750 - Purchased Feb ‘13, Doesn’t run, in project “queue” to fix
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