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Discussion Starter #1
Well, sort of. I got a 1997 VN750A from a friend of mine for free. It turns and has been run off of some starter fluid once or twice but needs serious TLC. So anyway, today I hooked up the carbs. I had to put on a single-port petcock from ebay, sadly, so I had to tee the fuel lines and then have a long-ass hose for a fuel filter. I got all that hooked up, and the vacuum hoses (though I need replacements, I need some help with that) are connected. I however could not find the hoses for the two middle nipples on top of the carb. The one that has an OEM Tee, my buddy never gave me those hoses. So anyway, all that's hooked up and I try to fire it up... Nada. The gas is flowing, but only one side of the carb so far has any fuel in the bowl drain. The other side is dry as a bone. Not only that, but apparently my battery lost its charge over time in the cold from the garage, so it won't fire that way at all. What am I missing, or what should I look for and do the next time I go over to start fixing it up?
 

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Could be a stuck float/needle? A bit of judicious tapping on the side of the bowl might be enough to loosen it up.
Have you checked for fuel in the line going into the dry carb to eliminate a crimped hose, clogged T branch etc?
 

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Discussion Starter #3
I checked and none of them were crimped. It's possible it's a stuck needle and I'll give it a tap to see. This is the first time in a while it's had gas flowing through a tube at all so is it possible that gas hasn't gotten into the float yet? The hose I used is a bit longer than stock, by like 5 inches. Having to tee the hoses also may not have been proper. Not sure.
 

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I've heard different opinions about a T after the petcock, but unless you're REALLY pushing the fuel through the engine at high RPM it shouldn't be a problem.
 

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FREEBIRDS MC CENTRAL NY
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can you blow through the hose on the carb not getting fuel?

Sent from my LGL34C using Tapatalk
 

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Discussion Starter #6
Hey all! I just got back from visiting the bike to work on it. I got it fired up and it will run, but only with throttle. I also have no choke cable so it's even harder to work with honestly. Anyway, both cylinders ran fine, which leaves me wondering how gas is getting to the dry one. Another issue that's cropped up is that over time fuel just won't deliver through the hose and in-line fuel filter, it just goes dry. I'm using the setup I attached for it, let me know how awful my job was. I believe one of the vacuum hoses is blocked up a bit but I'm unsure. I've also yet to blow into the hose for the dry carb, so I'm not sure about that one either. I need advice on how to get her to idle, mainly. I can set the bike's fuel back up, but I don't want to get excited and then have to take it all off again.

So! Main question: How can i get her to idle AND run on throttle properly? Is my hookup to blame? My carbs? Or something I'm missing?

Fuel lines in question: https://imgur.com/gallery/CBqkJgc
 

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your fuel line is to long/ run poorly. the carbs are gravity fed not vacuum. so shorten the line after the filter and run it more horizontal. the less the fuel has to climb the better.
 

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Shorten the hoses so they all run downhill, it's trying to gravity feed through that hose that is looped down, then upward.

The filter isn't helping fuel flow. Some have been able to use a filter, others have to remove them to get flow.
 

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Also, check that filter to see if there's an arrow for flow direction. Looks like it's backward, it's filtering from the inside out. edit: Maybe it is the right direction ... If the hose looping down the front cylinder is coming from the petcock.

edit: The hose sizes don't look right to me, but it might be the picture. The line on the filter looks like the larger automotive size, (maybe 3/8"?) and back toward the carbs it looks like smaller windshield washer hose size (1/4"?).
 

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Discussion Starter #10
Nope, the hoses running from petcock to filter to carb tee is 1/4", then the two branches into the carb nipples are 5/16" OEM hoses. I'll take into account the hose length. I thought it was vacuum fed though? Otherwise what's the point of vacuum hoses and, you know, the petcock not having an off option.
 

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Nope, the hoses running from petcock to filter to carb tee is 1/4", then the two branches into the carb nipples are 5/16" OEM hoses. I'll take into account the hose length. I thought it was vacuum fed though? Otherwise what's the point of vacuum hoses and, you know, the petcock not having an off option.
The vacuum just opens the diaphragm in the petcock, the gas is gravity fed to the carbs. It should run better when the hoses are leveled out.

If that fails to help, I would try it without the filter.
 

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Discussion Starter #12
For real?? Strange, actually. Guess that's how it's possible to make the petcock into a manual. I'll try that next time, taking off the filter and running straight hose, preferably not too long either.

However that still leaves one dry carb bowl and a potentially sticking float needle/pilot jet. Is it possible to fix that without removing the carbs again? I really hated doing that last time.
 

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the petcock is vacuum operated, a small vacuum actuated valve to allow fuel to flow when the engine is running. you said you replaced yours with a single, was it the Yamaha replacement mentioned on here? If it is I don't think it is vacuum actuated, so you can cap those lines without any problem.
 

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Discussion Starter #14 (Edited)
It's the Yamaha one, it's off of Ebay and it's 100% vacuum actuated. So what I'm going to do next time, is hook it up like I did before, and shorten the hose and ditch the inline filter until I can get a smaller one. If it still refuses to run and idle, it's an idle jet problem. So can I run Seafoam into it and try that to clear it up? Or is there a way to clear those jets without carb removal? All I need to do is get it running and idling, then I can finish the front end issues and get it running properly.

This is the one: https://www.ebay.com/itm/Kawasaki-Vulcan-750-VN750-Fuel-Switch-Valve-Petcock-Assy-1988-2006/182210774850?epid=2268615849&hash=item2a6c9bc742:g:2T4AAOSwRgJXjhRc&vxp=mtr
 

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It does look like the earlier Kawi with the 'prime' setting. Have you tried it on that setting? 'Prime' setting opens the petcock manually, bypassing the vacuum, so the carbs can fill up. With the newer (no prime) petcock we have to use short bursts of the starter to build vacuum and get the fuel flowing. One carb tends to dry out while setting a week or so.

Seafoam can help if you catch it before the jet clogs shut, if it doesn't flow through, seafoam can't do much. About mid-season I catch mine starting to act up, and the correct dose of seafoam clears it up in about 1/2 a tank.

If the jet is clogged, you'll have to tear them down and clean the jets and passages. Pretty sure I left mine bolted together, might have even left the cables on.
 

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Discussion Starter #16
Alright, sounds like I'll need to take off the carbs again. This time I'm paying someone else to do that pain in the ass, I don't have the patience for that sh** this time. For around 300 he can work magic.
 

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Don't blame you. I just recently sold a 75 KZ400 because of the carbs. She was immaculate when I bought her. Only issue was the tank was rusted inside, bad. I did the Caswell kit and the tank came out great. Yet I couldn't get the carbs to stay good. Tried flushing it, sea foam, replacing lines and filters, new kit for petcock, leveling the gas in the bowls, sucking/blowing out various tubes. I'd be golden for about 2 weeks then I'd be left stranded in the middle of Oakland. I didn't want to deal with those carbs nor try to win a kit on eBay. They were/are going for crazy money.
 

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Discussion Starter #18
That sounds awful. I know a guy who could help me out for the carbs pretty well, but he's a last resort. The carbs are fine... Just not the one float valve, but that might be a simple enough fix.

Anyway, major question! I need to know what size vacuum line to get from Autozone to replace the OEM vacuum line of 5.3mm. I imagine it would be either 3/32, or 5/32, but I'm not sure. I just need a second opinion.
 

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That sounds awful. I know a guy who could help me out for the carbs pretty well, but he's a last resort. The carbs are fine... Just not the one float valve, but that might be a simple enough fix.

Anyway, major question! I need to know what size vacuum line to get from Autozone to replace the OEM vacuum line of 5.3mm. I imagine it would be either 3/32, or 5/32, but I'm not sure. I just need a second opinion.
Size: ¼ “ Fuel Line ---3/16 “ Vacuum Line

I bought CLEAR line by the foot -off a roll @ Ace Hardware. Slightly stretchy with no clamps needed, but I did replace factory clamps on the carb connection ends. :carryflag
 

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Discussion Starter #20
Hey so quick update! I backblew the carbs with cleaner and air, and ran in some B12 cleaner. I managed to get it to idle really well, but turns out the front cylinders weren't firing. I just now managed to get all 4 firing, but not without choke. And now, when I try to add throttle it stalls out. Not to mention on Prime gas leaks from the vent hoses on the carb really quickly. I fixed the fuel lines so they're better off now, but it's still giving me issues.

Also! I have yet to clamp the boots to the carb and cylinders yet. So that may be an issue too. Need some pointers! I'm so close to being able to drive!!
 
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