So many issues - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #1 of 4 (permalink) Old 07-03-2012, 04:07 PM Thread Starter
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So many issues

So, I'm a new vn750 owner. Its actually also my first bike. Anyway, I'm currently getting backfiring and no startup when I try to start the engine, but let me walk you through how I got to that point....

1. Bought a 1994 vn750 off craigslist. Knew nothing about bikes but brought a good friend of mine who has been riding his whole life to check it out for me. It seemed like what I wanted: a bike that would get me through at least 1 season without any need for significant maintenance. A bike I could learn on without spending too much money or time on repairs. That was in April

2. I started to get a very slow leak around my fuel tap. I noticed it but ignored it. Because I'm an idiot.

3. Over time, I noticed that I was having to choke the bike more and more to get it started. I blamed this on the cold weather we were having and dismissed it.

4. One day, it was nice and warm out and I couldn't get it to run even with a full choke.

5. I looked at the petcock and there was fuel gushing out. I figured that could be the problem.

6. I posted a picture of the leak on these forums, researched a little, downloaded the service manual, ordered a seal and diaphragm replacement kit off amazon.com, and stopped the leak.

7. It still wouldnt run, so I blamed the carbs. I decided it would be simple to take them out and clean them. I found videos on youtube. It should be no problem right?

8. I got all the hoses, cables and lines disconnected and tried to finagle the carbs out of the bike. I couldn't do it. It seemed like the radiator hose was in the way, and I, like an idiot, disconnected it, spilling antifreeze everywhere. I quickly reconnected it and looked around for another solution. I had never read that I'd have to drain the radiator to get the carbs out.

9. I found a vacuum hose disconnected all the way at the front of the bike. I figured, "a-ha" ,that was the problem all along. I reconnected it and put everything back together.

10. The bike still didn't run. Then, I realized that I had never touched the idle adjust. I ran it up and it started up like a champ. I took it out for a victory ride.

11. I went about 25 miles out and parked at a friend's place. I had dinner and came back out to find my bike dumping fuel out of a gash in one of the fuel lines between the petcock and the carbs. It apparently got pinched between the carb and the fuel tank when I reassembled my bike.

12. Since I was absolutely in the middle of nowhere and my friend had left while I was trying to start my bike and since I had no cell phone reception, I decided to try and make it home...

13. I rode 25 miles home, smelling the fuel spill on my left leg, knowing there were no gas stations on the way. Part way there, I was running on one carb when the other stopped getting fuel altogether.

14. I got home, took the tank off, cut the line short to get rid of the section with a gash, reconnected it, and tried to put the tank back on without pinching.

15. The next day, I went for a more conservative test ride. Same problem. Opened up a new gash. Then I realized: "If the fuel tap was shut off, it shouldn't have leaked right?"

16. I looked in the bag of o-rings I bought and realized I had left one out. I took apart the petcock and replaced the final seal- the disk with 4 holes that goes behind the handle.

17. I looked on this site for a cheaper alternative for fuel line than paying $20 a length for the official ones. I ended up buying 1/4" line from Autozone. Its a little smaller inner diameter but everywhere I looked online said it would work, but be a little stiff.

18. I replaced both lines and everything worked fine. For a while.

19. Over the course of a few days, I noticed that if warmed the bike up on its kickstand, setting the idle adjust so that, with no clutch, I was idling at 1200 RPM, as soon as I stood the bike up, it would shoot up. If I rode on it, at the next stop, I would be idling at 4-5k RPM. Then, I would roll the adjust down to 1200 and the rest of my ride would be fine. If I put it in neutral and set it on its kickstand at the end of my ride, it would eventually cut itself off if I didn't do it first. Then, the next time I started it up, still warm or not, I'd have to start the whole process over. Of course, I'm an idiot and didn't become alarmed yet.

19. Last week, I was 20 miles out and I had left my keys in the ignition.... The bike wouldnt start. Luckily, I got someone to jump me.

20. Of course, I was already running on reserve and wasn't going to make it home. I went as far as I dared and stopped for gas. I filled up and then prayed it would start. It didn't... I got one good turn over and then nothing on subsequent tries. I think if I had remembered to roll my idle adjust up, it wouldve started, but I didn't and it didn't.

21. I ask the attendant if he'd jump me. He said he'd just push start me. He talked me through it and successfully push started my first bike... Of I went.

22. First intersection I come to is uphill and I havent rolled down my idle adjust so I'm trying to hold in the friction zone against 4000 RPM. In the process of trying to hold the brake, clutch, balance, and reach for the idle adjust, I stalled out.

23. I called a friend to jump me and I got home.

24. The next day, I tried to start the bike and all I got was incredibly loud backfiring.

25. That's 25 steps to me feeling like an idiot and exposing my stupidity to the vn750 community, hoping someone will have a clue how to help me get my bike running

edit: wow- that's ridiculously long. I included everything because I don't know if little things I did along the way screwed me later on. You're a saint if you read the whole thing

Last edited by coasterboard; 07-03-2012 at 04:09 PM.
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post #2 of 4 (permalink) Old 07-03-2012, 04:28 PM
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OK, first and foremost, glad you replaced the fuel lines. You should have done that after the first time. They were obviously dried out and brittle, and if they broke once they were likely to break again.

Next, there could be an issue with the vacuum system. Since all the fuel lines were bad, it might be safe to assume the vacuum lines are also bad. Replace them.

Third, pull the carbs out and clean them out real good. While you have them out, check the jets to make sure they are right, and check all the levers (choke, throttle, idle adjustment) to make sure they are moving smoothly and correctly.

After that, someone else will have to suggest something because I'm still learning myself and don't know everything yet. But I would bet with some work you'll get it back to good working order.

EDIT: Oh, and another thing, there's a pretty good chance the charging system is having a problem somewhere. Either the stator or the regulator/rectifier. If the battery keeps draining so much that it won't start again after some use, it seems like it may not be getting recharged while the bike is running. Pray that it's only the R/R and not the stator, cuz the R/R is easy to replace; the stator means you have to practically pull the engine to replace (or use the tilt trick).

'95 Vulcan 750 - Purchased 8/2003 w/ 21,124 miles - passed 50K 9/3/15
* VN900 seat * Daytona handlebar * Converted ACCTs to MCCTs * Relocated R/R * Drilled clutch basket * Coastered * Repainted *

Last edited by DaveT319; 07-03-2012 at 04:33 PM.
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post #3 of 4 (permalink) Old 07-03-2012, 04:58 PM
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Sounds like a vac leak to me...I'm no expert though. Try a through carb cleaning and hook everything up. With the bike at normal.idle speed grab a can on carb cleaner w/ the straw attached. Start in one area and spray everywhere (carefully and only in small areas) to pinpoint your leak.
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post #4 of 4 (permalink) Old 07-03-2012, 04:59 PM
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Would like to add a few things that I have learned from the folks on this forum.

1). This bike has an electrical system that could of been designed a bit better. Its a bit weak. Not sure if its like this on most bikes but if the battery is a bit on the weak side it can be very hard to start, it takes everybit of the battery to operate the starter and have enough power for the ignition. With that said, what type of battery do you have and how old is it? A good maintenance free battery is what the folks recommend here.
https://www.vn750.com/forum/showthread.php?t=1062

2). Spark plugs, Have you had them out and seen what they look like? Maybe its time for a change there as well. Heres a link that someone asked about plugs
https://www.vn750.com/forum/showthrea...ht=spark+plugs

3). Seafoam. Instead of pulling the carbs try some seafoam first. Its a carb cleaner that you can get at the auto parts store. I would say use 1/2 the can in a tank of gas. Its more then usually needed but it could clean up the carbs on the inside. Then if you think your still having carb issues then you can try to pull them for a cleaning and new seals. Also can use seafoam every few months or twice a year of if the bikes gonna sit for awhile.

4). Hows your air filters? Make sure there clean and are not rotting out would not want them falling apart and getting sucked into the cylinders. I clean mine with dish soap and water, dry them completely then coat them in oil and ring them out good.

5). Theres a section of the forum called VERSES. It has lots of good knowledge and would be some good reading to help you learn a bit more on the bike.

Welcome to the madness, good luck and keep us informed how your doing.

Last edited by ifixf18s; 07-03-2012 at 05:04 PM.
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