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Discussion Starter #1
Hi its been a while since I been on here. My Vulcan has been giving me some issues lately after rebuilding the carbs and re-jetting from the ear shave procedure I did last year. I thought putting in new jets would help it run smoother, and I felt like it was true. Lately I have been having serious issues getting my bike to turn over. Just crank, crank, crank, crank, until the battery dies! Every morning I have had to give up with a dead battery and a few backfires and just go to work in my truck. I'm losing it with this thing. I had it running smooth enough with the stock jets, it felt a little erratic and lean though...

I was wondering if I made a mistake rejetting my carbs, I used the recommended sizes I found in every guide in this forum, the 142 mains and 42 pilots. I also shimmed both needles with 2 shims each. I have the pod filters, but I don't have any kind of exhaust mod. My spark plugs are very brown, not black, I was wondering if that was a bad sign too. I can get one good spark after freshly removing a trickle charger but that's it. I even replaced my battery today with a new one from the store! I'm at my wits end with this bike. I'm so close to just ditching it. I thought I would give it one last shot here and ask if anyone knows what I should do here.

Thanks.
 

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Just looking at the numbers, it's probably too rich.

But, need to find out if it has spark or is just flooding out.
 

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Discussion Starter #3
I manage to start it the first time I try fresh off the charger, but afterwards I can't reliably start it. Sometimes I get a loud backfire as well. I just replaced the plugs last summer, so they haven't been in there a full year yet. Do you think I should switch my jets back out?

Another thing I should mention is that for some reason it only really wants to start when I have the throttle adjustment knob turned WAY up.
 

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Not sure what you're calling the throttle adjustment knob?

A cold engine can use more fuel, as it warms up it can flood out if it's too rich.

Have you checked to see if there's spark?

My bike is earshaved with stock pipes and stock jets.
 

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Discussion Starter #5
I do have spark, so that's not the issue. The throttle adjustment knob is right near the fuel petcock. The more you turn it towards you the higher the idle. Idle adjustment knob maybe? Idk
 

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Ok yes, idle adjustment. If one cylinder isn't firing the idle needs cranked up 50% more, so you may be only running on one cylinder.
 

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I ran 40/140 jets with an earshave and no mufflers. 42/142 is probably too rich. When I put the mufflers back on, I had some rich misfires at WOT. What choke setting are you using? 42/142 might start fine cold with no choke.

The ignition system is a bit weak on this bike. The fact that you only get a spark on a topped off battery, but not later, implies an electrical issue.

Check your ignition coil resistance.
Check the voltage at the coil primaries.
Check the resistance of your spark plug wires (I had an old wire arcing to the block). I posted a good source for new wires about a year ago on this forum.
Check for corroded connections at your coils.
Consider doing a direct coil mod and a ignition pick-up mod.

People have also reported improvements with hot-starts using iridium spark plugs. I just switched to Denso Iridium Power plugs (IX22B) and it seems to have helped hot start issues.
 

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Discussion Starter #8
Now that you mention it I think I'm probably opening the choke too wide. I'm not sure if there is an electrical issue though I got it started with a partially charged new battery.
 

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Now that you mention it I think I'm probably opening the choke too wide. I'm not sure if there is an electrical issue though I got it started with a partially charged new battery.
Jason is correct, it will probably start in winter without the choke.
 

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Discussion Starter #12
Put the stock jets back in. The trickle charger was on the battery the whole time. I started the bike, no luck. I jumped the bike with my truck and it started right up. I then checked the battery, rode it, and checked it again. The voltage has been steadily declining as I rode it. Seems it just isn't charging the battery anymore.
 

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You think it was running on a dead battery? So charging issues and a re-jet. ??
 

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Discussion Starter #15
My brand new battery was dropping voltage while the bike was running. I'm thinking this is electrical.
 

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Do you have a copy of the service manual to check the stator? It could be the rectifier as well. Stator replacement is QUITE a job, while rectifier replacement is comparatively easy. It's easy to check with a multi-meter. Spockster has a link to it in his signature.

If you do replace the stator, look in the electrical forum for information about the Tuxedo mod. I did a variant on that on my bike that went pretty well. Unfortunately, I had an entirely unrelated issue seize the engine before I could get significant time on the mod (A valve dropped into the piston while running!!!).

My variant:
https://www.vn750.com/forum/19-electrical/105465-tuxedo-mod-tips.html

The difference is that my version retains the ability to remove the side cover and it uses the factory gaskets instead of gooping on a liquid gasket. I never solved an alternate route for the wiring, as my original stator was still working. I did the mod since I already had the engine out and I didn't want to have to pull the engine in the future.
 

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Discussion Starter #17
Do you have a copy of the service manual to check the stator? It could be the rectifier as well. Stator replacement is QUITE a job, while rectifier replacement is comparatively easy. It's easy to check with a multi-meter. Spockster has a link to it in his signature.

If you do replace the stator, look in the electrical forum for information about the Tuxedo mod. I did a variant on that on my bike that went pretty well. Unfortunately, I had an entirely unrelated issue seize the engine before I could get significant time on the mod (A valve dropped into the piston while running!!!).

My variant:
Tuxedo Mod Tips

The difference is that my version retains the ability to remove the side cover and it uses the factory gaskets instead of gooping on a liquid gasket. I never solved an alternate route for the wiring, as my original stator was still working. I did the mod since I already had the engine out and I didn't want to have to pull the engine in the future.

Got good news. It isnt the stator. The readings from the stator wiring are fine. I ordered a new R/R and I'm gonna see if that does the trick. Either way I'm putting the bike up for sale soon.
 

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