Kawasaki Vulcan Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hi all-

Just picked up a '86 vulcan 750. it's been sitting for a number of years, so I went in and did all the usual stuff--cleaned the carbs out, fresh gas, fresh oil, fresh plugs, fresh(ish) battery.

When I hit the starter button, it turns over and it fires up, but it only runs while I'm still holding the starter button and then maybe for 1-2 seconds after I let go and then it dies. Definitely fires though, sometimes backfires. just can't get up to idle speed and stay running.

I'm going to go through and double check some stuff later--vacuum hoses, battery, probably try different gas, etc. But I figured that I should check here first and see if this is a common problem and if so what kinds of things I should check first. All too easy to like tear the bike down because it won't start and then realize the kill switch was of hehe.

Any thought on places to start troubleshooting?

thanks!
 

·
Registered
Joined
·
238 Posts
Did it run good when parked?

The first thing that comes to mind is the carb. Depending on how well you cleaned it out, there still may be some gummy stuff in the bowl, needles, etc. I'd definitely run some good fuel cleaner through it for the first couple tanks. Also, it could just be that your carb mixture screws are out of adjustment if they've been messed with. I'm not really sure where the standard starting point on a 750 is, but as a general rule, 2 turns out should at least get you somewhat close and you can adjust from there.
 

·
Registered
Joined
·
11,756 Posts
Hi all-

Just picked up a '86 vulcan 750. it's been sitting for a number of years,

thanks!
The above is the clue.

The carbs have to be torn down, cleaned, inspected, suspect parts replaced and adjusted to factory specifications.
Also, tank and fuel tap should receive the same consideration.

To do otherwise will just cause you grief and the job will have to be done correctly sooner or later. Might just as well do it now.
 

·
Registered
Joined
·
213 Posts
On the crabs, did you mess with the air/fuel mixture screws? Factory setings were approximately 2.5 turns out from being fully turned in.

Does the bike have the factory OEM air filters, or have they been removed and replaced with aftermarket filters such as K&N pod filters?

Make sure the filters are clean and properly oiled.

What kind of battery do you have? Is it a maintenance free battery (AGM/gel type?) the 750 are well known to perform poorly on Wet lead acid batteries.

Make sure all you ground cables are bolted down tight, and that the terminals are clean and not corroded.

What does your spark look like? Blue and strong, or weak and yellow? Another common problem with the 750, especially with the old wiring, is a loss of voltage at the ignition coils. you should be getting as close to the same voltage at the battery as possible ~12.6-13 volts on a fully charged battery.

If you want VERY bike specific quick and knowledgeable answers, I would recommend coming over to VN750.com. lots of good people over there who know a lot about these bikes and can almost definitely sort out the issues.
 

·
Premium Member
Joined
·
3,146 Posts
Check fuel lines and replace fuel filter as well. Gasoline that sits for a long time solidifies and becomes gummy.
 

·
Registered
Joined
·
213 Posts
the 750 didn't have filters on its fuel lines, (unless you count the screens on the petcock straws) but definitely not a bad idea to add a filter to each of the fuel lines.

Another thought.... Make sure the idle adjust screw is turned in far enough.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #7
Hi all-

Thanks for the feedback and replies. After a good amount of searching and troubleshooting, i realized that there was a tiny bit of bare wire grounding to the frame. letting enough through to start it, but not enough to keep it going I guess.

Fixed that, so it's better but I'm still having similar problems. Now I can get it to idle at a relatively low speed.... like 900RPM or so. It will idle for a good minute before it dies, but the RPM's never go up and I can't throttle it or it will die. Same goes for the idle speed screw... open it up too much and it'll die.

WHile it idles, I was listening for anything that might be wrong. I am now realizing that there's a hissing coming out of the left carb. Sort of like a leaky-type hiss sound. Right carb seems to have the same noise but much fainter.
I'm really hoping that this isn't like a torn vacuum boot or something. those carbs were a real stinker to get off and get back on. Any chance this is normal? Or is there other stuff I should check before I take the carbs off yet again?

I'm going to go through and like check the intake boots and try to pinpoint the sound a little better before I tear it down again, but in the meantime, wanted to ask the experts :)

Thoughts? What could this hissing noise be?

thanks!
 

·
Registered
Joined
·
213 Posts
Sounds like you don't have your carb boots aligned properly. They have to be positioned JUST right or they WILL leak. Also, you need to make sure that front is on front and rear on rear, they are slightly different.

There is a little nub/nipple on each boot that aligns with a similar mark on the head.

Check this post out for photos:
http://www.vn750.com/forum/showthread.php?t=70010
 

·
Registered
Joined
·
238 Posts
My 1500 is set up a similar way with 2 carbs. You'd think they'd be the same, but they are slightly different with different sized jets and all that nonsense. I never really understood the need for 2 carbs in the first place and then why they wouldn't be identical since the combustion chamber is identical as far as I can tell.
 

·
Registered
Joined
·
213 Posts
if memory servers me correctly, the carbs were pretty much identical on he 750. At the very least, they came stock with the same jets.

I agree about the 2 carbs being unnecessary. There has been talk for quite some time on the 750 forum about modding the bikes out to a single carb. and there is only 1 guy that I am aware of that actually successfully did the mod. He actually posted the results of the mod on this forum in the 750 section. Looks pretty cool, and seems like it would be a LOT easier to deal with
 

·
Registered
Joined
·
238 Posts
I looked around a little bit for some bolt-on FI systems (TBI system mostly) I could drop in my 1500, but didn't find anything reasonable, much less, cheap enough to make it worth while.
 
1 - 11 of 11 Posts
Top