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Old 10-21-2007, 12:43 AM   #1
Tobey
 
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Vulcan 500 Cylinder Misfire

I have an '05 Vulcan 500 (parallel twin). It was stored all summer, so it didn't surprise me much when it wouldn't start. It ran just fine when I parked it.

I cleaned the carbs, and put in new plugs, and it will now idle, but won't rev at all. Twisting the throttle doesn't make it die, but it won't rev either. I made sure the pilot jets and the main jets were clean. The new plugs look OK. The most visible symptom is that one cylinder isn't firing well. It takes 30-40 seconds for the exhaust pipe to get hot (I'm talking about within 8" of the engine). Also, I think I'm hearing an occasional backfire through the carburetor while it's idling (indicates lean condition, right?).

My plan for tomorrow is to pull the carbs again, clean everything again, then swap the pilot and main jets and see if the problem follows the jets. If not, I'll swap coils and see what happens. Anything else I should be looking at?
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Old 10-21-2007, 01:36 PM   #2
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Re: Vulcan 500 Cylinder Misfire

Symptoms do sound like a lean condition.

Check the fuel level in each carb.
Sit the bike upright (or as close as you can since there is no centerstand)
Set the petcock to PRI
Attach a clear hose to the bowl drain and turn the other end up higher than the carb.
Open the drain screw.
The fuel will flow into the hose and settle at the same level as inside the carb. It should be about the same as the bowl gasket surface.

What does the spark plugs look like?
Air filter and housing ok? Pests have been known to move in to an air filter housing that sits dormant.

If you need parts, let me know before you run off to the dealer. I have a 2001 parts bike in the garage.
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Old 10-21-2007, 02:05 PM   #3
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Re: Vulcan 500 Cylinder Misfire

Thanks for the tip on checking float height. They're both good.

I've got it running on both cylinders now. It idles perfectly. It will rev, but if you open the throttle too fast, it bogs really bad, stumbles a bit, then revs up. I'm going to spike the gas with Sea Foam, and ride it around the neighborhood for a bit.

Thanks again for the help. Once I get it running good, I'm selling it. I don't need a second bike.
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Old 10-21-2007, 02:17 PM   #4
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Re: Vulcan 500 Cylinder Misfire

Be sure the fuel, vent and vacuum lines aren't pinched or kinked.
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Old 10-21-2007, 04:47 PM   #5
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Re: Vulcan 500 Cylinder Misfire

Did you actually pull the pilot jets and examine them under a magnifying glass. I had a similar problem once; thought I had them clean. A closer inspection showed build-up that I wasn't seeing at first.
If you pull just a fraction of choke on, does the problem get better?
does it have rubber intake boots between the carbs and cylinders? Maybe a leak there?
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Old 10-21-2007, 06:13 PM   #6
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Re: Vulcan 500 Cylinder Misfire

Quote:
Originally Posted by Tracker View Post
Did you actually pull the pilot jets and examine them under a magnifying glass. I had a similar problem once; thought I had them clean. A closer inspection showed build-up that I wasn't seeing at first.
If you pull just a fraction of choke on, does the problem get better?
does it have rubber intake boots between the carbs and cylinders? Maybe a leak there?
Not under a magnifying glass, but I can see daylight through the hole. One of them was completely clogged, and it quite a bit of effort to knock the stuff out. Any tips on cleaning them? I put the jet in a drill, and while spinning it fairly slow, ran a single bristle from a metal brush in and out. And yes, it runs better with the choke on. However, even when I get it to rev, there's no real power. The Italian tuneup did no discernible good. All signs still point to lean.

With the jet out, I sprayed carb cleaner through the mounting hole, and got a good spray out the carb throat.

The gas has only been in there since June; I guess I could drain it, but I doubt that's my problem.
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Old 10-21-2007, 06:52 PM   #7
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Re: Vulcan 500 Cylinder Misfire

I would say gas starts to go bad after 60-90 days. I would throw a little seafoam in if you think it's going to sit more than 30 days, especially with them putting ethanol in gas these days.

Gas would go through mine, but not at the rate required because of a partial clog. I'd be afraid of resizing a jet with a drill bit. I've heard of using guitar strings and bristles out of a broom. I ran aerosol carb cleaner backwards through my pilot jets until they looked nice and clean.

If it runs better with a little choke (after warmed up) then you have a lean condition for some reason. Was there sediment in the bowls when you cleaned it. Any evidence of rusting in the tank?
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Old 10-22-2007, 10:15 PM   #8
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Re: Vulcan 500 Cylinder Misfire

Just to be clean, I didn't drill it out. I mounted the pilot jet itself in the drill chuck to spin it, then ran a bristle from a brush in and out. Followed by a liberal application of aerosol carb cleaner. I'll pull the carbs again one night this week and try again. I'll also drain the tank and refill it with fresh gas, just in case.

There was a little sediment in the bowls, but no signs of rust in the tank.

Thanks for all the advice; I'll get this thing running yet.
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Old 01-29-2008, 10:45 PM   #9
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Re: Vulcan 500 Cylinder Misfire

All right, picking this back up. It obviously hasn't been a priority.

Current Symptoms:
-Starts and idles perfectly. After it warms up a minute, it idles with the choke off.
-With full choke, it will rev, and sounds good.
-With half choke, it will rev, but barely. If I'm easy with the throttle, and get the RPMs up (don't know how high; no tach), it smooths out and runs clean. This is on the kickstand; no load on the engine.
-With the choke off, it will barely come up off idle.

All signs still point to it being lean. The pilot jets are spotless. I pulled the pilot screws, cleaned the passage, reinstalled them 1.5 turns out. Tried backing the pilot screws another turn, and it made no noticeable difference.

Is there anything else, specifically, to look at before I haul it to the dealer? The carbs are dang near spotless; maybe there's a little passage I missed or something?
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Old 01-29-2008, 11:03 PM   #10
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Re: Vulcan 500 Cylinder Misfire

sounds like you've got them clean.

my VLX was very cold natured. It would spit and backfire for 5 minutes if you got on the throttle at all, even with the choke on. I'd try opening the pilot screws a 1/4 to 1/2 turn and see if that helps. Once I put the dynojet kit in it, it only took about 30 seconds on choke. The factory setups are usually very lean to make the EPA boys happy.


Does it get any better once it warms up really good?
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Old 01-31-2008, 08:44 PM   #11
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Re: Vulcan 500 Cylinder Misfire

Here's something peculiar that happened to my bike.

After not being ridden for a few weeks, I prepped the bike for ride. Set petcock to PRI. Let the bowls fill. Cranked and the engine fired up, but only on one cylinder. Obviously, it didn't want to rev and idled very rough. The right carb would not fill up with fuel until I lifted the bike off the sidestand and leveled it. After doing that, it smoothed out and all was fine.

Of course, since you're getting both cylinders firing and have gas in both carbs, this isn't the problem you're having.

Almost sounds like the ignition timing is off (but it's not adjustable) or a valve is hanging open.

Is the air filter in place? Since the jetting is lean, the lack of a filter may be the deal breaker.

This bike doesn't have a factory fuel filter and when I tried to add an inline on mine, it didn't like it. It would act like it was out of fuel after 30 minutes of riding. After I took it off, it ran fine.

I'm scratching for ideas here......
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Old 02-01-2008, 01:00 PM   #12
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Re: Vulcan 500 Cylinder Misfire

Quote:
Originally Posted by dukey33 View Post
Is the air filter in place? Since the jetting is lean, the lack of a filter may be the deal breaker.
Actually, I left it off to facilitate taking the carbs on and off. I'll have a chance to work on it again tomorrow. I'll put it all together right, and see what happens.
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Old 02-11-2008, 12:59 PM   #13
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Re: Vulcan 500 Cylinder Misfire

Sounds like carbs are still dirty. Sometimes you have to clean em out more than once.

I'd drain the gas from the tank, put it in the mower or something. Put good gas in it, clean those carbs out all over again. I've found modern gas starts to get noticeably bad after about 3-4 months, terrible by 6 months.

Varnish/sludge can build up in the fuel line, the petcock, the screen in the tank etc. and keep coming loose for a while and getting in the jets etc.. I've had to clean out carbs a few times due to that.

The best gum/varnish cleaner I've used is B12 Chemtool in the pour in can. Just don't use too much as that stuff will eat a lot rubber parts if it's too strong. You might be able to dose it with B12 with a gallon or two of fresh gas and go ride that gallon out and then some, don't let it it sit up for months with B12 in the tank. If it starts running a little better after 10 miles keep it up until it cleans out.
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Old 02-11-2008, 09:05 PM   #14
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Re: Vulcan 500 Cylinder Misfire

Quote:
Originally Posted by Tobey View Post
Actually, I left it off to facilitate taking the carbs on and off. I'll have a chance to work on it again tomorrow. I'll put it all together right, and see what happens.
leaving the breather off will make it run very lean. That's why you usually have to rejet with K&N Pods or any major airbox mod that improves airflow. My VLX would backfire and bog in a serious way if the breather was left off--even if it was warmed up.
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Old 03-09-2008, 12:26 AM   #15
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Re: Vulcan 500 Cylinder Misfire

Next to last update. Another cleaning, put it all back together, with the air cleaner, another set of new plugs, and no improvement. Start and idles, although not smoothly, and dies when you give it gas.

So I've sought professional help. It's at the Kawasaki dealer in Pasadena. I'll report back with the results.
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Old 05-18-2008, 10:11 PM   #16
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Re: Vulcan 500 Cylinder Misfire

Tobey,
any update on this? I am having the exact same problem... Thanks!

Jason B
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