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post #1 of 31 (permalink) Old 07-30-2017, 10:41 AM Thread Starter
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After Crash Repair

So recently, I had crashed my Vulcan 750, and am currently trying to repair it. I had to jump start it, which took a few tries. However, now when it was running, the oil light came on. I just wanted to ask what this light is for, level or pressure.

Also, it seems to run rough, & sometimes throttles itself slightly without me touching it. When the choke was fully open, it began shaking erratically until I put it down.

These are the first 2 problems I see, so what should I look at first here?
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post #2 of 31 (permalink) Old 07-30-2017, 10:46 AM Thread Starter
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It took a while to crank, so I don't know if I accidentally flooded a cylinder. Just now, I tried to start it, and it gave a loud pop out the pipe. Sound flooded?
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post #3 of 31 (permalink) Old 07-30-2017, 10:55 AM
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Sounds like idle rpm could be low, which can cause oil pressure to drop too low. The light is for oil pressure, but a low oil level can cause low pressure, tripping the light as well.

Not sure about what caused the rough idle. Describe it again using "Choke on/off", "choke open/down" has me confused. Choke on is pulling the lever back, choke off is pushing the lever forward.

Does sound like one cylinder wasn't getting enough fuel, so you got a low idle speed and rough idle.

What happens if you give it throttle?

Does the oil light go out when you rev it higher?

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #4 of 31 (permalink) Old 07-30-2017, 10:57 AM
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Quote:
Originally Posted by SergheiS View Post
It took a while to crank, so I don't know if I accidentally flooded a cylinder. Just now, I tried to start it, and it gave a loud pop out the pipe. Sound flooded?

On this bike, that's usually a sign of low voltage during cranking, or a really lean condition such as opening the throttle during cranking.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #5 of 31 (permalink) Old 07-30-2017, 11:28 AM Thread Starter
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I meant it with the choke pulled back, as in to open it up on a cold start. It would idle, then once it got warm enough, just start shaking until I put the choke forward to close it off. Giving it throttle seemed normal, but I didn't see if it put the oil light out. It did have a (what I suppose, I understand motorcycle engines sound different than car engines) somewhat knocking sound though, so I just shut it off as quickly as possible. It wouldn't start the second time, battery just died. I pulled one spark plug, it looked black but wasn't wet.

As far as low voltage, I did have to jump start it from a car, which took a while to charge the battery.

I am trying to jump start it again. On the first time it started, I had to let it sit for maybe a half hour hooked to a non-running car. It cranks, I do smell some gas, but it keeps making popping noises, with the last one being louder than the others. It just keeps popping and not starting, I will let you guys know what happens if I can get it to start again.

Last edited by SergheiS; 07-30-2017 at 12:19 PM.
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post #6 of 31 (permalink) Old 07-30-2017, 12:33 PM
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Hmm, not sounding good. Oil light, shaking, knocking.... Could be one big problem, or multiple problems. Bearing failure, damper failure, carb/fuel problem, and a dead battery.

With low voltage, it's going to pop and not want to start.

With chokes, open is for normal operation (lever forward), closed is for a cold start (lever back).

Technically, this carb has no choke with a butterfly, it's just an enrichment circuit in the carb. But using the terms, choke/open/closed is simpler to communicate.

On this bike, pulling the choke lever back while running usually just results in a faster idle if the engine has warmed at all.

edit: what is the rpm at idle when you're hearing it knock somewhat? It may just be noisy from a low idle rpm.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 07-30-2017 at 12:36 PM.
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post #7 of 31 (permalink) Old 07-30-2017, 01:14 PM Thread Starter
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It seemed to make the noises at idle, I didn't rev it when I saw the oil light go on.

So after letting it sit hooked to the car for half an hour I finally got it to crank & start a second time... It was acting erratically when cold, but as it warmed up it smoothed out. No knocking noises, no oil light. Occasionally just shook like crazy. For maybe 3-4 minutes, however, the pipes gave out a gray smoke. Also, the RPM's did hang sometimes and either had to be waited out, or I had to rev it again to let them drop. Same thing with the choke, runs wild when it's pulled towards you. I was also trying to spray the carbs with carb cleaner, and I got a small reaction out of it. I let it sit and run for a few, it seemed to function better once warmed up, but still seems slightly off...

I tried to get some videos of it running, if that helps at all. (the smooth jiggling around 1:20 in the first video is actually hard shaking, I don't know why my camera took it like that). I'm also wondering if that's normal RPM drop rate on these things, I've never had a motorbike before, and I'd rather get it all in tune before it throws me off again...

Also wondering if there is any way to make the throttle less sensitive, unfortunately my lead foot made its way to my hands as well...



Let me know if I should clarify anything/any further questions.
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post #8 of 31 (permalink) Old 07-30-2017, 02:11 PM
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Not sure what I'm hearing exactly... The heat shield rattling or maybe ACCT noise.

Explain to me what's going on with the left handlebar around 1:20 of the first video. Looks like the bar is broken and the cables on both sides are heaving up and down? I installed my damper gear 180 off by mistake, I couldn't see the handgrips because they shook that bad. Can't say for sure but you may need damper bushings if nothing else is causing the bar noodling.

My bike has new dampers, runs smooth as possible ... I have some saddlebag tethers on the license plate, and one of those will shake at idle, much like that loose heat shield is doing.

Sounds like it's running ok, rev hang didn't seem real bad, but it did react slightly when you sprayed it. So maybe a small air leak.

The gray smoke is a rich mixture, same with black plugs.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #9 of 31 (permalink) Old 07-30-2017, 02:14 PM
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The rpm racing when the choke is pulled on, shows it's working. But I would check to see if the cables are hanging for a bit after you turn the choke off.

That could cause a racy idle and gray smoke.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #10 of 31 (permalink) Old 07-30-2017, 05:40 PM Thread Starter
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Quote:
Originally Posted by Spockster View Post
Not sure what I'm hearing exactly... The heat shield rattling or maybe ACCT noise.

Explain to me what's going on with the left handlebar around 1:20 of the first video. Looks like the bar is broken and the cables on both sides are heaving up and down? I installed my damper gear 180 off by mistake, I couldn't see the handgrips because they shook that bad. Can't say for sure but you may need damper bushings if nothing else is causing the bar noodling.

My bike has new dampers, runs smooth as possible ... I have some saddlebag tethers on the license plate, and one of those will shake at idle, much like that loose heat shield is doing.

Sounds like it's running ok, rev hang didn't seem real bad, but it did react slightly when you sprayed it. So maybe a small air leak.

The gray smoke is a rich mixture, same with black plugs.
The heat shield is loose, so possibly that came out better in the audio than the motor.

The camera very poorly captured it, it was vibrating hard, and it took a while for the bike to calm down and stop shaking like that. Honestly, it seemed as if it had to be fully warmed up before it would run half decently. I did bend the forks & handlebars, so bushings might be included in the repair.

What's the best way to tune the carbs? I figured I'd at least start there. Guessing also plugs might help?

The gray smoke stopped after a while, I'm guess the cylinder got flooded from multiple failed cranks, so it finally burned everything off.

Far as air leak, I'll have to look at the carb again, see what I can find. Again I'm not sure how these things are supposed to idle naturally but, it definitely doesn't seem right/seems way more erratic than it was before the crash.

I did not look at the cables, I will have to do that.
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