Engine revving strangely - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 12-17-2011, 05:54 PM Thread Starter
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Engine revving strangely

So the other day, I had a little electrical issue. Trying to start the bike, the main ground connector had broken, causing a wire to short and overheat and melt the insulation. I was sitting on the bike at the time, so when the smoke started coming up from between my legs, it startled me and I jumped off the bike. In my hast, I forgot that I had already lifted the kick stand, so the bike toppled over (no major damage, caught it on the way down, just damaged one of the turn signals).

So I got the electrical issue sorted out. But now when I run the engine, after it's warm and I turn the choke off, when I let off the throttle when coming to a stop, the revs will hold at around 2000 for about 5 seconds before dropping back down to where they're supposed to be at about 1100.

The bike was running smoothly before this, and I have no idea what's causing this. I simply don't know enough (yet) to be able to diagnose this myself. Did the carb get flooded? I would have thought it would have burned that excess off by now (I've ridden about 30 miles since). Or is it something else I'm not even thinking of?

'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 *
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post #2 of 9 (permalink) Old 12-17-2011, 06:07 PM
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Since the bike fell over I would check the throttle cables for bind or kinks,it may be slow pulling the cables back to the throttle stop.open the throttle with the engine off and shine a light on the ends that goes on the carb first and see if when you let off of the throttle it is returning fully and immediately.




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post #3 of 9 (permalink) Old 12-17-2011, 06:15 PM
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X2 ^ Might want to check for a vacuum leak too. A line may have come off, or partially off when it toppled. If I remember correctly an engine slow to return to idle could be caused by a vac leak... but don't hold me to it. There's a vac line that goes to the valve under the seat too (if you still have the air injection components that is). Maybe it got a little damage from the melting wire.

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Converted ACCT's to manual (thanks wib714)
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Hmm....she was on the back when we left.... ??
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post #4 of 9 (permalink) Old 12-17-2011, 06:22 PM
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Try seafoam in the feul. The falling over may have moved trash around in the carb bowls. This may help to dissolve it and move it through the system.

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post #5 of 9 (permalink) Old 12-17-2011, 06:50 PM Thread Starter
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Thanks guys, I'll check all those and let you know what I find.

FWIW, while I was stopped at one point, I turned the throttle and then released it while keeping an eye on where the cables connect, and I could see no movement when the revs returned to normal.

'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 *
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post #6 of 9 (permalink) Old 12-18-2011, 01:06 AM
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You might want to check all your carb boots for tightness...many times a tiny air leak will cause the rpms to fail to fall quickly.

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post #7 of 9 (permalink) Old 12-18-2011, 02:43 AM
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Slow dropping revs after blipping the throttle is a typical symptom of too lean idle mixture. So, as already advised, you probably have a clogged idle jet or an air leak.
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post #8 of 9 (permalink) Old 12-18-2011, 03:22 PM
If only it had 6th gear..
 
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Too lean, that's right. I think the vac leak would cause more of a rough idle and stalling, no? I got too much crap in my head from my current carreer and stuff gets mixed up at times.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #9 of 9 (permalink) Old 12-20-2011, 11:45 PM Thread Starter
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To follow-up: the issue seems to have cleared itself up. I didn't really have time to check it before I rode it again, but it no longer behaves the way it did. So in the end, I still don't know exactly what it was, but it seems to have resolved itself, so that probably means it was just some gunk in the carbs that has cleared out on its own. But thanks for all the suggestions.

'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 *
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