Bike will not rev down - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 22 (permalink) Old 10-18-2011, 02:06 PM Thread Starter
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Bike will not rev down

Just bought my 1995 VN750 about 130 miles ago and I have a problem already. After riding for about 20 minutes the engine seems to stick in high rev mode (about 4K). Whenever I let off the gas to shift gears, the throttle seems to snap back but the bike keeps revving at about 4K. When I shift into neutral the high revs keep up. Any ideas? Thanks.

09/29/2011
1995
19,000 miles
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post #2 of 22 (permalink) Old 10-18-2011, 02:27 PM
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Have u messed with/ turned the Black Idle adjust knob, possibly having the idle set too high ? That was my first thought, but i now doubt it... sounds like a throttle cable problem.
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'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery
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Dampers went out @ 13+K !
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post #3 of 22 (permalink) Old 10-18-2011, 06:05 PM
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Sounds like a problem with the decelerator cable. Check my post#4 here
https://www.vn750.com/forum/showthread.php?t=19761

JM2001

" Loud Pipes Risk Rights "

2001 Vulcan 750
marbled
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
rectifier relocated
splines lubed
iridiums
decals removed
upgraded mirrors
Pic up coil mod done
degoated
All LED lighting
Upgraded Mosfet rectifier
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post #4 of 22 (permalink) Old 10-19-2011, 01:20 AM
If only it had 6th gear..
 
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Quote:
Originally Posted by JM2001 View Post
Sounds like a problem with the decelerator cable. Check my post#4 here
https://www.vn750.com/forum/showthread.php?t=19761
Could be that, but also you might want to look at your intake boots and check for cracks. A crack might be closed when the bike is cool but after it warms up It could open a little letting some air in. Also if you start your bike with choke maybe one of the enricher (choke) plungers isn't returning to it's seated position. That could make it rev without dying out if it's up or on just a little.

If you're still having the prob, give more detail if you can. how high does it rev and when it does is it smooth or choppy and popping, stuff like that helps.

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.... ??

Last edited by DavesVulster; 10-19-2011 at 01:22 AM.
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post #5 of 22 (permalink) Old 10-20-2011, 07:02 AM Thread Starter
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Thanks JM2001 for your tip on the decelerator cable.
I followed your thread and did my best to adjust both throttle and decelerator cables per instructions, but sadly no luck. Everything started off well, but after driving about 15 minutes the engine locked into its 4K rev mode. I have learned to drive home with a tricky combination of break and clutch, but it doesn’t seem too safe.

DavesVulster, as soon as I figure out where the intake boots are, I plan to give them an inspection for cracks. Will I have to remove the gas tank to perform this inspection? Will I be able to see the choke plungers with the gas tank on? It revs around 4K and builds to about 5K. By then I turn the bike off. The revs are smooth with no popping.

Thanks guys.

09/29/2011
1995
19,000 miles
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post #6 of 22 (permalink) Old 10-20-2011, 08:53 AM
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Silly question I know but you don't have the choke on do you? Also, check your vacum lines, you could have one pinched or loose.

An easy way to check for cracks or bad seam on your carb boots is to spray some carb cleaner around the connections. If the idle drops, you found a leak.

Another check, Do you have a propane torch? You can run an unlit propane torch with the valve cracked open over the suspected hoses/connection while your engine idles. If you pass it over a hose and it idles up and take the torch away and it idles down - then you found your leak. The propane going in the system will cause it to idle up.
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post #7 of 22 (permalink) Old 10-20-2011, 09:06 AM
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Quote:
Originally Posted by pashley View Post
Thanks JM2001 for your tip on the decelerator cable.
I followed your thread and did my best to adjust both throttle and decelerator cables per instructions, but sadly no luck. Everything started off well, but after driving about 15 minutes the engine locked into its 4K rev mode. I have learned to drive home with a tricky combination of break and clutch, but it doesn’t seem too safe.

DavesVulster, as soon as I figure out where the intake boots are, I plan to give them an inspection for cracks. Will I have to remove the gas tank to perform this inspection? Will I be able to see the choke plungers with the gas tank on? It revs around 4K and builds to about 5K. By then I turn the bike off. The revs are smooth with no popping.

Thanks guys.
You stated everything started off well. I would asume that means the bike started ok, idled well, and ran well for 14 minutes. This leads me to believe the cables are ok, the choke plungers are ok, and no air leaks. If you run the bike to 4000 rpm and then the reving condition happens I would suspect the throttle valve ( carb slide) in one or both carbs is sticking open.

JM2001

" Loud Pipes Risk Rights "

2001 Vulcan 750
marbled
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
rectifier relocated
splines lubed
iridiums
decals removed
upgraded mirrors
Pic up coil mod done
degoated
All LED lighting
Upgraded Mosfet rectifier
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post #8 of 22 (permalink) Old 10-20-2011, 09:09 AM
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I had a similar issue and it was nothing more than adjusting the idle setting. The idle setting was set to 1100rpm when the choke was turned off, but the bike was not completely warmed up yet. After a few miles of riding the idle would creep up to about 3500rpm and stay there.

Re-adjust the idle knob on the left side of the bike once the engine is hot. It may be a little tricky because when the bike is cold it will tend to idle a bit low until it completely warms up again.
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post #9 of 22 (permalink) Old 10-20-2011, 09:20 AM
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Stuck float?

I had a similar problem last fall when I got my 2006. Previous owner didn't ride much, and I think things got gummed up. Seafoam did the trick for me, adding 3-4 ounces with each fill up.

https://www.vn750.com/forum/showthread.php?t=2914

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post #10 of 22 (permalink) Old 10-20-2011, 06:03 PM
If only it had 6th gear..
 
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Wow I answered you yesterday but I don't see it here. Musta not clicked reply. Anyway, the boots I was talking about connect the carbs to the engine heads. They are thick rubber tubes, about 2 inches in length. That's where you would spray to check for a leak. The suggestions are good but what JM2001 said about a slide sticking sort of floats to the top of them. To check the slides you'll have to take off the airbox boots <opposite side of the carb from the intake boot , and both airbox boots go from the carbs and turn up under the tank.

This is just a guess - never tried it, but you might be able to test for sticking mechanics inside the carbs this way; when the bike is stuck in high idle, take a screwdriver and with the handle side rap on the side of each carb to see if it frees up and the idle drops. If it does, remove an air cleaner and spray some lightweight top cylinder oil or "fogging " oil in there while the bike is running. It'll smoke out the exhaust some so don't be concerned, just spray a little wait for the smoke to let up, spray some more and wait, not too much oil, just a little at a time. This may or may not help depending on where it's getting hung up, and if it actually is the problem, but it's worth a try. You can use the fogging oil to check for leaks on those boots and to protect your engine's top end if you put it away for off season so either way it won't be wasted. Most hardware stores have the stuff. Good luck.

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.... ??

Last edited by DavesVulster; 10-20-2011 at 06:31 PM.
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