Engine Over-Reving - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 45 (permalink) Old 01-19-2009, 09:49 PM Thread Starter
 
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Engine Over-Reving

Howdy Folks --

My '94 Vulcan with 9k miles is "over-reving." When I close the throttle there is a delay before the engine stops reving. It's bad enough that I'm unintentionally doing speed-shifts, that is, the engine continues to rev while I pull in the clutch and close the throttle to shift.

My first thought is that the throttle cable(s) is sticking; however, the throttle seems to snap back quickly into the closed position.

Any thoughts on what's causing it and how to fix it?

Thanx in advance!
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post #2 of 45 (permalink) Old 01-20-2009, 12:21 AM
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Quote:
Originally Posted by FlaRider View Post
Howdy Folks --

My '94 Vulcan with 9k miles is "over-reving." When I close the throttle there is a delay before the engine stops reving. It's bad enough that I'm unintentionally doing speed-shifts, that is, the engine continues to rev while I pull in the clutch and close the throttle to shift.

My first thought is that the throttle cable(s) is sticking; however, the throttle seems to snap back quickly into the closed position.

Any thoughts on what's causing it and how to fix it?

Thanx in advance!

You may be having a coasting richener problem, do you have a Clymer manual? Is your choke all the way off? Check your choke cable at the carb. and make sure it is in it's socket and there in no tension on the cable in the off position.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

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post #3 of 45 (permalink) Old 01-20-2009, 12:42 AM
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How about an air leak on the intake carb boot.

02 honda sabre 1100
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post #4 of 45 (permalink) Old 01-20-2009, 12:18 PM Thread Starter
 
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Originally Posted by niterider View Post
How about an air leak on the intake carb boot.
Lance and NiteRider --

Yes, I have a Clymer manual. I'll check both of your suggestions.

Thanx for your responses!
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post #5 of 45 (permalink) Old 01-20-2009, 03:07 PM
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That problem is usually caused by an air leak (per niterider), so you'll want to check a couple of things. Check the boots off of each carburetor and make sure they are snuggly seated against the carbs and up into the airbox. Then check the boots that go from the airbox to the air filter housing units - again, check connections at each end.

I bought a down-and-out bike a few months ago - had worked with PO on trying to find the leak (which was causing some really really scary overrevving) and we were never able to identify it. During the teardown, I discovered that there was a nice split in the airbox itself... so, sometimes those leaks can be a little hard to detect.

Good luck!

C
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post #6 of 45 (permalink) Old 01-20-2009, 03:48 PM
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An easy way to test for air leaks is to use a can of WD-40 or carb cleaner or starting fluid. Using the red straw tube spray around the boot to carb then the boot to cylinder head. Then spray around the air chamber to carb inlet, then air filter to air chamber. Starting fluid will be more sensative and you will need to spray very little. If you have an air leak an RPM change will be apparent.

I know you just got he bike so the more info you can give the better. Did the problem just start or was it like that when you bought it? What RPM does the engine idle at after it has reached opperating temperature? Your problem could be as simple as an idle adjustment, set rpm between 1050 and 1100.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote

Last edited by lance328; 01-20-2009 at 04:23 PM.
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post #7 of 45 (permalink) Old 01-20-2009, 04:36 PM Thread Starter
 
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Quote:
Originally Posted by Crobins365 View Post
That problem is usually caused by an air leak (per niterider), so you'll want to check a couple of things. Check the boots off of each carburetor and make sure they are snuggly seated against the carbs and up into the airbox. Then check the boots that go from the airbox to the air filter housing units - again, check connections at each end.

I bought a down-and-out bike a few months ago - had worked with PO on trying to find the leak (which was causing some really really scary overrevving) and we were never able to identify it. During the teardown, I discovered that there was a nice split in the airbox itself... so, sometimes those leaks can be a little hard to detect.

Good luck!
Crobins--
Great tips on checking the boots and air box!
Many Thanx for your help!
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post #8 of 45 (permalink) Old 01-20-2009, 04:55 PM Thread Starter
 
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Quote:
Originally Posted by lance328 View Post
An easy way to test for air leaks is to use a can of WD-40 or carb cleaner or starting fluid. Using the red straw tube spray around the boot to carb then the boot to cylinder head. Then spray around the air chamber to carb inlet, then air filter to air chamber. Starting fluid will be more sensative and you will need to spray very little. If you have an air leak an RPM change will be apparent.

I know you just got he bike so the more info you can give the better. Did the problem just start or was it like that when you bought it? What RPM does the engine idle at after it has reached opperating temperature? Your problem could be as simple as an idle adjustment, set rpm between 1050 and 1100.
Lance--
I appreciate your easy-to-understand description of how to use the starting fluid.

I noticed a slight over-rev problem on the first test ride but it's slowly getting a bit worse. According to the bike-mounted tachometer it's idling a bit over 1100 rpm.

I'll be trying all suggestions over the next few days and let you all know how it goes. I got my fingers crossed.
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post #9 of 45 (permalink) Old 01-20-2009, 06:13 PM
 
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Had similar-sounding problem but it was a sticky choke cable which cleared up with two applications of cleaner-lube as per can instructions. Choke seemed to be off on top but was not closing on bottom end without a push with finger.
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post #10 of 45 (permalink) Old 01-22-2009, 07:22 AM
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The reason I asked if you have a manual is that you might have to clean or replace the coasting richener diaphragm. If it sticks or has a perforation in the diaphram it will cause your problem. It can be accessed easily with carbs on by removing 2 screws. It allowes a little extra fuel to flow when going from open to closed throttle so the engine does not stall due to the sudden drop in vacuum.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote
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