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Discussion Starter #1
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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The Professor
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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. :beerchug:
 

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Discussion Starter #4
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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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!
 

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The Professor
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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.
 

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Discussion Starter #7
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! :beerchug:
 

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Discussion Starter #8
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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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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The Professor
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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. :smiley_th
 

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Discussion Starter #11
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. :smiley_th
Thanx Lance! :smiley_th
 

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You know, I had this happen to me when I set the idle too high. It would delay before backing off. I think after monkeying with it for a while I had it back to where the idle was originally and everything was fine again. Just a thought of something simple - maybe. :)
 

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Discussion Starter #13
You know, I had this happen to me when I set the idle too high. It would delay before backing off. I think after monkeying with it for a while I had it back to where the idle was originally and everything was fine again. Just a thought of something simple - maybe. :)
I'll be working on this over-rev problem this weekend. Since I've also been monkeying with the idle:doh: I'll try this first.

Thanx JaBarry! :smiley_th
 

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The Professor
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I'll be working on this over-rev problem this weekend. Since I've also been monkeying with the idle:doh: I'll try this first.

Thanx JaBarry! :smiley_th
Make sure it's good news before you post. LOL :rockon:
 

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Discussion Starter #16
Carb Rebuild Recommended

Make sure it's good news before you post. LOL :rockon:
Hello All --

Here's the latest on my over-reving problem:

I wanted to rule out a sluggish throttle cable--big mistake! :( While removing/reinstalling the throttle cables for lubrication I accidently broke the small plastic ears that hold the cable onto the plastic throttle. The throttle is such a safety issue that, I decided to drop off "Mr. Spock" at the dealership for installation of a new throttle assembly. It'll take about a week to get him back.

In the mean time the dealership tech says he's diagnosed my over-reving problem as needing a carb rebuild for about $550----ouch:doh: I said no thanks--at least for now.

When I get the bike back I'm going to try Lance's advice in another post about Seafoam: ""remove the fuel lines, drain the carbs and fill with seafoam and let set for a day or two. Install the fuel lines and start, you do not have to drain the seafoam. If you don't want to remove the fuel lines you can drain carbs an pour the seafoam into the carb vent hose. ""

The tech also mentioned that "the bike is running on one cylinder, so something is wrong." I don't understand this because it runs strong. It doesn't feel like it's only on one cylinder:confused:

In addition to the Seaform, when I get Mr. Spock back I'm also going to try all of the ideas offered in this thread.

My sincere thanx to everyone who contributed to this thread!

OldFlaRider---"Missing Mr. Spock"
 

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Old Twistie Sticks Rider
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OldFlaRider-That is begining to sound like a stealership and not just a dealership... Runs strong, but only running on one cylinder..????
Sounds to me like they really want to tear into your pocketbook...lol...
I think I would tell them the Government was the ones giving the bailouts, not me...
Have a good one...Old Dog...
 

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The Professor
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Hello All --

Here's the latest on my over-reving problem:

I wanted to rule out a sluggish throttle cable--big mistake! :( While removing/reinstalling the throttle cables for lubrication I accidently broke the small plastic ears that hold the cable onto the plastic throttle. The throttle is such a safety issue that, I decided to drop off "Mr. Spock" at the dealership for installation of a new throttle assembly. It'll take about a week to get him back.

In the mean time the dealership tech says he's diagnosed my over-reving problem as needing a carb rebuild for about $550----ouch:doh: I said no thanks--at least for now.

When I get the bike back I'm going to try Lance's advice in another post about Seafoam: ""remove the fuel lines, drain the carbs and fill with seafoam and let set for a day or two. Install the fuel lines and start, you do not have to drain the seafoam. If you don't want to remove the fuel lines you can drain carbs an pour the seafoam into the carb vent hose. ""

The tech also mentioned that "the bike is running on one cylinder, so something is wrong." I don't understand this because it runs strong. It doesn't feel like it's only on one cylinder:confused:

In addition to the Seaform, when I get Mr. Spock back I'm also going to try all of the ideas offered in this thread.

My sincere thanx to everyone who contributed to this thread!

OldFlaRider---"Missing Mr. Spock"
$550.00 is a great deal if they are installing brand new carbs! While the carbs are soaking check your choke and make sure it is releasing fully. While the choke is closed see if you can push down on the plungers. As suggested you may need to lube your choke cable. If the tach is working that rules out the front cylinder. Remove the rear plug wires start the engine, note how it runs. Install the plug wires start the engine, if no change rear cylinder is not firing. It sounds like your standard Stealership BULLSHIT!!! :smiley_th
 

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Discussion Starter #19
OldFlaRider-That is begining to sound like a stealership and not just a dealership... Runs strong, but only running on one cylinder..????
Sounds to me like they really want to tear into your pocketbook...lol...
I think I would tell them the Government was the ones giving the bailouts, not me...
Have a good one...Old Dog...
Thanx for the caution, Old Dog. I need to beware :wow: of the "Stealership!"
 

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Discussion Starter #20
$550.00 is a great deal if they are installing brand new carbs! While the carbs are soaking check your choke and make sure it is releasing fully. While the choke is closed see if you can push down on the plungers. As suggested you may need to lube your choke cable. If the tach is working that rules out the front cylinder. Remove the rear plug wires start the engine, note how it runs. Install the plug wires start the engine, if no change rear cylinder is not firing. It sounds like your standard Stealership BULLSHIT!!! :smiley_th
Hey Professor Lance-- $550 was quite a sticker shock!:wow: I'll check the choke and keep my fingers crossed it's that simple. Yes, the tach has always worked, so I'll check the rear cylinder by removing/installing the plug wires as you described.

My thanx to the Professor and everyone. I'll post an update in about a week as soon as I get Mr. Spock back from the Stealership :(
 
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