Shaft problem - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 07-01-2013, 08:54 AM Thread Starter
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Shaft problem

Hi,

I have a 2003 Vulcan 750. The last 2 times I have gotten off the bike, the drive shaft has come off at the transmission. I know it is happening when I get off the bike and no other time...so far.

The u-joint is in good shape. The splines on both ends are in good shape. The motor mounts are in god shape (the motor is not moving). The rear end is tight (no movement in the back wheel). The drive shaft is in good shape.

After talking to some mechanic friends, the only thing we collectively could think of was a problem in the rear shocks. My theory is that I'm a big guy, and if the shock are blown, the springs may rebound too much and too quickly causing the rear wheel to effectively drop too much and pulling the drive shaft off the transmission.

If anyone has any thoughts on this, I would love to hear them.

Thanks.
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post #2 of 10 (permalink) Old 07-01-2013, 09:18 AM
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Sounds like the spring in the driveshaft itself is broken or missing.If you have not had it apart ,it must be broken.

Here is a parts fiche from Cheap Cycle Parts that you can use to see if every thing is as it should be.
http://www.cheapcycleparts.com/oem-p...aft-final-gear




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Last edited by denny6006; 07-01-2013 at 09:40 AM.
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post #3 of 10 (permalink) Old 07-01-2013, 09:38 AM
..have a vulcan good day!
 
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Quote:
Originally Posted by denny6006 View Post
sounds like the spring in the driveshaft itself is broken or missing.If you have not had it apart it must be broken.

Here is a parts fiche from Cheap Cycle Parts that you can use to see if every thing is as it should be.
http://www.cheapcycleparts.com/oem-p...aft-final-gear
Good thought Denny ! Right On !


'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
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!
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post #4 of 10 (permalink) Old 07-01-2013, 10:34 AM
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Maybe the rear splines are stuck, pulling it off the front when the suspension moves? I wouldn't think it possible, but I doubt you're making it up either. Could be dangerous at speed, be careful until you get it fixed. Or fix it before you ride another mile.

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post #5 of 10 (permalink) Old 07-01-2013, 10:36 AM
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I don't think I have ever heard of this scenario before.

PLESAE do check back and let us know what you find out so we can take note of the solution.

good luck!
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post #6 of 10 (permalink) Old 07-01-2013, 02:52 PM Thread Starter
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I'm not sure what spring you are talking about. I am certainly glad to look at everything. After it happened twice, I took the whole rear end off. I suspected a problem in the drive shaft, but it is in good shape. The rear splines were in good shape, but they were a little dry, so I lube them when it happened the first time.

You're right about it being a dangerous problem. These 2 times it only happened when I got off, but I worry that I may think I'vefixed it, and then I hit a hard bump, and it comes off while I'm riding. Both times, the shaft has cocked sideways and locked up the back wheel.

I seem to have a knack for having non-routine problems.

Thanks for your help.
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post #7 of 10 (permalink) Old 07-01-2013, 03:29 PM
..have a vulcan good day!
 
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Quote:
Originally Posted by CJKoehn View Post
I'm not sure what spring you are talking about. I am certainly glad to look at everything. After it happened twice, I took the whole rear end off. I suspected a problem in the drive shaft, but it is in good shape. The rear splines were in good shape, but they were a little dry, so I lube them when it happened the first time.

You're right about it being a dangerous problem. These 2 times it only happened when I got off, but I worry that I may think I'vefixed it, and then I hit a hard bump, and it comes off while I'm riding. Both times, the shaft has cocked sideways and locked up the back wheel.

I seem to have a knack for having non-routine problems.
Quote:
Originally Posted by denny6006
sounds like the spring in the driveshaft itself is broken or missing

http://www.cheapcycleparts.com/oem-p...aft-final-gear

This one http://www.cheapcycleparts.com/oem-p...aft-final-gear

92081 Spring,Drive Shaft 92081-1717 $4.87


'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
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!

Last edited by WilliamTech; 07-01-2013 at 08:12 PM.
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post #8 of 10 (permalink) Old 07-01-2013, 08:08 PM
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I have a a set of 11.5" Harley shocks for sale...that'd keep ya from bottoming anyway....just how big ARE you ?



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post #9 of 10 (permalink) Old 07-01-2013, 11:15 PM
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Dude, we need visuals. I'm sitting here thinking about this and none of it makes any sense. I had my FD off not that long ago and the FD spring is not that big and I wonder if there is even enough space in the coupler for the drive-shaft to move back and fall out? As for the shocks, I think the inner rod would have to pull out of shock body just to allow the rear tire to drop far enough for the DS to fall out.

A weird problem indeed!

Here is a pic of the spring in question:

I only understand what I don't understand.

Last edited by blazblu82; 07-01-2013 at 11:37 PM.
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post #10 of 10 (permalink) Old 07-02-2013, 01:19 PM
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.....but who knows what the PO may have done....shaft from another bike, extended swingarm...etc....

...anybody close enough to him to take a look see ?....NE Miss....




Last edited by Wolfie; 07-02-2013 at 01:21 PM.
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