Fork Adjustment? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 11-09-2009, 09:22 PM Thread Starter
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Question Fork Adjustment?

While my bike was down awaiting parts and repairs - I Rode my son's VN750 (he was at school during the week) The first thing that I noticed was that His fork would dive with even moderate front brake pressure can I adjust it to take out some of the dive and bounce?

That can't be my bike - it aint movin'
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post #2 of 12 (permalink) Old 11-10-2009, 01:10 PM
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Change the fork oil. And swap in new Progressive springs for the very soft stock ones that may be dead (depending on how old this bike is).

Because of the little holding clip ring it's best done as a two-man job, unless you want to risk the clip ring flying away like a Jesus pin.

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post #3 of 12 (permalink) Old 11-10-2009, 01:17 PM
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Swaping out the fork oil should mkake a lot of difference, esp if you go with a heavier weight.

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post #4 of 12 (permalink) Old 11-10-2009, 06:02 PM Thread Starter
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so the fork is not adjustable ie. air it up between fork oil changes?

I wasn't sure if it worked like a bicycle fork or not

That can't be my bike - it aint movin'
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post #5 of 12 (permalink) Old 11-10-2009, 09:34 PM
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Quote:
Originally Posted by trekbiker View Post
so the fork is not adjustable ie. air it up between fork oil changes?

I wasn't sure if it worked like a bicycle fork or not
Think I read a post by lance that the first model year or two had air adjustable front forks. But I've been wrong before!

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post #6 of 12 (permalink) Old 11-11-2009, 07:40 PM
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Quote:
Originally Posted by flitecontrol View Post
Think I read a post by lance that the first model year or two had air adjustable front forks. But I've been wrong before!
You are right, for the first year or two there was an airvalve in the front fork tubes.

Edit: 1985 to 88 models had an air valve.

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post #7 of 12 (permalink) Old 11-13-2009, 01:58 PM
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Just my 2cents.

If your bike has air valves in the forks and you want to add air pressure to them, use a bicycle pump. Anything stronger can quickly blow the seals.

Using thicker oil in the forks is a horrible idea in IMO. What that will do is increase the resistance to diving and also increase the resistance to going back to the normal riding position. So imagine riding over a series of bumps on rough pavement. As you hit the bumps you would force more (thicker) oil through the tiny oil passages in your forks, but the normal pressure for the oil to move back inside the forks to the normal riding position would have a hard time doing it with thicker oil. As you hit a series of bumps the forks would compress and compress and compress. The lower they get the worse the ride over those bumps would be until the forks had a chance to eventually spring back to the normal ride height.

My suggestion would be to invest in some new Progressive Suspension fork springs and drain and replace the fork oil with the proper weight of fork oil as per the factory specs.

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post #8 of 12 (permalink) Old 11-13-2009, 03:37 PM
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I agree with sloppy...you need new springs not just heavier oil.

I would first drain the forks as it is possible you do not have any oil in them and that is the problem...

But stiffer springs, or at least adding some more preload would be better than just using thicker oil.

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post #9 of 12 (permalink) Old 11-13-2009, 09:32 PM Thread Starter
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Thanks - We will give it a shot - how do you know if the old springs need replacing?

That can't be my bike - it aint movin'
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post #10 of 12 (permalink) Old 11-13-2009, 10:43 PM
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Quote:
Originally Posted by trekbiker View Post
Thanks - We will give it a shot - how do you know if the old springs need replacing?
When the " fork would dive with even moderate front brake pressure " ...or the forks seem a bit to easy to compress just holding the brake and pushing down.

Fork springs, and shocks tend to get mushy over time. The stock springs were pretty soft to begin with, so just a bit of wear and they pretty much are toast. The rear shocks however are a bit too harsh, and don't have enough rebound or compression dampening. Most riders that are over 185 lbs don't seem to be as offended by them, and because they also take air one can live with them a bit easier.

But the front forks, even the ones with the air fitting, (which does not really do that much) are kinda weak for any rider. And really seem soft if you add a large windscreen or fairing.

The progressive springs are one of the better bang for the buck improvements you can make , I strongly suggest them to all Vulcan riders.

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