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2009 Vulcan 500
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Just as well go with 20 weight..we know that 10 weight in these doesn't offer much damping...its hard to get all the oil out unless you disassemble and clean every thing...so whatever you use is still going to be diluted some with 10 weight...so if you ended up with two parts 20 and one part 10 weight as a ratio..you are still going to be aways from 20 weight.
 

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Sounds like you have some internal problems in the forks. Deteriorated seals? From your description of the oil that came out of one fork, I wouldn't be surprised. If that's the case, even if new oil makes it better for now, if it is still bottoming out, it will only get worse and even new oil won't help for long.

The springs could be damaged. Your manual should have had some tests, even something as simple as measuring the spring(s) length.

I suggest you stick with Maxima Fork oil, but going to 15 wt (just make sure it is NOT the racing version!), once the other problems have been fixed, is not a bad idea. Whatever brand you use, stick with that brand and weight. Unlike engine oil, there is no standard for fork oil viscosity. One brand's 15 wt may be equivalent to a more or less viscous oil from another brand.
Your post caused me to do some research...I found a list...and wow..you are so right..there isn't any kind of standard...its all over the place ..so he needs to first find the actual viscosity of what the original oil is and go from there.
Thanks for pointing this out...that fork oils are all over the place and have no standard...My damping is kinda weak itself and this will help me when I change it.







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@The rider: Most Kawi models that I know of come from the factory with an oil that is either close to, or actually is Showa 8 (~10 wt, the 8 is just a number) rebranded by Kawi. It's a pretty common OEM fork oil for Japanese bikes.

@NSky: It's your bike and your decision, but I would strongly recommend a rebuild. If you have the correct oil level, even with a light weight oil, then there is an internal problem if you are still bottoming out. In particular, if you ride any at highway speeds, my concern would be a catastrophic failure resulting in loss of control, but it could happen at any speed.
 
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Discussion Starter · #24 ·
So today I had Round 2 fixing the bottoming out fork. Long story short - I won.

I drained oil one more time. It was mixed with the old oil. It looked better but there still was obvious difference in color.

I measured springs and they were 300mm and 301mm. Perfectly fine according to the service manual.

So I refilled the tubes with the new Maxima 15WT fork oil. And the first thing I noticed pumping the tubes manually (without the springs) 15WT really makes some more resistance (hard to notice when assembled with the springs though).

Assembled everything back. And now I can't bottom it out pumping the fork from the seat! It feels soft, but there is still about 1/2 inch to the bottom, just like @The rider described above.

I had a long ride then and I can now feel that suspension actually works on a bumpy road, instead of bouncing on it (as it was before). I managed to bottom it out once using really extreme breaking with moving weight to the front wheel but I suppose that's fine for such extreme conditions.

So it looks like there is some potential for adjusting Vulcan's suspension and it's not necessary that the oil viscosity for an average rider will work well for everyone (especially taking into account there are no uniform standards for the fork oil). There are at least two variables to consider - your weight (which you can measure) and the oil brand/declared viscosity (which you can find empirically). That's actually not news at all for dirt- and sport-bike riders...

Thank a lot guys for your help!
 

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I'm a little late to this party, but I had that "clanking" noise on my Nomad a few years ago. It was so loud it could be heard by anyone in the vacinitiy! It was under warranty and I took it to my dealer for repair. I have a close relationship with management at the dealer and they kept me in the loop. Under Kawi's direction they tried adjusting the steering stem (we didn't think it would work), replacing the steering stem bearings (we didn't think it would work), then finally replacing both front forks which did the trick. Kawi spent a lot of money by not listening to the dealer and trying to outguess them. I asked the dealer how much the final bill was to Kawi and all he would tell me was "a whole lot"! The dealer never inspected the forks to figure out what was going on because they had to be held for return to Kawi, but they were able to duplicate the noise with the forks off the bike. As others have mentioned, there was obviously something wrong or broken inside one of them.
 
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