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Old 04-25-2011, 05:29 PM   #615
The Jerk OP
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Joined: Mar 2006
Location: Brooklyn, NY
Oddometer: 2,450
OK the Race Tech suspension upgrade. I should have taken pics of all this stuff but it was rainy, cold and miserable so I didn't feel like it. To answer speedo66's question, there is nothing hugely technically complicated about the fork work but there are some gotchas and special tools that are handy to have around. Taking that into account and taking into account that I had never been into a set of forks before and didn't know what I was doing, I had the work done by ADV Legend and Hero Mechanic jdaniele. But before we got to that part, the pre-game: parts ordering.

I decided to go with Race Tech for the front end partly based upon their reputation as guys who know what they're doing with suspension and partly based on the recommendation of some trusted friends who were very happy with their work. I was also intrigued by their Gold Valve Cartridge Emulators for damper rod forks like the W650 has. I read up on them and the theory behind them makes sense to me. Also people seem to love the results.

Race Tech also does straight-rate springs for forks and their web site gives some good reasoning as to why they do that. The gist of it is that the oil level in the forks adds some progressiveness to the front end just by the nature of how it works. That is, when the forks are compressed, the oil compresses the air pocket at the top of the forks, giving kind of a built-in progressiveness which can be fine-tuned by adjusting the amount of oil in the forks (and consequently the size of the air pocket).

Race Tech also has a cool spring rate calculator on their web site that takes into account the bike's weight and your weight and then suggests the Race Tech recommended spring rate for you. It also shows the stock spring rate so you can compare. The stock spring rate for the W, according to them, is .620 kg/mm. Race Tech offers springs from .80 kg/mm to 1.0 kg/mm (and it looks like their spring rate calculator did not survive their web site upgrade as the section for the bike weight is currently missing and thus the calculator can't do it's job). For me they suggested the .80 kg/mm springs and I can tell you they're plenty stiff for my 150-lb weight. So I ordered up a set of those and a set of the gold valve emulators.

The emulators are tuneable in two ways: Race Tech supplies them with two sets of valve springs, one at 40 lbs/in. and one at 64 lb/in. Being a lighter guy I elected to install the softer springs. The emulators are also tuneable for preload on the valve springs. I went with their recommended two turns for street use as a baseline.

You also have to order all the one-use fork items to include inner and outer bushings, oil seals, dust seals, the spring clip seal retainer, and the copper washers for the allen bolts at the bottoms of the forks. Beware, I ordered all my stuff from bikebandit and it was all right except those copper washers - they were the wrong size. I don't know if it's an error in the parts fiche or if someone at bikebandit or Kawasaki grabbed the wrong baggie.

You also need some fork oil, 1 quart should cover both forks for the W650 - Kawi says 379 mL 4 mL for a dry fill which comes out to just under 1 quart. Race Tech recommended their 15 weight fork oil so I ordered some just because it was convenient given that I was ordering all the other stuff from them.

Getting the forks off the bike is easy enough and the service manual does a good job explaining how to do it. Once they're off, the tricky part is supporting the forks while working on them. JD has a cool rubber-clawed bench-mounted vise which supported the forks without scratching them up.

Another tricky bit is removing the allen bolt from the bottom. You need to fashion a tool to get down into the fork and stop the damper rod from turning. A couple nuts double-nutted onto a long threaded rod will do it. And maybe a third hand.

Once you get the bottom bolt out you can separate the inner and outer parts of the fork.

You then have to drill out the holes in the damping rods. Basically what you're doing is disabling the damping rods so that damping will be handled by the emulators. You do this by drilling out the existing damping rod holes to 5/16" and then adding more 5/16" holes until you have six holes total.

Basically at this point you clean everything up and then put it all back together with new bits. But since the Race Tech springs are about 2.5 inches shorter than stock, you gotta cut new preload spacers because the stock ones will be too short. Race Tech supplies a good length of aluminum tubing with the fork springs so you can cut new spacers.

So you gotta figure out how long they need to be. Race Tech's instructions are great and go in-depth into how to do this, but basically you reassemble the fork, put in the damping rod, emulator, spring, and washer, then extend the fork all the way and measure down to the top of the washer. Then you measure the length of the fork top cap. Then you subtract the length of the top cap from the inside length, which equals how long the spacer would have to be to have zero preload on the spring. Then you decide how much preload you want to have and cut the spacer to that length. Race Tech suggests a "standard preload" of 20mm but provide a typical range of 15 to 30mm or "extremes" of 5mm to 35mm. As they say, there's no magic number so pick a place to start and you can fine tune it in the future by changing the length of the spacers. I decided to go with the "standard" of 20mm, so the math was like this (these were not my exact numbers):

Inside length (155mm) - top cap length (15mm) = 140mm. That's my zero preload spacer length. If I want 20mm of preload, I add that to the 140mm and that = 160mm. So I need to cut the Race Tech tubing into two 160mm segments and those are my new preload spacers. JD had a nifty tubing cutter which was much neater and quicker than using a hacksaw would have been.

So you put it all back together with the new stuff, add fork oil, and put it all back on the bike and go for a ride.

You can later fine-tune the damping behavior of the emulators by removing them which you can do with the forks on the bike using a parts grabber. You can also fine-tune things with the weight of the fork oil and you can fine-tune the progressiveness with the quantity of fork oil. You can fine-tune the preload later by changing the length of the preload spacers. So there are plenty of variables to play with.

I'm very happy with it so far. Took a two-up ride to Bear Mountain on Sunday. The front end is a lot firmer and brake dive is much less. The bike handles big bumps better without blowing through the front end travel and bottoming out. It definitely is more confidence-inspiring in the curves.

I'm probably not a good enough rider to really benefit too much from messing around with all the variables so I'll put some miles on the "recommended" configuration and see how I like it and if some aspect of the setup needs attention I'll tweak it.

I never really knew how poor the stock suspension was until I put some good stuff on it. This is a dangerous (read: expensive) revelation.
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