Probably the most common modification made to the VX is to replace the front fork springs, generally considered to "soft", with Progressive fork springs ("Progressive" is a brand name, as well as being a description of how they work, by the way.) These springs have two different sections, with a different spring rate to each section. The soft end maintains the ride, but the rest of the spring is stiffer, and won't bottom out as quickly. (It should be noted that the stock springs are progressively wound, they're just too soft overall -- the replacements from Progressive are stiffer.) Replacement is simple -- lift the front of the bike, remove the fork caps (carefully, they're under spring tension), take out the old springs, cut down the old spacers, remove some fork oil, put in the new springs, and replace the caps. The springs will cost under $50 from most mail-order houses. There's a somewhat more complete sequence in the "Maintenance Procedures" section.
The Progressive part number for the VX is 11-1129. The installation notes say to cut the stock spring spacers down to 3". Or you can use a piece of PVC pipe that just fits in the fork tube, with a flat washer between it and the spring top. If you do this, get high-grade (schedule 80 -- it's a gray color) PVC from a plumbing shop -- there have been reports of cheap PVC gradually deteriorating (shredding), which isn't a good thing in your fork tubes. (Note: see below -- 3" may actually be too long.) The springs go in with the close-wound end uppermost. Progressive Suspension Inc.: (760) 948-4012.
There's been some debate about the amount of oil to remove. Some folks don't remove any, and have no trouble. Others report premature fork seal failure unless you reduce the oil volume. One person "would recommend reducing the fork oil volume from about 380 cc per leg to about 280-300 cc leg".
I think it was Roland Oliynyk who said:
"I calculated the 240 ml ( 8 oz) of 10wt fork oil that I use, based on the weight difference between the standard spring and the progressive spring, assumed that would correspond to the difference in displacement volume between the two springs (assuming same density of steel). Percentage increase in spring weight is proportional to percentage DECREASE in oil volume."
Someone else pointed out since the spring isn't totally immersed in the oil that this might not be a completely accurate theory. But in any case, it seems people have success with a variety of oil volumes in the 240-300 ml range.
A solution that has worked for Tom was proposed by Robb Wong. Remove your spacers, washers and springs; compress your forks completely then add oil until it's 150mm (~6")from the top of each fork tube. You can measure that using chopsticks, or in my case, a turkey baster. With the baster method, pour in oil to a little past the the proposed mark, insert the baster to the 150mm level which I've marked on it (150mm from the tip of the baster) and squeeze the bulb to suck in excess oil until it burbles. The oil is then at the proper level.
Apparently Works Performance (818-701-1010) sells a similar system of springs for the VX. From Thatch Harvey, who has a set that he likes on his 1100G:
"This is a two spring system (per fork leg) with a spacer inside one of the springs, and a proload spacer on top. The small spring is softer and does most of the work on small bumps. On a big bump or under braking, the small spring compresses until it is the same length as the spacer, and then can't go any further. Then the spacer/spring combo simply act as a spacer pushing on the big spring which is a higher rate and resists bottoming."
It's also possible to firm up the front end by simply installing a longer spacer. It turns out Mike Heathman has tried this:
"I put in a longer pre-load spacer when I first bought the bike and rode it that way for about 10,000 miles until I put in progressive springs. It does help a bit, keeps the front end from bottoming out under heavy braking as easily, which was the biggest problem with the stock springs."
"The Progressive springs are better. They are very harsh with the 3" spacer recommended by Progressive. With a 2-1/2" spacer they're beautiful."
I've installed Progressive's on my bike, with 2-1/2" spacers as suggested by Mike, and I like them. There is much less "pogo"ing on rough pavement (something I thought was caused by too stiff a suspension, but I guess it's from being too soft), and I just have more confidence in turns that the front end will behave predictably. For what it's worth, I have no idea how much oil I have in my forks by volume -- I did measure from the top of the tube (fully compressed, spring removed) and the height is set to about 150mm.
The newest Front Suspension option is a pair of Race-Tech Cartridge Emulators (Part # FEGV S3801). These reasonably simple-to-install parts do a great job of making the front end as planted and compliant as any sport bike that we might expect to ride on the street.
Installation, as reported to Tom by Andy, is straight forward. Remove the forks caps and then the spacers and springs. Use the Paul Fox or Jim Chen damper extraction tool described below under Fork Seals to remove the damper rods. Drill two holes of similar diameter to the holes already in the damper rod. These holes should be drilled midway between the existing holes and rotated 90 degrees from them. Precision drilling is not essential as the holes are there only to permit fork oil to move more freely. However they should be deburred to prevent metal fragments from damaging the system.
Reinstall the damper rods, adjust the Cartridge Emulators to 2 1/2 turns from the tightest position, drop them onto the damper rods, replace the spacers (they should be shortened by 1/2 inch) and the springs. Fill the forks to the proper level with fork oil (15w recommended). Replace the fork caps and go riding.
If you want to adjust the ride, all you have to do is remove the Cartridge Emulators again again adjust them according to the instruction sheet and drop them back in; a 5 minute job
Tom had a chance to ride Andy's VX with this improvement and will be adding them to his in the Spring (2001) together with a Superbrace. The front end was exceptionally good.
People have reported good results with both Progressive (1200 Series) and Koni (part no. 7610-1520) aftermarket shocks. Glen Farney writes: "Progressive makes a good shock for the VX, non
adjustable, but far cheaper than the OEM unit, and works quite well. They will gladly tell you exactly what shock and spring combination will work, in fact they have a downloadable application program
at http://www.progressivesuspension.com"
Fork seals seem to last as long as they want to, between 10,000 and 50,000 miles. Replacing them isn't that hard in principle, but in practice, many people remove the tubes themselves, and have a mechanic do the actual seal replacement. Removing the fork tubes is fairly easy -- remove the front wheel, remove the front fender, loosen the clamp bolts on the upper and lower fork clamps, and the forks will fall right out. Hang onto them.
There are two trick parts to replacing the seals yourself. One is that to remove the damper rod, you need to a) turn the allen head pointing down from the bottom of the tube (that's easy), and b) keep the rod from spinning (that's hard). The rod has a 24mm allen head on it, but you need a very long allen wrench (or a 24mm bolt fastened to a long bar somehow) to get to it. Some people have success using an air wrench on the bottom allen screw while there's still spring tension on the damper rod (i.e. before taking the caps off). Wes Kendall fashioned a tool using a nut and a socket of the right size -- he shimmed the the nut out with washers so it protruded from the socket enough to engage the allen head on the fork rod. The sudden high torque breaks it the bolt loose.
Robb Wong suggests:
... after you pull the forks out, open them up, take out the springs and spacers and drain (or clean) the forks. THEN - add the springs and spacers again and I WOULD BRING THE FORKS TO A SHOP AND HAVE THEM AIR DRILL THE SCREWS OUT. This single step saves so many headaches and dirty-words! My local shop will drill them out for a "tip" ($5 to the mechanic). Tightening the bottom bolt is 1000 times easier than loosening - and cleaner too.
Scott Tunney fashioned a tool like so:
I found that using a deepwell 24mm socket on two 10" extensions and a 1 1/2" 5/8-11 bolt with two nuts ∓ a lock washer made it very easy to remove the bolt. Using the bolt with two nuts I could use the lock washer to hold the second nut outside the socket to engage the damper rod so that it would not rotate. I used a 8 mm allen wrench on the bolt and a rachet to hold the damper rod. Everything came apart easily without using my air impact wrench.I tried to sketch the socket/bolt combination below:
SSSSSSSSS s = 24 mm deepwell socket
S S B = 1 1/2" 5/8-11 bolt (15/16" head)
S BBBBB S n = 5/8" nut
S B S w = 5/8" lock washer
S nnBnn S
S nnBnn S
wwwBwww
nnBnn
nnBnn
I had to use english bolts because my local hardware store does not carry large metric bolts.
Perhaps the simplicity prize goes to Jim Chen, though:
"BTW, I fashioned a tool out of an old broom handle to lock the nut inside the fork tubes. I used a rotary table top sander to flatten one edge of the handle and then tapered the handle to fit inside the nut. The flattened edge worked like a charm to hold the nut - and it was the cheapest tool I've used on the bike thus far!!"
Paul then topped everyone with the following:
The tool for the forks is really easy to make: a length of 5/8" threaded shaft, with two 15/16" headed nuts lock-nutted together at the business end, with a pair of vicegrips applied at the other end as a handle, and you have an instant Suzuki special-tool replacement. no muss, no fuss. I got the 5/8" threaded rod at a local home-center -- any good hardware store should have it, and I can practically guarantee that the only nuts they have to fit it will have 15/16" heads. Click to see a picture of mine. It's not pretty, but it works like a charm. (btw, 15/16" equals 23.8125 mm, which is plenty close enough...)
The other tricky part is the actual removal and replacement of the seals -- seating the new seal must be done carefully.
Juan Goula described his experience installing the seals himself:
"Then came time to re-assemble the whole thing. Sliding those seals the last 1/16" was driving me crazy! I used (as any desperate man would) a punch. Bad mistake. The seal just sat there, snickering, now with a dimple on its surface. Dang! Out I go to my local hardware store, bought an 8' length of 1.5" PVC pipe. Cut a 2' length, made a longitudinal cut so it would spread open and presto! Instant seal driver. One good whack with a rubber mallet and the seals grinneth no more. Then came the dust seals, no problem."
Scott used this trick as well, and claims it works great.
The seals would last longer if the fork tubes were protected by "gaiters", the kind off-road bikes usually have, as well as older street bikes. At least one as person reported success fitting a pair to the VX. A couple of people have used BMW fork boots. Wes Kendall reports: "BMW has a pair that fit the VX perfectly. Exact fit on the fork tube. Ditto for the fork leg. Thin enough to get between the leg and fender bracket without modification. Short enough so that it doesn't look funny on a street bike. The BMW part # is 31-42-2-311-077. Of course there is a catch. These cost $27.90 EACH !!!"
Andy Sobkovich has replaced the OEM seal with Leak Proof seals reasoning that if the OEM seals were OK there wouldn't be so many seal problems.