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Setting Up the Stock VTR Suspension
First off let me say that this is a "Use
at your own risk" information page.
I had a lot of success with this set-up and I've set-up a few friends VTRs as well, and they liked the results too. I've done my level best to make sure the info here is correct, but if it is not, don't come crying to me, you have been warned.
I've been very luck to find someone to help me set up the suspension on my VTR1000F FireStorm (Super Hawk to the Yanks). Roger Ditchfield at Revolution Racing has helped me out greatly with setting up the VTR's suspension. I don't race, but I do a few track days every year, and I like to ride the twisty roads around here in Japan when I get a chance.
I'm a big guy, I am about 240 Lbs in my full kit. The VTR's front suspension was way to soft when I got the bike. the bike is a used silver 97, that was a domestic Jap model, that was totally de-restricted. I got turned on to Roger at the VTR1000.org BBS. Most of the guys there are from the UK. Roger really helped me out, and answered a lot of e-mail from me to which I owe him a great big thank you!!
First off I wanted to change the fork springs, this alone would make a huge difference in the way the bike handled. I got new springs from Racetech that were matched to my weight, and while talking via e-mail to Roger I found out that I should put 7.5wt oil in the forks if I am keeping the stock valves, and 5wt if I am going to the Gold Valves.
Don't fuss with this, take it off, and be done with it. Trying to take accurate measurements with it on is difficult at best, and the fairing is a whole lot less likely to be damaged by tools if it is sitting on the floor well away from where you are working.
The Racetech springs I got were 340mm long (longer than stock) and the spacer I cut for them are 60mm long, for a total of 400mm spring and spacer length. This is only the spring and spacer, not the washers, or end caps, just the spring and spacer.
-This is very important-
Roger told me to set the spring and spacer length at 410mm, but when I did this I could not get the sag to set correctly. I then found out that the springs that Roger was using were 325mm, mine were 340mm, so I had more spring, so I needed less space, so making the spacer and spring length short let me get the sag correct. Getting the sag set right is the whole purpose of this operation.
The Air Gap:
The "Air Gap" should be set at 140mm. I made up a tool to do this, it consists of a large syringe a piece of flexible tubing, a piece of rigid tubing (I used some brass tubing I had, about 300mm long and has an inside diameter of about 4mm). I then got a chunk of aluminum about the size of a quarter and abut 10 mm thick. I drilled a hole through the center of the chunk of aluminum the same diameter as the rigid brass tubing, then another hole from the edge of the chunk bisecting the hole through the middle, this hole on the side I then threaded to take a small thumb screw. I can then use this to set the air gap, you measure from the bottom of the chunk of aluminum to the end of the brass tube to the desired length, (140mm on the VTR), tighten the thumbscrew then stick the tube into the fork full of oil. The fork tube should be pushed down all the way, and you should have filled the fork with the specified amount of oil, or just a bit more. When you put the oil in the fork you have to pump the fork tube up and down a few times, do this slowly or you WILL get a glob of oil in the face (don't ask how I know this). The air gap is made without the spring or spacer in the fork. The brass tube should then sit slightly below the level of the oil, so you can suck some oil up the tube. Pull on the plunger of the syringe, and the extra oil will be sucked up, when the oil is no longer being sucked up you are at the desired air gap.
Put the spring in first, then a steel washer that came with the Racetech springs, now the spacer that you cut goes in here, then another washer, and finally the washer like think that looks like the letter "C" or Pac-Man (for all you old guys).
Now for some other things to do to the VTR to make the bike better.
Grinding the taper on the rebound adjuster rod:
This is something that I just recently did to the VTR. In talking with Roger I found out two other mods he does to the stock suspension to make it better. The first is to grind the taper on the rebound damping rods to a straight taper, instead of the stepped taper that is stock. Now I have to admit that this is a little scary, because if you screw it up, you are in trouble. I would only recommend this to someone who is confident in their skills to try it.
Here is a diagram I made to explain what I mean:
The end of the stock damping rod has a stepped taper on it, what I was told to do was to grind this step off the end of the rod.
Measure up the rod 5 mm from the step, that is were you want to grind until. You also want to keep the same angle on the taper, and the tip of the rod is flat, that to is retained. What I did was set-up a very simple jib on my work bench with the rod held against a stop with the tip of the rod against the side of my bench grinder. I then turned on the bench grinder, pushed the rod forward and spun the rod around while holding it against the stop, this kept the taper angle the exactly the same, and it let me have control on the rod to do it gradually. When I was done, I then took some #600 wet & Dry sandpaper and sanded the tip more to make it smooth
Sorry about the poor pics, but at least you get the idea
What I did was screw my bench grinder to the workbench, then I used a couple of 2 x 4's to make a platform for the damper rod to rest on, so the rod was in the middle of the grinding wheel, I then put a stop to rest the rod against at the angle needed to match the stock taper on the end of the rod. This provided a very easy way of grinding the taper on the rod. Make sure that you can easily spin the end of the damper rod, use very light pressure and keep that rod spinning, you do not want flat spots.
I have had some people ask why not just buy the rebound valves that RaceTech sells. Well the long and the short of it is that the rebound valves that RT sells end up giving you the same results at the taper grind. I guess it you don't have the place or the tools to do the taper grind, the rebound valves would work too. If you can do it yourself, why not? That is my approach to bikes, I do what I can myself, and save my money for paying a shop for the stuff I cannot do.
Here is what Roger has to say about it;
The biggest fault on VTR forks is on the
compression side not the rebound.
The rebound valving is adequate as standard but the stepped shape of the taper does not give a fine enough adjustment for long enough in my opinion. That is why I change the taper profile and length. I have always found that you can get the correct speed of rebound on springs up to 1.25 kg/mm.
If you are able to install the correct speed of return why spend money on getting more rebound that you will never use?
The kit that RaceTech sell contains 2 plastic tapers to fit in the damper rod - you have achieved the same by grinding the taper!
I gave you my best and honest advice in
order to help you with no commercial gain in mind.
You are a guy that asked for my help from Japan and I gave it.
Enjoy your riding and take care.
I hope that settles the "Taper Grind" question.
March 23rd 2003
I' sorry I meant to put this in here sooner, but in talking with Roger at Revolution racing about the "Plastic Tapers" for the VTR Gold valves kit, it seems that RaceTech has changed the kit, here is what Roger had to say...
"Dear Stuart, March 7th 2003
The SO1 kit contains tapers as well valves etc.. You had to modify the rod to fit them. They must have dropped this for the SO2 - perhaps it was too difficult to fit for the amateur. Leaving the taper as std will reduce the amount of adjustment. I consider it unnecessary to fit Gold valves in the rebound side. Race-Tech want to sell as many valves as they can - that is their aim.
So it seems that the Plastic
tapers are not in the Race-Tech kit anymore,
Thanks to Michael Nelson San Francisco, CA
for pointing this out, I want the info here to be as accurate as possible!!
1mm Relief hole in the Cartridge Body
If you are going to put in the RT Gold Valves do not drill the 1 mm relief hole!
The next thing to be done you drill a 1mm hole in the cartridge body 27mm UP from the start of the silver cartridge foot. Remember to pull the inner rod fully out of the way so you do not drill into the valve.
You have to take the cartridge apart to be able to de-burr the inside of the cartridge tube, and not damage the compression valve. To take apart the cartridge, you have to push the valve into the tube a bit and then take out the snap ring from the inside of the cartridge tube, now you can remove the compression valve. The compression valve is the one on the very bottom of the cartridge, it has an "O" ring on it. The rebound valve sits above it, it does not have an "O" ring, but a Teflon like slider ring. After drilling the hole, I put a long skinny piece of emery cloth over the tip of my finger and stuck my finger up inside the cartridge tube, in this way I was able to de-burr the inside of the cartridge tube where I drilled the 1 mm hole, you MUST do this. The flush the cartridge tube out with brake kleen (Contact Cleaner) and make sure it is very clean inside and out, you would not want any metal chips or grit from the emery cloth left anywhere on the cartridge tube.
Here is an exploded view of a fork....
Reassemble the fork, and put it back on the bike, now do the other fork.
Once you have both forks done, go to the list below to set the sag, you have to do this just like it says.
Here is a list of stuff to do that I put together...
First you have to have the correct springs for the combined weight of the rider and the bike.
All measurements from top of oil seal to underside of bottom yoke - silver tube!!
1) Set forks with 5mm more pull through the top yoke than standard i.e. lower the bike down the fork legs by 5mm (MAX 10mm)
2) Set Rebound fully off (screw all way out)
3) Set Preload fully off (all way out)
4) Raise front of bike off the ground and measure. (This is Full Travel) = A
5) Return bike to floor
6) Push down firmly and allow to return steadily (do not bounce) - measure = B
7) Lift up with clip-ons (keep wheel on the ground) and allow to settle down (not crash down) - measure = C
8) Measurement B + C divided by 2 = D
9) Measurement A minus D = 26mm - 28mm
10) Wind pre-load in until this figure is achieved, keep repeating 6 to 9 until it is correct.
11) Set rebound to "fastest possible return, but under control” (screw fully in & than back out probably ¾ to 1¼ turns out)
All the measurements are done with the bike sitting on it’s own wheels, no stands or blocks etc. but I did find that the first measurement “A” was easiest to do with the front of the bike still jacked off the floor, with the wheel hanging in the air, but after that one the bike sits on the ground, no rear stand or side stand.
No one sits on the bike either, the bike is sitting under it’s own weight. You can do this (I understand) because you have put the correct springs in there for the combined weight of you and the bike.
Go to a site like RaceTech www.racetech.com and they have a rider & bike weight calculator there that you can use for free. I happened to order my springs from them too.
If you have successfully installed the fork settings and the settings for the rear shock you may consider fitting a 4mm "slip plate" on the rear shock. This is a square piece of alloy sheet 4mm thick with a slot cut into it. The slot is made slightly wider than the top shock-mounting rod that passes through the frame and has a nut on it at the back of the tank. It sits on top of the brass colored "U" shaped bracket and underneath the frame thereby raising the rear by 4mm. To fit it you just loosen the nut up the vertical thread raise the bike by the rear subframe and slip the plate into position. Re-tighten the nut. Job done!!!
Now you have to set-up the rear shock, using the same method
above to set the sag at 8mm (we set the sag at 28mm on the forks) This is
usually almost impossible with the stock shock, but at least it is a target to
have. The preload will most likely be on either level 1 or 2.
Once that is done as close to 8 mm as you can make it, then you have to set the rebound on the shock.
- this is important -
It the same as the setting rebound for the forks "Set rebound to the fastest possible return, but under control” it is the same criteria. Turn the screw at the bottom of the shock all the way out first, then press on the seat and you will see that the return rate is very fast. The turn the screw in until the bike returns under control. Start looking carefully after 5 turns, keep going until you get it
As I said in the beginning, I do not have the gold valves, or any trick rear shock (want!) but for me now doing track days etc. (NOT racing) the bike is very good. Would the gold valves make it better? Yes, I think they would. Would a trick shock (Penske) make it even better, you bet, but, the bike handles great, very very well in fact, the biggest limiting factor is me, my lack of skill :)
Take a look at what I have spent, $99.95 US for the springs, about $20.00 for new fork oil, the bike had over 20,000 Km on it and the oil should have been changed as maintenance anyways, so if you want to split hairs you could say that for about $100.00 US my bike handles very well, and a heap better than it did stock.
If you need any help with this, please send me a mail at firstname.lastname@example.org
I hope this helped someone!!
Thanks again Roger at Revolution Racing for all your help!!
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