weak fork springs? Other bikes interchange?

[bwiencek]

Did a search and didn't see a whole lot of info on this - the front forks on my newly acquired 93 katana 600 seem a little weak - the bike sits nearly "straight up" when on it's sidestand. The bike nearly tips over when touched!

I put in a couple of washers that just fit in the fork tubes between the thin-walled spacer and the caps (about a half-inch's worth) - that seemed to fix the immediate tippiness when on the sidestand. What I would like to know is if the springs off a GSXR750 or 1100 katana would be stiffer and handle better or if the only option is to spend a ton of cash with someone like progressive (in which case the stock with a spacer is going to have to be good for a little while...)

[Court93kat]

I also have a 93 600, but never had any issues with the bike wanting to tip over on the kickstand.

I replaced my spacers with longer pieces of PVC pipe instead of the spacers others have used. If I remember correctly I went with 8.5" long pieces. I found them at a hardware store and only cost me $1 for both of them. Do a search on here for "fork spacers" with MD86 as the author. He did a nice little write up on how he did his. Good pointers and a discussion on how long to make the spacers for your body weight.

[md86]

I didn't do a write-up really , just tacked what I did on someone else's thread . Search "PVC fork spacer mod" , and you SHOULD find it .....

[fixer]

the Progressive springs are about $99 and will require new PVC spacers.
i had the progressive springs on my first KAt.. WELL worth it. you'll probably want to change the oil and adjust the oil level to your weight and riding.

simply trying to stuff more preload in the factory springs will change the sag of the suspension, make the forks more resistant to start responding to bumps and is just a stopgap measure. it also increases the chances or crossthreading the fork caps.

Cyber Poet has the Öhlins springs for late model Kats for $150

[87vert]

Re: weak fork springs? Other bikes interchange?

Did a search and didn't see a whole lot of info on this - the front forks on my newly acquired 93 katana 600 seem a little weak - the bike sits nearly "straight up" when on it's sidestand. The bike nearly tips over when touched!

Was it lowered by the previous owner?

[bwiencek]

PVC - really??? I would be worried about using PVC for something that's holding the bike up from diving to the ground... during a failure - doesn't PVC shatter/splinter when it breaks and the metal that's in there would distort.. Of course I was really supprised how THIN the spacer really was.

87vert - I really don't know if the bike was lowered - is there a measurement that can be taken? Wouldn't suprise me if it was indeed lowered a bit.

There was really NO preload on the springs when the caps were taken off - should there have been if it was at stock height?

[professorman]

Nice 1$ (Pre98)Fork Improvement

http://www.katriders.com/forums/viewtopic.php?t=9614

[bwiencek]

After reading the post - I'm going to measure the length of the spacer to see if it's been cut - the top didn't look like it (unless it was done on a lathe), but I didn't take it out to check the other side.

Also - it mentioned getting the rates for the front springs and ordering ones to match one's weight - where can I find a chart or something with a spring rate and rider weight listed? I noticed the $80 "sonic spring" place that was listed had 6 choices of spring rate for this bike...

[Black_peter]

PVC - really???

Personally I don't think PVC is a good idea. But hey.. What do I know??

87vert - I really don't know if the bike was lowered - is there a measurement that can be taken? Wouldn't suprise me if it was indeed lowered a bit.

The top of the fork should be pretty close to level with the bar mount.

There was really NO preload on the springs when the caps were taken off - should there have been if it was at stock height?

Yes!

Check racetech.. I think they list the standard spring rate.

[professorman]

After reading the post - I'm going to measure the length of the spacer to see if it's been cut - the top didn't look like it (unless it was done on a lathe), but I didn't take it out to check the other side.

Also - it mentioned getting the rates for the front springs and ordering ones to match one's weight - where can I find a chart or something with a spring rate and rider weight listed? I noticed the $80 "sonic spring" place that was listed had 6 choices of spring rate for this bike...

Personally, I would go with just adding a spacer instead of using the PVC. That is what I plan to do. I think most pre-98s have saggy front suspension over the years. I hear these guys rave at how much of a difference this mod makes though. I want to try it out pretty soon. I would say it sould like it is worth the $1 to do this mod.

[bwiencek]

Black_peter - don't think the forks were moved in relation to the clamps - I was wondering if they lowered it by cutting the spacer shorter - guess probably not - and I'm guessing also that there should have been some sort of pre-load on the springs so these springs are shot and since I've added 1/2 inch to the springs I've probably not even got it back to where stock is/was.

I guess I need to get some better ones....

What is everyone choosing for spring rate? They list everything from 80 to 1.0kg/mm - they didn't list a stock spring rate - just said "call"

[Black_peter]

Not a lot of people here have changed fork springs.
1Kilo / mm is pretty "standard" for sportbike springs.
If you are on the, shall we say, large side..
That might be a good choice.

[fixer]

PVC - really???

yes, really.

i installed Progressives in my '89 within a few months of getting it, along with stainless front brake lines.

i got a broken piece of PVC from the local hardware store for free, and chopped it to what i needed. at the time, i was living in a modest appartment and only had a small selection of handtools. PVC is easy to work, and inside the forks, it won't be exposed to UV, so it won't degrade. IIRC, Progressive recommends PVC and i was skeptical at the time, but i put over 60kmi on that in a little over three years with no problems.

while you can use steel tube, it's harder to cut and many people might have trouble getting it square. PVC is easy to cut with a hacksaw, easier with a tubing cutter.

i'll try just bumping the preload on the "new" kat, because saving $100 is cool, but i don't have a problem buying the Progressives for it either.

don't forget to loosen the top pinch bolts on the triple clamp before removing the caps, or you can chew up the hex on the caps. re-torque them to whatever the spec is. (anyone have that handy?)

on the KLR, with it's long, skinny forks, most people are not satisfied with simply increasing the preload... it makes the handling harsher on rough roads. some vendors provide steel spacers withthe Progressive springs and that eliminates the need to cut new spacers, unless you find you need more or less preload than the supplied spacer provides.

i'm running ATF for fork oil in the KLR, and plan on trying the same with the Kat.

[bwiencek]

Anyone run these springs:

http://www.sonicsprings.com - $79.95 for Katana springs seems like an awful good deal...


fixer - from what I understand ATF is around 7.5W to 10W which is a good fork oil weight in most cases - plus it's dirt cheap, has seal conditioners in it and can be bought anywhere - I've run that in older bike's forks as well as in a couple street bikes - doesn't offer the "tunability" of dedicated fork oil, but if you're not racing and just going to run a 10w fork oil then this is probably the ticket...

Black_peter - went to Racetech's spring calculator and for my larger stature they said almost 1.0 for 'street' and almost 1.1 for race... guess when I get everything else sorted out I'll order up some 1.0's as it's in the middle and should be a good compromise.. Think I'll put in a couple more washers or use a PVC connecor as a spacer in the mean time since I probably am not even back to "stock" preload with what I've got in there now!

[Black_peter]

.

Black_peter - went to Racetech's spring calculator and for my larger stature they said almost 1.0 for 'street' and almost 1.1 for race... guess when I get everything else sorted out I'll order up some 1.0's as it's in the middle and should be a good compromise.. Think I'll put in a couple more washers or use a PVC connecor as a spacer in the mean time since I probably am not even back to "stock" preload with what I've got in there now!

I know my springs I guess...