GSXR USD Fork Spring and Oil Question

[Guest]

I am in the process of replacing the fork seals on my 1995 USD GSXR 750 forks that I currently have on my 1983 GS1100esd since they are leaking but wanted to ask a few questions before proceeding.

Should I replace the fork springs too while Im at it or would I be ok with just going with a heavier oil?

I did some research and found that others have recommended going with a 15w fork oil which would also stiffed up the front end. Is this right?

If you think I should change out my springs, what do you think with going with a set of Race Tech springs?
When I did the on-line fork spring calculation from racetech, I came up with a recommendation for my weight (around 200lb) and with the 20 lb weight difference from the GSXR 750 to my GS1100 of about 20 lbs (total 200 + 20= 220 lb) to go with a .95kg/mm spring.

Can I just redo the seals, dust covers, spring and oil or will I need to go further and do a re-valve job too?

I am not planning on racing my bike and mainly plan on using it as a commuter vehicle. Any feedback would be appreicated!

[80GS1000]

Dunno if this helps but my GS with the GSXR 1000 front end is getting resprung with some Racetech springs. It's much too soft with the stock GSXR springs.

[kichigai]

Dunno if this helps but my GS with the GSXR 1000 front end is getting resprung with some Racetech springs. It's much too soft with the stock GSXR springs.

Are also going with a valve kit too or just springs??

[80GS1000]

Just springs for now.

[Mark M]

Should I replace the fork springs too while Im at it or would I be ok with just going with a heavier oil?

I did some research and found that others have recommended going with a 15w fork oil which would also stiffed up the front end. Is this right?

If you think I should change out my springs, what do you think with going with a set of Race Tech springs?
When I did the on-line fork spring calculation from racetech, I came up with a recommendation for my weight (around 200lb) and with the 20 lb weight difference from the GSXR 750 to my GS1100 of about 20 lbs (total 200 + 20= 220 lb) to go with a .95kg/mm spring.

Can I just redo the seals, dust covers, spring and oil or will I need to go further and do a re-valve job too?

I am not planning on racing my bike and mainly plan on using it as a commuter vehicle. Any feedback would be appreicated!

1) Springs and oil solve different problems, so one will not compensate for the other.

2) 15W is way too heavy in the GSXR forks. Stock is 5-7.5W and the 7.5W should be fine even with heavier springs. That's what the adjusters are for!:-D Oh yeah, don't cheap out and use ATF or something else to save a couple $$ over real fork oil. Use the good stuff and enjoy.

3) RT springs are decent quality if you want to change out the stock ones. 0.95kg/mm sounds about right, maybe a touch on the low side for your weight. Softer is generally better unless you ride hard on a track, though and RT specs softer springs that almost any other aftermarket suspension tuners. They will be much stiffer than the OEM stuff, though.

4) For your uses, just change the seals, springs and oil and then set the forks up properly for your weight. A revalve is a waste of money for you, use what you save to buy more gas and enjoy your bike. You may want to consider replacing the bushings as well, just in case the original ones are getting worn. They will add about $40-$50 to the cost of your rebuild but your fork will be completely freshened at that point and good for years of service. If you are not in a hurry, you can check the bushings once you have the fork apart (you are flushing and cleaning them out with kerosene or varsol, right?) and order some if you need them. It usually takes 3-4 days for my local dealer to get them in if not in stock.

Mark

[kichigai]

1)

RT springs are decent quality if you want to change out the stock ones. 0.95kg/mm sounds about right, maybe a touch on the low side for your weight. Softer is generally better unless you ride hard on a track, though and RT specs softer springs that almost any other aftermarket suspension tuners. They will be much stiffer than the OEM stuff, though.

Mark

Mark, do you recommend that I go with a set of 1kg/mm springs?

80GS1000, what spring are going with on your bike?

[isleoman]

I concur with Mark on the fork oil weight. 15W is too heavy. In my GSXR1100 (95) I'm using the 7.5W. Some of the Gixxer guys suggest 10W for the 1100 but I think your 750 forks are made by Showa, and it would be a waste to mute the superior abilities of those forks with heavier oil.

I personally like stiffer weight springs without a lot of preload placed on them. 1.0 or 1.05 would be my advice. The guy I bought my forks from said they had the stiffer R/T spring in them but I didn't have a way of verifying if that was accurate when I had them apart. I'm happy with the way mine are handling.

I bought some of the longer Ohlins rear shocks meant for the Honda CB1100 in the group buy.
They are about 1.25 inches taller than the stock Suzuki shocks. The added ride height in the rear should sharpen the steering some.

[80GS1000]

Using Rachtech's online calculator, they recommended 1.0 kg/mm springs for my weight and the weight difference from the GSXR 1000 and my GS1000. I like a firm spring so I can feel what the front end's doing and plan on doing a trackday with this bike so I used the "racing" option on their online calculator.

[kichigai]

Thanks fellas!

I just placed an order for the 1.0 kg/mm springs from Race Tech. They said that they will be shipping them today and should have them by tomarrow! Yea!!!\\/

[Mark M]

Mark, do you recommend that I go with a set of 1kg/mm springs?

80GS1000, what spring are going with on your bike?

I see you already ordered the 1.0's so it doesn't matter now. Either the 0.95 or 1.0 will work fine, mostly you will just use less initial preload on the 1.0's. I like heavier rate springs with less preload myself, so if I am in between rates, I would go for the heavier ones.

You will love how it handles with the forks properly sorted and 17" radial rubber. If you need a set up guide, PM me your email address and I can mail you one on how to set up preload and damping to get you started.

Mark

[kichigai]

Ok, I got my Racetech springs in the mail for my 95 GSXR forks and am attempting to change out the spring and seals. The seal replacement went well but I am a bit stumped on if I need to use any of the pre-load washers or spring washers that came with the spring kit? The kit said to use if needed so I wasn't sure. Have any of you rebuilt your own GSXR forks and upgrade your fork springs on your project bikes? If so, where did you place the washers and how many? Any recommendations and/or suggestions would be appreciated. Thanks Kich.

[Mark M]

Ok, I got my Racetech springs in the mail for my 95 GSXR forks and am attempting to change out the spring and seals. The seal replacement went well but I am a bit stumped on if I need to use any of the pre-load washers or spring washers that came with the spring kit? The kit said to use if needed so I wasn't sure. Have any of you rebuilt your own GSXR forks and upgrade your fork springs on your project bikes? If so, where did you place the washers and how many? Any recommendations and/or suggestions would be appreciated. Thanks Kich.

No idea on the GSXR forks firsthand, but I do know that typical sport bike info says to run 10-15mm of initial preload on your springs. You need them to be preloaded a bit at full extension to avoid the forks having uncontrolled motion in the full droop condition. Set your fork cap adjusters to the middle of their adjustment range, then test assemble each fork on your bench to see how much initial preload there will be on the springs. If it is less than 10mm, add washers as required to get to 10mm or more.

Mark

[kichigai]

Thanks Mark for the tip!

I actually took my fork and my new spring kit and drove over to RaceTech factory today and met with their tech support guy Louie to get some answers. Boy, I learned a lot while I was there!

After trying to piece everything together, Louie soon found out that my forks were not from a 95 GSXR750 but instead a 93 which the fork springs is actially smaller by 2.5mm in diameter. (Note for 94 and 95 models, the spring outer diameter is 38mm, for the 93 model it is 35.5mm). After getting the correct springs, he put the stock springs and the new spring side by side to determine the difference in height.
He stacked up a total of 8 washers to make the springs the same height.
After that, he told me to take the new parts home and to install exactly 8 washer in each of the fork tube before installing the spring and start putting my forks back together.

Besides answering my washers questions, he also gave me a few pointers on what to do when re-assembling my forks:

Make sure to put in the proper level of fork oil.

The preload adjuster should be back out all the way prior to install and set after I finish putting my bike back together and have performed the sag test.

The rebound and the other adjuster near the axle (sorry for got the correct term) should be screwed in 1/2 way as a starting point. The half way point can be figured out by screwing the adjustment screw all the way out and all the way in and counting the turns and back the screw half of the turns.

Hope this help others that maybe stumped while doing their fork spring replacement.

I will post up later once I have everything back together to let everyone know how things turned out.

Thanks everyone for your recommendations!