Extended 750 USD forks?

[Upshotknothole]

So my GSXR750n(US) has a blown fork seal and I’ve been putting it off for ages to get it fixed. Someone stripped the left caliper bolts at one point, drilled and tapped the caliper for larger bolts, and drilled out the holes to fit. I’d been holding off until I could either swap the lower, the whole fork, or the whole front end as I have a nice set of PM calipers and rotors to put on it. Over the past week it’s started to finally really leak when parked, and today I was going to swap in a W fork just as a temporary fix while I get that seal replaced. Then I noticed this.

The fork on the left is the stock fork, the one on the right is a 750W. They’re supposed to be the same length, 740mm. My stock forks are 762mm from the bottom of the caliper to the top of the cap, the W is about 740. Did anyone extend these forks for racing? I don’t know the history of the bike, but it came with some nice Yosh bits, including a Yosh top triple. The forks are also raised pretty high in the triples, but it always handled really well so I left them alone.

If these forks have had a lot of work done to the internals, I’d like to keep them. Can I swap out the lower from a W to fix the drilled out caliper holes? They’ve got the same part number, other option would be bushings, but I’d rather not. I’ve got new seals and oil for the forks, but I hate working on suspension and would rather not attempt it myself. 

I’m going to reassemble the bike today to get it off the stands, here’s the bike and the lower with the drilled out caliper holes.

The last thing that I noticed was that the backs of the caliper mounts have been ground down, I’m guessing to fix different calipers in the past. I really wish I knew the history on this bike, but the guy I bought it off of had no idea about any of the mods. Here’s the other fork lower showing the ground down area for the caliper.

 

Thanks for any information on these types of fork mods and what parts are interchangeable. 

 

[Duckndive]

Could be 1100 Stanchion  clip-on's on top of yoke "750 are under"  

[Upshotknothole]

Were the 750 or 1100 USD forks KYB? As the right fork has giant KYB stickers on the front. 

[Upshotknothole]

51 minutes ago, Duckndive said:

Could be 1100 Stanchion  clip-on's on top of yoke "750 are under"  

The markings on the fork lowers are for the 750 forks, unless the 1100s used the same lowers, but I don’t think they did. 

[Upshotknothole]

Checked Eblag, the 1100 forks have different part numbers on the lowers, and I believe they were Showas. 

[Upshotknothole]

I also measured up the forks, 50/54. The 1100s and Ws had different shaped bottoms as well on the upper stanchions where the seals sit. These are definitely oil cooled 750 forks, maybe 1100 internals? 

Edited May 4, 2023 by Upshotknothole
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