Slabside/slingshot forks/yokes

[wraith]

Easy one this but my book dose not say the forks size of the gsxr rwu 750 and the slabside forks.

So will the rwu gsxr750 slingshot forks fit the slabside yokes?

Cheers.

[Macduff]

I could be wrong but think the slingy forks are 43mm and slabbie forks are 41mm

[dupersunc]

No they won't fit. Sorry.

[wraith]

I thought that was the case, best checking 

[micktodd]

list of 41mm forks on this site  http://www.dotheton.com/forum/index.php?topic=20950.0

might help

 

[Swiss Toni]

15 hours ago, Macduff said:

I could be wrong but think the slingy forks are 43mm and slabbie forks are 41mm

No! You're right. 

[suzook12]

the yolks swap out tho if you specifically wanted j/k rwu's

[Macduff]

Are the J/K rwu forks better than the slabby ones? I find my slabby front pretty could for coping with the shit roads I ride on though my speeds these days probably don't test them that hard. 

[wraith]

I have a set of 1100k forks on the Kat and find them to be quite poppy ie  when you go over a bump they rebound quickly.

But I do need to set them up more and have some progressive fork springs for them.

[canamant]

Slabby forks are OK if set up properly.  The 43mm conventional forks fitted to 88/89/90? GSXRs have compression and rebound damping adjustment whereas the slabby units only have compression (or single) damping adjustment.  However, the range of damping adjustment on any production bike fork of the day will be minimal.  The factories will have configured the range of adjustment so that the owner (who may well have zero idea) cannot completely screw it up to the point of dangerous and then try and blame the bike manufacturer for a subsequent instability and crash.

 

[nlovien]

9 hours ago, canamant said:

Slabby forks are OK if set up properly. 

can you expand on this - i've recently fitted these to a project, would be interested in the hard gained knowledge of how to get the best from them ?

apreciated

 

 

[GixxerDale]

I made a big improvement to my slabby forks , by fitting some YSS PD valve cartridge emulators in them . I also put some fresh progressive springs in as well.  the PD valves improve the 'suppleness' of the forks and made the ride much more compliant, they can be adjusted , although it does involve fishing them out of the forks with a coat hanger, which is a bit of a faff until you get the hang of it , but at least saves dropping the forks out. Fairly basic level of engineering required , main element of the works is drilling some holes in the damper tubes.

here is a description cut and pasted from wemoto:

Improving the performance of damping rod forks

A common problem with bikes that have damping rod forks instead of cartridge forks is that the damping can be too harsh, or too easy to bottom out. In the past, this could have been addressed by changing the weight of the fork oil, or adapting the size of the holes in the damper rod that the oil passes through. The drawback of this method is that, quite often, the quantity of oil passing through isn't controlled enough and either too much or too little oil passes through – a bit of a black art, and very hit and miss with results - not an effective solution to damping issues.

PD Fork Valves — The better solution

PD Fork Valves are the cost-effective solution to this problem. Fitted at the top of the damping rods and held in place with the main springs, PD fork valves control the way the oil is distributed, so that the forks emulate cartridge forks, thus increasing their performance. They offer better control with a progressive feeling, better steering response and a more comfortable ride.

How PD Fork Valves work

The key to the effectiveness of PD fork valves is in their unique and innovative design. Once installed, they change the shape of the damping curve so that the oil is passed in a more controlled way. Low oil viscosity passes through more quickly, providing more damping; and high oil viscosity passes through more slowly, providing less damping.

PD fork valves take the control of compression damping away from the damping rod; once fitted, it will be controlled by the spring preload you set on the valve. They don't make a difference to rebound damping though this can be managed with the oil, which will provide more or less rebound depending on its viscosity.

Where can I buy PD Fork Valves?

Wemoto stocks YSS PD fork valves, which come in six sizes, suitable for a wide range of applications. YSS provides a full two-year warranty on all its products, for added reassurance.

Pics from when I did it attached, the damper rod showing before and after, make sure absolutely no swarf left after drilling.

 

 

 

PD valves ready for re assembly:

 

 

 

 

 

 

Hope that helps , if you shop about only about £60-70 so cheap fix for slabby forks......

https://www.Eblag.co.uk/itm/Suzuki-GSXR-1100-GSXR1100-1986-1987-1988-YSS-PD-Fork-Valves/172320614454?hash=item281f1be836:g:W88AAOSwMtxXrEdy

 

 

 

 

[Macduff]

Cheers for that , very useful. 

 

[suzook12]

I've used racetech valve emulators in the past on a different bike (Triumph) and was impressed by them....Having used a multitude of gsxr forks in my street bikes, my 750 j chassis was at its best with the stock forks, I replaced them with oil boiler USD's and it lost something handling wise. The WP forks and later seemed much better. I lived out in the fens at the time and the back roads there are horrendous, so apart from the regular fork seal changes, when set up the early slingshot RWU's are the pick of the bunch for me for riding hard on proper shite roads.... However, if I was building again would go more modern...

Edited November 2, 2017 by suzook12

[nlovien]

thanks - good useful info ref: 41mm slabby improvement and the real world fens road feed back = sounds like similar play ground for myself - my own best of best for similar bumpy and rippled country roads is a set of 45mm original fireblade forks with a maxton tweak  - I like to twiddle with things but these - I fitted them to my Harris and forgot they had adjusters

you really can have yir cake and eat it - they soak up the bumps and even better the faster ripple/chatter stuff- give you the kind of feed back that makes you feel your in direct contact with the tyre yet keep things controlled under heavy braking - problem now is I want every bike I build to behave the same way ( these are a relatively short fork though)

[Macduff]

Of all my bikes I've had  I'd say the slabby forks I have cope with the rippled local tarmac better than any bar the WP forked KTMs and they were meant to cope with the rough. This could be that most modern  sports bike forks are too stiffly sprung to give a good feel over such roads 

[canamant]

nlovien

Slabby forks are simle to do.  As long as the seals and the bushes are in good condition I just set the fork oil level at 110mm from the top of the tube with the springs removed and the forks compressed.  I also put 4 pre-decimal pennies on top of the spacer tube and flat washer.  Fork springs are standard.  Oil weight was #10.  I am 18 stone.  Bike has lost a lot of weight as all the road gear is junked.

 

[micktodd]

Just about to refurb some early gsxr 1100 forks  good reading