Sandman

I am using the same setup on my GSXR-750RR and GSXR-750J. The front forks are from a YZF R6 03/04 with K-Tech cartridges and spring rate 10 N/mm . Rear shocks are ohlins SU503 (GSXR1000 K5/K6) With spring rate 95 N/mm. Both are racebikes With gsxr 1100 engines and the setup is realy good.

An ohlins spring with no. -29 has spring stiffness equal to 90 N/mm (9.18 kg/mm=514 lbs/inch) and is ok for rider Weight (without gear) of 85-90 kg.

Have you checked the fatigue strength and number of stress cycles?

It is evident from the pictures above that you do not use a standard front fork, but an upside down fork of a newer brand. It may be that this fork is longer than a standard GSXR slingshot fork , and therefore you don’t have any ground clearance issues? ( I know that ground clearance is also dependent of suspension setup, but assuming correct setup for static and race sag, rebound and compression damping). The standard fork length for GSXR 750J is only 555mm, which is the shortest of all GSXR forks. The upside down forks for GSXR-750/1000/1100 is in the range of 715mm-740mm.

If you don’t have problems with ground clearance on a GSXR slingshot, than you’re not riding fast enough…and the corner speed is too low :-)

Spec for GSXR 750RK Rake: 24.5° Trail: 102 mm Wheelbase: 1405 mm (55.3 in) Spec for GSXR 750J Rake: 24.8° Trail: 99 mm Wheelbase: 14010 mm (55.5 in) The RK frame is slightly higher than the J frame. It is possible to get valve cover off the engine while it is in the RK frame. The engine has to be removed from the J frame to take off the valve cover. Compared to my latest superbike (CBR1000RR 2010) Rake: 23.3° Trail: 96 mm Wheelbase: 1407 mm (55.4 in) Weigth: 168 kg with oil and two litre of fuel. One of the problems with the GSXR750RK and GSXR750J is the lack of ground clearance. This can be modified by altering the height of the bike, both front and rear. The original front fork is to short. By using a longer front fork, the height of the front can be increased. The rear height can be increased by using a longer rear shock. The Ohlins rear shock for the GSXR 1000 K5/K6 is approximately 10mm longer than the standard shock. The length of the Ohlins shock can also be adjusted and lengthened additional 5mm. The adjustable shock mount (Optional kit part for the RK) also gives additional adjustments of the rear height. In this manner, the total height of my bikes is increased by approximately 50 mm front and rear. Another problem with these bikes is that they are quite top heavy, which is the reason for the heavy handling, especially in chicanes.

If we are talking about standard frames without extensive bracing, then the GSXR750RK frame is the best frame. It is possible to modify a slabside frame to handle very well, but this frame needs a lot of bracing. Whatever is done with respect to suspension setup of slabsides and slingshots, these bikes are quite heavy handling bikes compared to modern superbikes.

In my opinion, the GSXR750RK is the best handling frame. I have one GSXR 750RK-89 and one GSXR 750J-88, both of them are race bikes, as shown in the Picture. Specification for GSXR 750RK-89: Frame: GSXR 750RK Rear swing: GSXR 750RK Engine: GSXR 1100 (1052 ccm) Sylinder head: GSXR 1100, shimmed and race ported, heavy duty valve springs Camshafts: Webcam grind 236/223 Carburetors: Mikuni RS 38mm Bodywork: Sebimoto race fairing GSXR 750-91 and custom made race tail (molded by me). Exhaust system: Akrapovic Race, stainless steel headers/Titanium muffler Front fork: YZF R6 -03/04 (43mm) with K-Tech 25 SSK (RDS) race cartridges Wheels: Marchisini magnesium, 3.5-17 front and 5.5-17 rear. Tyres: Pirelli Rear suspension: GSXR 1000 K5/K6 Ohlins SU 503 with spring 1093-29/90 Ignition: Dyna 2000/mini coils Brakes: Brembo P4 30/34 calipers and 320mm SUNSTAR Neo Classic Front Disc Rotors Specification for GSXR 750J-88: Frame: GSXR 750 -88 Rear swing: GSXR 750 -95 Engine: GSXR 1100 (1052 ccm) Sylinder head: GSXR 1100, shimmed and race ported, heavy duty valve springs Camshafts: Webcam grind 236/223 Carburetors: Keihin CR Special 37mm Bodywork: Sebimoto race fairing GSXR 750-91 and custom made race tail (molded by me). Exhaust system: Yoshimura steel headers/alu muffler Front fork: YZF R6 -03/04 (43mm) with K-Tech 25 SSK (RDS) race cartridges Wheels: CBR1000RR -08, 3.5-17 front and GSXR-600 01 5.5-17 rear. Rear suspension: GSXR 1000 K5/K6 Ohlins SU 503 with spring 1093-29/90 Ignition: Dyna 2000/mini coils Brakes: Brembo P4 30/34 calipers and CBR1000RR -08 320mm brake discs.

No problem to fit a 750-j,k head on 1127 shim headed motor.

I got one GSXR 750 RK and one GSXR 750 -88, both with GSXR 1052 engines. It is poosible to remove the camcover when the engine is in the frame for the RK but not for the -88 J.