I just installed a JBS Hot Rod Sheave Kit last week. The kit included a machined primary sheave, 16g Mr Pulley greaseless weights and cam plate sliders, and an EPI purple spring. The install was really easy. It only took me 2 hours after I had all the correct tools. The hardest part of the install was finding a 45mm socket. I finally gave up and bought a 1 13/16" socket and it worked just fine.
I just took my 700 and 550 out to Chesterfield Trails this past Saturday and Sunday for the first ride since installing JBS sheaves in both bikes. I absolutely love this kit!
First, let me compare what I noticed in my bike between stock tires and 28" Zillas before the JBS sheave for a baseline. Before the sheaves were installed, I noticed only a little loss in bottom end with the bigger tires. Most noticeably in mud holes and in situations where I was trying to climb over something like a big tree limb, out of a deep mud hole with a steep exit, over a tree root in a deep rut, etc. It seemed like it took more throttle than it did with the stock tires to get the same response out of my bike. I could get the front wheels light and sometimes a little off the ground in high gear from a stop on flat ground with both sets of tires as long as I could get enough traction. In low gear I could stand the bike all the way up on the back rack if I wasn't careful. I also thought engine breaking was to sudden. As soon as you let off the throttle it was instantly full engine breaking. When your riding down hills on snow or mud covered rocks the sudden hard engine breaking can easily put you into an unwanted slide.
After installing a JBS sheave, greased 16g Mr Pulley greaseless sliding roller weights, cam plate slidders and a purple spring I immediately noticed a huge improvement in bottom end and mid-range. The bike seems to run at a little higher RPM. It's just enough to keep it right in the power band all the time. Throttle response and engine breaking seem smoother. I no longer have a slight delay or almost a stutter on hard acceleration from a stop like I did before the install. That is something I noticed every since it was new. The service department at the dealership told me it was normal. I now know it is either from the way it was geared from the factory or from the heaver stock weights. I'm not sure which, but this kit took care of it. Climbing over obstacles is much easier to control and takes less throttle. I noticed the same powering around tight turns on the trails. I can now easily stand the 700 all the way up in high gear provided I have some traction. It was a little difficult on Saturday's ride because we were getting a wintery mix of rain snow and ice. Sunday was better, but still cold and wet. The 550 definitely has more bottom end torque than my 700 had stock. It will stand all the way up easily in low. It was also pulling the front wheels up a little while spinning the rears in high. With better traction, I think it would be possible to pull it up in high too. I haven't had an oppertunity to open either of them up to test top speed, but I can say that the Grizzly's will get up to top speed quicker. On my 700, I was able to hit 55 mph on a short stretch of paved road leading up to where we parked the trailer. Before installing the sheave kit, I could only hit 47 mph on the same stretch of pavement. To say I am happy with this purchase would be an understatement. Everyone told me tires are the best mod you can do to your bike. I don't think that is true anymore, but without the tires I wouldn't have bought this kit. It is definitely worth it and I recommend to anyone wanting to do a clutch kit!
Please let me know if you have any questions or if there is anything that I didn't address.