If you do not hit the brake to slow the rear tire spin and are above 5000 rpm how long do you wait for the clutch to release? Even with the clutch lever pulled in. Blipping the throttle, hitting the rear brakes, waiting yes, they will are work great! If you have the time....40+mph and you are going to fit this all in 50' with the down shifting and recovery of the hit and pull a left turn off all in this 50' before you have to be WOT? Don't forget your lifting the front end as you come off the drop off. I know I don't wan't to hit the brakes as I come off that.
Of all the people that should be yelling the wonders of the Rekluse it should be me with a fused left wrist that does not work. When racing I would rather have a real clutch then the Rekluse.
Ya, it's great for the trail rider, but, it will force damage if you ride hard.
This issue only happens when you're running ~5/8 to wide open throttle and you try to down shift from a high rear wheel speed under those conditions. If you're coming off a 4ft drop and you keep the throttle pinned as you come off and all of a sudden you have to shift down a gear or two in 1/10 of a second at a high engine RPM with a high wheel speed, you'll have difficulty doing so unless you wait for the engine RPaM to come down a bit which can take less than one second after letting off the throttle. If you're riding at WOT and jam on the rear brake as you let off the gas, you can downshift even quicker since rear wheel isn't loading the gearbox at that point.
I can downshift from 5th to 1st if I desire and the rear wheel will freewheel if I don't give the bike any throttle. It's like coasting at speed with the clutch lever pulled in. Once I blip my throttle, I'm locked in first and doing this at speed can float the valves and throw you over the bars.
If I'm riding WOT and need to immediately down shift, I jam on the brakes at the same time I'm pulling in my clutch lever while I'm off the gas for a fraction of a second and then rapidly downshift as opposed to rapidly power downshifting at a high engine & wheel speed without using any brakes. It generally takes less than one second before the engine RPM and or rear wheel speed drops enough to where I can blip the throttle for rapid & smooth downshifts. If I try to immediately downshift from a higher engine RPM (i.e. ~6000 RPM) with a high wheel speed without jamming on my rear brake, shifting can be very difficult and gets worse with increasing engine RPM, but it's easily something I can work around, especially riding off road. The hard core motard racers would be way more affected on this issue than the off road weekend warriors or off road racers in my opinion.
It's too easy to damage the gearbox when power downshifting at higher engine RPM with or without using the clutch and rapidly power downshifting the 650r from high engine RPM even with the stock clutch is much trickier than say a crf450r or cr250, etc. Watch the superbikers real close as they end a long straight and scream into a corner. Take note of their throttle wrist rapidly blipping the throttle as they rapidly down shift gear after gear and you'll hear the bike going vrooom...vrooom...vrooom, etc. They're not doing this to sound cool, but to match the engine speed to the rear wheel speed so the downshift happens under minimal load (easier on the gearbox). Mastering the timing of your downshifts while blipping the throttle (engine speed ~ rear wheel speed) will make downshifting easier with or without the z-start and and when you add in some rear braking, you can make quicker and smooth downshifts with a z-start equipped xr650r.