My target is to bring the rpm down to 5,000 rpm at 85 mph – the maximum that cruise control will hold. That's a drop of around 500 rpm. For the front I went +1 with a 19T Vortex sprocket from vcyclenut. At the rear I’m going 2 teeth less with a 42T steel sprocket from SuperSproxUSA.
I’d hoped to change the front sprocket and try it out before winter but, when I went to make the change, I found out that changing sprockets on this bike is not the quick swap that I’m used to. There is a guard around the engine sprocket. To remove that requires the clutch slave cylinder to be removed which, in turn, requires the water pump cover to be loosened which, in turn, requires the coolant to be drained…… I didn’t have enough time for all that, so I left it alone and put the sprocket cover back on. I revisited the task last weekend.
If the description below looks long that’s because it is - the whole process took about 2 hours (really did!) and I started with the left fairing already removed for another project. I haven’t had a chance to see what it feels like to ride with the new front sprocket but I’ll share the experience of fitting it. When I get around to changing the rear I’ll provide a write up for that too. Meanwhile, here’s Champ87’s suggested sequence for front sprocket removal:
- Remove the engine sprocket cover
- Flatten out the lock washer and loosen the engine sprocket nut. I put the bike on the sidestand, in gear with a tie to hold the front brake on. I stomped on the rear brake while leaning across the bike to use a big breaker bar. No surprise, it took some serious grunt to break it loose, but break loose it did. A one man job but it would help to have a friend available to hold the bike and stomp on rear brake
- Drain coolant – there is a drain bolt on the water pump cover. Not much coolant will come out until you release the radiator cap. I collected 1.8L. Leave the bike on the sidestand. You’ll get slightly more out that way – less to spill on the floor when you remove the water pump cover
- Put the bike on the center stand/paddock stand and loosen the chain to maximum slack
- Remove the shift lever
- Loosen water pump cover. You can leave the hoses attached – the cover just needs to be moved to get to a bolt
- Remove clutch slave cylinder. The service manual says pull the clutch lever while holding the piston then tie the lever back to bar to prevent piston from coming out. I did that but still felt nervous about the piston creeping out, so I also used a clamp to hold the piston in place
- Remove the bolts holding the engine sprocket chain guard. Remove the clutch slave cylinder holder and lift the chain guard away
- Replace the sprocket. Refit the lock washer and nut. Torque to correct setting and bend the lock washer tab into place
- Replace the chain guard and slave cylinder holder. Service manual says to use thread locking agent on the holding bolts. Torque the bolts
- Refit clutch slave cylinder. There is a gasket – the service manual says to fit a new one, but it looks like it would be reusable. I had a new one to hand so I replaced anyway. Use thread locking agent and torque the bolts
- Refit the water pump cover. There is an O-Ring in a groove in the water pump cover. I bought a spare just in case. New O-Ring works better on the bike than in the packet, so I fitted new. Check that locating dowels are still in place before positioning the cover. Torque the bolts
- Refit the shift lever using the indent mark to align the lever on the shaft
- Replace the engine sprocket cover
- Adjust chain
- Refill coolant. Run engine up to normal operating temp to purge air from cooling system. Allow to cool down then check coolant level
