My 12T front sprocket was absolute toast and the 71T rear sprocket a mistake, so I tried something different this time. I was looking for max torque using the Zero rear sprocket, which is ultra-light and readily available. As others here have noted, 10% more torque is a
very significant increase, even on my 2.8 (a 5.7 / 6.5 FX would've been much more impressive, especially on the street). The brief initial road test was a bit disappointing, but recent dirt rides were another story. Above 90% SOC most of the gain was lost in wheelspin in the dirt, but definitely good for a near loop-out in my driveway.
It was great having the added 'pop' and drive out of corners, but even better was maintaining a decent power level down to lower SOC's which made the last lap nearly as fun as the first.
Here's the complete installation - the entire lower chain guide was replaced as the old chain had cut it in half (!), and the new mini chain guide and motor-mount protector are visible in the upper left, ahead of the shock:
Removing the old front sprocket wasn't too bad, but had its moments. I held the sprocket with a
Motion Pro 08-0008 clutch-holding tool & heated the M10 shaft screw for 60 sec. with a propane torch (no effect), then another 80 sec. after a 1 min. cool-down (screw came right out, using an M6 key socket & impact gun). The hollow motor shaft was half full of PB Blaster or similar anti-rust fluid. The setscrews came right out with an M3 key socket / impact gun. A gear puller was then used to pull the sprocket off the shaft; it was on there pretty tight. I ran the center bolt of the puller thru the bearing hole, with the clamps either side of it to the sprocket O.D. I wouldn't recommend using a pry bar against the motor casing, even briefly.
Here's the new 10T front sprocket, retaining dome washer, and M10 shaft screw:
The front sprocket machining requirements are also mentioned in
this thread (10T & 11T are the same). The end of my ¼ " motor-shaft key end had been peened over the shaft end, so I smoothed it down with the Dremel so the new sprocket could slide on easily. I tapped the new sprocket on using a 30mm socket thru the frame bearing hole (my bearings were out for replacement at the time; if they're in, an M20 bolt thru the bearing center with a flat plate over the sprocket end should work).
The OEM sprocket retaining washer is too large to use with a 10T sprocket (it might be OK with an 11T, I don't know). It can be turned down on a lathe, or
these washers can be used (the M8 hole & countersink will have to be enlarged for the M10 shaft screw head, but the O.D. and strength are fine). I used a thin steel washer under the aluminum one to give a hard stop for the washer & bolt against the motor shaft, rather than just letting the aluminum bow inwards into the air gap (torqued to 35 ft/lb). Clearance from the motor shaft screw head to the 'stub axle' swingarm pivot was @ 1mm / .040". Rear sprocket screws (M8x25 black-stainless flatheads) were installed w/Belleville-type lockwashers, flange nuts, & blue Loc-Tite, then torqued to 20 ft/lbs; if these loosen up, they can oval the hub holes & gouge the hell out of the swingarm.
The chain was replaced with the same excellent D.I.D. 520NZ non O-ring racing chain as before. The new chain/sprocket setup sounds completely different, though. Before it was a cyclic zipper-type noise, but now it's a strange chordal drone; it reminds me of the intro to the 'Ancient Aliens' TV show, during the episode-title screen. I think most of it may be chain/knobby-tire noise interaction. It isn't super loud, just weird.
Current Zero motorcycles are clearly designed mainly for belt drive, which has little in common with a chainsaw.
In addition to wasting the Zero guide, the chain began taking bites out of the LH rear motor mount and chipping powder coat off the swingarm after it got worn a bit. I made up a steel motor-mount protector (seen in the next pic, covered w/JB Weld) which halted the damage and worked OK, but then I decided it would be better to keep the chain away from that area altogether rather than let the chain and protector duel to the death.
Here's what I call the 'mini chain guide', which mounts atop the LH swingarm using another M5 Riv-Nut type threaded insert (the notch cut in the top edge is only needed if the swingarm is lowered as in
this thread):
Here's the diagram:
This does an excellent job keeping the top chain run on the straight & narrow, and is very easy on the chain. If the end 'rub' is removed, this guide can also be used to hold the front / top end of a belt guard plate between the tire and belt run (the bottom of the plate could be bolted to the chain-guide mount, and channels could be mounted top & bottom to partially shield the belt runs).
It's also very important to use the swingarm crosstube protector sleeve included in the chain kit, but unfortunately this did not fit well or clamp tightly. I had to cut off the screw flanges & secure it to the crosstube using double-stick tape and two giant tie-wraps, which works great and hasn't budged at all.
Ray
Author
Topic: 10T / 65T sprockets & chain protection (Read 8442 times)