MX BIKE CONVERSION

Im trying to convert a Honda CRF250 to electric as my first electric bike project. i plan to do some posts on the build as it hopefully progresses..
so far i have :
CRF250 2005 rolling chassis that i got for £500
QS 138 90H 4kw motor
VOTOL EM200 cost of motor/controller/throttle/wiring £800 after duty etc
22s2p AIG lipo cells with 300amp BMS cost about £600
ive bench tested the electrics and can get the sprocket turning(fast) even with the $10 QS throttle !

my main concern is GEARING ?
ive read loads of threads of some amazing builds and it seems like 8:1 reduction is the right choice?
i really dont want a noisy jackshaft so am going to try direct drive as its way easier
the motor comes with a 428/14T sprocket so has anyone found a solution for fitting a 10 or 11 t on the tapered motor shaft?
i cant find the details of the taper and key

the rear sprocket needs to be a 428/80t plate sprocket which is big but not ridiculous at 335mm diameter
my local laser cutter can only make one if i supply the material and a cad file ... has anyone already done this ?
for refence the CRF fitment is a 125mm diameter hole and 6 x 8.5mm counter sunk holes on a 154mm PCD
the standard 51T 520 sprocket is 270mm diameter
plus it would need some larger holes ffor weight reduction while retaining strength and looking finished
ive heard water jet cutting distorts the finished product
any advice on bespoke sprockets would be greatly appreciated

i hope my information is of some help to the community
thanks in advance
Matt (uk)

Have you seen this thread (scroll down on this page for the gearing):https://endless-sphere.com/forums/viewtopic.php?f=12&t=103800&start=125

Will be following your build.

You're worried about noise, but you're looking to go to a 10t or 11t drive sprocket that will be extremely noisy???

Still less noisy than double reduction i’d say!

There is data on the axle and key in the 3000w mid drive thread.

What you can do easiest is to bolt or weld a sprocket on the outside of the 14t (or turn it/grind it down so you can keep the sideways position of the sprocket) to make a mounting for the sprocket to axle. I think either user ee291 or bionicon did this.

On 1:8 you’ll have power wheelies with the 70h motor and you’ll get about 30% more torque with 90H stator so this’ll push you up almost anything.

have you seen the new QS motor with reduction gearbox? maybe less chain noise and wear..

But was that the 90 motor?

I’d rather go 13/80 on the 90H motor than switch to 70H with internal gear for same torque.

The 90H with internal reduction (next addition from QS?) would be ideal although will be very long in total length.

hi Guys
thanks for the interest and information.
my project bike is up and running.
its better than i had hoped it could be
plenty of torque with 14/80 gearing (custom made steel 428-80T plate sprocket)
run time with plenty of power for an hour doing undulating off road riding.
struggling to post pics tho
ill try and post
ive put stuff on Electric Motorcycle Builds Facebook group

Any updates Matt?

Would love to see some pictures or videos