Aprilia RS125 2-STROKE conversion

**MrModify** · 05 February 2020

Hi to all of you - I am new to this blog. Busy converting an Aprilia RS125 2-STROKE to electric. Have slung a QS Motor 34kW hub-mounted motor in the swingarm. Beast of a motor but I am struggling to find a matching controller. Burnt out 2 Kelly KLS 8080I 400A controllers already. Both failed to cut back on high temperature and / or shut down completely on over temperature. I now have an APT96600 controller. Anybody tried this combo? Help

**gregjet** · 22 March 2020

That's a huge amount of torque for a frame designed for muich less.
One of the greatest handling road frames EVER. Might be worth de-powering a little, though itwould be fun to ride it like it is.
I reckon an RS250 running chassis would be a better match for that much torque.
Would love to see a pic or better yet a track video!!!

**tylerwatts** · 25 March 2020

I think that is a typo, it's a 4kw rated motor, probably does 12-14kw max with the new controller.

Cheers
Tyler

**MrModify** · 05 July 2020

It's a QS Motor 14kW (nominal) and 34kW (maximum) hub-mounted motor. 43kg. 350Nm of torque.

**gregjet** · 05 July 2020

Take one of the best handling motorcycles on Earth and add 43kg to the back wheel of a bike that weighs not much over 100kg total. Unsprung to sprung mass is not exactly ideal. Rear suspension will be completely overwhelmed.

**Stevo** · 06 July 2020

Can the rear shock be resprung and dampened? I checked my suspension go to RaceTech and they only have kits for RS250

**gregjet** · 06 July 2020

Definitely can be resuspended. You need a friendly experimental and knowlegeable suspension person hands on.
The big problem with suspending it properly is the crazy unusual weight distributions
. You have a crazy light chassis and swingarm, mated to a crazy heavy wheel, with massive torque across the rev range. It is completely out of the realms of the experience of almost everybody. I am NOT saying it can't be done, just that it is going to take a VERY intelligent and clean slate approach. Pretty much every chassis and suspension parameter will be wrong for optimium handling.
Good luck. It is the sort of problem I would love to be involved in solving and ,I bet, so would any creative suspension person .
My approach would be a mid engine but I would love to see an elegant solution to the rear hub motor problem.

**Stevo** · 07 July 2020

Finding the right spring is key and will take some experimenting ($$$)
Heavier oil and reshim the dampening and rebound shim stacks translates into more time experimenting.
Hopefully you can get it close in a few shock rebuilds. It would be an expensive project to get it dialed in right.

**gregjet** · 07 July 2020

Spring rate is the least of the problem. 43kg+ of unsprung weight on the end of a swingarm, will require really custom damping curve and complex SSV. Even on a flat road, if you get brake chatter, the damper will be severly stressed.
Getting the CoG anywhere near the pendulum axis will be a feat in itself.

**Stevo** · 08 July 2020

The shim stacks will need to be redone like I said. Heavier oil and reshimming the valves will do the trick, but it will take some experimenting and that means shock rebuilds. Lots of time and nitrogen refills. It would be a challenge and expensive for sure. That's why I chose to stay away from hub motors.
With that said, there are still some advantages to hub motors that are compelling. I think they are perfect for smallish scooter type builds,but that's just my 2 cents of opinion.