Honda CRF 250 to Honda CRE Build QS138 70h EBMX Amorge

[fmxxx666]

Hey all,

have been a quiet read only user here in this forum so far but now I found some time to share my Build with you.

I was riding MX for about 8 years then stopped about 10 years ago due to Work, Wife, House, Kid... now in my mid 30`s I have to do something against my Daddy Belly so I was looking for MX bikes went to the local track with my son and saw dudes on Electro Bikes and noticed the stark, then noticed there are ways to convert (I was always a Honda guy back in the days so it had to be a honda again )

so had the idea semptember 2024 and started a deep dive learning curve until I understood all these battery specs, controller details etc

A friend of mine had a Honda CRF250 from 2009 he wanted to get rid of so I took that opportunity:

sold the Engine
sold the carb
sold the exhaust
gave away the plastics and seat

and was left with a rolling chassis for a little under 1000 bucks

deep cleaning like really really deep and intensive
changed all bearings

then it was time to source all the parts needed
after reading through forums for weeks I sattled with this parts:
Motor: QS138 70h V3 (late 2024 updated version)
Controller: EBMX X-9000
Battery: Custom Amorge 22S13P with Molicel P45B Cells
Motor mounts and sprocket: from Lithium King

my poor photoshop skills on how it should look finished


and somewhere in March 2025 I was "done" with the Build:


I upgraded a few more things besides the electrical stuff:
-Haan Wheels
-CRF450 2019 Suspension and Triple Clamps
-CRF450 2021 Plastics (TX-Race restyle kit) and Custom Graphics
-CRF450 2021 Carbon Tank Cover

Regarding Rear brake I had also a learning curve:
first off I eliminated the rear foot brake and installed a left hand rear brake master cylinder on the handle bars.
Only to find out during the first two rides, that in every "emergecy" situation,
I instinctly hammer my foot into the brake wich isn´t there anymore
and that cost me always two seconds before my head could tell my hand to reach of the left hand rear brake lever...
Its a cool idea to have both brakes on the bars like a mountianbike but since I haven´t ridden motocross or any bycicle in 10 years I first have to get more used to riding again before I start with such things
so for this season I installed the oem rear foot brake again.
Additionally my EBMX controller came with a Thumb throttle that I have set to be a regen brake for now and put it on the left hand side its fully adjustable in the app and its powerfull enough to block the rear wheel so I more and more now use this as the rear brake.


Battery gave me the hardest time
like finding the right spec and size for my build.
I was pretty fast confident to let amorge build me one.
but it took me nearly 2 months to settle for size shape and spec after a ton of forth and back with amorge.
I have come up with a pretty good design to use all space available and be quick swappable as well,
but Amorge was not able to produce it in a stainless steel case:


so I had to simplyfy it and gave up some space on the bottom of the battery but then went for an angled top to gain some space there and follow the like of the gastank so I sattled with amorge with this design:



Battery specs:
22S13P 81,4V 58,5AH Molicel P45B Cells giving the battery an incredible 650Amps Peak
Battery is open discharge so BMS only for charging and balancing to elimitate the heat generated by the BMS during discharge (riding)

I went for 22S as this is the maximum my controller supports.
I went for a fully overpowered battery so my battery is laughing at the 350Amps that I am pulling and is never really under stress.

here is how it sits in the frame:

Its changable quiet quick I just need to take off whats left from the tank and the seat, then I can slide it out of the top.
Takes only about 4 min to change the battery if needed.


then it was time to design a Battery cage:





here a video of the bike in action:

it was really fun to build it and I am totally in love with the bikes performance.
as I said I havent ridden MX since 10 years so as my fitness rises again I will adjust it for more power.
But right now it suits me well and I have a ton of reserves to go higher in the settings.

 

[fmxxx666]

few more details from during the build:

that one moment you just for testing connect everything together and the motor spins for the first time and you actually see that this might gonna work in the end

while finishing up the bike I had several Ideas how to set things up.

so for instance I was full on using a Cable Throttle for the feel.
I had ordered a Surron E-Throttle in advance but the twist travel way felt totally wired to me as it is super short:

So I decided to go with a Cable throttle.
Ordered a E-Cable Box and a 2 Stroke Throttle and set it all up:

super smooth and snappy after some adjustments with the dremel tool
it felt awesome like a real throttle connected to a carb.
I was happy.
But at that stage I was still 2 months away from my first ride with the bike...

so in the meantime I had the idea that this should also be possible with the OEM 2 Cable Throttle from the CRF like one cable to actively open the throttle and one cable to actively close the throttle this helps to eliminate the chance of a sticky whisky throttle.
so I DIY´ed myself a double cable setup:

but here comes the devastating truth....
test riding it round the house with the cable throttle all fine felt great:

(Ignore the ratteling noise the chain was way too tight it was the very first test ride of the build)

but first ride on the track it was a big no no the twist way was too long when you hit near full throttle your hand is in an awkward position that gives you armpump instantly plus it was hard to handle the bike like that.
How U use the throttle on an Electric bike in the end is totally different from a gas bike so I had to bow my head in shame for wasting so much time and money to make a cable throttle work when just the 20 bucks surron E-Throttle would have already gave me all I need.

So surron E-throttle is what I use until now and I am actually happy with it.




but bin eyeballing this FX Throttle for some days maybe Ill give them a shot once they are back in stock:

Fully CNC and they are 3 way adjustable in the spring tention.




next my findings with the left hand side of the handlebar:
as written above the very first thing I did was installing a rear brake master cylinder but that idea was berried for this season as my foot was constantly looking for the brake paddle in risky situations.

I didn´t liked the idea of leaving the left hand side without a lever so since i have a few Surron E-Cable boxes left over now I soldered one to the 3pin that goes to the Thumb throttle that came with the EBMX Controller.

This connected to a standart Clutch Cable lever gave me the option to use the lever
A. as an E-Clutch or
B. as a Regen Brake
I was first full on the idea that an E-Clutch will be great.
But noticed again that you simply dont use it as it does not exactly feel like a real clutch.
then I set it up as a regen brake but noticed that it does not really react like I wanted it to... and sometimes it was even sticking and blocked my throttle as you cannot accelerate when the regen brake is engaged.

so I bite the bitter pill and installed the normal thumb throttle again on the left hand side and use it as a regen brake:

This little thing is ugly and does not belong on a MX bike in my eyes but it works like a charm and gets me used to use a rear brake other than the foot brake.


next up I wanted some sort of Kill switch.
If I fall and the bike goes full throttle on its own... and I am physically not able to get there quick and shut it off
so I had a look for ideas.
Went with a Magnetic kill switch connected to the Throttle Power line (throttle no power = throttle gives no signal back to the controller) will have the benefit the bike stays switched on and controlled but just cannot accelerate without the magnet

was the best solution I found so far

 

[amberwolf]

but first ride on the track it was a big no no the twist way was too long when you hit near full throttle your hand is in an awkward position that gives you armpump instantly plus it was hard to handle the bike like that.
How U use the throttle on an Electric bike in the end is totally different from a gas bike so I had to bow my head in shame for wasting so much time and money to make a cable throttle work when just the 20 bucks surron E-Throttle would have already gave me all I need.

You might take a peek at bananu7's post here:

2008 CRF250R - QS138v3 70H - ANT - Sanyo UR18650-RX 20s20p - Votol EM260

It sounds like you have too soft rear spring with that 24mm static sag, do you know how much preload? But the shock likely needs a rebuild too ;) I think I have changed springs 4 times, and it is still too soft.. I haven't measured the preload on the spring, just the sags. I agree that it...

endless-sphere.com

 

[j bjork]

Nice build
That FX throttle looks nice, might be interesting to try. But I am rather happy with the surron throttle I use now.
I think I actually would want slightly shorter twist than it has though, I for sure don't want longer twist..
It is more aggressive than the ones I have had before though, I had to tune the throttle curve to get it rideable.

About hand vs foot brake, it dont take long to learn to use the hand brake. But it takes longer to get rid of the reflex to hit the foot brake when things go wrong. But not more than a month or so, and hand brake is better in almost every way.