1996 KX 125 EV Conversion

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7/19/2018 8:29 AM

Hey all, I'm a new vital member as of last week. I have browsed this forum a lot and have read a ton of the amazing bike builds on here. That being said, I have always wanted to do a full bike build. I am a senior physics major and for my senior research project this coming school year I will be building an electric KX 125. I have a lot of plans for this build, but would love some input from you guys as well as any advice you might have for the EV conversion. I plan to make this bike perform just like it did before I pulled the perfectly good running engine out of it. Here is the bike I picked up for $800 which I didn't think was too bad considering it ran.
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Don't mind the 5 gallon bucket stand, working on getting one. Got it home on Sunday and began the teardown.

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Supposedly the previous owner serviced it regularly. I guess cleaning the air filter wasn't part of his maintenance. Always a nice surprise to find a wasp nest in the airbox.

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7/19/2018 9:07 AM

This will be fun to watch. The Vital MX podcast recently talked to the guy over at Alta who mentioned a couple times how they were unable to find commercially available motors and batteries that were very well suited for dirt bike applications. What are your plans for motor and battery?

He also talked about the need to control the power output to make it controlled and rideable, what are your plans for controlling the power output?

Cool stuff, best of luck!

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7/19/2018 9:37 AM

Nick Hagman wrote:

This will be fun to watch. The Vital MX podcast recently talked to the guy over at Alta who mentioned a couple times how they ...more

I have had a hard time finding motors that will be well suited for dirt bike applications. I am planning on using an AC motor but still need to do some research and find a well suited motor. I will have some help from professors once I am back in school and will start to spec out a motor in August. I plan to build my own battery pack using 18650 lithium ion batteries. Many people use these batteries for electric car conversions, the only problem will be securing them so they can withstand the jolts and forces of the bike being thrown around.

I haven't spec'd out a specific controller or throttle potentiometer that are used on most EV's but this is the route I am going. Have some ideas for connecting the throttle potentiometer to the current throttle set up.

Thanks!

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7/19/2018 12:35 PM

It is good if this bike has a strong engine but you should also work on backseat that is looking too weak.

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7/19/2018 4:05 PM

It's going to be a whole lot more fun as a 125 two stroke than some backyard Alta.

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7/19/2018 4:52 PM

Theneil300 wrote:

It's going to be a whole lot more fun as a 125 two stroke than some backyard Alta.

I agree that it would be more fun, but it’s for a research project. Still will be fun to build tho!

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7/23/2018 6:38 AM

Made some progress on the teardown a couple of nights ago. Will start polishing up some aluminum and other miscellaneous parts here soon and will post some more pics. Here are some of the teardown.

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10/4/2018 3:00 PM

Moved the bike to my schools shop and finished up with most of the teardown. I figured out which motor/controller/battery I will be using so I made some cardboard versions to mock things up. So far everything looks to fit well. Hopefully will be able to start ordering parts here soon and make some real progress on the project.
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10/11/2018 12:49 PM

Need some opinions. The second battery pack will have to lay perpendicular to the frame like the picture below. Do you guys think the battery will stick out too far from the frame? It sticks out roughly an inch at the bottom of the shrouds on each side. Good news is the seat lays in the same position with the first battery pack as it did with the gas tank.
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10/12/2018 6:09 AM

Are you making the battery packs or is it premade?

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10/12/2018 10:32 AM

bf884 wrote:

Are you making the battery packs or is it premade?

No, I will be buying them like this. I'm hoping that maybe I will be able to take the stainless steel box apart and make a smaller pack using the batteries.

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10/12/2018 1:36 PM

Just thinking. A lot of AF Frankenstein builds have issues with the front sprocket location.You could probably get by with a little variation from the stock location but not by much considering how the chain roller system works and swing-arm moves.

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10/12/2018 4:34 PM

Hondas4Life3 wrote:

Just thinking. A lot of AF Frankenstein builds have issues with the front sprocket location.You could probably get by with a ...more

Yeah that is another thing I am concerned about. Also will have to figure out the sprockets sizes I will need to run due to the differences in RPM.

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10/12/2018 4:38 PM

Hondas4Life3 wrote:

Just thinking. A lot of AF Frankenstein builds have issues with the front sprocket location.You could probably get by with a ...more

Oaktree1mx wrote:

Yeah that is another thing I am concerned about. Also will have to figure out the sprockets sizes I will need to run due to ...more

The motor I made from cardboard is also a bit misleading. The width of the whole box is actually the width of the motor and the shaft, so that chain should line up correctly but the motor shaft will be located further ahead in the fram so the chain will need to be longer.

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10/12/2018 11:04 PM
Edited Date/Time: 10/12/2018 11:14 PM

Hondas4Life3 wrote:

Just thinking. A lot of AF Frankenstein builds have issues with the front sprocket location.You could probably get by with a ...more

Oaktree1mx wrote:

Yeah that is another thing I am concerned about. Also will have to figure out the sprockets sizes I will need to run due to ...more

Oaktree1mx wrote:

The motor I made from cardboard is also a bit misleading. The width of the whole box is actually the width of the motor and ...more

If this is to be bike to be ridden with real performance in mind, you need to take in Hondas4life3 's comments.

Thus, you may have to make up a jackshaft / motor mount plates that incorporate mountings for the set up needed for a secondary sprocket and chain combination, to bring a sprocket to the center-point of where the original counter shaft sprocket was.

It's easy enough to make a neat little jig to key onto the flat sides on the KX's frame / subframe mount, or where ever, to then bring your 'solution' to for getting that final drive center line.

To reference the "AF Frankenstein" appellation from above : so many are just completely f**cked up by concentrating on the ancillaries, and ignoring just how massive an influence on suspension and handling the CS Center line is, in relation to the swingarm pivot, swingarm angle, and rear axle.

I've been involved with numerous Uni / College Engineering projects over the years, as an adviser / mentor /teacher. And, my goodness, I see the resources they have at their hands w00t . It's a bit of a lessen for the very, very few that I've allowed to get into my workshop (which is nothing but a home garage), when they see what can be done, and done properly, with equipment that is so very basic compared to what they have access to. My fellow engineers and teachers, often, try very hard for me to break my rules about people nosing around in my very basic, minimalist set up. As they (well, most of them) want their students to have at least an idea /appreciation of what can be done at a 'hands on' level, and not just rely on Computation and Hi Tech equipment. Mind you, I do love being let loose in their facilities - I'm like a kid in a candy store.

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10/13/2018 12:26 AM
Edited Date/Time: 10/13/2018 12:28 AM

Oaktree1mx wrote:

Yeah that is another thing I am concerned about. Also will have to figure out the sprockets sizes I will need to run due to ...more

Oaktree1mx wrote:

The motor I made from cardboard is also a bit misleading. The width of the whole box is actually the width of the motor and ...more

Bearuno wrote:

If this is to be bike to be ridden with real performance in mind, you need to take in Hondas4life3 's comments.

Thus, you may ...more

Ok, thanks for the advice! Once I get the motor, I would love to talk to you about the ideas to position the cs sprocket in the correct position. I go to a small private college, so the amount of equipment we have on hand is pretty minimal. I am actually a physics major currently and will go to grad school for engineering because my current school doesn’t have engineering. I definitely chose this project because I enjoy the more hands on side of things. Now that I have began to work out all the details with this project I am finding that there are far more complications than were expected. I just see it as good experience though!

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