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Thread: Need advice for my 1973 Kawasaki 100

              
   
   
  1. #1
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    Need advice for my 1973 Kawasaki 100

    Hi everyone!

    Attachment 8393
    Attachment 8394

    I am wanting to convert a '73 Kawasaki (G4TRC, I believe). It is a 100cc, 2-stroke little on- and off-road trail bike (see above pictures). Currently weighs about 200 pounds with engine and everything, empty gas tank. I have searched the interwebs and have learned a lot, including from this forum, but I still have a few unanswered questions. Hoping you'll give me advice on my specific scenario, I'd like to gain from your experiences.

    Background on how I want to use this motorbike:
    I know exactly how I want to use it, so I can clarify if needed. I've been riding this bike on the farm for quite a while as a 2-stroke. As electric, I will be using it on the farm as well as going to work at some powerplants down in a canyon near me.

    What I want out of it:
    I want to be able to sustain 60 mph for a max of 5 miles at a time. Most of the time, however, I will be doing 50 mph. On-the-farm riding will have a lot of stop and go (50 mph roads with the need to turn or stop every .5 - 1 mile. I don't care about acceleration except I don't want to hold up traffic, and there's the fact that I'll be doing a lot of stop and go (so a lot of slow accelerations). I need to be able to accelerate about as fast as is normal for a car in a hurry (I'm thinking 0-50 mph in 10-15 seconds?)
    Then there's also the roads going into the powerplants - one of them has a varying grade with a max of about 13%, and it's about a mile long grade. If I can make it up that, everything else will be fine. For range, I'm hoping for 50 miles at least (including getting up those hills). That would probably give me 2 days of use before I'd need to charge it overnight again.

    The questions:

    1. Motor
    I want to get away from chain-driven, so I'm looking at hub motors. Also, I want to make this 2-wheel drive so I can get up the grades at the powerplants as well as for more traction on the farm (kinda like the UBCO 2x2). If budget doesn't allow this, then I can at least just go for rear wheel drive for now and add the front hub later. Do you guys have advice for me as to what motors I should get? I'm thinking the EnerTrac 602 or the QS 273 are way more than I need. I need something more along the lines of a powerful e-bike (since I'll have a small e-motorcycle), but I can't find anything that makes sense to me and/or that's made for removable axles. What I've seen that will work spec-wise is made for e-bikes and comes with the axle. Anyway, please point me in the right direction here.

    2. Batteries
    What I'm leaning towards right now is a 96 volt system (so I can get the top speed). I'll do a dc-dc converter for headlights and stuff. Is 96v overkill? I want to put as much as I can in parallel for range, so if I can go for less in series, that would be cool. Currently I'm thinking of using 18650 cells. Right now I can get 240 Samsung 30q cells for $663. That would make a 24s10p pack for 30 Ah and my "96" volts. Help please - I have no idea if this battery capacity makes my range expectation feasible, partly I guess because I don't know what motors to get.
    I would like to steer away from Nissan Leaf cells, just because they're used, and wouldn't they be bigger than an 18650 pack? Unless you change my mind, of course, cause I'm open to anything. Feel free to point me towards something other than 18650s.

    One other good thing about going with hub motors is that I have all that room where the engine is to put batteries and controllers and such, on top of where the muffler etc. used to be. This motorcycle has a good frame I can start with.

    3. Controllers - No idea right now what I need, cause I figure that will depend on what motor I want. Oh, wait, I do want regen braking. I figure going down those long hills at the powerplants will get back some of the power it takes to go up them. Are there any problems you foresee with regen braking for a whole mile continuous? Heat issues or anything?

    4. This actually goes back to batteries. Can I safely build a 24s10p pack, or do I need to hook multiple packs in parallel? Will this big of a pack present problems? Like heat? I know heat has to do with the current being pulled, but if I've got the pack in a sealed, waterproof container, that means heat dissipation suffers. Will I need to have a way of cooling the pack?
    Also, about BMS'es. Will I need one? I haven't seen a BMS for a pack that big. Or can I hook smaller packs each with a BMS in parallel?

    5. Budget
    I'm wanting to do this for $3,000 or under, at least initially. I think that might be hard to do with 2 motors, but hopefully I can at least get it done for that originally (with 1 motor) so I have a working bike with rwd. I know this project will pay for itself eventually, no matter the cost, since currently I'm driving my pickup, which is only getting 10 miles/gallon. That gets expensive.

    6. Okay, back to batteries again. I don't have a soldering gun or a spot welder. Not good for building a battery pack, except I found vruzend.com's kit - http://vruzend.com/product/vruzend-battery-kit-v2-0/ This would make it easy for me and provide an extra level of protection against shorts, though it is expensive. I'm also not sure if I would be limited to a rectangular pack. Is there a better way? I can't find any packs for sale as big as I want. Anybody want to build me one (for a fee, of course)?

    Thank you so much for reading this far and answering any questions!

  2. #2
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    Pictures

    Maybe I did it right this time? Here's those pictures.

    download_20190912_202031.jpgdownload_20190912_202037.jpg

  3. #3
    Senior Member Stevo's Avatar
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    The bike I built can do what you want except for the 50 mile range. You are asking a lot for that little bike. The batteries weight and mass is your limiting factor for sure and always will be. Battery technology just isn't here yet for what we all want.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.3
    WORX.VOR.v3.2

  4. #4
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    Thanks for the reply, Stevo! Nice build on your eVOR. How many Ah is your battery pack? I see you got a Thunderstruck BMS. How do you like it? Still recommend it? Also, how do you charge your battery now (what charger)? You must have been using a hobby charger before to balance the cells? Sorry so many questions, I'm learning.

    Yeah, I'm beginning to realize I'll probably have problems with the volume of the batteries. Haven't gotten far enough in my research to tell if it will actually be possible to fit everything. I think I can make it work though. As for weight, I'm thinking the batteries will replace the engine and transmission (I'm thinking they're around 25 pounds? Not going to take it apart yet). So I'm betting my bike will be heavier than it was originally, it's just a matter of how much. At least I only weigh 140.

  5. #5
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    I found an awesome video on choosing a motor, complete with downloadable spreadsheet to do some calculations on. Thanks to BigGuyLittleBikes!

    I still need to do some more calculations and research, but it looks like a possible motor for me is the QS 205 50H V3. It's a 3000W hub motor, I'm hoping I can install on both the front and the back to make it a 2x2. We'll see.


  6. #6
    Senior Member Stevo's Avatar
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    I like the idea of a 2x2!
    Think about the weight increase of the wheels. Your gonna want to respring the shock and forks with stiffer springs and heavier oil. Some bikes have shocks that are not rebuildable, or no stiffer springs are available for, so do some more research on what you are going to do before spending a bunch of money.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.3
    WORX.VOR.v3.2

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