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Help FZR250 conversion to electric

Discussion in 'Yamaha 250cc In-Line 4's' started by soyachips, Jan 4, 2019.

  1. soyachips

    soyachips Member Premium Member

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    Hi all,

    New to this forum and would really appreciate some help. I’m thinking about converting a 1988 FZR250 to electric but need to check a few things before going down this path. By convert to electric I mean replace the petrol engine with an electric motor ... hopefully I didn’t just lose everyone :)

    Frame
    • Is the engine a stressed member that forms part of the structure of the frame? I’ll be removing the engine and putting the battery pack there so need to make sure the frame forms a solid structure without the engine.
    Suspension
    • I’m planning to use a hub motor on the rear which weighs 20kg. I understand this will have some impact on performance so I’m wondering if stiffening the suspension will help and whether or not this is possible? Can I use a stronger spring? Any other options?
    Swing Arm
    • What’s the distance between the swing arm arms where the rear wheel bolts in? I need at least 200mm to fit the hub motor.
    Brakes
    • l need to get an engineer’s certificate for the conversion and if I can use the existing brake system then I may not have to also do brake testing which may add another $3k to the project. I’m hoping if I keep everything standard but use the brake rotor that comes with the motor I won’t need to do the testing.
    • What is the outer diameter of the rear rotor? Most places I’ve read 210mm but I’ve also seen 220mm which is what the electric motor comes with.
    • Does the thickness of the rotor affect braking performance?
    • The motor itself will perform some of the braking as it can do regenerative braking.
    That’s all the questions I have for now.

    Thanks in advance!
    Andrew
     
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  2. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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  3. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Welcome Andrew, interesting project.
    The FZR frame will need some sort of frame from headstem to footpeg/swingarm area to carry your batteries. This (if designed right) will give some added strength to the frame as well.
    Rear suspension should not need to be adjusted for the hub motor.
    I don't know what is involved in an ADR brake test, but if you can use the original calipers on the new rear disc (width will not matter) and say nothing to the tester then all should be fine. From what I've seen of these type of electric bikes there is so much motor braking that a rear brake does not do much at all.
    Keep posting your progress so we can see what is happening. :thumb_ups:
     
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  4. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    :welcome:

    If its a 1988 FZR then its a 2KR with a steel frame .... 89 onwards is a 3LN with an aluminium frame

    https://www.2fiftycc.com/index.php?...0-3ln-bodywork-frame-engine-carburetors.3469/

    Common mod on a 3LN is an R6R rear shock

    https://www.2fiftycc.com/index.php?threads/fzr-r6r-rear-shock-conversion.8813/

    Front ends are known to be mush so theres everything from using heavier fork oil to FZR400 race springs to emulators to adding preloaders

    https://www.2fiftycc.com/index.php?...rk-preload-adjusters-34mm-x-1-5mm-pitch.9852/

    https://2fiftycc.com/index.php?threads/front-suspension-upgrade-fzr.1850/


    I saw , as opposed to heard, Mick Doohan on the ebike at the MotoGP .... it was just weird!
    So you will also need to do what we did as kids with our push bikes to make engine noises so we can hear u coming :D

    card.jpg
     
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  5. Andych

    Andych Well-Known Member Premium Member

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    That only works with spokes @GreyImport :lolsign:
    Probably wont do much on the FZR rims...
     
  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    FZR250R 3LN 89 onwards the rear disc is 210mm, pretty sure the earlier one's are the same diameter
    3LN swingarm is approx 210mm between the inner edge's,
    but the rear caliper mount goes through the axle inside the swingarm and is approx 25mm wide so that leave's you with 185mm room to fit your hub motor
     
  7. soyachips

    soyachips Member Premium Member

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    Wow thanks for all the quick replies!

    @my67xr thanks for the link, lots of interesting stuff there that I’ll have to re-read to fully understand! Also thanks for the specs. Do you happen to know the swingarm dimensions for the 2KR or where I can look them up?

    @Murdo @GreyImport I’m pretty sure it’s a 2KR frame which has the 2 cradle arms that go from the headstem to the footpeg/swingarm area. I’m hoping that this then creates a solid structure without the motor. Is this correct?

    And thanks for the tip about the playing card ... not sure how long it will last :)
     
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  8. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    @risky might be able to measure the swingarm inside width for the 2KR ?
     
  9. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Didn't realise you had a 2KR steel frame, if so then all you will need to do is make your battery mounting platforms fit in the space where the engine bolted to.
     
  10. soyachips

    soyachips Member Premium Member

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    Excellent, thanks for the info!
     
  11. soyachips

    soyachips Member Premium Member

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    If I can get the swingarm inside width and the width of the rear caliper mount where it goes through the axle that would be awesome, thanks!
     
  12. soyachips

    soyachips Member Premium Member

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    Hi all,

    I’ve made some progress on my conversion and will post some updates soon but in the meantime I have a question. I’ve just started taking the bike apart and drained the coolant which use to pass through the frame ... I don’t need coolant in the converted bike but am concerned if the inside of the frame will start to rust. Does anyone know if this might happen and how to prevent it?

    Thanks!
     
  13. risky

    risky risky

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    dry the frame out -[hot air gun- and spray fish oil in the water passage or grind the nipples off and weld up.
     
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  14. soyachips

    soyachips Member Premium Member

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    Thanks, good idea. What about just leaving coolant in the frame even though I'm not using it for anything. Would that provide more protection than drying out and fish oil?
     
  15. soyachips

    soyachips Member Premium Member

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    Here are some specs for my project:

    Chassis: 1989 Yamaha FZR250 2KR
    Motor: QS 273 6000W V3 hub motor
    Speed Controller: Kelly KLS7250H
    Batteries: TBD

    Top Speed: TBD
    Range: TBD
     
  16. soyachips

    soyachips Member Premium Member

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    So I originally thought about doing an electric cafe racer motorbike as there’s something appealing about the way they strip everything back to just the essentials and expose the way it all works but I struggled with how to make the batteries look good. In general, EV batteries don’t look that good so I then changed tack and started looking a bikes with fairings so I could hide them! I’m also keen to use a hub motor to simplify the conversion and leave plenty of space for everything else. The other thing I am trying to do is make this as easy as possible to get an engineer’s certificate for the conversion. I spoke to a few engineers about the project and a common theme was don’t touch the brake system otherwise you’ll need to do brake testing which could add another $3,000 icon_e_surprised.gif

    I had read good things about hub motors from QS Motor and they have a pretty extensive range of options. The bad thing was the hole pattern for mounting the brake rotor seemed non-standard so I thought I’d have to use the rotor that comes with the motor which is 220mm. So some more research to find bikes that use that size rotor on the rear and fairings to hide the batteries. The other thing was using a frame that has a cradle under the engine so when I take the the engine out it’s still structurally ok. Most new bikes seem to use the engine as part of the structure so that ruled out a whole lot of newer bikes. This really narrowed down the options so I finally settled on a late 80’s Yamaha FZR250 as my donor bike and proceeded to buy a swingarm and rear brake bits from a wrecker to do some prototyping.

    Below are some photos of 3D printed custom axles to get everything fitting and the wheel centred and modifying the slots in the swingarm where the axle normally goes through into dropouts like on a push bike so I can get the motor in. On motorbikes the axle gets inserted through the swingarm into the wheel but on the QS hub motors the axle is fixed in the wheel.

    file.php?id=1117.jpg

    file.php?id=1116.jpg
     
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  17. soyachips

    soyachips Member Premium Member

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    I also tested where the rear rotor would end up relative to the existing brake calliper and mounting bracket setup. In the prototype below everything looked like it was going to line up but then I realised the wheel was a bit off centre! So after fixing that, I will now have to use an adapter plate between the motor and the brake rotor to line everything up ... which means I wasn’t limited to using a bike with the size of brake rotor that comes with the motor in the first place!

    file.php?id=1118.jpg

    file.php?id=1119.jpg

    file.php?id=1120.jpg
     
  18. soyachips

    soyachips Member Premium Member

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    Because the axle is built into the motor and needs to be held firm while the motor spins, there will be a lot of torque where the axle passes through the swingarm. To make this stronger I’m going to use solid blocks of aluminium? inside the swingarm. The tolerances need to be quite tight as there are acceleration and regen torque forces that need to be counteracted.

    file.php?id=1121.jpg
     
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  19. soyachips

    soyachips Member Premium Member

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    Here are some pics of the custom axle and motor

    file.php?id=1122.jpg

    file.php?id=1123.jpg

    file.php?id=1124.jpg
     
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  20. soyachips

    soyachips Member Premium Member

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    This is the donor bike I just bought. The previous owner put a lot of TLC into it so it looks like it’s in really good condition. As mentioned I selected this bike because of the size of the rear rotor icon_lol.gif but turns out it’s a really good bike and one of the better 250’s from that era.

    file.php?id=1125.jpg

    file.php?id=1126.jpg
     
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