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Installing Honda Elite CH250 Trailing Arm Forks on a GY6 Scooter

Discussion in 'Battle Scooters' started by MJSfoto1956, Nov 13, 2019.

  1. MJSfoto1956

    MJSfoto1956 Been here awhile

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    So I have decided that I have had enough of the nasty front shocks on my Chinese Zuma clone (see: https://advrider.com/f/threads/my-ezuma-project-electra.1340153/). While I "could" take a chance that some $400-$600 performance forks from AliExpress might help, I decided to go old school -- specifically a set of forks from a 1986 Honda Elite 250.

    These are trailing arm design, so in theory I can install any brand of 300mm shock I want (within reason of course). My expectation is that even with the stock shocks, it will be much smoother than the harsh ride I'm getting at present. That being said, some folks customize their Hondas with trailing forks as shown in the following photo:

    Honda Helix front suspension (custom) 3.JPG

    Anyway, here are two photos of the actual forks I purchased via eBay a few weeks ago:

    s-l16003-J2T-giga-mask-transparent.flat.1280.jpg

    s-l16002-J2T-giga-mask-transparent.flat.1280.jpg

    All in all, not too shabby for gear that is 33+ years old.

    I started by using a wire wheel to clean off the rust. Additionally, I wanted to grind off the extraneous bits that held the covers and speedometer cable. But I guess I got a bit carried away... There is not a lick of paint left on these puppies! Given how clean they are now, I'll probably opt for powder coating the forks themselves. I'd like to keep the connecting bits shiny metal, but given that they are steel not aluminum I'll have to paint them either way.

    Note: the tab on the right is to hold the speedometer housing in place -- given that this is for an electric eScooter, I'll probably grind that off but for now it is what it is.

    IMG_9755.1200.jpg

    More to come...
    #1
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  2. minimac

    minimac Been here awhile

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    Looking forward to seeing how you accomplish this. I know you will, I just want to see how!
    #2
  3. Wentwest

    Wentwest How's that work?

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    Are you using a drum brake up front?

    The front shocks on those old Hondas were pretty squishy. I see you replaced them. And the pivots were just bushings, no roller bearings, so just keep them lubed.
    #3
  4. MJSfoto1956

    MJSfoto1956 Been here awhile

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    I will be keeping my current 220mm front disc.

    I haven't replaced them yet -- that is on the list once I get it all road-tested. The shocks in the "after" photo are in fact the same stock shocks, just without their covers.
    #4
  5. Wentwest

    Wentwest How's that work?

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    Impressive clean-up job. I look forward to seeing the job assembled.
    #5
  6. MJSfoto1956

    MJSfoto1956 Been here awhile

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    I happen to have a spare GY6 wheel lying around and so I did a quick test fit to see how things work (or not) with the CH250 trailing link forks. For starters, it is now clear to me that my 110/90-13 wheel will fit nicely with no clearance issues. I'm going to have to fashion some custom-length axle spacers but that was to be expected. A 220mm rotor looks like it will just clear the fork but may slightly interfere with the through-bolt, so I'll likely have to come up with something to address that. Overall I'm pleased. Things are moving slowly in the right direction.

    IMG_9758.1280.jpg
    #6
  7. Wentwest

    Wentwest How's that work?

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    The tire in the the photo is a 120/70 x 12. A 110/90 x 13 might be on a narrower rim, giving more clearance for the rotor.
    #7
  8. MJSfoto1956

    MJSfoto1956 Been here awhile

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    Ah, but my current 110/90 is not on a narrower rim. So while the 110 tire will provide slightly more clearance, the rotor mounting face will be on the same plane. Don't forget, most Chinese GY6's have very similar (but never identical) geometry.

    Or put another way: Honda CH250/CN250's have narrower forks than typical Chinese GY6 scooters.

    M

    P.S. here is a photo of my current wheel compared to the previous stock GY6 wheel:

    IMG_8162.1280.jpg
    #8
  9. MJSfoto1956

    MJSfoto1956 Been here awhile

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    Yet another issue is that the Chinese GY6 stem has a wider diameter (at the bottom) and is much shorter than the Honda CH250. Anyway, one of the key things will be to "merge" the bottom half of the Honda with the top half of the GY6 stem. No biggie, but something that definitely needs to be done down the line. The overall plan is to keep Honda-style bearings on the bottom and the GY6-style bearings on the top.

    compare stems IMG_9562.jpg

    compare stems IMG_9562.v3.1500.jpg
    #9
  10. MJSfoto1956

    MJSfoto1956 Been here awhile

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    Speaking of bearings, I'm likely going to "upgrade" the 1986 Honda CH250's old-style ball bearings with newer roller bearings. All Balls Racing has them for the CN250 (part number 22-1011) which is the same as the CH250. Photo below.

    All Balls Racing F_POP_STEERING.jpg
    #10
  11. The Virginian

    The Virginian Long timer Supporter

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    Outstanding job on what you have accomplished and I love these kind of threads that think outside the box. Maintain speed and heading good sir.

    Eric
    #11
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  12. minimac

    minimac Been here awhile

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    Would it be easier to have the upper portion of the Honda stem turned down (and shortened) to the GY6 dimensions rather than cutting and 'splicing'? It would be a lot stronger, I would think.
    #12
  13. south

    south Been here awhile

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    The standard--and best, IMO--approach is to grind off the weld around the bottom lip of the stem(s), press it/them out, and then press in the desired stem--along with a bushing/spacer to make up the difference in diameter--and re-weld.
    #13
  14. MJSfoto1956

    MJSfoto1956 Been here awhile

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    The thought was to insert a steel "plug" inside of both cut stems and weld both stems to that. I have no doubt that approach would be stronger than stock. But I may change my mind as this winter project progresses.

    M
    #14
  15. MJSfoto1956

    MJSfoto1956 Been here awhile

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    Yet another tweak needed to pull this off. Turns out the diameter of the Chinese GY6 lower bearing is 62mm compared 50mm for the Honda CH250. The bearing needed for my use case is known as a 30206 and is readily available. However, this bearing will interfere with the metal "cup" at the top of the Honda fork. So I'll have to grind that puppy away as shown in the photo below. Going to also need to source a "Nilos Ring for 30206 Series Bearings" -- so that the bearing is sealed against the elements.

    IMG_9776.1280.jpg

    P.S. I'll also have to weld two metal "bumpers" to the top of the fork to align with the GY6 headset stop.
    #15
  16. MJSfoto1956

    MJSfoto1956 Been here awhile

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    FWIW, this is a sketch of what I hope it will all look like when I'm done:

    after slice1.jpg
    #16
  17. MJSfoto1956

    MJSfoto1956 Been here awhile

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    After doing a lot of research on what is readily available (and doable) I've come up with the following plan for the lower roller bearing interface between the Honda CH250 fork and the GY6 headset. Note that the proposed 55mm bearing is slightly larger than the stock 50mm Honda and slightly smaller than the stock 62mm GY6 bearing.

    Just need to find me someone to fabricate that custom SS insert...

    CH250 headset modification.1280.jpg

    P.S. this concept has been superseded a bit later on.
    #17
  18. MJSfoto1956

    MJSfoto1956 Been here awhile

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    The other alternative is to have a custom 35mm OD SS "collar" created that would be TIG welded to the existing 30mm stem. I could then use an All Balls 99-3545-5 bearing kit. The only obvious downside is that this bearing is 4mm taller than the stock GY6 which would likely leave a bit of bottom of the bearing housing exposed to the elements.

    CH250 headset modification.alt2.1280.jpg

    P.S. this concept has been superseded a bit later on.
    #18
  19. villageidiot

    villageidiot Long timer Supporter

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    A small cut piece of inner tube from a bicycle tire is great at keeping crap out of steering head bearings.

    just slip a piece over the steering stops when you install the fork, then move it into place. Very simple. Works great.
    #19
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  20. MJSfoto1956

    MJSfoto1956 Been here awhile

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    That's an excellent idea. I will incorporate that into the design. Thanks!
    #20