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Thread: YT125 rear suspension build

  1. #1
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64

    YT125 rear suspension build

    Love this little trike for cruising around at the lake but it's killing my back! Time for some rear suspension. I found a YTM200 roller with a rear suspension kit but it won't fit the 125/175 frames so I'll have to modify it to fit. The 200 swingarm is way too long , so I have to shorten it. Does anyone out there have a pro-tec or S&D kit that they could measure the swingarm length? Pivot to axle. It'll probably be easiest to cut the tubes out and make a box section arm using the existing pivot tube and carrier brackets. I'll have to fab a top shock mount and chain tensioner. Get a 520 front sprocket and probably some YTM200 rear brake cables.
    First step is a little frame strengthening around the swingarm pivot.
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  2. #2
    Join Date
    Jul 2010
    Location
    Arkansas
    --
    2,196
    I'm on the fence about permanent modifications to a good frame, considering most of those kits were for when suspended trikes hadn't filled the market and now many are available.

    I do hope you get a solid build out of it though.

    Shortening the existing swing arm, the way it's made, is probably going to be more work than you think. Starting from scratch may actually be easier. I think the kits for the 175 actually had a very short, cast aluminum swingarm.
    The story of three wheels and a man...

  3. #3
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    A little bracing around pivot. Shortened the swingarm 5". Mocking up for sprocket alignment and shock placement.Click image for larger version. 

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  4. #4
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Got back at the little 125. Finished the swingarm and the top shock mount.Click image for larger version. 

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  5. #5
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Modified the chain tensioner to a spring type. Widened the ridiculously narrow yt pegs with the ytm donors.
    Click image for larger version. 

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  6. #6
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Figured I might as well freshen up the engine. New top end, seals, clutch plates with heavy duty springs, rebuilt injection pump and new recoil spring.
    Rebuilt a gen 1 250r shock I had laying around.
    Click image for larger version. 

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  7. #7
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Realized the 250r shock is WAY too stiff both in spring rate and valving for this kind of suspension leverage ratio. Ended up using a 79 Suzuki RM100 shock I pulled out of the shock pile.
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  8. #8
    Join Date
    Jul 2010
    Location
    Arkansas
    --
    2,196
    That turned out nice.


    Kudos on keeping the oil injection too. It certainly makes refueling simpler. Something to think about is a lot of people remove it from bikes and trikes, but I don't personally know a single person who's removed it from their boat engine, which is more expensive to rebuild.
    The story of three wheels and a man...

  9. #9
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Still waiting for the top end to be finished. Gotta order some cables too. Going to try to make an airbox by modifying the original and using a Uni pod filter.
    Click image for larger version. 

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  10. #10
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    Well, finally finished. Works great. Lifting the rear end changed the steering geometry enough to allow the front end to bite WAY better. Opening up that ridiculously restricted airbox made a world of difference in power for the little 125. I've gone from a 110 stock main to a 160 and I think I'm going to be up over a 180 before it's correct. Just been cruising around on it breaking in the top end. Haven't had it on the main a whole lot yet. LOL. The rear suspension makes this a whole different riding experience as you might expect. Terrain that used to bounce you around, try to kick you off and destroy your spine, is a piece of cake now. It's too bad Yamaha wasn't able to suspend these things from the factory. It really makes it a fun little trike.Click image for larger version. 

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  11. #11
    Join Date
    Jan 2015
    Location
    MB, Canada
    --
    64
    1981 185s is next! 1st gen 250r front end with probably a 200x based rear end. Unless someone has a suspension frame or kit I can buy......!!!!
    Click image for larger version. 

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  12. #12
    Join Date
    Mar 2014
    Location
    Bunbury Western Australia
    --
    62
    I have to say very nice job of that rear suspension. You should make & sell kits, there are alot of people with 125/175 out there wanting them.

    82 Honda ATC 185s SOLD
    82 Honda ATC 185s restoration project (Restored & SOLD)
    81 Yamaha Tri-Moto YT125h (SOLD )
    82 Yamaha Tri-Moto YT175J
    83 Yamaha Tri-Moto YT175k
    83 Yamaha Tri-Moto YT175k (SOLD )
    85 Yamaha Tri-Z YTZ250N

  13. #13
    Join Date
    Feb 2022
    Location
    Lilburn Georgia 30047
    --
    1
    Sell me that swing arm for the yt125. It looks great.

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