Yamaha SR400 Big Block Motor Swap for the TW Is It Possible
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Thread: Yamaha SR400 Big Block Motor Swap for the TW Is It Possible

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    Senior Member PlacerLode's Avatar
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    Yamaha SR400 Big Block Motor Swap for the TW Is It Possible

    I know an X forum member had tried to do this conversion and he said the output shaft was the main hold up

    Now that I know how to overcome that I wonder if this 31.5 HP Brute could be installed w/o changing the axis of the earth

    they are FI so it may be easier to run a carb although I'd go for the FI if it could be done

    I have heard these can be turboed to get 100 HP but I bet it has a nice bottom end and mid range for mud slinging with a big ATV rear tire

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    Senior Member Maxpower's Avatar
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    With money anything is possible
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    YBW
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    Just eyeballing it, I would think the major hold-up would be the height of the motor. I wonder if (similar to BW conversions) it wouldn't be easier to mate wide triples and swingarm to the larger displacement host frame? But I understand that for those who have a stockpile of TW parts its not as attractive.

    With those semi-bare motors only being around $1000 shipped, seem the cost isn't too bad for what you could theoretically get out of it. What would be neat is if someone would figure out what would fit and design a bracket mounting package like they have to put the CB300 motors in the Groms...

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    Senior Member PlacerLode's Avatar
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    I plan to buy a wrecked parts bike so I'll have all the parts to fit and tinker with
    the guy I knew claimed he made it fit with little problem
    he also claimed Yamaha approached him and paid him to shelve the idea saying they had something similar in the works but that was a few years ago and I never saw any concrete evidence the story was true
    I know my BW350's seem to have insane power so that would be a great TW swap too unless the heavy weight makes the TW handle even clunkier than it already does
    These big motors might be good for road riding only
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    YBW
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    Hahaha I think I'm remembering the member of whom you speak. Did he have a habit of making other rather large claims with a mysterious lack of ability to show proof in the form of pictures?

    My phone won't let me copy the link, but of you search for "WR250R motor" on eBay there is currently one listed for $1666 shipped with everything from the throttle to the ecu to make it run. I think that would be a much better fit size wise and supposedly has the about the same power.

    I really think fabricating pieces to bolt in that would more or less convert the TW from a stressed member to twin cradle setup would be the way to go, and $1666 seems cheap for what you are getting--especially with it only having ~6500 miles on it.
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    Senior Member Darth's Avatar
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    You have to wonder how the TW chassis & suspension would handle the significant gain in weight & power?
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    Senior Member Fred's Avatar
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    I fear the stock suspension is already the weak link in the TW.
    One of my TWs features longer fork and shock travel and is so much better off-toad at speed. Riding buddies who have upgraded from TWs to 250cc machines have really pushed up the trail speeds beyond what is safe for the other bike, the semi-stock Betty Boop.
    Thus Darth makes a very good point.
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    Senior Member PlacerLode's Avatar
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    ProCycle springs front and rear will definitely be in order and it is fully possible it will be too much for off road but maybe scrambler logging roads etc might be fun

    I'll weigh the motor and see just how much weight we are talking if it's only say 20 lbs I just won't doll it up with racks and other accessories like I normally would lol
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    Senior Member PlacerLode's Avatar
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    Quote Originally Posted by YBW View Post
    Hahaha I think I'm remembering the member of whom you speak. Did he have a habit of making other rather large claims with a mysterious lack of ability to show proof in the form of pictures?

    My phone won't let me copy the link, but of you search for "WR250R motor" on eBay there is currently one listed for $1666 shipped with everything from the throttle to the ecu to make it run. I think that would be a much better fit size wise and supposedly has the about the same power.

    I really think fabricating pieces to bolt in that would more or less convert the TW from a stressed member to twin cradle setup would be the way to go, and $1666 seems cheap for what you are getting--especially with it only having ~6500 miles on it.
    Yes I look at my YZ450 motor and dream of shoehorning that bay in but it would not be suitable for the TW style of low end riding
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    Senior Member Fred's Avatar
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    Like someone's lady once said "Six inches just isn't enough".
    Amazing what three more inches of travel will do to raise the minimum safe speed in the hack, whoops, surprise cross trail ruts, etc. on a TW200.
    Stiffer springs aren't the answer in my experience compared to the benefits of longer travel.
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