Mt125 To Wr125x Engine Swap

Discussion in 'WR125X WR125R Discussions' started by ThereIsNoSpoon, Jun 9, 2017.


Has anyone else been this stupid

  1. Yes

  2. No

    0 vote(s)

  1. So... i had this hair brained scheme to do an engine swap on my wr with one from an mt.

    Same engines thinks me....

    Buys engine. whips out flaky wr engine and set about installing the spangley black mt bad boy.

    No injector manifold came with so i will just use my wr one.


    It has a different orientation...

    Plus the temperature sensors are different......

  2. Blazer

    Blazer Member

    Can't the temperature sensor be removed and replaced with old one ?. The basic engine should be the same, so i'm surprised the intake manifold from your old engine won't bolt straight on to the new engine. The only problem i would have expected is that the exhaust port is longer, so the exhaust header pipe may have to be modified to make it fit correctly.

  3. Soz. didnt see your reply until today.
    I will take a few snaps. sooooo frustrating....
    The new temp sensor is a smaller diameter and a different connector type and as for the inlet manifold... urghhh...
    It seems to be just the cylinder head that is proprietry to the mt... will be due to the frame layout or something.


    Bought a intake and a used mt harness that i have picked up too. ebay still can be great. sometimes....

    If i ever do something stupid like this again....
  4. Blazer

    Blazer Member

    Have been doing a bit of research and see what you mean, thanks for the pics ;). From 2014 onward the temp sensor was changed to a new and cheaper one, the old ones cost around £50.00 to buy but the new ones only cost around £12.00. The the engines in the pre 2014 model yzfr's and wr's were basically identical, apart from some small gearing differences. From 2014 onward the cylinder heads were changed like you say, the yzfr 125 and mt 125 actually have heads with different part no's. One problem you will find is that they also reversed the gearbox on on the yzfr and mt from 2014 onward, so after fitting the engine to your bike the gearing will be first gear up and the rest down. Not exactly the end of the world, and i'm sure with a few modifications you will get everything sorted. :)

  5. is that right about the gearing?? wow thanks for that... it would have confused the hell out of me.
    thurs is the day all the bits supposedly arrive so we shall see if i can salvage this boob.

    will hopefully have her going by this weekend.....

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