the yz250 engine

[bikersupermot...]

can the yz250 engine be made ( with a bit of adaptor plate welding and engineering ) to fit into the engine space on the latest wr125x supermoto bikes as the current 4stroke fuel-injection lump is a bit ermm weak lol.
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tinybikes

[stevo as b4]

Take some measurements of the frame mounting points once you've got the 125cc lump out. Then take your measurements of a YZ250 lump and the where the mounting points are on the crankcases etc.

My reservations with what your suggesting are:
1, The WR125X doesn't seem to have very big frame tubes or look anything like as strong in terms of the frame design as the YZ250 does.
2, The YZ250 will be quite a vibey engine compared to the 125cc unit in your bike.

3, Why not go down the Malossi 182cc conversion kit route instead, as I believe some companies offer 200cc trailbikes using the Malossi kit fitted to the WR125X engine, and if they are reliable enough to be offered as a factory model, then it makes sense to fit the conversion kit instead of trying to swap in a far less suitable engine that probably would not make for a very good bike overall when said and done.

[dangerousdave]

[G]

Remember that I'd expect the WR125 frame will have been made to handle a 4 stroke commuter.
You're sticking in a 2 stroke competition engine of twice the capacity - so a lot more power everywhere.

Were it me, I'd go with a YZ250 frame and componentry - which are better quality and available pretty cheaply these days.
Bodge on the wheels if you want supermoto.