250 2 stroke into a YZ400 frame?

We got a few bikes (99 YZ400 and 2001 TTR125) from the same customer earlier on this week. Too make a long story short, the YZ's head is trashed and the TTR needs an exhaust.

So after calling the guy and telling him the news, he asks if we want the clapped out bike for some money off the repairs on the TTR. Uhhh.....Hell YEAH!! :bonk:

So TT'ers, any of you tried putting a 250 smoker engine into a YZ400 frame? and is there anything I should be prepared/watch out for?

Also, suggestions on best motor to use ? I figured most any would do considering they are very similar, but if anyone has suggestions it would be appreciated.

This is my first time trying a motor swap on a dirt bike so bare with me.:smirk: I will also be parting out the bottom end and carb at some point in time so If anyone needs anything let me know.

I'm sure you could get a '99 or later YZ250 2 stroke to fit. I'm pretty sure the width of the engine where it fits between the swingarm and the swingarm pivot are the same diameter. This would make thinks like chain alignment relatively easy. You'll probably have to to some major surgury to get the YZ250 2 stroke exhaust to fit though.

Too make a long story short, the YZ's head is trashed.

What's wrong with the head? Used ones can be had for a lot cheaper than a used YZ250 2 stroke engine.

What's wrong with the head? Used ones can be had for a lot cheaper than a used YZ250 2 stroke engine.

whoever did the valves last torqued the exhaust cam cap too tight. So the cam journal and head are scored real bad.

I tried to tell buddy he could probably find a used head on ebay for not too bad of a price, but he said he hated that bike anyways and didn't wanna put much into it. ok??

I was thinking of going the yz route anyways. Seeing as they still make them, I wouldn't have any trouble getting parts from various yet to fit. and it would be cool to keep it all Yamaha.

Seems like a lot of money and work for a bike that won't really be worth anything to anyone but you.

But......if that's what you want, go for it.

whoever did the valves last torqued the exhaust cam cap too tight. So the cam journal and head are scored real bad.

Engine Dynamics can repair most of those for about $300.
Engine Dynamics can repair most of those for about $300.

Where exactly is Engine Dynamics? I'm up in Canada right now so shipping might be a bit pricey both ways.

The link I posted takes you to their web site. They are located in California.

why not sell it for parts or part it out, why would you want to put a motor with less power in a steel frame?? im sure someone could use it rather than tearing it all apart?

why not sell it for parts or part it out

I like the idea of parting it out, just not so much the part where i have to wait and hold on to these parts for a while. Maybe I'll put her in the local classifieds as a complete parts bike.

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