mx125 to mx 175 ??

Hello all, I picked up a 74 mx 125 for a project to restore , and as i was thinking of redoing the motor , i had the thought of making it a mx 175 . The cylinder should bolt right on, w/ new piston top end etc.. ?? But would the pipe/carb be the same ?? Anyone have any ideas on this subject ?? just a thought .. Thanks for your advice in advance , Chad:cheers:

ANYBODY ???? (crickets .........) ?

What use is a 175. What class does that run in the 250?

When I first looked into converting my CR125 into a 175cc bike, here's what I did:

1) searched the Web for anyone who had already done the conversion. I was lucky, a bunch of people had already tried it successfully and took the time to document it online. If you can't find a single instance of anyone having even attempted it anywhere on the Internet, this tells you something.

2) studied the parts diagrams of both motors, starting from the spark plug down - photos from eBay auctions can also be helpful.

If you do a thorough job this will take you a while, but you may not have to go through every single part; sometimes you'll come across a "deal-breaker" difference that clearly indicates the conversion cannot be done without great difficulty, and you'd be far better off doing a complete motor swap. An example might be completely different transfer passage sizes and shapes in the 125cc and 175cc cases. Also, since a large displacement increase like this requires either a much larger bore or a change in both bore and stroke, I think it's unlikely you'll be able to just bolt on the bigger top end.

One shortcut is to examine the head and base gaskets, which can at least give you an idea of whether the conversion will immediately turn into a machine-shop fiasco. And one last piece of advice; if the part numbers are different, never assume the parts are identical no matter how much you wish they were. :ride:


I put a '79 mx175 cylinder,carb,head,and pipe on a '78 dt125 bottom end. They use the same crank in those years. I don't know in your case, but you can use the exploded views and part numbers at to cross reference. Good luck!

It looks like the 74 uses the same crank and case on the 175 and 125.

so it might work...

I did a 1980 YZ 125\IT 175 years ago. Only issue was the pipe.Never could get it perfect. Knowing what i know now,i think i could do it..

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