I believe this one will work on the MT125 flywheel, but I've only used it on the MR175.
http://www.186mph.com/prod_16010.htmlIt's a K&N 82-0150, or Motion Pro 08-0026. The threads are 27mm x 1mm, left-hand.
It's hard to find definitive answers about pullers sometimes - seems like the puller might fit 20 different models, but only 10 are listed. I looked in 3 separate catalogs just now, and none mention the MT125 or the MR175, just "Honda 2-stroke MX bikes" or whatever.
If you get it thru Amazon and it doesn't work, you could probably return it without trouble.
Ray