In the UK the 125m's were converted to ATV's, I had two some years back. There was a company that specialised in these conversions as I beleive the sale of them as a trike wasn't legal due to the high risk of accidents.
The two I had were vertical cylinder engines and I think they were both 86, they were tagged (the stickers on the frame) as trx though not ATC. After much research was when I found out that they were the result of the above mentioned conversions.
So (from what I know in the UK) the engine may well be exactly the same (year depending) as a trx125.
Hope that helps.