Where will I find the engine #. Looked but cannot find

On the top of the crank cases behind the barrel

no cannot see it there. Antwhere else to look?

On the front motor mount right under exhaust .

will it be a mix of numbers and letter like the frame?

The number should be the same as the frame. The casing have other numbers that are matching numbers as the cases where graded in the factory and matched together then have the same number stamped on the two halfs of the case. These numbers are usually on the engine mounting lugs and usually are a two digit number.

There are 2 digits on each side of the casings at the rear mounting point of the engine where it is bolted to the frame/swinging arm(36 stamped on each casing). The frame number is 51m1646

On the front motor mount...

OK found it and matches the frame.

Thanks