are these engines all interchangeable in frames, what about using the top end of one with a bottom end to another?

 

The motors can be switched.
90- 1981? 110
1983-85 110 - 84-85 125
The 79-81 110's has points and the cam shaft if different on the end and they don't use a CDI box. The wrist pin is smaller.
The 86-87 125 are not interchangable, because they're vertical motors and not horizontal.
As far as parts goes I believe they're all interchangable beside the one I posted.

 

Like BigRed was saying, they can be switched from to frame. You do have to have a 125 head stay when putting a 125 into a 110 frame though.

As for parts interchange, the 110 and '84-'85 125 are completely different engines although the do look alike. No major parts will interchange...cylinder, head, crank.....nothing.

The '86-'87 ATC125s are totally different in design like BigRed said.

You have two different 110 engines, although they appear the same from the outside. The earlier models are beefed up 90 engines.

The later models ['81-up] use the same topend as the old one but everything below the piston is different enough that part swapping is limited to very few parts.

 

Knows:

I remember beating a piped 84 110 with my old stock 79 110. Did the older 110's "the beefed up 90's" run any better?

 

A pipe on a stock 110 engine robs power. That has been proven. The engine is so small and needs the backpressure to get peak power. They will run slightly faster on the topend because of the lak of backpressure, but that's about the only gain. Once the compression is upped along with a few other mods here and there, a pipe starts to help it out.

I don't know how to explain the older one beating the newer one other than maybe rider weight, tire type and airpressure, or fine tuning.
A 110 is affected greatly by even an extra 10 pounds of weight....LOL

 

Thanks for the help, although, about the piped 110, i had a '76 atc90 that I put a supertrapp muffler on it, and it screamed, of course this is after we couldn't shut it off and the old pipe was beat red before we turned off the bike with the headlight, great wiring job, but after we nearly blew it up, and put the pipe on it screamed like crazy.

 

Ok ,what about a 125m intake and carb, as well as the exaust pipe fitting on an early 90cc engine?

 

hey BIG RED how fast does your tri-moto-175 go and aint it 2 stroke?