Hi all,

I have a Honda ATC90 that is ready for a rebuild. I had heard that a lot of the parts were interchangable between the 90 and the 110. I also heard that the 110 cylinder could bolt on to the 90 bottom end. Does that sound right? I'm just wondering if I could bump up the power a little that way.

 

The 1979 and 1980 model 110 engines are very similar to the ATC90 engine, but the later 110s have quite a bit of different engine parts and will not swap with the early models. Even the recoil starter wont bolt on!!

It's my understanding that no one has pistons available for these engines any more. [Not taking the .20 and .40 Honda pistons into acount]
A aftermarket company called "Wide Open" imports a 3mm oversize piston kit that will actually exceed the 110 in displacement and is compatible with your ATC90 cylinder. Just have it bored to accept the piston. You can't use a 110 piston in a 90 due to the different stroke of the crankshaft. The wrist pin location is in a different place than the 110 and if you did that, the 110 piston would stick out of the top of the cylinder at TDC.............not a good thing
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Ok, thanks for the info. So just to make sure. If I get one of the pistons from Wide Open and then have the cylinder bored I would actually end up with more displacement than going with the 110?

 

Exactly.

WideOpen doesn't do any direct sales to the consumer. You have to go through a Honda dealership that is setup with a company called J&M. Just ask the Parts Department.
If you can't find anyone there locally, PM me and I will let you know who to call.