Man, wish they were the same, other wise I would not have NEEDED a spacer plate when installing an 89 TRX lower with 85 ATC upper. They are not the same!! Wish I could attach photo's to show you.

 

Kasey,
THose are some super sweet trikes. Nice work on them, I especially like the 70.

 

Sorry Hondamechanic but they are correct. The reason they did this was because of the extra forces that are created on the sides of the cylinder because of the low pin location on the 85-87 cylinders.

 

its to bad some people can't learn anything,, just throw out some stupid comments and leave,,, well its to bad,, i just hate it when people throw out wrong info because they don't really know the right answer,,, it would be worse when you bolted the topend on spent the cash for a cylinder gaskets and time to build it and realized the piston is 5mm short of the top of the cylinder,,,,, DOH! WOW NOW THAT I READ YOUR POST AGAIN ,,, YOU CAN'T DO IT,,, you will need a 85-86 piston,,, the short rod piston needs a spacer plate on a long rod motor,,,,, the other way around you need a earlier piston,,,, without a spacer,,, SORRY i was to busy trying to teach someone else the facts,,,, you can use a short rod piston in a long rod motor ,,just not a long rod piston in a short rod motor,,,,

 

no i think u guys miss under stood me, and the first guy that read this is a dumass to . all i wanted to know was if i needed a 88-89 crank to run a 88 cylinder on a 85 atc

 

i guess the spacer plate and piston threw me off too,,, all you need to do is have a 85-86 piston fitted to that cylinder and bolt it on,,,,,,,, no plate just a cylinder,,,

 

I feel i need to put my 2 cents in the ring
i have that exact set up. make sure you use a 85 piston or it will bottom out on the crank i promise that. another thing you should know is that the 88 jug has its ports in a different position in the stroke. it will run completely different. im not saying its a bad thing but your gonna have to change your pants after you ride it for the first time. the power curve will be very peaky and the motor will rev way higher than it used to. i wish you luck have fun spanking the new fourstrokes!