Cam options for ATC 90

[shortline10]

Don't forget the 90 cases will have to be bored to accept the 110 cylinder.

Yes I forgot about boring the cases on the atc90 bottom end . The other option is to use the atc90 cylinder bored to 54mm and a spacer under the cylinder to compensate the length of the longer 110 stroke .

[turbowrenchhead]

Ok just to let me get this straight. If I go with the 54mm DrATV piston at 9:1. I can use my stock cylinder. All I have to do is bore the stock one and no modifications to the case. Puts me at 104cc
Cost:
54mm piston $60.00.
Bore cylinder $40.00

If I go with the 56mm 10.5:1. I need to get a 110 cylinder, bore it. Bore the case and change the crank and rod. Also install a 110 timing chain. Puts me at 125cc? Also how thin with the cylinder wall be? I have seen opposing opinions on the 56mm piston. Some say its safe others disagree.

Cost:
56mm piston $30
Crank&rod $60
110 cylinder $50
Boring $40
Plus modifications to the case. Can this be done by hand with a die grinder? I am assuming that the opening has to be large enough so the rod doesn't hit it.

I have not seen a 55mm piston anywhere.

I want to understand all the in's and out's of these mods before I decide to start buying parts. I have the funds available but first I need to know what processes I must go through.

Thanks for all the input, its greatly appreciated.

[shortline10]

Sounds like you got it . The 56mm piston does make the cylinder pretty thin but your not making a 10,000 RPM monster so I wouldnt worry to much and the 55/54mm atc110 pistons are very hard to find . Not exactly sure how much material has to be removed from the 90 cases but I dont think its much , prob 1 to 2 mm .