ST90 & CT70 parts interchangable?

Epic_username

Epic_username

Member
An ST90 frame and swingarm popped up on craigslist (almost never see ST90 or CT70 stuff). $50, just a frame and swingarm. I have an S90 engine to put in it, and could whip up a wiring harness in an afternoon. But would my CT70 seat, tank, bars, swingarm, forks, and wheels all go on the ST90 frame? I may trade my CT frame for this ST frame. The 90 would be much more capable off road than the 70. And im tired of f***ing with the stupid CDI I put in it.
 
W

WonderMuscle

Member
The ST90 Frame and CT70 frame are nearly identical. The only difference being the motor mounting holes, two for the CT70 and 3 for the ST90, but you knew that already. I have had both off road and the best part about the ST90 is the larger wheels which give so much better performance off road. I prefer the ST90 14" wheels for off road.

I have had both bikes and am nearly certain the CT70 seat, tank, bars, swingarm, forks (must your the CT70 triple clamps, and wheels all go on the ST90 frame. The ST90 swingarm is longer so the CT70 rear brake rod might be a bit short. The rear shocks are the same length. The rear brake spring tab is in a bit different location on the rear brake arm but it might still clear the motor.

BTW I bought a S90 clutch cable off ebay for $.99 which worked perfect.
 
Epic_username

Epic_username

Member
Ok, thats a little promising. I would love to have the 14" wheels, its the same guy selling them for $25 a peice, which I would go for but I dont even have the $50 for the frame. But the 90cc 4 speed would be faster on the straights than the 70cc 3 speeed or the 90 cc 4 speed that doesnt run :p. And considering I would be riding with a 6 speed 125cc and a 5 speed 227cc, I need all the speed I can get for cheap.
what was shipping for that 99 cent cable wondermuscle?
 
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W

WonderMuscle

Member
I think shipping for the cable was $5 or something. It was cheap but totally worked.

If you are riding with 125's and larger I would put a china motor in your ct70 and call it a day. The 90 won't run much faster than a well tuned 70. My ST90 with the 4 speed would top out at 51mph on the flat and would get up to 55mph down hill with the wind behind me. Getting power out of the 90 motors is expensive not to mention the ST90 feel much heavier than the CT70 but that could all be in my head.

Russ
 
Epic_username

Epic_username

Member
I know but I have no money for a china motor and it would have to be shipped in from the states. Ill probably end up riding alongside the truck with the tools and beer in it untill I find another $150 125cc dirtbike. The 125 id be riding with is really mine but when we ride with my uncle with the 227 my dad has nothing to ride. But atlease I will have something to ride...
 
Epic_username

Epic_username

Member
I was just thinking, and remembered that the ST90/S90 engine mounts are wider than CT70, so would the frame be wider? Would I have to ad spacers if i were to use the CT70 swinger?
 
motodevo

motodevo

Active Member
ct70 swinger will not fit at all. The ct70 one is mounted inside the frame, the st90 one mounts outside the frame, the 2 frames are different in this area. Just eyeballing them tonight i dont think the frame on the 90 is wider, i think the spacers on the mounts on the 70 frame are wider.
 
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