1976 CT90 125m swap

JMZ400

New Member
Hello all, first post here.

Several years ago I came into possession of my friends, fathers 1976 CT90. As kids in the 80's we rode this thing everywhere when his dad wasn't hauling it to Colorado to elk hunt. For some reason his dad decided he wanted the added cc's and electric start from the ATC 125m. I remember clearly his dad purchased a brand new 125m (1984??)and promptly had someone swap the engine... 0 miles!!!!
If I remember correctly he never got it running due to an interference with the frame and carb or intake???

I'm considering digging this thing out of the shed and see if I can get it running. My question is if anyone is familiar with this exact swap and if the interference I mentioned above now has a bolt on work around or knows what type of set up I should consider.

Thanks in advance for any replies.
 
You'll just need an intake manifold that angles the carb away so that it doesn't hit the frame. They also make adapters, that let you vary the position of the carb up to 360 degrees.
 

JMZ400

New Member
Well here's a few pics. By the orange clay residue on the engine he must have had it running enough to take it up to Georgia. Really too bad this thing sat outside for several years. At least the engine and carb appear to have been sealed. I now see where they just cut the plastic to clear the carb. Anyway a bigger job than I have time for now with a move coming up, but I would like to ride it again some day.
20211121_163246.jpg
20211121_163254.jpg
20211121_163425.jpg
 
That's a neat engine and should make plenty of power. That rear sprocket is strickly for hill climbing, you'll need a much smaller one. Also, I would invest in a Chinese carb if the oe gives you any trouble, they're cheap and work well.
 

JMZ400

New Member
That's a neat engine and should make plenty of power. That rear sprocket is strickly for hill climbing, you'll need a much smaller one. Also, I would invest in a Chinese carb if the oe gives you any trouble, they're cheap and work well.
Thanks. I'm hoping that since the engine has so few hours that everything comes clean and functional.
 
Looks like a lot of motor to use a recoil start. Whenever I run a bike that won't be used for a while, I'll turn off the fuel and let it run out of gas. Hopefully that was done. I keeps the carb free of that tar formed by evaporated fuel.
 

MountainMini

Active Member
I don’t know very much about the CT 90’s. I saw this bike for sale in my area and had to post this pic for you! its listed as a 1967. Could this carb orientation work for your application, with a pod air filter?
F0B426CA-4618-4B67-9BCC-817DDFD9C28B.png
 

JMZ400

New Member
Great pic, thanks. After looking at mine it seems they decided to solve the problem by just cutting the frame cover. Everything is lined up so I'll let it ride.
 
Top