PlanetMinis Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Been into building old choppers for a while but decided to get into mini bikes because well why not? I don't really dig the way pitbikes look and in my neck of the woods it's hard to find a decent old mini period. I ended up purchasing a 72 st90 roller for way cheap (I thought it was a ct70). Then I purchased a piranha 140cc motor for it and I couldn't be happier with the setup.
 

Attachments

·
Registered
Joined
·
8 Posts
I just got the same st90, I love the "Mighty Green", I unfortunately don't have a motor for it. I understand the st90s have a different motor mount (3 vs. 2) than most standard Chinese aftermarket motors. Did the Piranha 140cc swap right in w/o modification? Any help would be greatly appreciated.
Thanks!
 

·
Registered
Joined
·
3 Posts
Discussion Starter #5 (Edited)
I just got the same st90, I love the "Mighty Green", I unfortunately don't have a motor for it. I understand the st90s have a different motor mount (3 vs. 2) than most standard Chinese aftermarket motors. Did the Piranha 140cc swap right in w/o modification? Any help would be greatly appreciated.
Thanks!

Just hung the motor with the top/front mount and made the rear out of flat stock. No cutting or welding of the frame required.
 

Attachments

·
Registered
Joined
·
8 Posts
Oh, forgot to update. I picked up an atc90 with the hi/low gearing. Working on rebuilding & getting it running. Looks like I'll be cutting, grinding & drilling some flat stock tonight! Woo!
 

·
Registered
Joined
·
8 Posts
As far as I know, that's for swapping chinese motors into ct90/110s (Posties). I fabbed up the motor mounts this weekend. Here's a couple pics. Now to weld the pieces together and get this motor running smooth! Thanks to Frankrichards89 for the great idea!
image.jpeg photo.JPG
 

·
Registered
Joined
·
338 Posts

·
Registered
Joined
·
8 Posts
That will be the first pull-start ST90 with hi/lo trans I have ever seen!
I'm cruising along with this project. Wiring is going to be a challenge though. Here's a pic with the pull start rebuilt and installed, and the other is of the inside of gas tank after the first Apple Cider Vinegar treatment. It was soooo gunked up & rusted, now it's starting to look new again!


image-2178714842.jpg



image-2150165858.jpg
 

·
Registered
Joined
·
5 Posts
The SL CL S 90 motors have the 3 holes. All the 90 parts inner change ( to some degree). The ST is a fairly rare model (a couple years at best). Hate to see cutting and grinding on them.
 

·
Registered
Joined
·
1,804 Posts
That almost does look like a ct70.
did u all get a street legal title with em?
 

·
Registered
Joined
·
9 Posts
Am new to this forum, and like what I've read so far. Can use some advice here on restoring a '74 ST90 that I salvaged from my father-in-law's garage last year. He's passed on and I'm trying to get this bike running & looking as it did back then so I can pass it on to my older grandson (Henry's great grandson Robert, just turned 7).

Can post some photos soon but basically it was rusty, crusty and somewhat dented. Had broken kick-start spindle and 30 plus years of garage dirt. Replaced the spindle and broken 2nd gear, stripped and painted the frame (since I had to get the engine out anyway), and replaced or painted/cleaned up all the other crapped out parts. Am trying to keep the bike as original as possible (it's just me, kind of OCD about bringing a bike back to it's original look and life). Have had quite a time getting correct parts (duh).

Have the Clymer's manual but it doesn't give as much detail as I'd like (covers 50-110cc bikes over 30 damn years).

Latest problems are with the carb. All jets are original but they're clean, is feeding gas well.

Have already dealt with stripped threads for the plug (Heli-coil).

She runs but doesn't want to shift out of first gear (think plates are just gummed up).

Any help from you gearheads would be appreciated.
 
1 - 16 of 16 Posts
Top