Thread: ct90 in ct70 frame? *pics*

Hello. First post, new to ct70's. I recently purcased a ct70 frame and have also aquired a ct90 motor. I am curious will this motor directly bolt to my ct70 frame? If not what modifications are needed exactly? Wont get a chance to work on the machine till later this week. Any helpful links or information is greatly appreciated.

Thanks!

No, the CT90 motor will not fit into a CT70 frame. Not to sure what the mods are to make it so. I think the engine mount holes are in the wrong spot on the 70 frame.

The Honda 90cc motor case/mounts is a tad wider than a 70cc motor. Bet bet would be to use a CL, or ST90 frame, or find a 50, or 70cc motor.

Thanks for the info guys. Does anyone know good places or ppl to source ct70 parts/motors from in Ontario, Canada?

Thanks again!

Regular spots: check your local bargain hunter, and classified ads, or better yet, put an ad in one of them for a CT70 engine.

Good news! I am going to be able to use the ct90 motor afterall. I will have to modify things slightly but not very much. Will keep the thread updated if anyones interested.

Cool project!
Keep us updated (W/pics if possible).

The deal-breaker, for most, are those deceptively-simple looking frame mods. Doing them right is a bit more involved than they might appear at first blush. You're dealing with alterations to the weakest points of the frame that gets its strength from carfeully engineered geometry. CT70s are, for all practical considerations, unibody bikes. The brake pivot (welded into the frame), swingarm pivot and lower engine mount form a triangle. There's not a lot of built-in overkill here, even the motor mount bolts are critical (and must be tight to prevent frame damage). As I recall, the brake arm pivot is in the way. If you have to move it, then you'd do well to weld-in a replacement in a suitable location and add .125" thick steel plates, tied-into the swingarm reinforcing plates, to the new motor mount locations. That will add some needed structural strength and prevent frame cracks from developing. It should be possible to use a long bolt, with a bushing to fit the brake arm, as an integrated lower engine mount/brake arm pivot. It's been a while, but if memory serves there's enough room to add the weldments to the inside of the frame. At least they'll be invisible once the bike is assembled.

The CT90 motor has a beefier lower end and some have a 2:1 sub-transmission which gives you a dual-range tranny. These also have real charging systems, good for road lighting. It seems like most parted-out CT90s have 15-18000 miles showing. It's a bulletproof motor but at a price. These things are boat anchors and parts availability, especially tuning parts, is thin . Nearly all have semi-automatic clutches. If you like the semi-auto, you're in luck. If you want a manual clutch, the parts are ultra-rare these days. If you're committed to fitting one of these engines to your CT70, you might want to consider a CT110 motor instead, at some point. The added displacement is a good thing and later examples are 12v/CDI; we're not talking about huge power with either engine, an additional 20cc would nice to have.

I see you got the bike up for sale on kijiji already. Don't give up so easily. Your starting point dispite not having a usable engine is far better looking than what I started out with!!
For engines in Ontario, try searching ebay stores for fast trails performance.

I have the ct90 motor model with semi-automatic clutches and 2:1 sub-transmission dual-range tranny. Is this a rare desireable motor?

I have recently acquired another ct70 in better shape. I can post pics if anyones interested.