A Crazy Idea, Advice Welcomed

[Old Guy Too Many Bikes]

I have a Zonsheng 140 powered CL90 with over 2000 miles on engine and still running great. However, I ran across a Honda 250 Custom (precursor to the Rebel) I can buy dirt cheap. I am familiar with these engines and was wondering what it would take to shoehorn this engine into my CL90. This thing would run effortlessly at 55 mph, be 85 mph capable and be super smooth to boot. I am a proficient welder. machinist, and fabricator, and have seen 175 twins in CT70's. I was wondering what issues would arise, like the drivechain offset, front wheel clearance, foot controls, etc. I figure notching out the frame and gusseting is a given.

 

[Gordy]

I'd suggest upgrading the swing arm. I want to jam a 125 2 stroke in my ct90 and I've been seriously considering replacing the swing arm

 

[Old Guy Too Many Bikes]

I can gusset the hell out of mine if needed. I'd be more concerned about a wider engine causing an offset between the drive and countershaft sprockets.

 

[Rallan]

Sheesh... I have no idea or comment.

But it sounds like an awesome project

 

[Robert thran]

I’ve thought about doing something like that but just always thought it would be an extream long shot that the sprockets would line up. Maybe there’s more room to move around a rear sprocket on a ct90 then sl,ct,an cl70’s? But if you could pull it off it would be awesome…

 

[Old Guy Too Many Bikes]

I figured I could use the bottom cradle and mounts off the donor bike and weld it to the CL90 frame. I probably would offset the engine enough to make the sprockets line up. I think the 250 would use a 520 chain or similar and would be easy enough for me to weld a ring gear from the 250 onto the center of the 90's sprocket.

 

[Gordy]

I figured I could use the bottom cradle and mounts off the donor bike and weld it to the CL90 frame. I probably would offset the engine enough to make the sprockets line up. I think the 250 would use a 520 chain or similar and would be easy enough for me to weld a ring gear from the 250 onto the center of the 90's sprocket.

This is what I was planning when my motor gets here. I will build a secondary cradle that bolts to the original mounts

 

[scooter]

Look for some old posts from Ctynot associated with his 250 rebel into an ST90 frame build. It was tight but it is an awesome build. I helped him get the extra engine mounts designed and lined up either a 1/4 clearance of the head to frame. It’s a sweet bike and a fun ride

 

[Gordy]

Question; when I go to build my mount, should I use an angle grinder or pay to have them cut? I don't want to spend alot, but if I have to I will

 

[Old Guy Too Many Bikes]

Cutting is the easy part, Use some photographs to aid making some scale drawings of both your frame and the engine going in, then like paper dolls, see how they should fit and clear before deciding on where to cut. Measure at least twice, cut once. The hard part is the fitting and welding.

 

[Old Guy Too Many Bikes]

Hey Scooter, thanks for the tip on Ctynot's posts, saw a lot of crazy swaps, the coolest was a 1967 C77 with a 400cc four in it. Shows you anything is possible.

 

[Old Guy Too Many Bikes]

Did a little cut and paste and I think I may have a problem. Seems if the engine is too far forward, it'll interfere with the front wheel, but if I move it back, there's no room for the carb and air filter. The 250 has frame rails that the intake fits in between, but on the CL, the stamped frame would totally get in the way. I have to do some more thinking.

 

[Rallan]

Banana seat and raked out chopper front end?

 

[Gordy]

You could get an after market teiple tree that would move the front forks out a little more. If you can find a different place for the battery you could put the intake/carb inside the frame

 

[Old Guy Too Many Bikes]

I don't mind adding to the frame, but I don't want to cut it up. Otherwise, I would just attach pieces of the CL90 frame to the CM250 frame as well as the wheels, tank, fenders, seat, etc. including the vin and trim tag. It's a thought, but would seem like cheating somehow.

 

[Gordy]

I don't mind adding to the frame, but I don't want to cut it up. Otherwise, I would just attach pieces of the CL90 frame to the CM250 frame as well as the wheels, tank, fenders, seat, etc. including the vin and trim tag. It's a thought, but would seem like cheating somehow.

I'm 100% leaving the frame alone. I'm going to build a secondary cradle for it.

 

[Old Guy Too Many Bikes]

Well, I pulled the trigger and brought this $150 jewel home today. But, the engine turns overs, has compression, clutch seems to work, and is still pretty much all there. With a little luck, I'll get it running in a week or two, and then plan the engine swap, worse case. I'll clean it, flip it and should at least get my money back.

 

[Gordy]

Shoot for 150 bucks that's sweet. You can even go as far as pulling the engine and line things up, and if you don't like it you can put the other bike back together and sell. I paid 150 shipped for my engine.

 

[Gordy]

Even if that engine has low compression it will still be way faster than the original

 

[scooter]

I remember Ctynot found some carb manifolds that angled the carbs outward and allowed the engine to be positioned as far back as possible