5/8 to 3/4 crankshaft conversion

E

Evil_EdwardO

New Member
#1
#1
Was just thinking, has any one ever tried using metal bonding epoxy to attach a sleeve with key to the crankshaft? Since the torque converters key isn't long enough to get down to the original shaft, I thought I try it. I figured I give it a shot and if I ruined the crankshaft then I would replace it with one with a 3/4" shaft.

Has anyone tried this before? Am I wasting my time?

Was just trying a quick fix without having to tear the engine apart. I was going to remove the governor this winter but if this doesn't work I might do it sooner to replace the the shaft or just put the clutch back on until winter.
 
C

cfh

Well-Known Member
#7
#7
you can still use the adapter with the tall key. there's a trick to it. definitely works, i just upgraded a ct200 that had a 5/8" shaft to a 3/4" torque converter.
 
E

Evil_EdwardO

New Member
#9
#9
cfh said:
you can still use the adapter with the tall key. there's a trick to it. definitely works, i just upgraded a ct200 that had a 5/8" shaft to a 3/4" torque converter.
Click to expand...
So what's the trick? Or will it be self explanatory when I get the sleeve? I have one ordered but won't be here until Friday.
 
E

Evil_EdwardO

New Member
#12
#12
Charles S said:
Maybe a $99 Predator 212 would be the easy solution.

Here's a thread where a member bored the driver to remove the integral key, then broached a keyway.

https://www.oldminibikes.com/forum/index.php?threads/want-to-put-a-tc-on-a-coleman-ct100.141989/
Click to expand...
I'm just curious, and want to see if I can get this to work. I had a few other ideas I was going to try and the epoxying was going to be the last thing I tried if my other ideas failed. I was either going to get a new crank for the Hisun or buy a Predator if I screw it up royally.
 
Charles S

Charles S

#13
#13
Evil_EdwardO said:
Hisun 196cc
Click to expand...
In that case, I think you probably have a 16 mm shaft, which is slightly larger than 5/8". 16 mm = 0.630" while 5/8" = 0.625". 0.005" isn't much but you need to fit the adapter to the outside of the shaft and inside the driver, so if you spread the adapter to fit on the shaft, it may not fit inside the driver; that's why the adapter needed reaming in the thread linked above. The ease or difficulty of the installation will depend on your particular adapter and how accurately it was made; if you're real lucky, the bore may be slightly oversize.
 
C

cfh

Well-Known Member
#14
#14
did this on a ct200 with a stock engine. bought a complete $55 torque converter kit. would not fit because engine shaft was 5/8, not 3/4". bought the $10 adapter. The problem with the adapter was it's set up for a clutch, not a torque converter. It has a tall key that goes into the slot of the crank and the slot of the adapter, and stick up. problem is the TC has it's own key that goes down into the shaft. So the tall key doesn't work because the TC doesn't use a separate 3/16" key.

The answer is to cut the tall key, about in half, and insert it first. The TC built in key is about in the middle of the shaft. So you put the tall keyway behind it. This locks the adapter into place, and still allows the TC's built in key to lock on to the shaft.
 
E

Evil_EdwardO

New Member
#18
#18
cfh said:
did this on a ct200 with a stock engine. bought a complete $55 torque converter kit. would not fit because engine shaft was 5/8, not 3/4". bought the $10 adapter. The problem with the adapter was it's set up for a clutch, not a torque converter. It has a tall key that goes into the slot of the crank and the slot of the adapter, and stick up. problem is the TC has it's own key that goes down into the shaft. So the tall key doesn't work because the TC doesn't use a separate 3/16" key.

The answer is to cut the tall key, about in half, and insert it first. The TC built in key is about in the middle of the shaft. So you put the tall keyway behind it. This locks the adapter into place, and still allows the TC's built in key to lock on to the shaft.
Click to expand...
Now that I have the sleeve, it is pretty obvious. With the spacers I need to align the TC, looks like I'll have plenty of space for the key once I get it shaved down. Hopefully I have time this weekend to finish it up and try it out. Thanks!!

IMG_20190726_094836297.jpg
 
E

Evil_EdwardO

New Member
#19
#19
Just an update: I stuck everything on with the adapter without the key and everything seemed to grab. I didn't have to trim the adapter, I had a 3 inch one. I forgot the enclosed screw was for a 3/4" shaft and tried the one from my clutch and it was too short. I ended up at the hardware store and got the right length screw and saw they had adapter keys. I took a chance and bought a short one too see if it would work like CFH said. I got home and the key fit under the washers so I didn't have to file down the tall key that came with the adapter. I did have to cut it in half though since it was too long. I didn't want to try it without the key because I didn't know how much the TC key was grabbing the shaft. It seemed like it could of worked though.

Anyways everything is installed and with a 60t sprocket, I'm popping wheelies on take off!! I didn't get to open it up yet but definitely going faster than I ever was before too.

Thanks everyone for your input!!
 
You must log in or register to reply here.
Top