Thought I would share my first build as I have seen some conflicting info about using a 30 series torque converter with a small engine like with this 49cc 4-stroke. I did not document this very well, as this was done over 2 months. The bike has run perfect and has about 300 miles on it. You can start off from a dead stop and drive at very slow speed or cruise at 30-35mph depending on your weight. The belt has minimal wear and I expect it to last a long time. This 49cc engine works extremally well with this 30 series torque converter. This build required a bunch of custom modifications that I have probably not mentioned below.
I used a 49cc 4-stroke kit you can get off of ebay / amazon.
This kit came with the standard friction clutch / transition that requires you to pedal you bike and get it moving before engaging he engine.
I wanted to be able to just start off from a dead stop and not burn clutches so I also purchased a 30 series torque converter from amazon / ebay for $60.
The problem is that the 30 series torque converter fits on a 3/4 inch shaft and the 49cc engine has a 15mm shaft (not even 5/8), and the mount bolt pattern on the torque convertor did not match the engine bolt pattern. I designed and 3d printed a template to drill new mount holes in the torque convertor so it could be attached to the engine.
I used the above pattern to drill new holes in the torque convertor mount plate to match the engine mount holes. I placed the 3/4 to 5/8 shaft adapter onto the engine, but because the engine shaft was 15mm this was slightly to big. I used an aluminum can and cut it into sheets that I wrapped around the shaft and placed the shaft adapter over top of these wrapped aluminum sheets. This created a tight snug fitting for the shaft adapter. A knife was used to cut away the aluminum can for the key slot. Once the torque converter was slide overtop of the shaft adapter this provided a secure tight fit. The shaft adapter had to be cut shorter to mount the drive pulley for the torque convertor.
Once the torque convertor was mounted to the engine, I had to move the sprocket for the chain on the driven pully to the inside of the mounting plate. This was so the drive sprocket would line up properly with the sprocket on the rear wheel of the bike. This required a new 5/8 jacket shaft cut to length and the bearings in the torque convertor had to be replaced to match the shaft. A washer was welded to the end of the jacket shaft instead of using a snap ring like on the original jack shaft.
A custom chain tensioner with a spring was made from 1/8" this metal. I have heard that people use high quality chains without a tensioner. But this was easy to make and allowed some slop in the chain as well as engine placement. It swiveled and was attached to the torque convertor so the pivot point was in a similar location as the drive sprocket.
My cheap bike kit shipped without the twist throttle mount. So I just designed and 3d printed the throttle mount, along with a pushbutton stop for the left hand and an ignition mount for a key. This was all wired into the kill switch. A key is needed to start it, but of course it would be easy to by pass by just cutting the wire.
let me know if you have any questions.
I used a 49cc 4-stroke kit you can get off of ebay / amazon.
This kit came with the standard friction clutch / transition that requires you to pedal you bike and get it moving before engaging he engine.
I wanted to be able to just start off from a dead stop and not burn clutches so I also purchased a 30 series torque converter from amazon / ebay for $60.
The problem is that the 30 series torque converter fits on a 3/4 inch shaft and the 49cc engine has a 15mm shaft (not even 5/8), and the mount bolt pattern on the torque convertor did not match the engine bolt pattern. I designed and 3d printed a template to drill new mount holes in the torque convertor so it could be attached to the engine.
I used the above pattern to drill new holes in the torque convertor mount plate to match the engine mount holes. I placed the 3/4 to 5/8 shaft adapter onto the engine, but because the engine shaft was 15mm this was slightly to big. I used an aluminum can and cut it into sheets that I wrapped around the shaft and placed the shaft adapter over top of these wrapped aluminum sheets. This created a tight snug fitting for the shaft adapter. A knife was used to cut away the aluminum can for the key slot. Once the torque converter was slide overtop of the shaft adapter this provided a secure tight fit. The shaft adapter had to be cut shorter to mount the drive pulley for the torque convertor.
Once the torque convertor was mounted to the engine, I had to move the sprocket for the chain on the driven pully to the inside of the mounting plate. This was so the drive sprocket would line up properly with the sprocket on the rear wheel of the bike. This required a new 5/8 jacket shaft cut to length and the bearings in the torque convertor had to be replaced to match the shaft. A washer was welded to the end of the jacket shaft instead of using a snap ring like on the original jack shaft.
A custom chain tensioner with a spring was made from 1/8" this metal. I have heard that people use high quality chains without a tensioner. But this was easy to make and allowed some slop in the chain as well as engine placement. It swiveled and was attached to the torque convertor so the pivot point was in a similar location as the drive sprocket.
My cheap bike kit shipped without the twist throttle mount. So I just designed and 3d printed the throttle mount, along with a pushbutton stop for the left hand and an ignition mount for a key. This was all wired into the kill switch. A key is needed to start it, but of course it would be easy to by pass by just cutting the wire.
let me know if you have any questions.
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