Hello fellow OldMiniBikes enthusiasts!
I recently completed this longtime awaited 2 stroke mini bike project! I have always loved 2 cycle engines and mini bikes. What a perfect combination.
I first started this 2 stroke mini bike journey back around 2015. I followed another members idea of using a 141cc Lawnboy Duraforce lawnmower engine.
It involved a lot of custom fabrication work and $$. I was never quite happy with the performance. Part of that was due to the Comet 30 series torque converter set up.
I always had my eye on the infamous West Bend 820 138cc beast! Found one in Canada from a vintage snowmobile collector. Best part, Its NOS never been fired up! was so happy. Ended up disassembling the entire engine. New gaskets, HD rod bolts, oversize needle bearings for the con rod, billet stuffer plate and some gold paint.
All of my mini bikes have torque converters so this project would be no different. I haven't seen any other builds with a 820 with a TC...
I am using the cast aluminum driver weights, light blue springs and the driven spring in hole #3. This is around 3300rpm engagement. Using a china driven pulley with the red torsion spring. My final drive ratio is 12/72. First test runs were pretty disappointing, seemed to lack any real power. At first I thought I was the engines configuration (.062" head gasket and small 189 carb) but it turns out my muffler attempt was way to restrictive lol.
I figured a 820 could exhale through a 3.5HP Tecumseh 4 cycle round can muffler stuffed in the end of the flexible pipe. Dumbass lol.
After removing that Tec can muffler the power instantly doubled!!! Thing is a monster now. Pops wheelies on command and shreds the ground beneath.
The main issues now are its way too loud. 15 mins and my ears are ringing lol. The 24:1 premix makes an awful mess and leaks out of the flexible exhaust pipe. I am going to try a 1.75 id, 12 inch long exhaust resonator for a car exhaust and see how that works.
I think the Tec air filter I am using is too restrictive as well. I need to find a velocity stack and pod air filter. I have thinner head gaskets and a larger 232 carb. I feel this would be to much power lol. The small fuel tank gets drained quick too.
I recently completed this longtime awaited 2 stroke mini bike project! I have always loved 2 cycle engines and mini bikes. What a perfect combination.
I first started this 2 stroke mini bike journey back around 2015. I followed another members idea of using a 141cc Lawnboy Duraforce lawnmower engine.
It involved a lot of custom fabrication work and $$. I was never quite happy with the performance. Part of that was due to the Comet 30 series torque converter set up.
I always had my eye on the infamous West Bend 820 138cc beast! Found one in Canada from a vintage snowmobile collector. Best part, Its NOS never been fired up! was so happy. Ended up disassembling the entire engine. New gaskets, HD rod bolts, oversize needle bearings for the con rod, billet stuffer plate and some gold paint.
All of my mini bikes have torque converters so this project would be no different. I haven't seen any other builds with a 820 with a TC...
I am using the cast aluminum driver weights, light blue springs and the driven spring in hole #3. This is around 3300rpm engagement. Using a china driven pulley with the red torsion spring. My final drive ratio is 12/72. First test runs were pretty disappointing, seemed to lack any real power. At first I thought I was the engines configuration (.062" head gasket and small 189 carb) but it turns out my muffler attempt was way to restrictive lol.
I figured a 820 could exhale through a 3.5HP Tecumseh 4 cycle round can muffler stuffed in the end of the flexible pipe. Dumbass lol.
After removing that Tec can muffler the power instantly doubled!!! Thing is a monster now. Pops wheelies on command and shreds the ground beneath.
The main issues now are its way too loud. 15 mins and my ears are ringing lol. The 24:1 premix makes an awful mess and leaks out of the flexible exhaust pipe. I am going to try a 1.75 id, 12 inch long exhaust resonator for a car exhaust and see how that works.
I think the Tec air filter I am using is too restrictive as well. I need to find a velocity stack and pod air filter. I have thinner head gaskets and a larger 232 carb. I feel this would be to much power lol. The small fuel tank gets drained quick too.
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