small 2 stroke comparisons

[Thunderbird SC]

I have a few different small two cycle engine to choose from for my gas powered Gaucho. The Gaucho is a symmetrical torque converter system 20 series driving a 6 inch driven. The the 10t sprocket #35 chain and a 54t sprocket. The wheel's diameter is 13.5 inches and the finished kart weight is maybe 80lbs max so far.

I have the following engines 75, 85 and (3)98cc Tecumseh piston ports and a 102cc Briggs piston port. I hope to get a better less worn 102c BS one for cheap.

Lets start with the Tecumseh engines. The flywheel is light and features a straight fan blade design, measures 6.5 inches in diameter. The ports on this engine are designed for easy and cheap manufacturing which involves drilling 3 overlaping holes like that of an audi logo (intake).The transfer ports are long in length from the crank and are not formed in any way other than straight drill paths. The crankcase volume is rather large which I believe would lead to weaker vacuum/ pressure pulses. The intake mounts on an angle causing a bend in airflow and the exhaust is on the side of the engine which lands very close to the TC and requires routing the exhaust pipe through the belt. I can say this engine revs very quickly and is a hard one to idle at low rpm. There are lots of thin deep cooling fins which would lead me to think that this one is suited for summer use as well. In closing this engine fully assembled with carb and housing weighs a whopping 9 lbs!!

 

[bajagokart]

wow 80 lbs dry? that is fricken light man

 

[sideways]

I have a few different small two cycle engine to choose from for my gas powered Gaucho. The Gaucho is a symmetrical torque converter system 20 series driving a 6 inch driven. The the 10t sprocket #35 chain and a 54t sprocket. The wheel's diameter is 13.5 inches and the finished kart weight is maybe 80lbs max so far.

I have the following engines 75, 85 and (3)98cc Tecumseh piston ports and a 102cc Briggs piston port. I hope to get a better less worn 102c BS one for cheap.

Lets start with the Tecumseh engines. The flywheel is light and features a straight fan blade design, measures 6.5 inches in diameter. The ports on this engine are designed for easy and cheap manufacturing which involves drilling 3 overlaping holes like that of an audi logo (intake).The transfer ports are long in length from the crank and are not formed in any way other than straight drill paths. The crankcase volume is rather large which I believe would lead to weaker vacuum/ pressure pulses. The intake mounts on an angle causing a bend in airflow and the exhaust is on the side of the engine which lands very close to the TC and requires routing the exhaust pipe through the belt. I can say this engine revs very quickly and is a hard one to idle at low rpm. There are lots of thin deep cooling fins which would lead me to think that this one is suited for summer use as well. In closing this engine fully assembled with carb and housing weighs a whopping 9 lbs!!

I'd go for the 98cc Tecumseh engine, or maybe 2 of them?

More crankcase volume is good for low end power.

Hayden

 

[Thunderbird SC]

Now on to the Briggs and Stratton.
This one seems better engineered but may have its trade-offs. Assembled this 102cc weighs almost 12lbs, most of it being in the flywheel. The flywheel is smaller in diameter at 6 inches and features rounded fan fins. On the flywheel I find a 3 magnet system and a tradition magnetron ignition; the Tecumseh uses a small 2 magnet system (my info about it is limited other than its pointless, advance unknown). The crankcase is tight in size and the transfer ports are short in lenght and better designed with smooth flowing curves. The intake port also is quality with a small tab for ring support opening the possibility for widening it later. Also the intake port has a pulse line built into it that with the stock carb works well or a float one can be used as well. The head appears to be hemi shaped and is one piece with the cylinder.

 

[Thunderbird SC]

a video of the Briggs running

http://www.youtube.com/watch?v=MPpceb7DAVM

I wish i kept that odd flywheel that was about 1lb. It was aluminum and "ring" part was only two sections where the magnets were and the counter weight. That thing let engines really rev but also sheared its fair share of keys.
Any idea of the RPM max we hear?

 

[Thunderbird SC]

I got a max of 8362 rpm using a special sound rev counter program . Later i'll try the two Tecumseh of different sizes.

 

[Thunderbird SC]

oddly the Tecumseh 98cc seemed to max out around the same rpm at 8430 but needs some carb cleaning as it was leaning out too much. Dang fixed jets for now, all i can do is adjust float levels. The briggs at least had a mixture needle. Will post vid after another cleaned run

 

[Thunderbird SC]

This is the only oil I use till I need their version for methanol and eventually a 60% nitro mix

 

[Thunderbird SC]

going to try out my new lightweight flywheel on the briggs.

Original flywheel weight : 5.0 lbs
new :around 12 oz

Problem: taper on original is very slight, all other flywheels I searched through have high taper hole.