Do Torque Converters Limit Max RPM?

[Kartorbust]

Torque on a 4 stroke is lower end where as 2 stroke makes the torque in the upper end of the power curve. Basically from what I gathered from my own thread when I had asked it is pretty much a 4 stroke engine will put more stress on the belt than a 2 stroke will. I'm simplifying it at the moment. Take a read of it. But here's a picture from a comet 780 manual.

 

[Solomonster212]

Did you gain 4 mph with the clutch or lose 4 mph with the clutch?

The clutch allowed me to go 4 mph faster than the torque converter.

But one must understand the tradeoffs between each before deciding. Clutches have higher top speed but torque converters have better acceleration.

 

[Walter Keller]

I bought a Juggernaut after seeing and reading a lot of reviews - I replaced a 30 series ChiCom TC driver that was working fine. I had already replaced the driven pulleys spring with a yellow Comet spring. My engine is a 196cc Lifan (greyhound brand) rear sprocket is stock Baja size (48 tooth ?) with the following mods - I dont know how much HP its making
No governor
18 lbs springs (should I be using 24lb springs with this cam ?)
Hot 265 cam
PVL flywheel
Billet Rod
Stock size carb rejetted and better emulsion tube
K&N style air filter and adapter
Racing spark plug
Exhaust header

Right away you could feel the difference with the Juggernaut driver (using a used TC belt) It pulls a lot harder earlier - its using the engines power sooner. I need to install a new belt to compare belt wear to the old driver.

 

[KartFab]

Would it have been better to run a 780 then? They're rated for 30+ horsepower. That's why I plan on running one.

the 780's shred belts on v-twin high output engines.

the 40 series wont pull the cogs off of the belts they have.

This is 2nd hand info from someone who has ran the 780s a bit. the 780 is a bit too expensive for me actually. I plan on running a 40 series on an 18 and a 20 hp v-twin stock.

I also think that with gearing the 780s wrong, you just can hurt the belt rather than slipping. You need to gear correctly, and it wont stress the belt out.

Again, i have no 1st hand experience with the 780 but have talked to someone who has ran a bunch and he stopped running them and switched back to the 40 series because the belts on teh 780's would just not hold up.

You might get a better idea of the 780s' perfomance by trying out a mini-buggy forum. They are super popular on mini buggies.

 

[Solomonster212]

22lb or 24lb valve spring should be used with the HOT265 cam in order to achieve a higher valve float.

I personally am running the 18lb valve springs with a HOT265 cam with tons of low end torque. But it does top out way too early. You can upgrade to the recommended valve spring size for a small sacrifice of low end power in order to raise top speed.