3.5 hp Briggs and Stratton questions

[RiceCakes]

HELLO ALL! I'm new here, and I've got some questions about my b&s. Model # is 94212-0319 and I took it from a lawn edger/tiller. Didn't run so I fixed it up by replacing the spark plug and adding new oil, which got it started real quickly, then I stripped down the edger to get to the engine, bent the governor tab, took off the exhaust redirector, cut a hole in the air filter box, and lubed up some parts that needed it. My question is: how can I make more power? Also, what clutch could I use for this? It has a key lock on the crank and idk what to buy. I also don't know how to set up the rear axle but I can figure that out later. I'll attach some pictures real quick but I just want to know the ins and outs of this engine. I'm a broke 17 year old with a low budget, in the 150-250 range. Thanks! (Also got a gnarly burn from the exhaust on my forearm)

 

[Master Hack]

I also don't know how to set up the rear axle but I can figure that out later. I'll attach some pictures real quick but I just want to know the ins and outs of this engine. I'm a broke 17 year old with a low budget, in the 150-250 range. Thanks! (Also got a gnarly burn from the exhaust on my forearm

Power is expensive, only thing more expensive is wimmin.
Look for a used engine with more power. They can be found, l just got a 212cc predator for $40.

don't figger it out later. Have a plan, its way cheaper and mo efficient use of time and materials.

exhaust is hot.

 

[Denny]

The easiest way to get more power from that engine is to replace it with a bigger one. What do you have for a kart?

 

[panchothedog]

What kind of clutch you need depends on what you use the engine on and the diameter of the rear tire. You have probably already done the easiest horsepower gains by the exhaust and air box. DON'T put any money into that engine. It's not worth it. It will power your mini bike or go kart. It just won't be super fast. That's the way life is when you're broke, or poor. When it comes time for a clutch or a torque converter, it will probably be for a 3/4" shaft. If you were smart enough to get a dead engine running, then you can probably measure the diameter of your output shaft. From the picture, I'm guessing it's 3/4". If you buy a used 6&1/2 horsepower engine ( like a predator ) it will also have a 3/4" shaft so you can use the same clutch with either engine. No wasted money. Plus you are smarter already. You've learned that exhaust is hot enough to hurt real bad. We both know you won't make that mistake again.

 

[RiceCakes]

What kind of clutch you need depends on what you use the engine on and the diameter of the rear tire. You have probably already done the easiest horsepower gains by the exhaust and air box. DON'T put any money into that engine. It's not worth it. It will power your mini bike or go kart. It just won't be super fast. That's the way life is when you're broke, or poor. When it comes time for a clutch or a torque converter, it will probably be for a 3/4" shaft. If you were smart enough to get a dead engine running, then you can probably measure the diameter of your output shaft. From the picture, I'm guessing it's 3/4". If you buy a used 6&1/2 horsepower engine ( like a predator ) it will also have a 3/4" shaft so you can use the same clutch with either engine. No wasted money. Plus you are smarter already. You've learned that exhaust is hot enough to hurt real bad. We both know you won't make that mistake again.

The shaft also has a key lock, will that give me trouble when looking for a clutch? The clutches I've looked at never specify if they have a slot for the key lock

 

[landuse]

The keyway on the shaft wont give issues when looking for a clutch. Measure the diameter of the shaft and buy a centrifugal clutch that matches. They pretty much all come with keyways.

You are going to have to gear really low to get any movement out of a 3.5HP engine. Whatever you do, its going to be slow

 

[RiceCakes]

Yeah, I'm thinking about a 4:1 gear ratio on a 12 tooth clutch but I can't for the life of me find a 48 tooth 35 chain

 

[landuse]

Yeah, I'm thinking about a 4:1 gear ratio on a 12 tooth clutch but I can't for the life of me find a 48 tooth 35 chain

You have the gearing the wrong way round. You want to gear the engine low so that it more torque. That means that the ratio has to be higher. 4:1 is a pretty high gear ratio. With a 3.5HP engine you are going to have to at least have an 8 or 9:1 ratio. Maybe even lower. This means that the axle sprocket has to have 8 or 9 times the tooth count compared to the clutch sprocket. I had a minibike that had to be geared at 11:1 before it would move. To get a ratio that low you might even have to use a jackshaft that will allow you to use smaller sprockets. If you want to use a 12T clutch, you are going to have to either get a axle sprocket with more than 100 teeth, or use a jackshaft

 

[RiceCakes]

You have the gearing the wrong way round. You want to gear the engine low so that it more torque. That means that the ratio has to be higher. 4:1 is a pretty high gear ratio. With a 3.5HP engine you are going to have to at least have an 8 or 9:1 ratio. Maybe even lower. This means that the axle sprocket has to have 8 or 9 times the tooth count compared to the clutch sprocket. I had a minibike that had to be geared at 11:1 before it would move. To get a ratio that low you might even have to use a jackshaft that will allow you to use smaller sprockets. If you want to use a 12T clutch, you are going to have to either get a axle sprocket with more than 100 teeth, or use a jackshaft

I'll probably at some point pick up a more powerful engine, don't know what brand yet, but I might try out that jackshaft idea. Would using a gear system similar to a bike work? Like having the gears side by side and having a thing to manually switch them over?

 

[RiceCakes]

The easiest way to get more power from that engine is to replace it with a bigger one. What do you have for a kart?

Right now just the engine, I really want to avoid building my own chassis, mostly because it's time consuming and I would have to find someone to weld. If I have to I will, especially with these outrageous prices people have on fb marketplace. But if I can I'll just buy a used frame

 

[Denny]

Don’t buy anything yet, take the time to learn first.

 

[ezcome-ezgo]

Would using a gear system similar to a bike work?

No