Sunday, August 4, 2013

How to increase the power in a lawn mower engine?

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Mako


Right now I have a craftsman flathead engine making 5.5 hp.

I'd like to put it in a go cart or mini bike sometime, so more power would be more fun.

Any tips?



Answer
Get rid of those crappy mufflers and get a tuned exhaust from a 4-cycle small motorcycle engine (125-175 cc).

Put an extension on the air cleaner and grab air from a place away from the engine.Use low restriction air cleaner. Engine vicinity air is to hot, and hot air doesn't have as much oxygen in it as colder air. Ideally you could run your air thru a box with ice cubes in it so the air enters your engine as cold and dense as possible.

If you have access to a welder and grinder and drill press you can make an induction manifold for your carburetor. The longer the tubes between your carb and your intake valve the more time the gas has to completely vaporize and burn stronger. In an engine you want top heat production to make more power.

Use synthetic 50W oil and wrap a little insulation around the cooling fins. Since the lawnmower engine is made to run at walking speeds it has excess cooling fins to handle the heat of burning gas. Since your go cart moves, it doesn't need as much cooling. This is a trade off though. You want to keep your engine as hot as possible but not so hot you melt the valves or cylinder dome. So you got to experiment. Put a little insulation on engine..if's its ok with that, keep adding more until it smokes to much or power goes down (from oil not staying on cylinder walls)

Get a spark plug with multiple electrodes on the tip.

And most importantly and this is not the engine.. get a variable speed transmission (torque converter) and not a friction clutch. This transmission will make sure your engine is getting the optimum torque output no matter your speed.It's like having a hundred gear transmission.

Try to copy the design of a 125 cc four cycle motorcycle engine. These engines are smaller in cc's than a lawnmower engine but get about 15 hp out of them. Lawnmower engines are built for longevity and dirt and cheapness and heat. So they limit the horsepower on purpose so the engine lasts longer.

In all honesty you would be a lightyear ahead by just grabbing a used motorcycle engine and transmission and sprockets, chains and controls out of a wrecked bike rather than trying to use a lawnmower engine.

You could spend a 100 hr of labor and several hundred dollars trying to make your 5.5 hp engine put out 15 hp and Yamaha and Honda do this all day long. Don't reinvent the wheel and start with a proven engine and transmission. When I was a kid I tried those lawnmower engined mini-bikes and go-karts...they always disappoint. The clutches wear out quick and the motors arent designed for the high loads you put on them, so they break quick

How can a 13 yr old kid make 600$ in 2 months?




Brandon


I really want to get my first mini bike. Obviously my parents can't buy it for me because it's too much money to spend on me. So I have been trying to save up money. Except it's just not going as quickly as I thought. I do have chores that I do. I get about 15$ each week. Except it's not enough to get 600$ in 1 or 2 months. I know the goal of 600$ in 1 month is a little extreme, but I will be getting out of school soon, so the fster I can get the bike the better. I also have a really busy schedule so it will be hard to make time for work. So can you please give me a few suggestions on how I could make 600$ in 2 months? It would be greatly appreciated.
Also, I have started to sell some stuff on craigs list (it won't get me anywhere near 600$) and as of right now I have about 100$.
So yeah, thanks.



Answer
You can't. Sorry!




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