February 25th, 2018

# Go Kart Engine: Is my engine is going to be too powerful?

How do I tell if my engine is too powerful or just right?

Many times I have been chided by my friends, because I have a Briggs Vanguard engine that they think I should put on my gokart.  It is a 16 horsepower that someone gave me for fixing their go-kart, and it sits.  You are probably thinking that I should use it.  Well the time has not come to use it yet, but the question in people’s minds “Well why do you not throw it on your go-kart? “

Well I have run the calculations and a 16 horsepower motor is way too powerful for what I want to do right now.  What will happen is the wheels spin out of control and I really will only be able to go that one speed which is about 35 mph because if I actually ride my go-kart at top speed I have to crank it up to 6,000 rpm to get top speed!

A better use for that motor would be in a heavier go-kart.

So your question may be were did I come up with that?

Well obviously from my experience, but also because I am able to run a calculation.  Now, on our go-kart “Go Kart Building  201 series”  there are calculations with outlines that show you how to do calculations by hand.

One nice thing is that I have laid out for you in the go-kart guru website a calculations page.  Basically what you do is you throw in your weight that your go-kart is, how much you weigh, how much weight your rear wheels are going to hold, the gearing that goes in the calculation, then finally your horsepower your engine is putting out and how much rpm.

So the 16 horsepower motor had 3,600 rpm.  If you just go over to the calculation page program and plug in the 16 horsepower. You will see that the tires will spin too fast.

“Okay the tire is spinning but so what?  Maybe I want it to spin too fast!”

Okay that is a good question.

Maybe I have got a motorcycle engine and I want to put it on my go-kart.

“Well I have seen it done many times people are doing it.  But how do I know that is out of control?  Maybe I have a snowmobile engine and I want to put it on my go-kart.”

Well let me give you some word of advice.  Go-kart engines, once you get up to 20 horsepower or higher are just can be too much power so much power that you cannot really handle it.  It is really not fun.

The idea is to be able to max the horsepower reasonably so that you are not squealing the tires out of control.  What will happen is when you get up about 20 horsepower you stomp on the gas you cannot help but squeal the tires and it gets to be almost  frightening.

So the calculation will help aide you in figuring out how much power is too much or too little power.  So the first thing to do is to put in your best guess of what you’re design lines are going to be and then how much your go-kart is going to weigh, the horse power of the engine that you are going to put in there, and then press calculate.

Now the first thing you are going to be looking for is a time.  Now the time that I have put in there is for a 200 foot section.  It may get to be really fast like 3 seconds or something and it will give you a theoretical 0 to 60 mph.  That will give you an idea of how crazy this go-kart would be.

I believe if you have a 16 horsepower motor in there it would give you 4 seconds in acceleration from 0-60.  Well, the go-kart is not going to 60 mph but that would be the linear acceleration that the go-kart would be putting out.

I will just give you some perspective that most Corvettes do not even go that fast.
Most motorcycles cannot even accelerate that fast.  So what that really means is that your tires are just lighting up.  Now lighting up also can translate back into drive train problems where you need to match up your chain and make sure it is going to be able to handle it.  Your axel may twist or bend if you are not careful because once a load gets slammed into the chain then through the axel.  It may get twisted and bend the axel forward if you do not have enough support on your axel.

You need to refer to the stress calculations section (Go Kart Building 301) which will give you various types of bendings that you would refer to, and help you tell whether  or not your axel is going to bend.  If you are not careful because once the load gets slammed into the chain then through the axel you may twist it and actually bend it forward if you do not have enough support on your axel.  You need to refer to the stress calculation section, which will give you various types of bendings that you would refer to and help you to determine whether your axel is going to bend on you or not.

These are considerations you need to put in to place if you are going to throw on a high horsepower engine on a go-kart.

Well the better thing to do is to try to figure out how much horsepower there is.
Now let us say you have somebody that tells you well “I have got this weed whacker motor and I am not really sure how much horsepower it is, but I know that it has so many CC’s.”

If you got a weed whacker motor more than likely it is 1 horsepower maybe 2 and just so that you and I are on the same page here, 1 or 2 horsepower is not going to do a whole lot for a go-kart.  You can get it to move but you are not going to get it to move much faster than 5 mph because the motor just will not be able to push it.

Now you could put multiple 2 cycle motors on there that is up to you, or you could put multiple little 3 ½ horsepowers on there that is up to you as well, but the typical range to have a decent go-kart performance is around 4-10 horsepower.  Any higher than that and you are starting to get into the areas were it is almost too much power.

You can find someone on the Internet and he puts this V8 engine in his go-kart and he cannot but help burn his tires up.
Or  you will see plenty of these 4 wheel suspension dirt go-karts that have motorcycle motors on them.  You have got to understand they have some weight to them.  They got more weight than what we are taking about.  We are talking about 175 lb. frame and you are trying to throw on 50-60 horsepower motor on there,  you are going to twist something and you are going to smoke some tires, and it might be out of control.

So having a lot of horsepower is fun. It can be,  but it can also be dangerous.

You need to keep aware of that.  The first thing you need to do is determine how much effect this horsepower is going to have on this go-kart.  So you need to run that calculation first.

Say you have determined that the engine has just too much power what are you going to do?

You still want to build a go-kart. You got this motorcycle engine that you want to drive it with.

Well, I would not dissuade you from building it,  but keep in mind that the thing needs to be built to be able to handle it.  So you probably if you are using a motorcycle engine, you are going to need something bigger for a go-kart.  The size of a grand prix car.  Then you will be safer, and you will want to build yourself a roll cage in case you wipe out because now you are dealing with more horsepower.

The likelihood of loosing control,  is alot greater.
If you hit something that something is not going to give.  It is going to be the go-kart.  So the go kart is going to go spinning or flying because it has energy and energy needs to be dissipated and the only way energy can get dissipated is ether by crunching the gokart  or by keeping on moving and rolling and spinning.  So you need to keep that in mind when you are dealing with high horsepower and high speed.

What you need is balance, and the Go Kart Building 301 coarse goes into great depth on to how to do that.

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