MonsterMoto Go Kart MM-K80-BR Need more torque

[jmandawg]

Hi all,

I got my daughter a monster moto MM-K80-BR go kart for christmas, but i'm wondering if there is a way to get more torque out of it. It's very slow to take off, and struggles to get up hills unless you are already going at a decent speed.

Attached are pics of the engine. Do you think it could fit a predator?

Or anything else i could do.

Thanks in advance.

 

[mckutzy]

Hello and welcome..

Yes you'll mostlikely be able fit a pred in there with out too much problems... I dont recognize that engine, so Im assuming its just under powered.

What is the gear ratio(all the sprocket tooth counts will do)?

 

[jmandawg]

I just ran out and did a quick measure of the gears, the smallest one is 3" The one behind that one is 5", and the one on the wheel is 8". I did not measure the gear on the clutch, and it would take me a while to count all the teeth, but i can if it's necessary.

The engine on there now is a 79cc.

 

[B_Bimmer]

Go get the notorious harbor fright predator 212, a 3/4" clutch for #35 chain, and kiss your problems goodbye. Turn in the throttle screw for starters though, can always back it out later. I have the mini bike with the same engine, 'til the crankshaft broke in half, good riddance. It is just too small, and I would guess that is even more true on the go kart. Having looked at the kart in person I would say it should be a very easy swap. Worst case if it is too long you'd have to put the engine on blocks to get the cylinder over the back frame rail. We need actual sprocket tooth counts to suggest whether or not you need to keep the jackshaft with the bigger engine.

 

[jmandawg]

I'll try to get a count when i get off work, do you need it for all the sprockets or just the one on the wheel.

 

[mckutzy]

.....What is the gear ratio(all the sprocket tooth counts will do)?

As I said... all....

What you have is a under-powered and probably a way off ratio, that does alright on flat ground for what that was tested at the factory.
Alot of these types of machine come around here and have almost the same type of problems...

 

[jmandawg]

ok, here's what i got starting at the clutch sprocket and moving up.

11, 24, 40 and 65.

 

[B_Bimmer]

Sweet, dump all that crap, get a 212 with a commonly available ebay 3/4" clutch for 35 chain, and go right to the axle.

 

[mckutzy]

I think that first one is supposed to be 12(as that is a common tooth number).... But none the less that makes it about 3.250:1.
That's a problem for most if not all clutches...

 

[jmandawg]

Thanks guys. Might be a little while till I can get around to swapping it, but I'll report back.

 

[B_Bimmer]

Look at the pictures too. I think it's 11 to 40, than 24 to 65, so not a clutch problem, just a low power, trying to make up for with gearing problem.

 

[jmandawg]

Look at the pictures too. I think it's 11 to 40, than 24 to 65, so not a clutch problem, just a low power, trying to make up for with gearing problem.

My bad, You are right 11, 40, 24, 65. So sounds like the predator is the way to go

 

[mckutzy]

Ahh yes a second look at that... Looks about right....

9.848:1 ratio.

Well that leaves the motor is underpowered...

 

[B_Bimmer]

Do it, there is all the help you could need on this site. You've already figured out pictures, putting you leagues ahead of most new members.

 

[jmandawg]

Well, i got the engine and the clutch (max torque) but it does not fit all the way on. I tried hitting it with a rubber mallet, it did nothing, hopefully did not damage anything.

Do i need to grind down the key some that came with it.

The key on the predator shaft is not cut all the way to the back. I'm assuming i want the front of the clutch flush with the front of the shaft.

 

[mckutzy]

You can mount that clutch inboard(the sprocket to the motor), or outboard(the way you have it...)

Don't hit that again. It might damage the bushing or something else..
The key bottoms out on some variants of motor shafts. You can add a few washers to have a proper base for it to sit on, or run the clutch inboard...

If anything I'd mount the motor, and see where it lines up for the rear sprocket, then deside what way you want it...

 

[B_Bimmer]

I'd grind a hair off the key and make it flush. I doubt it actually matters but I like it when the sprocket is fully supported by the crankshaft. Then set it on and see how it lines up with your axle sprocket. More than likely the axle sprocket can be shifted over one way or another. How does the engine sit in there? Are you going to have to put it on risers or will it fit in front of that back frame rail?

 

[jmandawg]

Sorry finally got around to removing the old engine.

I don't think it's going to fit that easily. I had to push the chair all the way forwards, and the back of the engine hits the bar on the back. The front mounting bolts (towards the front of the car) overhang the existing plate.

Any suggestions?

 

[Whitetrashrocker]

Looks like motor mount slots peeking out behind the engine.

 

[sefishy]

sure does look that way, id cut the bar and extend it, or cut it out before the upturn, then cover the cut and slide the engine back