Monster Moto 80cc Help!

[OrionFelt]

Hello! I've recently purchased a Monster Moto 80cc minibike with the engine still intact and all. The seller said it wouldn't start, so I took a look at it and the engine is the rustiest thing I think I've ever seen in my life. I'm looking into buying a new one, maybe a 79cc Predator or a Briggs and Stratton snowblower engine, or just a generic snowblower engine. As I have no experience with welding, my question is: Is there any way to install a 79cc Predator without welding a mounting plate to the base? Furthermore, would a snowblower or generic engine work any good, and if not, is there anywhere to purchase a stock monster moto engine, or something similar? I'm eager to get this bike running and give it new life!

Thank you!

 

[landuse]

Have you googled for new engines for that bike yet? I just had a quick look, and there seem to be several sites you could look at. Ebay and Amazon might also be worth looking at.

Otherwise just put a Predator on if it fits. I would think the 79cc might be a bit too under powered if you are a adult

You are also going to have to look at the gearing, as the original engines might have had some internal gear reduction (I have no idea about those engines). This would mean that you would have to change out sprockets and chain as well. Also reroute the throttle, etc

 

[OrionFelt]

I have! I'm currently looking at the 79cc Predator I mentioned earlier, and an "MTD 208cc Horizontal Shaft Engine" I found on ebay for a similar price. I'm looking for more options. I'm mainly worried about mounting the engine it to the frame, and what exactly I need to put on the new engine to make it bare minimum usable. I can link both if needed!

 

[landuse]

I have! I'm currently looking at the 79cc Predator I mentioned earlier, and an "MTD 208cc Horizontal Shaft Engine" I found on ebay for a similar price. I'm looking for more options. I'm mainly worried about mounting the engine it to the frame, and what exactly I need to put on the new engine to make it bare minimum usable. I can link both if needed!

Without seeing the frame, it is hard to say anything about mounting the engine. You might have to weld on a new mounting plate, or even maybe a bolt on one

Post some pics

 

[OrionFelt]

Without seeing the frame, it is hard to say anything about mounting the engine. You might have to weld on a new mounting plate, or even maybe a bolt on one

Post some pics

I don't have access to the bike right now, but this is what it looks like.

 

[OrionFelt]

I have! I'm currently looking at the 79cc Predator I mentioned earlier, and an "MTD 208cc Horizontal Shaft Engine" I found on ebay for a similar price. I'm looking for more options. I'm mainly worried about mounting the engine it to the frame, and what exactly I need to put on the new engine to make it bare minimum usable. I can link both if needed!

Sorry- I'm also looking at a 208 CC Briggs Stratton Snow Blower Motor!

 

[mckutzy]

Whatever the motor type it is from... it needs to have a straight shaft for a clutch to mount to...

Off hand that 208-" MTD 208cc Horizontal Shaft Engine" Needs to have a straight cut shaft, those Ive seen to have a stepped shaft for a blower or other machines...

Dont get fooled by the price, they are that way because of the limited use they will be used/designed for...

A standard 21cc predator is what you be looking for..

 

[Mr_mcrib212]

just get a predator 212, they are fast and reliable but you might have to modify the airbox a bit to get it to fit or if you want to make this thing go really fast, get a Tillotson 212

 

[OrionFelt]

Thank you guys so much! I've decided on the Predator 212. A follow up question: What should I do to maintain the usage of the original chain and sprocket? If nothing, what size chain and sprocket should I purchase?

 

[Mr_mcrib212]

Well, you'll have to buy a clutch which should be about 20-30 dollars but you should probably replace the chain if it's all rusty, it should be a 35 chain.

 

[landuse]

How many teeth are on your axle sprocket at the moment. That would determine if you can keep it or not

 

[OrionFelt]

Well, you'll have to buy a clutch which should be about 20-30 dollars but you should probably replace the chain if it's all rusty, it should be a 35 chain.

Would a 35 chain work with a 212 predator appropriate 10t clutch? I've read that people are using 420 chains with 50t rear sprockets with their predators.

I've also seen alot being compared between the 79cc and 212cc, as I've read they reach similar speeds, and the 79cc is easier to install and pass by legally, which would be ideal, as I plan to use this minibike to get from point A to point B much quicker than with a pedalbike.

---------- Post added at 01:10 AM ---------- Previous post was at 12:30 AM ----------

How many teeth are on your axle sprocket at the moment. That would determine if you can keep it or not

75 I believe

 

[mckutzy]

So this is for a street legal application??
If so do you need to have this in a particular CC class? if so then a motor of that displacement is where you should start...

The minimal tooth count on a standard #35 chain clutch is a 12t, a #40/41 will have 10...
A 420 clutch might not be available....

What is the chain type on your bike?

 

[OrionFelt]

So this is for a street legal application??
If so do you need to have this in a particular CC class? if so then a motor of that displacement is where you should start...

The minimal tooth count on a standard #35 chain clutch is a 12t, a #40/41 will have 10...
A 420 clutch might not be available....

What is the chain type on your bike?

As close to street legal as possible, something to go as under the radar as I can while I get everything else for the bike in order!

The chain type for the bike currently, I believe, is a #35 chain.

 

[landuse]

I would just go #35 with everything. Get a 12T clutch and keep the 75 axle sprocket. It is a good gear ratio to start at (approx 6:1). If you don't like it you can always change later.

 

[slob]

I just "restored" a very abused one of these for a friend who got it for basically nothing with it in pieces. The carb on that engine is absolutely intolerant of sitting with bad gas and I guarantee it will be unfixable in ONE WINTER of sitting with bad gas. Replacements are cheap but the fuel inlet is in a different place and they give you a fuel line to work around this. If you want an entire exact replacement engine at a good price compared to many,

https://www.surpluscenter.com/Engin...-2-5-HP-Powerpro-Engine-2549-0042-28-1892.axd

The clutch is also worthless and you really do have to take it apart and oil it every several hours of use. Not fun. Get a clutch with a sintered bronze bearing.

My friend did not want to go the Predator route because his kids are fairly young and in no need of 40MPH madness on a bike with fat offroad tires and no suspension! There are videos of people who have done this on YouTube. However, I found the governor impossible to get right anyway on the original 79CC and a heavier spring "solved" many problems but you really lose the governing capability.

Many, but not all, spare parts are available for this (after the company closed up shop) and I needed some. I had to make an aluminum shield for the exhaust because the original owner lost it.

I found it to be fairly well made and sturdy but a bit heavy and clunky and with a surprisingly bad turning radius. It was a bit low and uncomfortable for me at 5 10 and 160. With the original engine, it is not fast at all off the line with anyone at or above it's 150 lb weight limit. The first image is of the aluminum shield (which is raised off of the muffler by spacers) that I had to make and the second is a size comparison of my really mini bike vs the Monster Moto 80cc.