First MiniBike ever Build

#1
always wanted one when I was a kid, 2 friends had them and they would tear up the streets with them

anyways I finally bought one
Ive been into scooters for a while now so im familiar with how some of this stuff works

Wanted to go simple, putt around on
although not street legal where I live im planning on using this with a small bicycle trailer to haul kids around

I have done this in the backyard with a mini dirtbike but not much room
so ive taken to the streets at least we can go around the block and have fun


I will be welding on a bracket so I can attach the tralier to the bike
just want to get it on the road first make sure everything works

I ordered a bike from this site, I didnt know they had a forum so thats cool
I still need the clutch, and thats it to get it running
Got the engine today the 212cc from harbor freight
Some of my scooters are 50cc, 70cc, 90cc, 155cc but I figured might as well get the biggest engine I could

Im not expecting too much performance from this single gear so might as well have the largest engine I could get to battle the hills around here
and for the price they go for, why not
super cheap

I was expecting a way smaller engine to be in that price range



Anyways here are some pics of the build

So far im planning on a rust paint job, hopefully it will work out
I got the paint coming in the mail
Want the bike to look old, so still undecided if im going full rust
or maybe few layers of different color primer and sand away some wear spots and then add small sections of rust


I do my own powdercoating, but I dont have a big enough oven to fit the frame or I would of just powdercoated it something crazy
I suppose I could build an enclosure for my oven to make it larger, but I always wanted to do the rusty paint so now is a good excust





Sadly it came missing alot of parts for some reason
But I found out these come directly from the manufacture so they were the ones that didnt send everything, have to wait until after the weekend for OldMiniBikes to see whats going on with the missing parts






So I had done a little reading about the engine I got
how the gas cap hits the frame, my problem too

Now I had thought alot about what to do
One option was take off the floor plate, cut away the bent edge or just flip it over so the engine would sit lower

But I decided to make a simple bracket to shift over the gas tank
I have no idea how well this will work, I ended up adding rubber washers under the front of the adapter and tank just to help with vibrations
Since this bike has never started I have no idea what to expect


This is the mount I made, welded studs on the bottom that tie into the engine
and offset holes for the gas tank studs to drop into shifting over like 1 inch maybe
I also added a stud to the back of the tank
that stud goes through the aluminum mount and I put a nut on it
just tight enough for the nut to lock on
but not super tight until I see how much this stuff vibrates
would rather have a touch of play to keep that stud from cracking the tank, well outer tank cover not actual gas tank







This is how far forward it can be and still be able to work the gas cap
Its about 1/2 inch back from all the way forward



this is all the way back



I was thinking about chopping out the frame and welding in a arched tube
but shifting over the tank worked out so far

It has not been tested yet, no chain or clutch has been installed
hopefully the engine does not need to shift over any on the mounts sideways

Im guessing these mostly bolt straight in and move forward or back for chain slack?






thats it for day 1
now just need to wait on the parts to finish

I may go out and start the engine just to see how the vibrations are once I bolt it down temporarily
 
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#2
Welcome aboard MaddBiker . :thumbsup: Looks like you have a good start on your build. Don't forget to add oil to that new engine before you start it !
I'll be watching this build. :wink:
 
#4
Get rid of that ugly tank and use a nice round tank or one of those bicycle gas tanks. :thumbsup: Let me find a few photos of mine.

Just my opinion. I wouldn't cut the frame.
 
#5
Welcome aboard MaddBiker . :thumbsup: Looks like you have a good start on your build. Don't forget to add oil to that new engine before you start it !
I'll be watching this build. :wink:
not only did I add oil, I added gas

the tag on the bike said to:laugh:
 
#6
Thought I was done until the clutch comes, and forgot I could mount the kickstand
I made sure to place it where I can still use my scissor lift under the frame to work on it





also started it
alot of vibrations at certian revs but guess thats expected


notice at least by hand working the stock speed lever not much movement, doesnt really rev too high
I see there looks to be a top speed screw on the hand lever I guess I could screw that back some to get a little more revs and I guess I need to loosen that hand lever
as its really stiff to lock the throttle position
to use the twist grip that should be loose correct

pressing some wire arms I can rev the bike by hand and really get it revving high, is that bypassing the governor? Im guessing it is







Im not planning on doing any internal work, so if I have to keep the governor connected thats cool

Just was expecting a little higher revving for such a large engine
 
#7
going to wait on the foot pegs until clutch comes in
want to make sure my foot or leg is as far away as I can get it from the clutch

I seem to remember as a kid getting my shoe wore away I think from the clutch probably because of where the pegs were

probably going to make a steel plate and weld to the frame then bolt on the pegs
so they are stronger
 
#8
Yes you need to loosen the throttle arm nut two or three rounds so it moves freely, and I wouldn't move the throttle stop screw just yet....wait till you ride it first.
But she is looking really good !!:thumbsup:
 
#11
Yes you need to loosen the throttle arm nut two or three rounds so it moves freely, and I wouldn't move the throttle stop screw just yet....wait till you ride it first.
But she is looking really good !!:thumbsup:

just got throttle hooked up, and kill switch
I did see you can loosen that arm and now the twist moves freely
and I did back out that stopper screw, but I will keep that in mind once I ride

actually did seem to rev decently, should hook up a tach just to see what its doing at max throttle

sounds low though maybe 7000rpm

im used to higher revving bike engines
 
#12
Nice bike, MaddBiker. I did one just like yours some years ago. I made a few alterations here and there, but it's a fun little bike. I'm still enjoying it too. Yours has a nicer engine than mine... you're going to have fun with it.


-Doug
 
#14
What parts are missing from the kit?
all axle spacers 4?
and I added pegs so some sort of clamp thing is missing for the pegs
pegs also were rusting, and white corrosion on them
maybe can be cleaned up so why I didnt mention that
im more concerned about getting the spacers, as thats really important

a big hardware store here didnt even have spacers
I could of bought some nice tubing that fit but it was expensive

so I bought $10 worth of huge washers and made my own just so I can have a roller and not worry about the wheels tracking weird

but I see my rear is off some, and its really hard to adjust 15 washers and slip in the axle but thats ok

they will get replaced once I get the spacers anyways


hopefully im not missing anything else
some parts on the instructions without pictures im not really sure what they are

but from the looks of it I can manage if some little part is missing just need spacers bad!!!!
 
#17
Looking good Maddbiker
I want you to get a safety warning before it becomes a big problem. The predator 212 engine is not designed the same as a motorcycle engine. It can safely rev a little past 4,000 rpms. It certainly will rev beyond that, however, NOT safely. If you intend to treat it like a Dirtbike or street bike engine where you can really crank out the revs you need to upgrade to a billet connecting rod & billet flywheel. Not just to keep the engine happy, but because when they blow up the potential for personal injury is fairly great.
With a few simple modifications these engines will make surprising power. No doubt you have a few engine tricks of your own that you picked up over the years. All basic engine principles apply to the little wonder predator. It is a great way to thumb your nose at the big boys.
 
#18
actually at least in the beginning until I see what it can do its going to stay all stock
I have many other bikes all tweaked out, tons of work done to them and im fine with keeping things simple too

since this wont see much use anyways no need to go crazy.....yet


as far as ive read as long as I keep the governor all connected its safe to run full throttle

and ive read if you take that off, then those new parts should be added to prevent it from blowing up


I think im just trying to remember a bike I rode when I was a kid, just a little larger engine to make up for the weight difference maybe to get the same experience I had felt


but this time it will have brakes :scooter:




speaking about brakes
so all ive seen so far, is some sort of band clamp brake for the clutch

does anyone make anything for the front wheel, since im using a stock azusa 5 inch wheel any type of bolt on rotor for that wheel
and weld on caliper for the forks?

or would my rear drum, and possibly a band brake on the clutch be good

I just dont want all my braking to rely on one brake
alot of hills here so dont want any downhill issues
 
#19
anyone know what size thread my shaft is on the predator 212 engine

I have a fancy bolt thread tool, but I can not put it on the bike to check
All I have here are metric bolts so the one that screws in one turn is a m8x1.25
so that tells me maybe the bolt I need would be a m8x1.0?

or is the threads standard on the engine?


and any idea on the length , this is assuming the clutch I ordered does not come with a bolt
I have no idea it didnt show a bolt in the item description
 
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