dirt bug #1

[txluke]

I have 2 Baja Dirt Bugs. One has a 212 haphazardly mounted to it and 1 was original. I decided to put my new in box 79cc predator to use so I decided to attack the stock one first. I can only find 1 pic of the bike before I started. the others were lost in the war I guess. it was blue and rusty. I got after it with a wire wheel and sandpaper. I happened to have 2 cans of safety yellow rustoleum so that is what I shot on it. After I finish mocking up I will probably have it sandblasted and powder coated. I took apart the brake caliper and cleaned it up and painted it. I was going to go with a hydraulic brake but I will see how this works and get the one that bolts right up if I need to have better brakes. I mounted the engine and drilled out some old pitching washers to make an air cleaner adapter. I have a huge exhaust and I might slap that on there with a monster sized air cleaner and call it a stage 8, 79cc. I added a weld to the bearings on the front wheel to see if I can get them out. the spacer inside is flush with the bearings and will not budge. I have new tires to mount on the rims once I get new bearings and paint or powder coat them.

 

[landuse]

Cool little bike, but I wouldn't use that exhaust

 

[Hellion]

I agree. That exhaust is riDlCKerous! (an homage to Tigger)

Then again, it's different and different is good...

 

[JTSpeedDemon]

But obviously, he wants the bike to have positive lift from the exhaust! World's first rocket powered minibike!
That pipe will actually counteract, or even reverse the expected effects of a header.
Why?
Look here:http://www.diygokarts.com/vb/showthread.php?t=22264
If the pipe is too big, the exhaust won't have as much velocity going through, so it will be louder, but won't really perform. Just go with a more standard diameter pipe.
Or are you trying to keep the neighborhood kids from blocking the pipe with oranges?

 

[txluke]

the big exhaust is just for show. I have a straight pipe and silencer that this will just slip over. I am doing a stage 1 and will drill my jet out. I am looking for a ridiculously oversized air pod too. This will be a little show off bike and probably won't be ridden much. I am just looking for a few laughs with the giant parts and a "79cc Stage 8" sticker on it. I still have another one with a 212 on it and a Baja Warrior to build a riding bike.

 

[txluke]

Mocking up. Can't decide if I want exhaust out or down. the black tape is about where the exhaust port on the head is. The exhaust is 7" down to 5". Haven't decided how much to shorten, how to attach to bike, how to run my exhaust in it, and if I somehow can also use as a clutch/chain guard. With some frame mods I can run it out the back and then it is a fender too.

 

[Bansil]

If you use that exhaust you are going to need air/train horns to make the brodozerierymotobike complete

 

[txluke]

Now my son wants a bike so the big exhaust will have to go on the next build. Since someone gave me the 79cc new in a box and because it is for a 9yo, I will not slap a 212cc on it. I will be doing mods to kick this 3hp up a bit. I tore into it and removed the governor. Everyone has seen this 100 times and it is pretty much the same on the 79cc as the 212cc. I don't know why people don't just take off the flywheel and knock out the governor from the outside in. It is so much easier. Since I have the flywheel off I decided to lap it and run without a key so I can play around with the timing. I have the head off so a little port and polishing is in order. I am looking for heavier valve springs. I have so far only seen 1 place that has them. I will research and see if another spring can be substituted. A billet flywheel and rod would be nice but I have yet to find them. I will check clearances and might shave the head a bit if I have room. I will build an exhaust and I will give the stock carb a rejet and see if later I want to try a 19mm. I enjoy tinkering and I like to have something different so putting time and a little cash into this tiny thing will be worth it to me. I will post pics when I start the head work.

 

[txluke]

I have done the porting and polishing the head. I need to go pick up some clay today to check clearances of valves and piston. I will shave down the head some to get higher compression and I need to see how far to go. The springs from a non hemi 212cc look the same but just taller. I am looking to see if anyone has used them in a 79cc. I guess I can pull out the crank and take the governor gear off too.

 

[Budget GoKart]

So your ricing out a mini bike eh? I want to do this and see how fast it sells a giant exhaust and air pod the size of my head

 

[txluke]

I was going to do all that but my kid wants this one so I am just going to try to hop up the 79cc motor. I have another doodlebug just like this one. After I get this one built I will slap a clone on it and add the giant exhaust.

 

[txluke]

I just got the giant air filter I was going to use on this build. They will go on the next one. I still have a baja warrior and another dirt bug waiting for some love.

 

[txluke]

I read that old school hot rod guys polished their steel rods to lessen the chance of stress cracks from any imperfections. I can not find an aluminum flywheel so I was wondering if giving the steel one a good polish would help it any. Could it hurt it?

 

[mckutzy]

It would need to be even overall in the polishing..... A dip in the wheel from the buffer could potentially set an imbalance and cause bearing failure or a crack/exploded flywheel...