New to building mini bikes

thtsjon4u

thtsjon4u

New Member
#1
#1
So i had a honda clone engine sitting around that i stripped off a previous project. I got bored with the other one, so i thought why not throw it on a mini bike... never had one before. I had come across a mini drag bike once and it caught my attention.
http://i1136.photobucket.com/albums/n498/thtsjon4u/th_0506104618.jpg
this is what i started with. honda gx200 "box stock project". I had repainted it and done some mild mods to it: 18lb valve springs, high intake and exhaust, throttle plate, removed governor, and added a crank case ventilation.

For the basis of the mini bike i went with the "drag bike" from bad dog.. pretty good starter.. didnt feel like trying to find an old mini bike and cutting it all up. heres what it looks like thrown together...

http://i1136.photobucket.com/albums/n498/thtsjon4u/th_0522232831.jpg

naturally i painted it flat black, its suppose to match the car in the future.


http://i1136.photobucket.com/albums/n498/thtsjon4u/th_0525221853.jpg

so far i welded on some wheelie bar brackets to the back. the gas tank is from a "C" oxygen bottle.. drilled and tapped a hole on one side and the opposite side and end i drilled out a 1.5 inch hole ( so far just using a wedge rubber plug). I got some 5lb nitrous bottle bracket holders to hold the tank, which i had to cut and rivet back together to fit right. The back of the tank is held with a bracket that has a 3in rise to it..i just bent it out to fit on the frame.
For the breather/oil catch can i had a mini fire extinguisher laying around that was converted. An old water spicket handle worked well to make the gas tank look like a NOS tank.

...still more to be done in the future.
 
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thtsjon4u

thtsjon4u

New Member
#8
#8
so i get the feeling the stock flywheel isnt that great? I ran the piss out of it in my other motorized project.. no problems. I had only done the removal of gov. and intake/exhaust then.. now i re jetted the carb to #90 and added the 18lb valve springs. when i scavenge some more money for it ill get a good flywheel with an advanced timing.
 
M

Mikesbike

Member
#9
#9
Theres people on here who have seen them explode, doing some damage. it would tear right through your leg its scary. Im sure theyll chime in somewhere.

flywheels

those are some nice parts there.....expensive, but not that much considering you could loose your jewels, and a nice project that you put money into.

i need to build my gx200 now....
 
thtsjon4u

thtsjon4u

New Member
#10
#10
progress update: polished piece of sheet metal for future kill switch and finally got the chain breaker to put a chain on it.

Pieces of sheet metal can be easily obtained if you go to your local sheet metal shop and ask for scraps or anything left over for free. you may get lucky and get some. I did, and they were more than big enough. The cost of metal bits at lowes and home depot are too high.





Drove it around some.. didnt even have full throttle and realized it is going to be a little fast. The speed doesnt scare me, its just the lack of braking that does.


...next is the wheelie bars... i may need them after all. (still mainly for looks)
 
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M

Mikesbike

Member
#11
#11
that thing is cool man.

i was going to say your just a little crazy for riding that with no brakes, then i noticed you have a drum.

you say the drum doesnt work that well or just not as you expected? might just need to get the shine/polish off the metal after some more riding.

i dont think it would be that hard to switch it over to a disc if you decide to. that is one looong brake cable as well suprised you havent run over it.:laugh:

always wanted to do a fat tire bike, how is it turning on a tire that is wide and flat like that?

what kind of exhaust do you have?, looks like 1 1/2" pipe. I do not have a gx200, is the exhaust port that big or does the pipe just expand out to that size?
:thumbsup:
 
thtsjon4u

thtsjon4u

New Member
#12
#12
i tightened the drum brake some.. havent tested it yet. As far as a disc break.. i really dont think i have enough room. even if i can get a disc to bolt onto the front wheel..bc theres a spot to do so on the hub..there is no room at all for a caliper. its a 5in wheel.

I need to find some zip ties for the brake cable.. it is a little long.

Turning isnt that bad.. its a 6in wide tire.. not too wide but a little wider than most.

The exhaust is one inch.. it flanges out just a little at the end for a muffler. I have header wrap around it.

Its a bad dog "drag bike" kit. which isnt too bad for a stock/mass produced start. The only complaint i have about it is the spacers they give you. the ones for the drum brake are not quite long enough. I will need a washer to get it snug. So for now the drum break kinda wobbles around in there. the rest of the spacers is just a long tube that you have to cut yourself.

...oh and thanks. Im going slow with this project to have something to do and to do it well.
 
thtsjon4u

thtsjon4u

New Member
#15
#15
Finally took the bike out for a real test drive the other day. Got it up to i think at least 50mph. I was trailing behind a buddy that got up to 45 and held it.. i was gaining. Im going to have to find a steering damper.. gets a little of the speed wobble. Someday ill get a video.
 
thtsjon4u

thtsjon4u

New Member
#16
#16


I dont really like fenders, so this is what i have done for fender/body work. Another rivet on piece. ( yes that's an old 305chevy engine in the back..for a glass table )
 
thtsjon4u

thtsjon4u

New Member
#17
#17



added more supports. Under the engine mount plate too. The torque of the engine was flexing the frame and engine mount, causing the chain to loosen enough and pop off. Im sure the frame was built only to go a max of 30mph and with a 5hp or under engine. Seeing how i beefed up the engine some and can go 50+ i needed the extra support.
 
thtsjon4u

thtsjon4u

New Member
#18
#18
I MUST GET BILLET FLYWHEEL!.. thought about it and i need to not ride it, even if just taking it easy, until i save enough money to get one and put it on.
 
thtsjon4u

thtsjon4u

New Member
#19
#19


made some wheelie bars today out of 7/16 steel rod and skate board wheels. decided to weld in the wheels so they're not removable. Not quite finished. still have to weld on some sort of tabs to mount onto the mounts i made on the frame. Plan to make them removable with clevis pins.
 
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