BMX Build

Brains · #1 (**permalink**) 08-09-2008, 09:09 AM

Putting together a motorized BMX, powered by 50cc pit bike motor, put an oversize piston & rod in it to bring it up to 74cc, we got the piston ceramic coated as well, refitted a new pin to change timing, match ported the inlet runner & exhaust, rebuilt the rear wheel to incorporate disk hub & fitted sprocket direct to it, got rid of the multi speed & simply added a feewheeler as well, the exhaust is a custom build which we done in our home made pipe bender, havn't fitted the fuel tank as yet & unsure where we are going to mount it, either direct over the motor or open to suggestions if anyone wants to throw some our way, some pics below for all to have squiz, If some of you like the build I will add more pics as we go along

Cheers

UncleKudzu · #2 (**permalink**) 08-09-2008, 09:25 AM

Quote:

Originally Posted by Brains

If some of you like the build I will add more pics as we go along

yes, please keep us posted on this. a very interesting build!

deacon · #3 (**permalink**) 08-09-2008, 10:08 AM

Its a brand new look to me.. Keep it going I would enjoy seeing it as you go along

Brains · #4 (**permalink**) 08-09-2008, 10:36 AM

Thanks guys, will add more pics as we progress, tomorrow have to find the pin from the chain link which is hiding on the cement pavement somewhere beneath my bench, hopefully in a couple of days it should be together for a test run, Im sure there might be some bugs to iron out before we pull it apart and get it ready for paint, hopefully we wont rip the flippen spokes from the rim when we give it some hurry curry

**Ilikeabikea** · #5 (**permalink**) 08-09-2008, 10:48 AM

Good looking motorized bicycle. For sure keep us posted on the progress. Pictures are always welcome....................

Brains · #6 (**permalink**) 08-09-2008, 11:02 AM

Once Ive got this project finished, Im thinking of trying to incorporate a similar motor into a v Frame bike I have & see what its like, as I also purchased a water cooled motor as well, so thats the next custom project I will post for you all to have a squizz at

Large Filipino · #7 (**permalink**) 08-09-2008, 11:11 AM

Wow! It looks sweet! Is that a freewheel sprocket? Can't see how it's mounted. Flip flop hub? Or is it fixed on a conventional freewheel?

Also just by looking at the pics is it possible to turn your pull starter 33 degrees so you can start it from the saddle? It looks like your three mounting bolts are spaced evenly allowing this.

Looking forward to the rest of your install. And skate park pics lol!

Brains · #8 (**permalink**) 08-09-2008, 11:39 AM

Its not a flip flop hub, I simply removed the original hub (seven gear cassette) which came with the bike & ditched it, I bought a new hub with disk break mount for ease of attaching the drive sprocket (standard pocket bike sprocket & theres heaps of different gearing available as they race these bikes on different tracks and they are always changing the gearing, so this makes it great for fine tuning) I had to machine out the center of the sprocket & drill the six mounting points thats all, I had to purchase a hub which gave me the same width as the original hub & could only do this buy purchasing one which was for a slide on gear cassette, I then simply machined the first spacer which went over the hub & threaded one end for the freewheler to screw onto & then machined another spacer to put in front of this to give me the width I was after, thats it. you could quite easily turn the pull start around so to be able to pull start while sitting on the seat, but I put it back to its original position as its got that much compression I could not crank it over, believe me you need to rest one hand on the seat & get an nice strong stance and yank, I am hoping that after its run in it might be a lot easier to pull start & then I will try starting it from the seated position, hope this makes sense

Large Filipino · #9 (**permalink**) 08-09-2008, 11:48 AM

It's short anyway so once it's running getting on should be no hassle.
You gotta make a video once it's all set.

Brains · #10 (**permalink**) 08-09-2008, 11:58 AM

Once you start these little engines its got an auto choke, so you got to let it warm up first and after a few minutes you tap the throttle & the choke auto disengages, its got an auto clutch so you got time to have a fag while its warming up and your putting on your knee & elbow protectors & kidney belt lol...I will be pissed if I can't pop monno's down the street, Im pretty sure it will, I got to work out how to post a video clip on You Tube as never done it before & then I will post the link for all to have a laugh, hopefully you all won't see me go through one of my neighbors front fence