Full Racemod Happy Time Motorized Bicycle Build

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CR500AF

New Member
May 20, 2012
78
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Ontarieo
I found a 1975 old rusted bike in the grabage and it was all there and as i was getting the other grabage off of it a guy on a motoreszed bicycle flew by and and now im hear.

I work at a custom bike shop so machine and body work is not a problem anyways i wanted to know if any other cylinder and head work with the happy time engine.

I want a top speed of 50+mph and lots of pull and singal gear

.wee.

Thanks

Brandon
 
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young grease monkey

New Member
Sep 20, 2011
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Chicago
Re: Full Racemod Happy Time Build

I can cast a head if you want, I will be making some this summer. I don't have any mill or lathe, I will have to talk to one of my dad's friends who runs a machine shop. He is also building a 1983 cr480 for my dad with a 87 front end and works shock, gonna be haulin @ss. I got a 97 cr125. What year engine are you running in your 500?
 
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CR500AF

New Member
May 20, 2012
78
4
0
Ontarieo
Re: Full Racemod Happy Time Build

young grease monkey said:
I can cast a head if you want, I will be making some this summer. I don't have any mill or lathe, I will have to talk to one of my dad's friends who runs a machine shop. He is also building a 1983 cr480 for my dad with a 87 front end and works shock, gonna be haulin @ss. I got a 97 cr125. What year engine are you running in your 500?
Click to expand...
Its a 86 cr500 engine with a milled head and ported with the kx500 carb and its in a 2002 cr125 frame

I had a 82-(4 speed) cr480 but the thing was so hard to ride, it would hit the power band randomly and flip over or run you into trees, sold it after i got an 86 cr500 and then i sold the frame 2 weeks later and all **** broke lose.

im looking for a name brand jug and head to put on this engine

im am going to scaned the crank and crank cases and make ones from tool steel and some kinda t6 temper alloy.

im not sure what metal these engine are made from, I can weld it with a mig like steel but i can't stick a magnet on it.
 
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young grease monkey

New Member
Sep 20, 2011
362
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Chicago
Re: Full Racemod Happy Time Build

What kinda wire did you weld it with? You must have worked with cast aluminum before. It's probably close to 356 alloy, good for casting. Try 7001 or 2 for machining, that's strong stuff. Get a Puch head and cylinder, then model the cases to fit it cuz I don't think its the same. And get the puch piston, of course. For the case, I suggest lowering the volume of the bottom end (because they don't have enough compression) by filling in the area around the bearing bosses, that is the common place to do it but we use JB weld, you are machining new cases so that is super cool. I bet a lot of people here would buy some from you. Also you might want to make a new con rod. But really, if ya want an awesome engine just figure out a way to mount a kx 65 engine. Probably want a new frame, Santa cruise scooter works can hook you up, they make great full suspension bikes for Italian motors. Just a thought. If you want to improve the Chinese design for a fun project, props to you.
 
Last edited:
C

CR500AF

New Member
May 20, 2012
78
4
0
Ontarieo
Re: Full Racemod Happy Time Build

young grease monkey said:
What kinda wire did you weld it with? You must have worked with cast aluminum before. It's probably close to 356 alloy, good for casting. Try 7001 or 2 for machining, that's strong stuff. Get a Puch head and cylinder, then model the cases to fit it cuz I don't think its the same. And get the puch piston, of course. For the case, I suggest lowering the volume of the bottom end (because they don't have enough compression) by filling in the area around the bearing bosses, that is the common place to do it but we use JB weld, you are machining new cases so that is super cool. I bet a lot of people here would buy some from you. Also you might want to make a new con rod. But really, if ya want an awesome engine just figure out a way to mount a kx 65 engine. Probably want a new frame, Santa cruise scooter works can hook you up, they make great full suspension bikes for Italian motors. Just a thought. If you want to improve the Chinese design for a fun project, props to you.
Click to expand...
I welded it with standerd steel gas mig wire, yes i don't under stand it


your getting me thinking but it would have to be a older air cooled engine

something i could make look 1975ish
 
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