Newbie - Interesting motor - questions...

D

Donorbikesdie

New Member
Hello fellas, my name is Josh. I'm in Australia.


I figure I fit in here. I've got a daily rider I built myself, the Jalopy. Its a special bike because I'm 6'4 and it needed to be long to fit.

I have seen loads of those kit motors around...but I have this aversion to anything thats "Off-the-shelf" y'know...No disrespect intended to the guys who have one here...

So I held out for years, and the Jalopy now has a healthy patina coming through the primer.

Last weekend I found an air-compressor being given away on a neighbours front lawn. I thought I could use it for work, doing paint on surfboards, my job.

On inspection I got more excited. The motor is petrol, and a small J.A.P no less!

J.A.P - John Alfred Prestwich - An English company, made some of the best engines ever in motorcycle history, including a 500cc that reigned speedway racing from the '20's to the 60's. This is the ultimate engine I seek for my "real" motorcycle project someday, someday...

But for my current resources and mechanical ability, the small J.A.P is a great start.



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Can anyone say more about this motor ? I found the number 02 embossed in the barrell. Maybe thats the model number. I can't tell what capacity it is.

Here it is off the compressor tank...



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JD
 
Here's the Jalopy - Plenty of room there for a motor!



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And the gas tank I have, from a 60's Jawa speedway motorcycle...



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Is it possible to have the engine driving through the derailler gears rather than a added sprocket on the other side? Some sort of double sprocket at the pedal cranks end, so that the pedals free-spin when the engine is running?

JD
 
Very interesting project. Good luck and please keep us posted on your build. That should make one heck of a motor bike. Is that a built in centrifugal clutch? Have fun and ride safe.
Tom
 
Thanks Gents...I'll need o do some more research to find out about the engine.

I'm so green I can't say whether there's any sort of clutch there. I'm coming at this from out of the dark with actual engine knowledge beyond the theory of internal combustion from high-school science class...and tuning my '68 Chrysler...

I did however find the answer to my own question regarding using the derailler as the powered side, with the cranks able to free-spin when the engine runs. It is common with "stretch cruiser" bikes I see elsewhere in the forums.

Torn between the red tank and my Jawa speedway one, which was earmarked for that someday larger bike...The blue one just fits so well.

I guess I'll be a while, but finding this foprum is a kick for inspiration.

JD
 
I got somewhere with the engine model research...Its a JAP model 80.

79cc! That should move me along just fine hey! I was afraid it would be too wimpy as there where other ones as little as 34cc used in outboard boat motors.

Here's a video -
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Time for a first basic mock-up. The motor is designed to sit with the cylinder horizonal.



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I'm thinking straight upright - more conventional old motorcycle look rather than pit-bike style. Sort-of like a Simplex. There might be a way to turn the cylinder barrel around 90deg. so the carby and exhaust are not poking out sideways...

But I figure I'll do the work on getting it running before I start pulling bits off.

And lose the red tank - I'm not keen on the way it looks like a chainsaw. So I'm planning to get hold of a welder again to make brackets for the Jawa speedway tank.


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Want a little gearbox - "Pre-Unit" style.

I have an alternative seat - undecided...



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JD
 
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