JAP 3

Jul 27, 2005 4 Replies

At the recent Bristol &SGSEC rally, I came across a JAP 3 on what was otherwise a fairly ordinary boot stall. Snapped it up for £15! For those who are unaware, the JAP 3 is the original maker's designation for what is much more generally known as the ALCO Featherweight.



Clamping the unit in the vice & filling the carb had it running quite quickly & it sawed away on the governor as there is a screw missing from the carb, so the mixture was less than accurate. Other than that, it was fine - even had an exhaust box to which I've added a stainless steel pot scrubber as a baffle as it was quite unfriendly in its noise making.



It was devoid of paint except for the steel bits & someone has previously vapour blasted the fan case and rocker box lid, both aluminium. I've decided to freshen up the rather cracked & dull red paint that graced the ferrous components & am investigating a small bronze pump I've had about for a while to give it something to do.



This set me to thinking. I've only seen these units used to drive a 300 Watt



12 Volt dynamo - surely they were used for other tasks?

regards,



Kim Siddorn.


"Kim Siddorn" wrote (snip):-

I for one am duly enlightened - is it identical bar the name on the timing case?

Absolutely the same. I'll post some pics later - just off to reassemble it after cosmetic touch up!

regards,

Kim Siddorn.

"Nick H"

I now know a lot more about the carbs than I used to - rather more than I wanted, actually!

The unit starts & runs OK, but will not run slowly, spits and bangs in a nasty fashion. I know what the problem is, the carb is too simple as it is only expected to run between 1,500 RPM and 3,000. But they are now old as well & worn & abused.

The air flow is metered by a butterfly valve, petrol entering the airflow unmetered through a main jet screwed into the gallery leading to the float chamber from the inlet tract. There is another jet screwed into the side of the float chamber gallery which bleeds air into the tract to weaken the mixture & I really cannot imagine why.

Anyway, one float chamber I have has the main jet bored out suitable for alcohol (!) and the other has the air bleed jetway bunged up with something. Of the two, the latter actually works better, the engine not firing at all on the big jet carb.

A long shot, I know, but I don't suppose anyone has a carb from an ALCO Featherweight going spare do they? The temptation to fit a PROPER carb from my spares box & use a throttle cable is very strong ....

regards,

Kim Siddorn.

Four pics of this pleasant little engine can be seen at

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The carb is sorted out now & it runs quite evenly at about 600 RPM with a whiff of choke to richen it up.

I've got three of these now, so would be open to interesting swaps for this one, especially for one of they OHV Norman singles that remind one so much of a 1930's motorcycle engine - or WHY?

Regards,

J. Kim Siddorn,

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