Howard Gem – JAP engine

[vhgmcbuddy]

Sorry about the confusing posts… I just subscribed but i don’t seem to have any editing rights yet, so I posted under the incorrect title before… that post was about the Howard 350. This post is about the Gem i just acquired:

So here it is – £75 it must be worth just the parts… but I want to get it running.

It’s a JAP engine, I don’t know what sort – possibly Model 5 or 6? I haven’t had a chance to get any serial numbers and now it is in my parent’s barn and I am away until the weekend.

It is missing the magneto I think…

Anyone any idea where I could find the correct sort, rough cost, suppliers?

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[stuart]

The “correct” JAP engine for a Howard Gem should be a dry sump type engine (the fuel tank has two compartments…..one for petrol and one for lubricating oil).I have a Gem too but I cant remember what model the engine is called.It appears yours has had a conversion to a different engine.As you say its either a model 5 or 6.The magneto you require is a Wico and it should have an impulse coupling on it.

[trusty220]

The correct engine (if it’s a JAP) should be a JAP 600 which is an adapted motorcycle engine with a circular crankcase and dry sump. Some were also fitted to later Trusty Steeds.

You are quite right in assuming that the engine you have is either a JAP 5 or 6. The serial number will be on the top of the crankcase above the output shaft. I’ll look up the type of WICO A magneto that you need to get it going and post later.

[vhgmcbuddy]

From the photo graphs it looks like whoever did the conversion used the original engined bell housing, in which case your gem would of originally had a British junior engine.( jap engine bell housings have 6 studs rather than the 4 that yours appears to). If you want to give me the serial on the long tube starting with a G I can give you an approximate date.

[vhgmcbuddy]

Thanks very much for the replies – I am away from where the machine is, but will see if my dad can supply the numbers.

I was having a bit of a google to see what A series magnetos there are available – https://www.ebay.co.uk/itm/Wipac-A-series-1-2-4-Cylinder-Magneto-spares-for-classic-inboard-engines-/371483225014?hash=item567e202bb6:g:-VQAAOSwQoFWQHLV

Not sure if that is a possible?

Will try and get the numbers..

[vhgmcbuddy]

Hi you will probably find admin will delete the link, however from the picture it looks like it’s one off a multi cylinder engine. The thing to watch with those mags is there are ones that rotate clockwise and anti clockwise. I personally would try and find another engine like you’ve e got with a mag on it and try and build one good one out the two. I would definatley leave the conversion in place as its part of your machines history and nice to see something a bit different.

[vhgmcbuddy]

Thanks S1 – hopefully I’ll get the details later, but my dad thinks it should be a Wico A936bz.

I don’t know if that is the only one which would work, or whether there are other which could be suitable…?

[trusty220]

For the JAP Model 4/2, 5 and 6 the correct magneto is the A-576BZ.

The A-936BZ that you mention seems to have many common parts with the A-576BZ but the main housing is listed as a different part number. What the difference is I don’t know, and both are stated as having a counter-clockwise rotation so it may fit.

[trusty220]

I’ve just had a brain wave after the last posting I made. The JAP 5’s and 6’s had two styles of magneto fitted depending on how old they are; the older ones that I have on my Trusty tractors are fitted to a horizontal platform cast into the crankcase, and three bolts secure it from underneath. The later type that seem to have been fitted from the 1960’s onwards are mounted on a vertical flange around the drive coupling with two studs that stick out from the crankcase.

That would probably account for the difference in part numbers for the body of the magneto.

[vhgmcbuddy]

Trusty – that’s great, thanks – I have seen a few of the A576BZ on eBay – again, there is one there for about £40 so that has to be worth a punt…

[trusty220]

Just check what type of fitting you have- does it fit on a flat platform with three holes in or does it clamp on a flange around the drive dog? Those are basically the two variations that it may be with the numbers quoted.

Best of luck with it.

[charlie]

Looking at the Wipac magneto data I have the 576BZ bolts down onto a flat plate and was fitted to JAP 4/2, 5 & 6; the 936BZ has a two hole flange mounting and was used on JAP4/3.

[trusty220]

……..and also on later JAP 5’s at least!

[vhgmcbuddy]

I’m doing all this remotely with my father, who has the machine in his barn, and he has found the engine number. Being my father, he has scrawled it on a scrap of oil-covered paper, probably using a blunt pencil, which he has then lost somewhere….if he had a beard, it would be in there somewhere.

Still, I can’t be overly critical as he has ascertained that it is a 1951 series 5 engine…. There is a platform with three holes.

There’s another just cropped up on fleabay – A576BZ, counter-clockwise rotation.

So, fingers-crossed I’ll get something soon – thanks for the advice so far.

[trusty220]

That sounds quite straightforward, then. Best of luck with the project.

[Author]

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