JAP 4/2 (Engine no. P15904UVX)

Digressed from my present Villiers project to pickup this little JAP 4/2 engine that was advertised locally which will be my next engine to work on.
Looks complete other than an air filter and starting handle. (anyone got any spares?) Good compression, clean looking oil and although no fuel in the tank it started first pull with a squirt in the carb and sounded good.
Doesn't look like it's been mucked about with, few small dents in the tank but otherwise I'm quite pleased with it. No past history available, it was recovered from an old guys garage. My first engine with a separate magneto.
Need to give it a basic clean up to make it more handleable!
I noticed in the manual I downloaded it describes the engine as having an aluminium crankcase and sump although this one is cast iron and consequently quite heavy!
Can it be dated from the engine number?

Alan

I think P is 1940. No doubt others will correct me!

Spent several hours cleaning the new JAP externally.
Underneath the grime it was a sort of silver colour and under that was the original black finish, not that there was much of either!
Bit of a disaster removing flywheel. Manual says remove crank handle support and undo flywheel nut, which was very tight but come undone ok. It then says replace handle support and using the thread in it's centre (5/8 whit) screw in a bolt to pull the flywheel off it's taper.
I heard a double crack and the handle support was in three pieces, not happy. Looking at it, where the bolt heads pull it onto the flywheel, the surface is as cast and far from flat. In fact the faces have quite an angle on them so it will only ever get nipped on it's outside edges and allowing the centre part to be pulled away, breaking as shown.
I have successfully silver soldered cast iron before although this is quite a lump.
Other than the above disaster it's showing itself to be a nice little (but heavy) engine. Some mangled studs where incorrect threaded nuts have been 'fitted' and a broken governor arm, also there was no head gasket fitted!
Oil was still oily, have seen far worse and I noticed the sump insides is painted.
Not sure what the casting numbers mean.

Alan

(don't seem to be able to add photos?)

Photos that should have been with the above!
(Phone got updated now doesn't appear to do what it once did - progress!

Alan

Ooops!

Had a similar 'accident' trying to get the flywheel off my Douglas SV54.
It's now under the bench until I finish sulking!

PS. Just noticed your calendar!

Helps me get through the bad times!

Alan

How do you silver solder cast iron, I use a small industrial hot plate to heat up the pieces or if the wife isnt looking they go in the oven, I braze mine but the castings have to be spotlessly clean.

Maryalice

Yes P = 1940.
I've very surprised that JAP recommend using that casting to remove the flywheel in the manner described. It simply does not have the structural strength in its design for this purpose, as you have ably demonstrated

I'd second that! I used a piece of 1 1/2 by 1/4 angle iron made up as a puller which given a tap while under tension worked well.
Removed cylinder today removing valves for a grind up. Noticed that it has been bored +.040 although no wear could be felt or seen in the bore, all rings nice and free. As said previously compression was very good so was a bit surprised to see exhaust seat as pictured although it ground in ok.
Also found a proper paper gasket, well actually a newspaper gasket!

Alan

(Sorry, trouble with photos again!)

Alan

Maryalice, I've silver soldered cast by heating and holding at red heat (I've only ever done a few minutes) this removes carbon from the cast iron
Once cooled clean up and flux the joint to be, heat and silver solder in the normal manner.
There's probably data available that suggests temperature and time at that temperature, but that's what I've done and it's worked well.
My only problem with this piece is it's mass so not sure I could hear to red hot!

Alan

I think they paint the inside of the crankcase/sump to seal in any residual casting sand.

Some particles will stick in and washing and blowing is not guaranteed to shift them; but the repeated heating and cooling, plus the vibration, when the engine is in service, will release some of them. I expect it is better to spend a bit on paint; than to get a bad reputation for reliability.

https://www.ebay.co.uk/itm/jap-stationary-engine/363258542718?hash=item5493e57a7e:g:EWoAAOSwHdJgAE1~

Dunno if it will fit....

Appletop wrote:https://www.ebay.co.uk/itm/jap-stationary-engine/363258542718?hash=item5493e57a7e:g:EWoAAOSwHdJgAE1~

Dunno if it will fit....

Worth asking the seller the centre distance of the bolt holes though.

Oldgit, good point on sand entrapment! In fact it looks like on of the corners in the sump has sand in it, encapsulated in the paint!

Appletop, well spotted! I have been trying to flush on out as I was feeling a bit uncomfortable about the effectiveness of a repair, although if I have to I would add additional material to beef it up. The idea of it breaking up in the cowling is not good!
I have enquired it's centres and await a reply.

Had some fixings arrive today so bolted the cylinder to crankcase and set valve clearances.
After lapping in the inlet was spot on but the exhaust didn't have a gap, I was surprised to find I was able to turn the required amount off the stem, I thought it would have been harder than that?

Alan

Bit more assembly of the governor this afternoon and must say it all seems very well made.
Not fitted the cylinder head yet as I wanted to check the timing once the Magneto has had the once over. Heads basically clean but stains remain between the fins so it looks dirty. Without taking it somewhere for a media blast how do you guys clean the alloy head?


Alan

On my Villiers heads I've got to what I can with a wire wheel in the drill then just rubbed between the fins with a sanding pad (the 'pan scourer' type) to clean them up as best I can. I used coarse sandpaper first on the MK20 head as it was quite corroded, doesn't look like yours is too bad.

You can't see much of it with the cowling on anyway...

I had a thought and made up 4 pieces of Bowden cable trapping them in piece of copper pipe I then used another piece of tube to guide the splayed end into the fins driven in the Piller drill.
Worked quite well although every now and then I had to 'distress' the ends of the cables again.
Made up some new studs this afternoon for the ancillary parts. Will wash the engine down with degreaser before etch priming it and spraying satin black. Head will remain bare ally and cylinder has already been finished in a VHT paint.

Alan

Like the cable in drill idea. Nice one!

Looking good. Last time I had a jap 4 stroke i was a kid it was a 2a.
Andrew

Woodsman wrote:Like the cable in drill idea. Nice one!

Me too, I may have to pinch that idea!

Dismantled the Wico A magneto today, has been wet at some time as some rust inside although it it cleaned off ok. Some chewed up fixings here and there but will manage to reuse them. Bit curious about the stop buttons, it hasn't any, am I missing something, it just has insulated threaded studs coming out the body?
Some rust pits on the cam lobe - so it should retain some lubricant! (optimistic)
Bit of a suprise was the crack I found in the mag drive plate not sure whether to attempt repair or try and replace it.
Bearing seems a reasonable fit so will leave that and not attempt replacement bushes.
Although the engine ran it looks like the original condenser, do you think it's worth changing? If I did I would carve the old unit out the back of the case and replace with a modern part.



Contacted my local metel refinishing company and asked if they would dunk the engine cowling to remove all the undesirables, remains of paint and rust. There's quite a lot that I can't get to for cleaning so will pop it along for inspection.
Found a couple of spot welds that had come adrift so opened up the joint for cleaning and silver soldered the area, probably stronger now than the original!

Alan

Be careful with dunking, complete car bodies have been dipped in the past and come out with more holes in them than before they were dipped, whilst apart replace the condensor, they dont last for ever.

Maryalice

Maryalice, thanks for the heads up, I have heard of similar stories myself although if it was that bad I wouldn't.
It has surface rust but I don't believe it would be in danger of becoming a collinder!
(fingers crossed!)

Alan

Reassembled the magneto today, I actually filled the rust pits on the cam with JB Weld and stoned it flush with undamaged surface, see how it goes.
Once the bearing was cleaned and lubricated it was a super fit so I pressed on with wrestling the clock type spring into it's case, I had cleaned all round the coils and once oiled it felt very smooth in operation.
Didn't understand how the inertia part of it worked as it was dismantled but once all cleaned up and lubricated it all became clear.
I put a meter on the condenser and found no leakage and a value of .2uf so left it as is
Didn't operate it without a plug connected as I understand the high voltages can cause coil damage. Once I had a plug connected up the result was a nice fat spark, best spark I've had from a small engine!
Interested as to how this engine would be stopped, I know fuel can be turned off and let it use the carbs contents.
But how are you supposed to use the shorting contacts on the magneto body?
Photo shows studs on both sides of the mag - short to earth with a tool?

Alan