Restoring a Marston OA

[Horsley-Anarak]

Jacob showed some interest in restoring an OA, so here is some of the rebuild.

This is the engine as I found it, had been used in the sea and was showing the results of years of corrosion, engine had been loved and had been repaired in the past, including a welded repair on the leg.

Cylinder was in bits

I thought that this motor would never run again, as cylinders are very scarce, so I decided to restore as a display motor.

Sand blasted cylinder and rebuilt maintaining water ways, I used JB Weld, which if you have not used it is quite incredible.
It is a strong 2 part epoxy.

In one piece, and would have run but there was a pin hole in the bore.

All painted and ready to fit, then put on the back burner as other projects took over, that was in 2014.

Then I found a replacement cylinder

H-A

[Horsley-Anarak]

The next bit I will mend is the pepper pot.
This one is a bit squashed, and is missing the central pin and washer.

Will turn a nylon former on the lathe, so that I can bash it back into shape.

Bit more involved than a regular seagull

H-A

[Dabtoe]

Hi Allan, sterling work,is the pepper pot a choke on the carb inlet ( I’ve never seen an OA) does it contain a filter? Back in the sixties,stationed on an island off Hong Kong I owned an Excelsior 150 which had a very similar choke,the filter was metal and had to be washed in petrol and oiled at regular intervals,engine was Villiers............
Please keep up the posts of the OA very interesting
Sid

[Horsley-Anarak]

No mesh in these, just the 4 holes.

Have rebuilt the ignition, new coil and condenser.
Need to make 2 new screws, as 2 broke off even after some heat, drilled them out and re-tapped.
have used 10x32 unf, should be 3/16 bsf I think, but from what I can see unf is 25 thou bigger and holes were a little oversize.

Have been cleaning up the other bits

I find a big heated ultrasonic tank very useful.

cylinder ready with new gasket 12.5 thou thick.

Now getting into the tricky stuff, gearbox and leg.

[Charles uk]

You should have asked Alan,
the register has had 3/16" BSF Pallister head screws re manufactured in the correct lengths & we have some of the points box screws, we also have a 3/16" BSF Helicoil kit & a fixture to hold them on the bed of a DRO equipt mill so that the holes/lamination's are exactly in the right locations.

The cylinder base gasket thickness is supposed to be the same as the current base gasket, 10 thou.

[Horsley-Anarak]

The cylinder base gasket thickness is supposed to be the same as the current base gasket, 10 thou.

I measured the original gasket and that was 12.5 thou, so went with that, should run

Back together now and it has a spark and compression.

Soon be going.

[Oyster 49]

Looking very nice. Keep the pics coming

My OG needed the throttle link shaft, that connects the FNR lever to the throttle. I borrowed an original part from a fellow Marston owner, and copied it. Works well, and I made two so I have one spare if anybody needs one. The spring and cable adjuster came from eBay.

I’ve also made replacement bayonet caps too. I reckon these alone have made the cost of the lathe worthwhile.

[Oyster 49]

I wonder if nudge could cast a Marston cyclinder in alluminium? Show only of course, with no piston or con rod!

[Charles uk]

If it's only an ornament why not use GRP, with a two piece mould split vertically, also made from from GRP, then drill & tap the spark plug thread & the holes for the 4 crank studs, 2 exhaust threads, then a bit of black paint.

Trouble is, then no OA's get broken for spares!!!!!!!!!!!!!!!!!!!

[Nudge]

I wonder if nudge could cast a Marston cyclinder in alluminium? Show only of course, with no piston or con rod!

You got one to use as a pattern?

Trouble is, then no OA's get broken for spares!

I do hear what you are saying.... but it would be good for a play.

[JERSEYMAN]

Aluminium barrel, and either a chrome/nikasil bore or a cast sleeve??? Now there’s a thought

[Charles uk]

Has to be a cast bore Rene, the rings are not suitable for Nikasil or Chrome bores, but you can buy a complete OA for less than the cost of a replacement re-manufactured cylinder, & there were doubts about the strength of the inlet stub.

Nikasil coating & grinding was £125 a cylinder 6 or 7 years ago.

[Horsley-Anarak]

Replaced the leg tube today, bit of a job.

There was an old welded repair

Bored out the old tube

Silver soldered new tube in

Cleaned it up, ready to be chromed.

[Oyster 49]

That’s a proper job. Nice one

[Nudge]

Looks a tad better than the old one.