Parts arrived to complete the Johnson OBL-70 and J-25. A number of us use Doug Penn to source spares and he's come up trumps again. Everything bagged and wrapped in padding and Import VAT fair, based on content.

Rapier wrote:And this one, a 1935 3.3hp Johnson Master Twin - bores, pistons and carbs now clean and waiting for missing parts to complete.

Finally got the tank clean (and the garage aired..) and all parts assembled on the replacement stator plate, with new plug wires, plugs & boots - good looking spark on both. Waiting for the tiller. Not one for the purists, but it is ready to use...

A25 piston and cylinder turned out to be the incorrect one. Is fine though, we have enough of the A-35 & A-45 Light Twins in the club to make keeping it worthwhile. Original on right has smaller intake and exhaust ports, no skirt and greater cutaway for the spark plug; cooling pipes are smaller diameter too.

Tank cleaning on that started...

Correct replacement piston and cylinder for the 1924 Johnson A-25 arrived from the US this week. Finally managed to get the flywheel off. All installed and the motor has been cleaned up somewhat. Tomorrow will solder new plug wires to the coil (which after 92 years looks a bit suspect) and setup the points on a clean armature plate. Lovely motor this; has signs of years of fixing & mending & looks like it's been someone's treasured possession.

Hi,
Nice work on that motor , what's the story with the NGK spark plugs that have a big hex/head are they STD plug or re engineed

Thanks, they're a lot of fun to work on. Those are the original NGK A-6 plugs, I use the replacement version, AB-6 from the Green Spark Plug Co with 13/16 spanner size, 18mm daimeter. The A-6 is still available in that large hex style. Staying clear of Champion after a few new plug failures.

Finished the A-25 a few weeks back, in an effort to reduce the clutter on my workbench. The coil was shot, which I thought might be the case with it's boil-like appearance, but Doug Penn can probably supply a used one. This motor is now up for sale, it turned out nicely.

Rapier wrote:1929 A-45 3hp finished. Will wait till it gets warmer to test run it.

Finally ran this one for the 1st time at Beale Park this year. It started 2nd pull so I must have got something right, unfortunately there was still residual sand(!) in the tank which soon clogged the fuel tap bringing an abrupt halt to the proceedings and causing the biggest backfire I've heard in a while. It needs a lower height transom than Mike's barrow boat to run properly though - these have a closed (pressure vacuum) cooling system, so no telltake and have to have uninterrupted water flow over the prop. We took it out again once the fuel tap was cleaned out and were much more successful until it clogged again, but was starting to get get hot, with smoke pouring out from the dirty old exhaust manifolds and silencer. Typically I clean the tanks with acetone first, then hot water and all the stainless nuts in my spares box...so did that again today, along with a carb clean and fuel line clean, followed by a razz with the heat gun to dry the innards.

The smell and noise (95db) were impressive. This video shows a late 1929 model & the starting / running sequence.

This recently aquired 1929 Johnson P-45 12hp is the next in line for the treatment. It's a scaled up twin and no longer a 'Lightwin'...Issues thus far appear to be a stuck decompression valve, a cracked stop switch and an ancient repair to the exhaust bypass system. Interestingly this also has an underwater exhaust system which will cut down on the racket they typically make. The much dented tank has been removed and it's foul smelling antique contents disposed of, in preparation to the flywheel removal.

Just love the engineering on this...these parts form part of the decompression system and came apart as if they were put together yesterday, not 88 years ago

Motor is about 20ins wide..and needs two to move it around.