Saving Old Seagulls

Picked up these two very crusty, seized engines as a lot a couple months ago (SJP40964L & FPL1348DD4). Needed a fuel tap and line for a project FP, and got these two for about what those bits would cost on their own. So, requisite parts retrieved and the two old birds sitting around = time to start tinkering! My goal is to get a single running bitsa out of them, with as few dollars as possible spent in the process (initial goal was $0 but this has gone up since getting them apart as I will need a new coil at a minimum!). I thought this would be particularly fun/educational project since I’ve never tried to reuse an seized/unseized piston/cylinder before; rather I’ve tinkered out of curiosity and mostly ended up breaking the parts during the inevitable whacking with a heavy hammer.

Here is where I am so far with a few pics along the way.

To start, both seized as expected. Let some penetrating oil soak in the chambers for about a week. Then, off with their heads! Bolts on FPL came off fairly easily, with the usual heavy dose of heat. SJP on the other hand, put up a fight. Lower left was a metric bolt rammed in there which came off OK. But those flat-head screws did not want to budge, as slots were already in poor shape from what must have been some heavy torque a long time ago. Gave them an extraordinary amount of heat to no avail, went through 2 heavy duty screwdriver blades and 2 bits on the impact driver before taking a different approach. Had to grind down the tip of the impact driver blade until it was much thicker, just enough to fit in the very top of the screw (I will start with this approach in the future). That was enough to get them out, took about 20 mins each alternating heat/impact driver. The SJP ports were pretty clogged but nowhere near as bad as FPL which had turned into solid rust.

Here is SJP with head off.
And above is the SJP head, probably a common sight for those reading. This raises a question in my mind. What caused the 3 heavily corroded spots? These were behind the gasket which was intact, and exterior of head was in good shape. Was it a leaking head gasket that caused scorching? If so is that predictable/preventable?

Next up, out with the pistons.

What caused the 3 heavily corroded spots?

Could be a hotsopt or where water was sitting when the engine was in storage.
With having a good mix of metals, aluminium and zinc being the ones that will get eaten away first. (that is why a lot of the carbs are so corroded)

First Update

FPL piston came out with a good knock on a wood block. Ports almost entirely solid rust, so plan was to use SJP cylinder which was in much better shape. SJP piston was properly seized however. Ended up finding some M18 x 1.5 brass grease nipples which fit the spark plug threads perfectly. Put the FPL head back on SJP block, much easier to get the bolts on/off. Filled cylinder with 2-stroke oil, screwed in the grease nipple, gave it some grease and...two stroke oil came out the threads . It took a lot of pumps of the handheld grease gun even though it was nearly TDC, but eventually the cylinder filled up with grease which displaced all the oil. Grease was thick enough to give pressure in the cylinder even though it slowly came out the threads. Once the piston finally cracked loose, have to say the slight feeling of that first movement was fantastic.

This showing the grease nipple approach: And this showing the grease coming out of the exhaust port once the piston had moved down a good bit: This was my first time using grease nipple approach but have to say it worked extremely well. Next time I will use a washer from a spark plug to make a better seal on the head, but otherwise very pleased.

NOTE: I had to buy a pack of 4 nipples, so have 3 extra if anyone is interested. I'll post a separate entry in the for sale section later. I paid $3.55 each and would ask the same.

So, pistons out and soaking for a day, time to get the rings off. Managed to get one good one from each, broke the other two. But happy to get two and on measuring them later it seems they are still decent. Decided to use the FPL piston since it was in better condition.

Next on to the cylinder. Spent a bit of time cleaning out the ports on SJP and was making good progress until I dropped it and, unfortunately, a piece cracked off right where the water comes out:
So back to FPL cylinder. After having to drill out some of the completely blocked ports I finally had enough room to get the dremel in there. Here it is after getting the ports open for cleaning:
And here it is midway through cleaning.
Then onto the piston and crank. Started off using the FPL con rod but somehow managed to crack a thread while screwing in one of the big end screws; I think possibly it wasn't seated completely and so before even getting it tight it came in at a slightly wrong angle and that was that. Pictures and next steps in next post.

Great work, its good to see seagulls being saved in the US! I think using the grease nipple is a great idea, so many things get ruined by application of the big hammer, a bit of science works well.

Big end caps are marked so they shouldn't be reassembled with the cap the wrong way round, that's the most common cause of fractures.

I don't think they sell 18 x 1.5 mm grease nipples in the UK, lucky you, we have to make our own!

Second update.

Starting with the cracked connecting rod. I barely gave the screw torque and it split, almost felt like the screw was too big but it was definitely the same one that came out. Maybe cross threaded, tried backing it out as soon as I felt resistance, but noticed that the cracks formed before it was halfway in.
I was trying to avoid taking out the gudgeon pin but alas, seems every part of this frankengull needed some attention. Removed the circlips and used dowel with hammer to give gudgeon pin a tap with no success. Then remembered there was something about this in the service manual. Service sheet number 3 suggests a dip in boiling water, which to my unsurprise worked perfectly, and the gudgeon pin slid out easily from both pistons having been in there roughly 55/44 years since new. That is yet another of those 'just follow the manual' processes where the simple published approach is a perfect solution.
Piston and bits back together easily this time, onto the crankshaft after that. And I remembered to put the wire back in the big end screws to stop them from rattling out. Felt good that I was then onto some of the rebuilding part of the project, which to this point had consisted of stripping, cleaning and breaking parts. Building it back up is way more fun!

Into the housing, and onto the cylinder. Good tight fits on all seals, bearings and rings. But noticed that on part of the stoke it was unusually stiff (the up stroke I think?). Turns out as I had made a gasket for the cylinder base, I completely forgot to cut a hole for the intake which comes through crank case. Oops! That was making a sealed vacuum. Cylinder back off and a quick cut later it was back together.
Nest stop was the carb. Other than being completely clogged with the usual brown stuff that results from sitting full for decades, it was in good condition (I find carbs usually are OK with a bit of TLC). Strip down was easy and other than the jet it was easy to clean. Jet was properly clogged but managed to blow it out with WD-40 contact cleaner. Have to say, other than being quite pricey at $6 a can, the WD-40 contact cleaner is a wonderful cleaning product for this and other parts on an old engine; it really blasts through decades-old oil and grease in all manner of tight spaces.

Carb disassembled:
And back on the cylinder. Starting to look like a real power unit!

Next stop was the leg. Pump housing clogged as expected, but not hard to clean out.
Rest of the gearbox cleaned up fairly well from the better donor, but cant remember which one at this point! Was pleased that I didn't have to take out the prop shaft/pinion etc. I think this was the only piece that didn't get dismantled completely during the exercise.

Below showing the various bits cleaned up and ready to reassemble. Chose the silencer from SJP as it was in quite good condition (and who doesn't like shiny), and used drive shaft casing tube from FPL. Drive shaft and casing tube had some typical rust, but gave a cursory cleaning and both came out as well as could be expected.
This raises another question. I can't remember which one this joint plate came off of, but I feel like all the other ones I have seen have been some sort of thick paper. Usually they are reusable, but occasionally they are soft and break up during removal. But this particular one looks to be fiberglass or similar. It is very rigid and despite the markings that shows in the photo, it shows few depressions and little to no wear. Was this a standard fitting or perhaps replaced at some point'?
Assembly of the leg, once bits are cleaned up and properly prepped, is a quick and easy process. Next photo is leg on the power unit.
And after this, engine bracket (from SJP I think) given a quick disassemble, cleaning, rebuild, and mounted to the motor. Nothing too complicated there.

At this point I had planned to take a break while I searched for a new coil online. Both the SJP and FPL coils had no readings as mentioned in my first post, and since both motors were seized when I got them, I couldn't give them a spin to check for spark. But, as usual, curiosity got the best of me. I quickly mounted the Mark II ignition which was still intact from the FPL and loosely dropped the flywheel and an HT lead with new spark plug on. Flywheel not even far enough down to cover the whole coil, gave it a quick spin by hand, and to my surprise it has one of the best bright blue sparks I have ever seen. I checked the resistance and once again nothing on the meter. I searched the SOS forum for this issue and came across a few comments about this. Tribal knowledge suggests that coil will work for now but is on it's way out. If that's the case, can anyone give an estimate of expected life? Are we talking limited hours of run time or is it more limited by time itself i.e. will degrade in a year or two?
I didn't have time to reassemble Mark I ignition for a test spin today. But I will certainly do that next chance I get; my preference throughout this process has been to use SJP parts as they simply look better.

I believe that if you have no resistance across the coil then you have what is called an air gap. Unfortunately this gap will increse as a spark will jump across. I dont think it will function for long. You are doing a fine job.

A great job enjoyed reading your progress, nice idea of using grease to build hydraulic pressure.
You do need a good metre to measure the coil resistance typical readings are Primary winding 0.5 ohm and secondary 3.86 kilo ohms. They are very high resistances small readings, so it’s easy for your metre to become overwhelmed with internal and probe resistances and give you a false reading.

Good luck with the rest of the build, Dave.
PS that joint plate between the leg casting looks like Tufnol. A resin heat bonded paper or cloth.

I have a tufnol gasket just like that hung on a hook - same colour too. Tufnol suits the Seagull generation. They used it a lot for sheaves in early boat blocks. I believe its still used in the power industry - high voltege etc. Don't see its qualities as a gasket though as its very hard and rigid ?
Is that the original leg - nice nick for an old bitsa !