Cosmetically Restoring Project 250 Mag’s Motor

My approach to restoring the engine was dictated by my lack of special tools to split the cases. Had I such tools I would have taken the engine completely apart. Instead I removed the cylinder, piston and right-side covers, and then taped the crankcase opening closed with duct tape. I worked on one section at a time – the top, the sides, the bottom. Massive amounts of paint remover and elbow grease lifted the paint pretty well; those resistive patches and paint in the crevasses of the engine succumbed to an onslaught of wire brushing and Q-tips. I repeatedly wiped the engine with stripper wash to neutralize the paint remover between sections. The first picture shows the end of the initial phase of this process, carried out on my wife’s kitchen table because the Nebraskan winter forbade working in the garage. The kitchen is not a recommended work area: slabs of paint covered in caustic goo get pretty much everywhere they’re not suppose to. (Later, after I finally got a flywheel remover, I stripped the paint in the magneto case. I did this on the basement bar – also not a recommended work area. But at least the tools didn’t stick to my fingers from the cold.)

After the paint was off I sanded all the surfaces with a fine grit cloth and then wiped them down with alcohol. This is an important step because any oil that you will invariably smear on the surface from your greasy fingers will interfere with the paint, and you will be stripping, sanding, and wiping again. And again. Trust me. I used PJ-1 Satin engine spray paint at about $8-10 a can. It went on nicely and dried quickly. Just like the can says, it helps immensely if you do this at room temperature, which for me meant that I had to use the furnace room in the basement. Also not a recommended work location as it fills the house with noxious fumes. The PJ-1 is gas resistant so far, but I have not yet run the bike and have my Bing float stick open, dribbling gas and oil over my handiwork. I used a spot of sandpaper to burnish the paint off the raised Husqvarna logos on both sides of the cases.

The cylinder and head caused me a lot of trouble. I wanted to go with the “sand cast” factory look, which called for bead blasting the fins. I taped off the gasket surfaces with duct tape (see second picture) and sent them – with detailed instructions – to the guy who was arranging the bead blasting and powder coating of my frame. When I took delivery of my parts, the head and cylinder had been powder coated a semi-gloss black. They actually looked pretty cool, but not exactly what I wanted so I had them blast off the powder coat. Which turned into an issue because they had to heat the cylinder up really high to get the coating to soften up enough to come off. I envisioned getting back a very expensive puddle of aluminum with a steel sleeve frozen in the middle. Fortunately all turned out well.

In spite of my clever taping of the crankcase (see second pic) a non-trivial amount of paint, dust, cat hair, and nuclear waste found its way into my crankshaft. I flushed it out repeatedly with premix until the effluent ran clear. (No paint came off the engine in this process.) The third picture shows the engine going together and gives you an idea of the paint’s semi-gloss sheen. I left the all the finishes as is; that is, I did not use any clear coat on anything. I think clear coating the blasted head and cylinder might be a good idea if there was no impact on heat transfer. Does anyone know anything about that? The fourth and fifth pics show the finished product from both sides.

I second that. Thanks for the info. Gonna go the same route.

Fantastic job that just looks GREAT! I'm very impressed that you got the original black off so well. I've been trying various strippers on my 82 parts and most of it does nothing. Looks like lots of elbow grease will be required.

The bare aluminum cylinder/head look just rocks. In fact, it's one of the reasons I liked the 82's so much. Again, very nice job.

wow, nice job