You must have some secrets to make old engines shine like new again… Hopefully, one or two that do not require taking it completely apart, repainting it, and putting it all back together again! The motor runs solid, but it looks like crap! Any suggestions?
Starrider –
Cleaning up an old air cooled motor can be a LOT of work. All sorts of dirt and oil and gunk can collect between the fins over a couple dozen years. Often times the old Jap motors are painted, and the paint will start bubbling and flaking off allowing the aluminum to oxidize underneath.
This is one of my old Yamaha TX500’s – it has an unpainted head.
And here is a more typical sight – a painted head.
The best way by far is to pull the head and cylinder off and have them media blasted. The whole thing will look brand new after. …… but that isn’t your question.
Generally to clean the fins up I’ll start with a wire brush. I have a couple different sizes of wire brush, one thats larger with long bristles, and another that is smaller like a toothbrush with short brass bristles. Have a look at your local hardware store and see what they offer.
I’ll scrub with the brush as best I can which will generally clean up all the flaking paint and larger clumps of junk. It’s typically best to power wash the motor first to get it as clean as possible to start with.
*note: you should always be mindful of the gaskets when power washing and scrubbing with wires*
After the big gunk is gone , spray it down with some degreaser in any areas that need it.
I’ll then use an emory board (a ladies nail file) and use it to sand up the tops and bottoms of each of the fins. This often does a great job. You can also use a fine grit sand paper, fold it a few times, then push it in and out.
I then will rinse the motor and use an oil like wd40 or similar to give the motor as much shine as I can. The oil will burn off a bit once the motor is hot again, but it’ll stay pretty clean.
*note: if you are going to be painting don’t use any oil*
Really that’s about as good as you can do without disassembling the motor and giving it a hardcore cleaning. If you spend a saturday afternoon with a few tools, put in some elbow grease, you can definitely clean those old nasty fins up quite nicely.
The Kawasaki KZ550 motor I repainted, because it just wouldn’t look ‘good’ otherwise:
The Yamaha TX500 motor I ended up scrapping, but thats another story. 
