Hydrochloric (Muriatic) Acid can be used for this. It is a mild acid,but still acid, so use care. Using an acid brush brush the acid on the aluminum, depending on the thickness of the aluminum it can that a while, but will remove all aluminum from the cylinders without causing any problems. The fumes can be rough, so ventilation is important. I have used this for years to save engines , so they can be repaired.
It could be many things. First thing I would do is get your carbs removed and clean them up. Next, I would clean your powervalve/exhaust valve ( if your model has them ). If still not doing any better, check your compression. If all cylinders above 110psi, clean your clutches.
Clean plugs new ones maybe new points
You can clean the aluminum particles by dusting them away.
Collect all the necessary parts. Clean the parts. Install piston rings on the piston crowns. Smear engine oil on the piston cover and the cylinders. Install the rods and the bearings. Add grease to the bearings and seal them with caps. Connect the rods and pistons to each other. Insert the rod end to the engine block. Connect the timing chain. Apply a new gasket and install the head plate.
To remove both oil and grease you should clean aluminum with a solution of water and mild dish washing liquid. Generally, aluminum items around your home just need a good periodic dusting with a soft, clean cloth, to keep clean and shiny. Thanks!
wash and polish it
You do not lubricate a clutch - You clean it. If you lubricate it will slip and it will collect dust and dirt from the belt and it will bung it up..
try using baby oil
You can use a power washer to clean aluminum pontoons. The power washer will remove most of the dirt. To remove additional discoloration you can use a product such as Barkeepers friend.
to clean unspent fuel out of the cylinders
Most people consider aluminum blinds the easiest to clean.
your have to remove the head from the engine slowly until one piston is at bottom dead centre.using clean oil,from a measured container, fill the cylinder.Work out what has been put in the cylinder by subtracting what is left in the container from what you started with. Multiply the result by the number of cylinders and then you have the cubic capacity.