Bringing the Honda SL350 Back to Life: Cleaning the Carbs

So far, for cleaning the gas tank, I've tried several solvents including acetone, new gas, mineral spirits, and carb cleaner. I've tried inserting several sorts of objects into the tank before agitating including ball bearings, nuts, and fish tank gravel. I've even tried using the dyer to agitate the tank. While I'm making some progress, so far I haven't found any magical solution. I found a post online claiming that denatured alcohol would dissolve the old varnished fuel, but that it takes a long time. So I've now put a quart or so of denatured alcohol in my tank (most of the remaining gunk is at the bottom) and I am just going to let it sit for a few days. In the meantime I decided to take a look at the carburetors.

I popped the float bowl off of the bottom of one of the carbs and took a look inside. It had some pretty nasty stuff inside. I decided that I was going to have to take the carbs off of the bike to clean them out. They probably need a complete rebuild. But for now I am going to try and get away with a cleaning.

First, I had trouble removing the carbs from the bike. The throttle cables on this bike are not attached to the carbs externally, but rather go inside the carb and attach to a piston that is moved up and down inside of the carburetor by the twisting of the throttle lever. The cable cannot be detached (and therefore the carbs cannot be removed) unless the pistons are removed from the carbs. However, on both carbs these pistons were frozen in place. After some wresting and liberal use of carb cleaner I managed to get them free.

Piston in carb that is attached to throttle cable

Here are some pics of the carburetors removed from bike and before and after cleaning pics. I'm not sure if I cleaned everything I needed to, but I did make sure that, for each carb, the main jet was clear, the needle valve moved, the floats were free of goo, and as I mentioned before, the throttle piston was free.