Continued work on the BG 55 today. I started by removing the carburetor, which allowed me to remove and clean the plastic intake manifold.
You don't need to remove the intake to change or service the carb, but the manifold also doubles as a guide for the throttle cable. The problem with this arrangement is as the cable stretches, it has a habit of slipping off the manifold and locking the throttle wide open. Stihl scrapped this arrangement in favor of a throttle rod as they were having a lot of problems with it, this unit has had at least one new cable.
Because of the age of the machine, finding a replacement throttle cable is proving difficult, so I need to make the most of what I have. With proper access, I removed and lubricated the cable, then cleaned the trigger and trigger post to hopefully make it move more smoothly. With the intake block off the engine, I cleaned it and the gasket, then reassembled. From here, I wedged and glued a "retainer" to the intake.....................a plastic bottle top cut in half. The idea is to prevent the cable slipping off the intake, let's see if this works as intended.
Next, I removed the muffler to check for carbon build up. The exhaust port was clear, likewise the entry to the muffler. After a little fit of stabbing, I managed to shake out a fair bit of carbon, some of it coming out in chunks. I then heated the muffler up with a gas torch to burn off what I couldn't scrape away. I then used a wire brush to remove the carbon around the inlet and outlet, followed by a rub down with sandpaper to give the exterior a little facelift.
As for the spark arrestor, it went awol a very long time ago. I remember very early on taking the unit to dealer complaining about a lack of power, this was well before me knowing how these things work. They took it out the back and chopped off the wire screen.................I guess that's one way of dealing with the problem.
While I had the muffler and intake off the machine, I had a good look at the piston and cylinder, surprisingly, both look beautiful. I may have worked this engine hard over a long time, but it always got premium engine oil and had clean filters.
The old Zama carburetor, well I am using this as a learning tool. I removed both metering and pumping sides, and as expected, both diaphragms were stiff and brittle. Otherwise, the internals were clean. Even though I bought a replacement aftermarket carb, I've decided to rebuild the original with a diaphragm kit and new primer bulb. Doing so, I'll learn how to do this, and I can perhaps sell it off at the end or keep for spares.
I will probably also remove the flywheel to inspect the three bolts that sit behind, which can work loose over time and cause the engine to lock up. I've had this happen on multiple BG 86's, the fix is to nip them up with a little thread locker.
I'm now just waiting for parts to arrive.