Today I finished rebuilding the carburetors.  It’s a fairly simple process, made easier since the carburetor bodies were cleaned with the vapor honing process I covered in my January 29 post.  The carburetor rebuild kit included parts specific to this model of motorcycle, so reassembling the carburetors was easy work.

The carburetor rebuild kit included new brass jets, springs, gaskets, o-rings, float bowl valves and adjustment screws for both carburetors.  The adjustment screws and throttle jet needles were set to the default setting, which should be fine for starting the engine.  Once the engine warms up and breaks in for at least 50 miles, I’ll go through the process of setting the adjustments to balance the carburetors and fine-tune the settings for a smooth idle.

I have all the engine parts needed to begin reassembly, so stay tuned.

I ordered a new aftermarket carburetor last week – only $49.  It’s slightly different from the original, and has a slightly larger capacity, but my research suggested that it’s the recommended replacement for the ATC 90.  With the body shell and fuel tank removed, I took the opportunity to clean the machine and replace the air filter.  I also lubricated the chain – something that probably hasn’t ever been done.

This ATC always seemed to lean to one side.  I had always attributed that to the mismatched rear tires, but even after I put new tires on it 4 years ago, it still seemed to lean a bit.  I studied the tires and wheels and it finally hit me – the front wheel is different than the two rear hubs, and they’re in the wrong positions.  The front rim was mounted at the rear right side.  Once I moved the wheels to the correct positions, the ATC sat level for the first time that I could recall.  That should help it steer straight, and it looks much better.

After the fuel tank was cleaned and refilled with fresh gasoline, I connected the fuel lines to the carburetor and switched it on.  I set the choke, pulled the starter rope, and after two tugs, it started.  I adjusted the idle setting, and the bike settled into a nice, relaxed rumble.

I had to re-learn the shift pattern of this machine – neutral is all the way up, and the 4 forward gears are all down from there.  I rode the ATC to the beach for a test drive, and it worked perfectly.  The engine has plenty of power, so the new carburetor did the trick.  Perhaps next on the list is a new aftermarket generic headlight to replace the damaged original.  This loyal little machine deserves it.