I inspected an RC30 that had been running rough before. At first glance, it showed wear appropriate for its age…
The owner said the fuel economy was terrible. Eight kilometers per liter!
Wow, that’s rough. When I checked the spark plugs, both banks on the right side had black plugs.
So what trouble comes to mind right away?
• Old spark plugs!
• Air filter is dirty
• Coil is shot
• Carburetor trouble
• Valve clearance is tight
• Engine itself is worn
And so on.
Going from the top is easier because the further down you go, the more of a hassle it gets.
I replaced the spark plugs (swapped them out when I lifted the tank) and checked if they’re firing properly.
Same with the air filter. Then I checked the carburetor.
It’s a critical component for fuel delivery. If it goes bad, things get pretty messy.
I took it apart and checked it right away. What’s this? Signs of corrosion before! And the jet is broken…
That’s nasty. So that was it—I completely disassembled it, inspected it thoroughly, then replaced everything and reassembled it.
First, I replaced the jet! Each one costs only a few hundred yen, and surprisingly some get dissolved by gasoline or carburetor cleaner.
For example, a #100 jet could dissolve and become 101.24 or so.
Same with the float valve and all the O-ring parts!
But synchronization was tough—the screw on the underside of the carburetor wouldn’t turn no matter what!
I used two types of angled screwdrivers to get it out and adjusted the pilot screw, and then it ran great.
The throttle cable replacement is showing results too.
Man, parallel twins really are the best.
