1987 Other Mitsubishi Models Carburetor?

The basic control system for your carburetor is the O2 and engine temp sensors. If the engine takes a long time to warm up, check or replace the thermostat. Running too cold will make it run rich. If that doesn't solve the problem, you may want to change the O2 sensor. There is really no accurate way to test them.

James,

Replaced thermostat and O2 sensor, no change. I think the fact that it's running too rich may be keeping it from warming up. To me that means the problem lies elsewhere, very possibly in the carb. Care to try again?

A lean motor does run warmer than a rich, but in a 4 cycle engine it's not that noticeable. A 2 cycle is a whole different deal. If you over richen a 4 cycle, they just flood and quit. Where as, a 2 cycle will burn up. Anyway, to adjust the idle mixture on your carb, you have to take it off, turn it over, drill a hole in the bottom to knock out the plug seal, and then you can get at the mixture jet. You'll see the plug in the front of the base plate.