How do Jetting Changes work on a Comer c50/c51?

2-Stroke Engines · 2026-09-03 22:43:24

How do Jetting Changes work on a Comer c50/c51?

Getting a jet swapped between sessions takes more time than it looks when there is a driver waiting to go out. I get that you drop jet size if the air thins out but I'm wondering how much of a change actually makes it worth the hassle on a Comer c50 or c51. Does anyone just set a baseline and only touch it if the day is really different or is there a practical check that doesn't eat the whole morning?

Comments (1)

Jakeolso21 on 2026-09-06 18:25:16 edited

On a Comer C50 or C51 the jet you start the day on matters more than the one you swap to between sessions. Pick a slightly rich jet, or whatever is at or just under the largest size that still pulls cleanly, and treat that as the baseline. Confirm it later with peak RPM on the straight and with lap time, but only after the driver is repeating laps. Until then those numbers mainly track the driver, not the jet. A 1 percent change in air density wants about a 1 percent change in flow. That is the only weather rule worth carrying. Smaller moves are not worth pulling the carb between sessions, and they are easy to undo with a sloppy bowl gasket or a rushed main jet. Save the change for a real temperature or humidity swing, or for an engine that starts to lean out and drop revs at the end of the straight. That last case is a reliability call, not a lap-time one.