Jan, thank you for weighing in. My engine has no large head and no anodization, and the muffler seems to be a rather small plain expansion type. Manual says it's a .26, which seems to be no longer made - I gather the .28 is the replacement - appearance is very similar.

What is the relative heat of those Rossi plugs? Will I be able to run a 10x4 on this engine, or does it need to rev more?

I may want a quieter muffler. Where would I get that? Thanks in advance.

Trent, I do the pinch test with a needle nose pliers near the carb. As the moderator said, you want a short rpm rise when you pinch the line. If it stops abruptly, it is lean. If it revs up for a few seconds then it is rich. For the high speed needle I just go by sound, but I find the pinch test very useful to set the low speed needle. Final test, if you let the engine idle several seconds and then quickly advance the throttle, it should accelerate quickly and smoothly. If it hesitates and produces smoke, it is rich; if it stops suddenly it is probably lean. If you have done the pinch test, it should be fine.

Maybe Jan will tell us if this is a good method for the MVVS.

Jim