I have at one time had at least a dozen different plugs in my tool box at the same time by trying to follow engine manufactures recommendations. I started a quest to find and limit myself to one two stroke and one four stroke plug that would work for all. Other than a few specialized engines I have found that the McCoy MC14 for two strokes and the YS plug for four strokes fit the bill. First I used the Fox Miracle Plug and the OS F but had a few duds with the Miracle plug so I tried others finally settling on the Hanger Nine HN3000 and HN 3002 performance plug. When they stopped supplying them I called and was told these were McCoy MC14's. I contacted McCoy and indeed that’s what they were. I have been running MC14's since and these plugs perform and last. Try one and see. For four strokes I use the YS plug over the OS it seems to last longer and run more consistently and is usually a little less in cost. I discovered the YS plugs when I bought my third YS motor and these were recommended to me. Be careful using the long reach plugs that they do not interfere with the piston. I find that the long reach plugs seem to perform better than the short ones. When you do a comparison compare two new plugs not one used and the other new. Use the old plug to tune the engine as best you can. Note idle, transition, midrange and top end. Now put the first new plug even if it’s the same as what is in the engine and re-tune for best performance. Swap it out with the second one and compare, re-tuning as necessary. You may be surprised that a simple plug change can turn an inconsistent engine into a rock solid performer with great idle, instant transition and as much as a 500 rpm increase at top end. There is a lot of talk about heat range but other than hot, medium and cold there is not much reference material as the plug manufactures have not standardized between brands.

If you have been monkeying with your carb you may have things out of whack so to get things roughly in the ball park set the carb up in this fashion to get you near factory defaults. You will need a small flat head screw driver, short length of fuel tubing and a 1/16 diameter wire or drill bit. Back the high speed needle out so it’s not going to be a factor. Place the fuel tubing on the fuel nipple with the other end in your mouth. Insert the 1/16 diameter in the carb throat and close the barrel until it just barely holds it. Blow through the tubing you should hear air escaping in the carb. Turn the low speed in until the air leak stops then back it out until you can just detect air passing into the carb. Open the carb and turn in the high speed until it just stops then open it the factory recommended turns. This will get you in the ball park to tune the engine.

Dennis