I'm not sure what Yamaha calls for but one thing for sure is if it's smoking running rough at idle and fouling plugs and the gas is fresh, then it's too rich. I read here where people say they would rather have too much oil then not enough..learn what ratio your motor likes best and mix it to that Every time..I have been Stihl mechanic for years, and I have watched the evolution from 40:1 to 50:1. when Stihl leaned things from 32:1 in the old days to 40:1, the burns on the plug went from black/wet to brown/wet, which was still too rich (to much oil) When they finally make the transisition from 40:1-50:1 it went from brown/wet to brown/dry. That's where a 2 stroke burns best. Read Your Spark Plugs. too much oil is just as bad as not enough..for those of you guys that have tore engines down and seen the black wet carboned deposits left on the combustion chambers, top of the pistons, and how badly it gums up the ring grooves on the piston know the effects of running rich mixtures in 2 stroke engines..I ran for years in my 2 strokes Ams-oil synthetic 100:1 but I mixed it at 90:1 and you talk about running clean..no smoke, smooth idle, and the engines don't load up like they do running 50:1 mineral base oils..Huge Difference..Too many guys put so much gas in their tanks and then guess as they dump oil into the gas..If you want to get it perfect Every Time, buy whats called a Ratio-Rite cup from your local motorcycle shop and it will tall you exactly how many oz's of oil to add for how many gallons of gas..it takes all the guess work out of mixing..Your 2 strokes will run so much better, you can't help but notice the difference..check your spark plugs, and if they are black and wet cut back on the oil just a bit, then run it through the next tank and keep cutting back and make note of how much oil you added to that tank until your plug reading is where you need it..your engine will thank you and last far longer..
Unfortuntalely we have no choice but to run Ethanol fuel these days, and it's the worse thing we can use in aluminum pistons engine such as all our small engines have in them..I run nothing But Premium gas in my small enignes with a small shot of Klotz octane booster..Ethanol cause premature wear and detonation. run the best gas you can get your hands on..As someone mentioned, do not run your engines out of gas to run them dry..the piston and cylinder wall needs fuel/oil to keep it lubricated and when you run them out of gas they run unlubricated and season after season it will cause major scoring due to metal to metal surfaces...drain the carb float bowl out instead...run a fuel stabilzer if you are not going to drain your tank..put a teaspoon of motor oil in the cylinders and turn the engine over slowly a few times for storage in the off season.. good luck and I hope this helps..
