Keep some ringfree in the fuel. Problems solved.
https://www.shopyamaha.com/product/details/ring-free-plus?b=Yamalube+for+Outboard&d=38|38&dealernumber=
Available at dealers or online, and that link doesn't show it but it's available in the little tiny bottles that treat like 5 gallons, and it's cheap.
2 stroke engines that idle a lot benefit greatly from ring free. It was originally designed for this purpose, to keep the rings from becoming carbon-stuck in 2 strokes that do a lot of idling. It also works well in all 4 strokes to de-bond the carbon deposits from valves, pistons, heads, ports, etc. I used to have some before and after pics of a lawn mower engine that spent it's entire life idling. Carbon fouled. Everything was thick black carbon. Put the head back on and ran a quart of fuel through it using ringfree-treated gas. There was a distinct "line" of "clean" from the intake valve across the piston. The stuff flat works!
Even mercury techs love the stuff.
I've saved customers a LOT of money by using it. At least 4 times, the big yamaha twin bike engines (1600cc, 1700cc, 1900cc)-especially the ones with carburetors. Guys riding them would "blip" the throttle a lot. When they do that, it goes rich for a split second, then back to idle. At idle, there wasn't enough heat made to burn the junk off. Over time it would build carbon up on the intake and exhaust valves and especially the intake valve stems on the rear cylinder (which ran richer than the front cylinder). Then one day, mr. Customer is out on a ride and notices that under power, the engine drops to one cylinder, but idles fine. The carbon is holding the valve open slightly and it was real noticeable at 2000 RPM+. I called Yamaha about the issue and they described that the carbon deposits were causing it, and said to pull the heads and clean them. Ok, so we had ringree in stock...let's try it. 2 gal of gas and a whole (small) bottle of ringfree. Idled for about 10 min, then run it down the road. It cleared up. So rather than spending a grand on pulling the heads (remove engine labor + gaskets), a $3.00 bottle of ringree solved it, every time.
Only bad part about the stuff in marine engines is that it WILL de-bond the carbon deposits while the engine is running, which obviously ends up in the water. But you're running a 2 stroke anyway, you're pouring a lot of unburned fuel and oil into the water already. Big deal.
Its also worth mentioning that excessive idling is one of the main advantages of the Yamaha 25, which had TWO carburetors. One for each cylinder. They were able to make them run leaner (and therefore cleaner) with 2 carbs as opposed to one carburetor which most everyone else used. 3 cylinder engines mostly used 3 carbs. At leas the Yamaha, suzuki did for sure. I remember a Merc 40 that had two carbs, but 4 cylinders....they were loud and smoky but good motors. And idled like poo, IMO, at least compared to even the twin cylinder Yamaha C40 (later C40's were all 3 cylinder/3 carb).
