Re: please help!
HD,
Elvin is right on the mark. The only tried-and-true method to clean the idle passages is to do a complete disassembly and 3-to-4 hour soak in carb dip. This is becoming more and more of a common service procedure, thanks to the US EPA -- with their required emission reductions, and promotion of lower-quality fuels.
The 9.8 carbs run very lean to satisfy EPA. The fuel passages in the carb (especially the low-speed circuit) are very tiny, and, as a result, they are more prone to the effects of varnishing.
Then too, today's gas is not anything like what it used to be. It's not as stable, and spoils much faster, leaving more varnishing in a shorter period of time. If you are unfortunate enough to be running E-10, that adds insult to injury, as it adds the undesirable dimension of absorbing water from the air, promoting corrosion, and it dissolves some fuel system plastics. Fortunately, the plastics that are used in the 9.8 fuel system can tolerate E-10 without breaking down.
What might have been insignificant buildup on loose, sloppy, old-style, pre-mix 2-stroke carbs becomes a real issue with the newer EPA-rated carbs, because that "miniscule" buildup is quite significant in the smaller passages. Shutting down the motor without running the carb dry is a factor as well. In our shop, we have been finding that the "magic" number of days sitting with fuel in the carb is around 1 to 2 weeks, depending on the weather (hot and humid makes it worse), and on the original fuel quality.
To combat the problem, we recommend that consumers not buy any more fuel than they can use in a couple of weeks. If the gas gets to be a month old, it's just as well to pour it into the truck or car tank to use it up. We also recommend always running the carb dry at the end of the day, unless you know that you will be using the motor the very next day. We recommend water-separator filters on all motors that have a separate tank. In fact, Tohatsu America has been including water separator filters with fuel-injected motors. Adding a good stabilizer (such as K-100) to every tank doesn't hurt.
Now the good news: Some of our customers have had limited success with some minor varnishing problems by running relatively large doses of fuel injector cleaner in a small amount of fuel. Chevron Techron comes to mind. I don't have experience with Seafoam, but it might possibly help a little. The problem is that a lot of the "snake oil" injector cleaners are promoted as having a "jet fuel" base. Unfortunately, that's just another name for kerosene, so it really is mostly just "snake oil".
If your dealer cleans the carb, ask them to look very carefully for any microscopic metallic or rubber/plastic debris inside the passages. While Tohatsu can't offer a warranty on the fuel you use (or how you use it), they do warrant that there isn't any manufacturing defect -- including a microscopic bit of machining fragment inadvertently left inside the carb. I recently had a case where there was a minor fragment in the carb, and it didn't show up as a problem until after a couple of months of running. It was covered by warranty. HTH.
