So when old gas gums up the carbs on your sled, what jets are most often affected? Usually it is the pilot jets; the sled doesnâ€™t want to run very well at just above idle or at idle unless the choke is applied is a typical symptom at fall start-up.
Typically, it is the smaller passages of the pilot jets that plug up with corrosion and crap first. Problem is, the carbureted four-strokes from Yamaha all have even smaller pilot jets than what weâ€™ve all been used to dealing with on two-strokes, and now as some of this population ages the sleds are starting to see fuel and carb related problems. For example, the RX-1 is fitted with #17.5 pilot jets! Weâ€™re talking small metering orifices here.
Moral of the story; be aware of the smaller pilots in the carbed 4-strokes, and their increased susceptibility to blockage due to fuel quality and storage issues. We continue to see exceptional success with the goofy little Fitch Fuel Catalysts that we drop into every gas can and fuel tank we have, from mowers and ATVs to weed wackers and snow blowers to every single gas can in the shop. We simply do not have any more fuel related problems.
At a minimum, the fuel should be stabilized with a liquid fuel stabilizer and the engine should be run long enough for the treated fuel to for-sure enter the carbs before storage, but even this process is not as fail-safe as in the past due to the constantly changing fuel formulas.