Make no mistake, a bunch of us will be greeted by plugged pilot jets when we go out and try to fire up our sled for the first time this fall. Fuel related issues continue to be a problem when storing vehicles, snowmobiles included. Sleds (and engines that sit during the summer) seem to be more prone to this due to the higher humidity levels and heat of the summer months. This is despite efforts to use some form of fuel stabilizer, that doesnâ€™t work all of the time with the wide variety of fuel mixtures mandated across the country (something like nearly 25 different types!).
The low speed fuel jet, the pilot jet, is the most often victim of fuel problems. This jet has very small passages, and when restricted or plugged, the sled may not even idle, or doesnâ€™t run very well at low engine RPMs, but may seem to work OK as the throttle is opened. This will likely be even more of a problem on the carbureted four-strokes that use pilot jets which are 1/2 to 1/3 of the size of two-strokes!
Many times for storage the owner will run the engine out of gas, thinking he just sucked the carbs dry. Almost. There remains a small amount of fuel in the bottom of the float bowl, down below where the main jet reaches. This remaining fuel dries up, and can leave a flaky residue at the bottom of the float bowl. When you come along and pour in some fresh premium, this residue is dislodged and then can block just about any of the jets.
The remedy? Be prepared to drop your float bowls and clean your carbs, regardless of what measures you took last spring. Fuel related issues like this are one of the biggest reasons for engine service, and this holds true across all products lines (bikes, sleds, marine, whatever) when fuel is left to sit for months.
We continue to have good luck avoiding most of these issues with the use of Fitch Fuel Catalysts in everything from lawn mowers to snow blowers, and now have one in every gas can. These small cages with some sort of metal inside act like a mini-refinery, helping to keep the gas fresher, longer.