Poor Gas mileage

[Ron Vroom]

I got my first snowmobile which is a 1986 Yamaha 340 Enticer which is nearly mint condition, runs great but I am going through about a half tank (3 gallons) of gas in 20 miles. Any ideas?

[panfishpounder00]

check the obvious first- leaks, can you smell an overwhelming amount of gas? check tank, lines, carbs. you said it runs great, but does it stay idling after warm up? i ask because i had a polaris indy trail touring dlx. that did the same thing. after checking for leaks and finding none, i realized my sled was not idling properly. went through carbs and adjustments, didn't help any. after hours of scratching our heads we took the top half of motor apart and found that a piston had melted down on one side, taking the ring with it and chewed the whole cylinder wall up. now what i descibed is probably a little extreme, but beware when you buy used. times are a little tight and people will try and sell anything that has some sort of value. hope this helps.

[Macgyver55]

If the motor "runs great" but it gets poor mileage the motor may be the wrong place to look. It could just be the kind of riding you were doing. First of all, what were you doing in those miles, lots of stop and go...or simply cruising? Were you on a groomed trail or fluffy snow?

It could also be a clutch problem.

Does the sled accellerate evenly all the way up to top speed?

What speed were you running at? If the clutch is dirty or sticking due to sitting a while it may not be upshifting properly causing the motor to rev too much at any given speed.

By all means check the plugs for color to see if they look all right and are not too rich, but also try different riding situations an see if that makes a difference.

[Ron Vroom]

I was cruising on groomed trails between 15-20 mph, not a lot of stops, flat terrain. I have thoroughly checked for leaks after sled sits overnight and while I am running, no gasoline smell or leaks are evident. Measured belt and it slightly narrower than new belt width and well withing wear range. I am going to spray the clutch with silicone and pull plugs to run compression test. After that, it is off to the Yamaha service dept.

[Ron Vroom]

You may have been on the money about the clutch. When I was going to spray the clutch with silicone, I note that one of the 3 nylon ramp steps or spacers was entirely worn away, so I replaced all 3 and will have to see if that makes the difference. You can tell we have a good snow year because when I went to the service dept. to pick up the ramp steps, the counter was about 3 deep with everyone apparently fixing their machines. Thanks for the help, that is what makes this forum so great!