2-Cycle Engine Question


Old 09-04-04, 10:02 PM
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2-Cycle Engine Question

I posted the following under ATVs as well, but thought, as it is basically an engine question, someone in this forum may be qualified to answer...

Recently purchased a 50cc Polaris ATV/Arctic Cat for my son (only 3 weeks ago). The ATV stopped running, so we brought it back to the dealer. The dealer called us and told us they found gas in the oil reservoir and we must have put it in there. The ATV has a 2-cycle engine. The oil is introduced into the system via injectors. Has anyone else had this problem? Does anyone know how this could happen? The dealer claims they have never seen this before. The dealer did agree to fix the ATV at no cost to me, but I believe they still think we put the gas into the oil reservoir.

After getting the ATV back from the dealer, there's a noticeable decrease in speed/power. The dealer claims the ATV should get back up to par (speed) after a few hours of use. Is it possible this is true? If they "flushed" the system and replaced the spark plug, what needs to happen in this "few hours" span of time?

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Old 09-05-04, 07:21 AM
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It's been a few years (okay, decades), but I owned and rode several species of 2 stroke motorcycles. I'm guessing the oil injection is similar to the Yamaha 2 strokes I had. In this sort of set-up it is, in my opinion virtually impossible for gas to get into the injector lube oil tank unless, as the dealer suggests, it was put in via the filler cap. Only you would know if this was, or could have been, done.

I'm not sure I buy the necessity to run it for "a few hours" to get back to normal. With a fresh plug and fuel and oil in the right place, it should be "normal" as soon as it gets up to operating temperature. If indeed there was gas in the oil injection tank, I would be concerned that the engine had been run on an extremely low, if not critical, fuel-oil ratio which would have the potential to do all manner of damage to the engine.

Having said all that, I'm also not sure you are going to get any help from the dealer as regardless of what happened they will likely stand behind having found gas in the injector tank as an operated-induced failure.

Old 09-05-04, 10:37 PM
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I appreciate the response tow guy.

Well...it happened again. The ATV stopped working after a few hours and I can smell gas in the oil reservoir. Don't know how it's happening, but it is.

Old 09-06-04, 05:29 AM
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Lightbulb "Thinking Outside Of The Box."

Hello: William

One rare possibility may be a plugged vent hole in the oil injector tanks cap. If the vent hole where to be plugged, as the oil injector pump removes oil, air is suppose to replace the oil.

If the vent hole where plugged, a vacuum would be created in the oil tank. When the pump stopped, the vacuum in the tank would draw fuel backwards from the carb into the tank.

Much depends on where the injector oil is pumped into the engine. If it is pumped into the carb bowl, fuel could be drawn out of the bowl and back into the injector tank.

If this where to be happening, fuel would be present in the oil line after the engine sat for several hours. By this time span the fuel would be making it's way back into the injector tank. Or a slight vacuum could or should be heard when the oil cap is removed, as the air rushes in to fill the vacuum, etc.

Try leaving the oil injector tank cap slightly loosened so some air can enter during engine operation and running. Look for fuel flowing backwards into the tank after the some time when the problem appears and or fuel in the oil line to the carb.

May be an anti siphon valve in the oil line. Which may be stuck open, not closing, working correctly or defective in someway. All above are rare but possibile causes which may be overlooked and or not happening to others. So the dealer mechanics have never encountered such, as they claim.

Regards & Good Luck. Sharp Advice.
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Old 09-06-04, 07:19 AM
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the only thing i can add is if you have to keep the unit as is, disconnect the injecter and mix your own gas. injectors, especially in boats, cause unnessessary engine failures in my opinion.
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