While recently riding my 2000 Polaris RMK 800 I smelled gas. I looked under the hood, and saw nothing leaking, but it seemed to get really bad mileage.
Back home, I removed the airbox and the carbs and noticed gas seemed to be coming back out of the carbs (somehow) and is draining out of the drain holes at the bottom of the airbox. The only sign of gas is a little outside of the airbox below the carb boots, with most of it inside the airbox. I find no leaks in the carbs, hoses and fittings, and the function of the floats seems to be OK.
I asked a dealer-guy for his advice, and he stated it is normal to have some gas coming back into the airbox. As it doesnâ€™t leak real noticeably nor while running, I thought he might be right. He did state a boost bottle would likely help some, so I am buying one. Any comments or suggestions?
I guess most every two-stroke fitted with carbs does this to some degree, and tend to agree that a small amount of fuel residue inside the airbox is pretty normal. Pretty much every airbox Iâ€™ve ever removed smells like gas and there is fuel residue present. This is one of the indications (traditional) carbed two-strokes are rather wasteful when it comes to fuel. There is a pulsing airflow that is moving in and out of the engine, a pumping action, and when the airstream is entering the engine it is pulling fuel from the carbs and into the engine. During the reversion, the pulse carries some of this fuel with the air and yes, some of it falls out of the air and ends up in the airbox.
The fact you smelled the fuel is of concern, prompting you to inspect the system. This is always wise. As long as youâ€™re convinced the fuel system is functioning properly with no leaks, you have exercised caution on the side of safety. Yes, it is pretty normal for a carbed two-stroke to leave fuel residue in the airbox.