MXA talked to Honda on several occasions about gasoline migrating through the fuel injector's throttle body and ending up in the crankcase oil (not the transmission oil). In the June issue of MXA, we ran Honda's first explanation, which was more of an admonition for 2009 Honda CRF450 owners to drain and change their oil at regular intervals.

After our first query was printed, MXA was flooded with a host of letters from CRF450 owners reporting that their engines would actually fill up with so much gasoline that it would overflow from the dipstick hole.

We requested a more detailed explanation from Honda, and they sent us a technical bulletin to their dealers that said, "The fuel injection settings on the 2009 CRF450 are designed to provide maximum performance by delivering a fine atomization of fuel at the earliest opportunity, even before the intake valve begins to open. At normal operating temperatures during race conditions, power, throttle response and acceleration are maximized. However, during low engine temperatures (such as warm-up and easy riding), fuel can condense and a small amount of unburned liquids can end up in the engine oil."

Honda's recommendation is to not snap the throttle during warm-up. The MXA wrecking crew agrees that injected fuel is much more atomized than carbureted fuel, and that a small amount can slip past the rings. But, in most reported cases we aren't talking about a small amount. And, con founding the experts, is the fact that many owners claim that their crankcases filled with gas while the bikes were sitting in the garage for periods as short as ten days. Honda doesn't believe that gasoline can get from the injectors to the engine oil when the engine isn't running. MXA isn't so sure.

There is no clear-cut answer to the problem, but there is a clear-cut solution. Check your oil constantly; smell it to test whether it has a gas odor; change the crankcase oil regularly; if the bike sits for any period of time, check the oil before riding the bike; if the gasoline content exceeds 15 percent of the crankcase volume it can cause damage; and, there have been reported incidents (not on CRF450s) of explosion caused by gas collecting in the crankcase. Caveat emptor.


Factory riders often become syn-omous with the brand of bike they ride. Broc Glover is closely associated with Yamaha, but he raced a KTM at the end of his career. David Bailey is remembered as a Honda rider, but he rose to fame on a Kawasaki. This month's quiz rider became famous on one brand and solidified his reputation on another, but in this photo he is riding a third brand. Name the rider, the bike, the place and the brands he rode.

How does fuel get from the fuel injection system to the crankcase? No one seems to know.

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