ASK THE MXPERTS: CAN GASOLINE GET INTO THE CRANKCASE OF A HONDA CRF450?

May 11, 2011
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Dear MXA,
    I have gas in the crankcase of my Honda CRF450. When I check the oil, I find gasoline in it. Has MXA had any issues on your test bikes with gas in the engine oil? Can I ride my bike without fear of it blowing up? What can I do?

    This is one of the big mysteries of life, but it is true that gasoline can and does seep down into the crankcase oil of some CRF450’s (it was especially noticeable on 2009 models, but has happened on the 2010 and 2011 models also). You need to keep an eye on it. Here is a simple trick that every CRF450 rider should use?before you ride your bike, especially if it has been sitting for awhile, smell the oil. Remove the dipstick and smell the crankcase oil. If it smells like gasoline, you should change the old oil. The odor of gas is easy to tell. MXA had a 2009 CRF450 that had so much gas in it once that it spilled out of the filler hole. MXA has talked to Honda several times on this matter and Honda, while aware of the fact that on some bikes gasoline has migrated to the crankcase (not the transmission), says that there is no danger, as long as you drain and change your oil at regular intervals. They think the problem is caused by riders blipping the throttle when the engine is cold (right after starting) and there was a bulletin sent out to dealers.

    We don’t think this is the cause. We have had CRF450s that get gas in the crankcase oil every other race (and gets even more gas in the oil when it sits for ten days or so when we aren’t blipping the throttle during warm-up). Gas in the oil means that the oil is diluted. That is not good for engine reliability, but additionally, there is some small degree of danger related to a crankcase full of gas.

     We have had several fuel-injected CRF450’s over the years and only had a major gas-in-the-oil problems with one of the bikes, a minor problems with a second bike and no problems with the others. We had the worst case in 2009 and it seems to have lessen with the ensuing years. Be aware that you won’t know you have a problem unless you check the oil. The only known cure is frequent and constant oil changes. This appears to be a Honda-only problem, but we since every brand uses the same Keihin fuel injection system it isn’t necessarily limited to one brand.

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