Blown Oil Filler Cap

By Dennis Santopietro

Question for Fix My Hog I started my 2005 XL1200R this morning, and in a few seconds, it blew the filler cap off the oil tank, and a large amount of oil started running down to the floor. I shut it off right away, then had to catch a ride to the DMV for renewal of my CDL. That took a while, but eventually I got back to look at the mess. The oil tank is still filled to the top with oil. The oil appears to have metal flakes in it. Bike has only 3776 miles on it, and oil has been changed on schedule. What do you think might have caused this? Guess I might need a shop manual or some such to guide me in dis-assembly and repair. Do you have something you might recommend? Got the Sportster DVD, very helpful, thanks. Any help you can provide would be appreciated. Charlie N.

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Fix My Hog Answers Hi Charles, There are way to many variables that could be the cause of a blown oil filler cap. My first guess would be a problem with the oil pump, either way the engine must be removed from the m/c and completely taken apart and cleaned. At this point you should find the cause of your problem. Have there been any recent modifications to the engine? Wrench Safe, Team FMH

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6 Responses to “Blown Oil Filler Cap”

  1. Mick

    Is your bike CARBY or EFI If it's carby I've encountered this sort of problem before on several occasions on earlier models, where the vacuum fails on the pet cock, and if the needle in the carby doesn't seat properly it may fill the crankcase with gasoline. Hence the engine will blow it back into the oil tank. Check and smell the oil and see if it's mixed with petrol? Check your gas tank see if you're gas level has dropped? To try and remedy this problem you first have to fix the fuel problem and then somehow drain the crankcase. Remember to replace the engine oil and filter. THIS IS ONLY WITH CARBY MODELS. I hope this helps, Cheers Mick (Brookvale Bike Centre Sydney Australia)

  2. Theron

    Dirt dinner nest in the crankcase ventilation.....?

  3. Danny Clay

    I recently purchased 1999 fatboy( last evolution motor)I'm thinking about synthetic oil instead of conventional oil. What are your thoughts?

  4. Bill

    Worked as a mechanic in a Harley Davidson Dealership for 20 years , seen this happen a few times and before you start tearing the engine apart , I have found that most times the oil tank is over full ,, when you check the oil level ,you should always check it at operating temp. Because oil expands when it gets warm , and you always check oil level on that particular bike with it standing straight up , not on the sidestand ,, therefore if you check the oil cold and on the sidestand , it will it will show low on the stick and if you add oil it will be overfull and heats up it expands and blow the cork out !!!! Just something to keep in mind before you start tearing things apart

  5. Kevin sale

    I have a 2oo1 roadking twin cam motor makes a lot top end noise has 30.000 on it this normal

  6. Todd Oesterreich

    "A large amount of oil started running down to the floor". "The oil tank is still filled to the top with oil."