fb460v question

Discussion in 'Mechanic and Repair' started by Scenic Lawnscape, Apr 8, 2004.

  1. Scenic Lawnscape

    Scenic Lawnscape LawnSite Senior Member
    Messages: 288

    I have a fb460v on a older bobcat w/b , well the problem is i have a leak in my gas tank (slow) and i went to change the oil today and noticed that the oil smells like gas and is very "watery" from gas in the oil. What would cause gas to get into the oil. The engine runs strong and doesnt smoke. is this something major??


  2. LynyrdSkynyrd

    LynyrdSkynyrd LawnSite Member
    Messages: 179

    Their are several things that can cause gas to enter the crankcase.

    Blow by:
    Worn, cracked piston rings. Worn cylinder. The combustion chamber does not seal during the compression stroke and this allows some gas to "blow by" the piston and collect in the crank case oil. Depending on how bad the parts are worn will determine how fast the oil gets deluted by gas.

    Intake valve:
    Worn or damaged valve/s or valve seals can cause blow by.

    If the engines floods. The cylinder can become full of gas. Then when you crank the engine. The excess gas is forced past the piston and rings causing blow by.

    Warm up the engine and change the oil. Run it for about 5 to 10 minutes and change it again.

    After the second oil change. All of the gasoline should be out of the system. Run the engine as you normally do for a day. Checking the oil often. If you notice that the gas is mixxing with the oil. Then you need to find the cause and repair it.

    I must say that a small amount of gas getting into the crank case is normal. But it should not be so bad that you can smell it or have it raise the oil level.

    I am very anal on oil changes. When I have an engine without an oil filter. I change the oil at the first sign of it changing color.

    I run 10W30 Castrol GTX in all of my gasoline engines that have a dip stick. I beleive that my engines start and run smoother and cooler with it, than they do with just a straight 30 weight. i have had engines that were 10 to 12 years old and look as clean as a new on the inside when using Castrol oil.

    NCSERVICE LawnSite Member
    Messages: 206

    Top gun, your float is hanging open or your fuel cap is not venting forcing fuel past the float needle in to the engine when its not running. Best guess.
  4. heymisterbill

    heymisterbill LawnSite Member
    Messages: 6

    Some aircraft engines have a cold weather start system where gasoline is injected into the crankcase or the oil tank, for dry sump systems, to thin the oil for easier cranking.
    I am an A&P mechanic and I can tell you that installing something on an aircraft that would have the slightest potential for any type of damage is unheard of. The fuel is quickly vaporized.
    Perhaps there is dirt in your needle & seat or float needs adjusted. This could cause your fuel to seep into your intake overnight.
    Anyone have a schematic for the throttle and governor linkage on the FB460V? Or a picture.
  5. rockytopp

    rockytopp LawnSite Member
    Messages: 120

    I am do not know this engine but If it has a fuel pump that is directly run by the camshaft it is possible the diaphram has a hole in it. I have found this problem for years in other engines. As the gas passes over the diaphram thru the check valves. Just a thought.
  6. barnard

    barnard LawnSite Senior Member
    Messages: 618

    You've got a bad float, a bad float valve assy(sometimes called a needle and seat) or debris caught in the float valve assembly.
  7. DIYJohn

    DIYJohn LawnSite Member
    Messages: 3

    Heymisterbill, I have a repair manual for the FB460V. Let me know if you don't get the info you requested. I can scan and email the info. BTW, I'm not a pro in your business. I happen to own a Snapper walk behind that I'm restoring. I know this forum is for Pro's, but if I can help I will. jkelly8870@adelphia.net
  8. heymisterbill

    heymisterbill LawnSite Member
    Messages: 6

    Thanks. I was just about to use your email address but then I thought that this forum really could use some useful pic's.
    A scanned picture or diagram of the Governor/throttle along with the recommended procedure for reseting the Governor and idle/mixture, would be a great addition to this site.
    If for some reason you cant upload to here you can email them to me and I will give it a try.
  9. MJLsLawnCareNmoreLLC

    MJLsLawnCareNmoreLLC LawnSite Senior Member
    Messages: 840

    I bet its the float in the carb hanging up. It happens quite frequently. Rebuild the carb and change the oil.
  10. DIYJohn

    DIYJohn LawnSite Member
    Messages: 3

    Heymisterbill, I scanned the pics from the manual and emailed them to you directly. Hopefully it worked. Feel free to post them on this forum to help others.

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