kaw FD620 eng problems

Discussion in 'Mechanic and Repair' started by fancsco, Aug 26, 2005.

  1. fancsco

    fancsco LawnSite Member
    Posts: 2

    Gentlemen; I have 1300 hours on a deere/kaw 20hp horzishaft engine. I have noticed my plugs foul due to oil being blown into card via PVC tube. Both cylinders are at 165# copmression. No vacuum in crankcase but positive pressure.Found and relpaced pvc reed plate due to it was stuck on back plate not closing the hole. Thought for sure this was the answer. This ended up keeping oil from entering the carb But still positive pressure in crank case. Checked out my friends same setup, he has a noticable vacuum at oil dipstick. Any ideas why I do not have vacuum???? FYI. I did replace the camshaft and tappets at 1000 hours
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Have you rechecked your valve clearance since you replaced the cam and tappets ? This should be done every 300 hrs., What did you set the valve clearance at ? Both intake and exhaust should be set at 0.01 in.
    Are the plugs still fouling out since you replaced the reed plate ?
     
  3. fancsco

    fancsco LawnSite Member
    Posts: 2

    Thanks for the reply. I just rechecked the the clearence again. 3 of the four were at .01 one was at .016 I could here it tapping. It seems the oil blowing through the pvc tube has diminished significantly plugs are not near as fouled after an 1.5 hours of cutting. The question is the vacuum my friend has when you pull the dip stick compared to the positive pressure I have. Do you know what creates the vacuum? I thought it was from the Carb???
     
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Well, The engine vacuum is created as the piston travels up the cylinder, Then creates pressure when coming back down. So it's a back and forth process between vacuum and pressure,This is how a vacuum impulse fuel pump works on other engines. I suggested valve clearance because if the exhaust valves were set too loose they could close before the piston would reach top dead center and cause the remaining exhaust gases to be blown past the rings and possibly cause the pressure.
    I have seen in the past baffles break loose or carbon build up in mufflers and cause a restriction of exhaust output which would build up too much pressure in the cylinder and be blown past the rings also causing too much crankcase pressure. These are the only two things I can think of right now, But a better test to check the condition of a cylinder, Rings and valves is a leak-down test, This would tell you exactly what percentage of blow-by you actually have.
    Sorry I can't give you a more diect answer to your problem it's a little difficult sometimes to diagnose problems without seeing them first hand.
     

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