YS 91FZ problems still

[Jerry Stebbins]

Sounds like you may have a heating problem that is vaporizing the fuel in the regulator. Running that long without extra cooling could be causing it. Had a 1.20SC that did it both on the ground and in the air. We and YS fought it for several months and finally found a tight bearing heating up-case got hot-vaporized fuel-same symptoms. Check to see if you are getting any signs of hot spots on the case when it happens.Watch for when the bubbles just apear, shut it off and check. If you let it run it will get leaner-hotter-same symptom but hotter all over.
Jerry
  ----- Original Message ----- 
  From: Dean & Melissa Williams 
  To: discussion at nsrca.org 
  Sent: Thursday, December 16, 2004 1:40 AM
  Subject: YS 91FZ problems still


  Hi 
  This motor was running great at last after my idle problems thanks to you guys (fix them by sanding the rocker cover) was getting 9000 rpm top end and 2100 rpm bottom end with A 14x 10 with a20/20 this is a new engine. 
  The plane has still not been in the air. 
  the engine has had about 5l of fuel through it. 
  The problem now is it starts runs up and tunes out to 9000rpm and runs for about 1 to 2 min. and then starts to surge and goes off tune with air bubbles in the fuel line from the regulator. 
  Please help as I am from the outback of Australia and have no assistance out here. 

  Thanking you 
  Dean (outback OZ) 
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