Another suggested that the engine was overly compressed thus the added head gasket. I have never heard of this with our glow engines.                                                                             

      Hello:

      The last time that I flew my Twister I had a severe problem with what was described as detonation.

       It went like this.  When the engine went from a rich 4 cycle mode to a rich 2 cycle mode, the engine ran very erratically with a lot of noise and a drop in power  I adjusted the engine to a 4 cycle to where it would break into a rich 2 cycle when the nose was pointed up.  This appears to be a good starting point for all of my engines.  After a flight, I would make final adjustments to what suited my flying style. It was not the crackle of an overly lean mixture but a loud misfiring like I had never heard before when flying model airplanes.  A couple of people suggested that it was detonating the charge rather than burning it in a smooth way. One person suggested that the engine was running too cold and I needed a hotter plug.  Another suggested that the engine was overly compressed thus the added head gasket. I have never heard of this with our glow engines.

      The set up was:
 
      Engine-HP Gold Cup .40

      Prop_ 11-5 or 11-4

      Fuel- 11 castor 11 synthetic 10 nitro

      Temperature 88 degrees

      Glow plug- Fireball Med. Yellow

      Air speed- 5 seconds on 65 foot lines

       Tank- 4 oz. metal uniflow

      I added an extra head gasket when I returned home.

      I will try different plugs at the next flying session.  I have used different plugs in the past but I have not seen any change in the engine running characteristics.

     Has anybody else experienced this problem ? If so, what is the cause and remedy?

                     
                                                                                                                                 Tia,

                                                                                                                                 Frank McCune

     Hello Randy thanks for the reply.

     Here are a few answers to your questions:

     The engine was rebuilt with new bearings and ring.

     The engine has run great in the past.

     The fuel was a commercial mix that had 10% nitro and 16% 50-50 synthetic and castor oil added.  I added 6 oz of castor  to this mix to get the total oil content to 22%. Perhaps this is not enough oil.  I did not think that 6oz would bring the oil to 22% but the information came from a site in the internet.  It must be true. Lol  It seems to me that one needs 1.28 oz to equal 1 percent of a gallon.  This would come out to 7.68 oz. additional oil to equal a 6% gain if one removed 7.68 oz. of exiting fuel prior to adding the oil. Is my logic flawed?  The fuel was "new."  Perhaps the fuel did NOT have good or enough ingredients when purchased.  This is why I prefer to mix my own!

     The glow plug is a new Fireball med. hot with the yellow seal.

     The engine has always been a one flip starter.

     I have run this fuel in another HP Gold Head .40 and it performed very well.  I may use this fuel in other engines for a test.  This mix is reserved for the HP engines.  My other fuel mix is 10% nitro. and 28% oil that is 50/50 synthetic and castor.  I use this fuel in my OS .35S and.40S engines.  When I run my Fox engines .35 Stunt and .40 Stunt, I use a mix of 28% castor oil and 10% nitro.  I hope that the fuels are fine for their intended uses.

     In the future, I am going to try to mix only one fuel for all of my engines needs. Suggestions?

                                                                                                                           Tia,

                                                                                                                           Frank