Does the mineral oil lube better than synthetic/castor mix?

Rdabaghian,

I just converted anolder os 160 Gemini(serial number is in the 600's!)to spark as well. Istarted with 5% nitro fuel and OS F's to get the benchmark (17/6 @ 8200 RPM). Then Itore the motor down so I could drill and tap screw holes for the ignition pickup,replacing all the bearings in the process. Same fuel on spark yielded a 100 RPMincrease (old plugs or 30 degree advance?). I've got the old style air bleed carb so idle is not as spectacular as yours is. Then I mixed up a gallon of E85 w/ 20% Klotz and gave it a whirl. Fired right up andafter Ileaned out the high end about 1/2 turn and got 7800 on the same prop, 8000 was possible but I was worried I was running too lean. Idle was the same, cylinder head temp appeared to be higher as well and it does seem to be sensitive to needle setting. As a test when running nitro, I added a catch can to the crank vent to see how much oil ran through the crank case after an6 oz fuel run, it appeared to be a little less thenan ounce (my ratio right only goes to 2 oz so it was a big guess). After a similar run with the E85 mix I got only about 1/3 the oil in the catch can (due in part to a leaner needle setting I'm sure). That has me slightly concerned that the motor is not receiving enough oil to protect the vitals. I'm on the fence about continuing with the E85. I love the cost, oh and it smells so good when the motor is running. I've got video of the engine running on both fuels, once I get them uploaded I'll post.

If you are running 20% oil I don't think you have anything to worry about.  On a four stroke the oil is not very diluted so a little goes a long way.  As long as the bearings are getting a good coating I wouldn't worry.  I would check to see if the cam and rockers are getting good lube.  Also I might see if some petrol oil or castor oil will mix with the fuel and your synthetic as synthetic glow oils will not cling to the steel bearings as long as petrol or castor and that could cause rust.

When you are getting better performance from gas than glow it often means you were not using the best glow plug temp.  Often with four strokes the plug is too hot because of the worries that it will cool too much during the intake stroke.  However with 5% you may have needed a hotter plug or smaller prop.  The RPM indicates that possibly the prop was too small as most 4 strokes deliver their best power above 9000, some over 10,000, but I am not sure of the best RPM for this engine.  Also the engine would deliver the best power at the same RPM regardless of the fuel, I would adjust that by switching to a smaller prop.

Also since you have at least some oil that comes with the 15% gas I would actually lower the oil percentage, maybe 17% or so.  This would also increase performance a tad.  With all gas I would go with 12%, unless it has roller rod ends, then I would probably go with 37:1.

Here is the FT160 on E-85,

<dd>http://youtu.be/4czJnxjED3g</dd>

I think I missunderstood your prior post.  You got 100 RPM increase on glow fuel on spark, not pure gas, correct?  Not bad as you cannot get a glow plug perfectly dialed in on timing.

Nice catch, you are correct! That's what I assume as well. better timing control with the spark.