tough one to call really i had to lean one engine and richen another
check this out its very good to help learn to tune your engine Nitro Engine Tuning 101 - HeliFreak

Because of the lower viscosity I had to put my 50 in a notch or two. I also use the link millerman posted above

Martin

It would need to be a little leaner, start as it is now and then click by click closing the main needle and checking the motor temp on the base plate. fly around then check again and adjust if needed, should be warm but not burning your finger.

Nice to read this post as I have about 2 more tankfuls of normal 20% left and my next is 20% SLV.

I also noticed that the engine seemed to be running a tad richer when I went flying last week.

Tony,

Leave setting as they are at first and fly a couple of tanks it will be a tad rich probably then lean off a tiny bit as required. Set the idle if indeed it needs changing at all, probably will not, set top neaddle next with full bore climb out, stop and hover then another full bore climb and stop to hover it should come straight off the pipe to the hover desend and land and it should go striaght to idle no hunting around. When top and bottom set work on the middle to give good transition.

The setting will not have moved much from where you are and I suspect if you leave as is it will be fine, check the backplate temp it should never be too hot to touch, you should be able to keep your finger on without burning.

Not sure what engine you are running but in testing OS55 we found the following to good:- High needle 35 clicks, mid needle 41 clicks and bottom factory +5 degrees. If its an OS91HZ then nearer to 51, 56 and idle at factory setting. These numbers are impacted by the pipe you use and the weather to a lesser degree, hot, damp, cold etc.

But the basic rule is start where you are know and it will be very close, you will be impressed with the difference in throttle response and it will run cooler overall, sound smoother and idle more sweetly. I use it myself.

Andy

Many thanks for all the information, hope to get out this afternoon and have a couple flights.