Also, the Shoestring runs better on the 10% nitro 22% 50/50 castor/syn. than it does on the 5% nitro 28% 26/2 castor/syn.
This engine likes 22-25% if you don't run it too lean.. The engine that likes 5/28 is the Enya... that is one engine that will run on anything.. no nitro to 20 % nitro.. Dukes Fuel and Super Fuel.. it ran great.. I have one Enya 35 that I flew in 1970-73 ..gallons through it.. I even ran it with a broken front intake lug.. fuel spilled every where but it ran great.. I didn't know better and didn't have any money ..
I remember flying RC in the winter and found that switching to more nitro really helped.. 15% and a little less oil. I was running the old OS 25s from the 1980s. Some of my small engines wouldn't even start by hand, I suspect the Castor was the problem , you can also make a cover that retards cooling out of a tin can, drill some 1/8th" holes in it so not to completely block all cooling, attach with a spring. This is a kin to covering the radiator with cardboard in sever winter conditions. .. when I was a kid, we would pour fuel on engine and light it on fire to warm them up.. I never owned a starter until about 2001.
The Max S 35 is one of my all time favorite engines.. I also switch to a thinner prop.. I use the Master Airscrew wood 10x6 and the TF 10x6 or 10x5 but another good prop is the Black plastic Master Airscrew 10x6 worked real well.. I sure wish I could switch props on the LA 46 the same way.. I love how the APCs run but I hate the look and they are a real bear to fit on a spinner..
The other issue I have had with this engine is burnt castor oil on the Head fins and cylinder.. running a new engine on half synthetic/half castor helps .. I stick with all castor on engines that have been run that way.. used ones from ebay can be a gamble... because of RC fuel..
Also if you have an early one (shiny case) with the black rubber exhaust plug don't leave it in the engine.. they get hard and deteriorate.. they are a mess to clean up once they do this..
I use a tongue muffler on one but am using the original Slipstream Muffler on my Dolphin .. a great little muffler but a bear take off and on in a hurry.. I also use a Dremel and "gut" the inside for less back pressure..I believe this engine runs better on a tube muffler than a tongue muffler. currently studying connecting rods .. a guy could sell 'em if they were made.. other than that, drilling the bottom crank bushing so more oil gets to the bushing it a good thing.. I only do it on new motors.. I am glad these engine are still plentiful ..
Jim