Fuel for testors .049

Hi everyone this forum is great, I'm still learning to post messages.I remember someone saying castor in a testors would foul spring starter,do I just increase syn lube.

It was a factory recommendation found in one of the later instruction sets, The discussion is somewhere in this forum. The Rotomatic spring starter, an amazing development on these engines (frictionless in forward motion but engaging in rearware motion) is hard to free up once clogged up with dry aged Castor oil residue.

What you lose is Castor oil protection against a lean overheating condition, which led to excessive wear and potential engine damage.

Bob @rsv1cox has developed a successful methodology in freeing up these gunked up engines by soaking them in Chemtool carburetor cleaner dip. His methodology seems the best by not doing a full disassembly of the engine, which is easy to damage, not designed to be disassembled like other engines.

Our recommended fuel for Coxes is 20% oil, which is 50/50 Castor oil and synthetic oil. This differs from earlier recommendation of 100% Castor oil fuel of the 1970's and prior. (I used a lot of the old stuff.)

The "Cox" blend mitigates frequent disassembly of the Cox engine to devarnish the cylinder, which I did religiously after each couple month's flying, when I used the 100% Castor fuel. (I was devarnishing about every 5 - 6 weeks when flying daily. The engine wouldn't develop its full RPM scream, which means Castor build-up shellac.)

Most of my Testor .049 engines were later acquisitions, which were mostly test runs. However, there are others in this forum who have extensively flown with these engines and even adapted a method to mount the normally unmountable Testors "pipe bomb" donor engine from a wrecked and destroyed plastic RTF plane.

My gut level feelings are that most of these really gunked up Internet engine buys with frozen starters were engines that were heavily flown on the RTF's (ready to flies) of the day using fuel other than Testors. I haven't yet received a really gunked up engine in my Internet auction acquisitions, which probably means that these were donor engines from one shot flights. I also have two engines I bought new marketed for use in kits.

Use of "Cox" blended fuel with synthetic Castor oil blend and a shot of afterrun oil or say, Marvel Mystery Oil in the starter assembly after a day would be my methodology, but that's just me. (I live with my consequences. )

You might locate these threads by using the "Google search" versus the "Inside" search, which does a slightly better job.