GMPheli
Posts: 144
Joined: 12/31/2001
From: West Bridgewater,
MA, USA
Status: offline
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I started flying planes about 28 years ago. Back then, mufflers were unheard of, full power starts were the norm, (we didn't know that they would actually start at idle), fuel contained only castor as a lubricant, and no one ever ran their engines dry or used after run oil. And guess what, we hardly ever had engine problems. When I started with heli's a while back, I showed up with Sig heli fuel which was 50 percent castor, and 50 percent synthetic. I was told not to use castor because it would cause all sorts of gumming and other problems. So I didn't. I ran Cool Power 15 percent with 4 oz. of Klotz sythetic per gallon. It ran fine. My first 60 size was a GMP Competitor with an OS 61 FSR. It was old, and I got it used cheap. I put new bearings and a ring in the motor. At the end of each day, I would empty the fuel tank, and then run the engine dry. I would leave the nistarter on, and spin it over until it all firing stopped. When I got home, I would remove the glow plug and put in after run oil (50 percent Marvel Air Tool Oil, and 50 percent automatic transmission fluid). When putting in the after run oil, I would always notice that the engine was "stuck". It would take a moderate amount of force to break it free, and then it would turn over normally. I also noted that the bearings never really felt smooth, always a little rough or gritty. I built my next heli, a PHI Huricane with an OS SFN and it acted just the same. So now I'm onto my next project, a Bergen Intrepid with an OS 61 SX that I have a brand new Performance Specialties AAC piston liner for. If you have never installed one of these, the fit is very very tight at TDC. PS recommends that you install it lubed with automatic transmission fluid, and turn it over by hand about 50 times. Then take it out, clean it and lube with Mobil 1 synthetic and then run it. I did the tranny fluid thing, but didn't have any Mobil 1, so I used the Klotz. It still turned over very hard at TDC, and if you stopped there, it would stick and take a huge amount of force to break free. In the mean time, after 3 cases of fuel through the Competitor, the bearings really started feeling gritty. I tore the motor down, and the rear bearing was shot. Not rusty, just really notchy. So I figure it's time to try something different. I got some Sig castor, and mixed 2 oz. Klotz, and 2 oz. castor to a gallon of CP 15 percent. Ran it in my Hurricane, same drill, run it dry at the end of the day. When I got home, guess what, the engine wasn't stuck, and the bearings felt smoother! So now I know that I am going to break in the SX in the Intrepid with castor. I pull the head off, clean out the Klotz, and coat the cylinder liner with castor. Reinstall the head and, OH MY GOD! It turns over SO much easier and smoother. It will still stick if you stop at TDC, but it doesn't take anywhere near the force as before to break it free. I broke it in with a gallon of Sig 10 percent heli, 50/50 castor synthetic. Since then I have run 2 gallons of Red Max 20 percent nitro with 18 percent synthetic that I have added 3 oz. of castor to. When you turn it over by hand, the bearings are silky smooth. I have an onboard temp gauge, and the back of the head is running at about 220 degrees. There is no baked on castor at all on the engine, but there is some on the bottom of the pipe. I figure this is because the pipe runs hotter than the motor. I recently pulled the head to try different head shims. I expected to find the top of the piston and head all black. Wrong, nice and shiny and clean. I think that the only time you will get baked on castor is if you get the motor too hot. I can deal with the baked on castor on the muffler. I will just cook it in antifreeze once a year. As for me, I will continue to use a castor sythetic mix in my heli's
Alan Angus
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