Guys,
I recently (like Saturday) had my engine bind up and loose power after flying one normal flight. This is the Fox 35 in my El Diablo that I have been flying for about 7 months. The engine has a tongue muffler and I have been running fuel with 26% castor 3% syn and 5% nitro. Because of the tongue muffler I run a light load 9x6 old Top Flite prop at about 9650 rpm release. The motor has run very nice with a classic 4-2-4 break.
This past weekend we finally got a decent day and I was hoping to get some good practice in before KOI. The first flight was normal and I got the cob webs out of the pilot. The engine had a slight crackle to it (has done this since the first flight), I had a K&B long idle bar plug which is one of the hottest. I had done some research and found that the Fox RC long idle bars is suppose to be a medium heat plug, so I thought I would give this a try to pull back the timing a bit. Once fueled I went to start and it popped back, loosened the prop. When I when to start again it was very tight near the top. I pulled it through a few times and it seemed to loosen, so we fired it off. Power was way down but steady. Next flight I went in on the needle 1/4 turn and the flight was flyable but soft, the engine was steady with no crackle. When I went to fly again the engine was tight again and I decided I needed to look inside.
Once on the bench I removed the plug and slowly turned over the engine as I removed the bolts thinking that maybe something caused the case to twist and cause the bind. None of the bolts caused anything and the bind was still there. I pulled the head and saw the vanish. I thought the 3% synth would keep it clean, it didn't. I'm going to go to the 50/50 mix going forward.
Has anyone used a few tanks of high syn oil fuel to clean out varnish? How well did it work?
Best, DennisT