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..The sun is out!...Let's go FLYING....False alarm...
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Heli-Log 6:21:2012

Posted 06-21-2012 at 01:51 PM by rcnut

I want to test fly the 3 heli’s I added to my DX8, however, the weather here in the Midwest has been hot…90+ degrees, and windy…35+ MPH. So this was a good time to start working on the Compass 3D+ motor…a Thunder Tiger 53…modified. I removed the muffler from the motor and expected to see piston debris in the exhaust port, but I didn’t. Now I’m really curious as to what happened to this motor.

As soon as I could get the motor out, I opened it up and found nothing! What? No metal shavings / debris (FOD) of any kind. It wasn’t until I moved the piston down, and removed it, that I found what happened. I found small bits of exhaust gasket RTV in the bottom of the motor. Apparently I applied a bit too much gasket sealer to the exhaust port and muffler. Some of it broke off and was lodged along the side walls of the sleeve and piston. This eroded the cylinder sleeve and piston causing a drop in compression.

I ordered a new cylinder sleeve, piston & ring, both bearings, and a connecting rod. The sleeve, piston, & ring were damaged…of course. However, the bottom of the connecting rod was sloppy loose on the crank pin. Now I’m kind of wishing I bought a new crank. The front bearing was bad; it leaked and was gravelly feeling. The front bearing came out very easy…after applying some heat; however, the rear bearing didn’t want to come out. So I cleaned it really well and checked it out, added some oil to it and it feels smooth, very smooth.

I installed the front bearing and crankshaft, removed the boss pin and assembled the new piston, connecting rod, and ring. I made the same modifications to the sleeve as the old one, and then put the motor back together…well for the exception of the backplate. Next is to modify the carb adapter. I bought this motor used, and the stock carb was replaced with an O.S. carb. However, the grub screws won’t hold the carb anymore, so I will drill two new holes, tap them and use socket head screws. This will give the carb 4 screws to hold it in place.

So time will tell how well this will work.
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