Cox Tee Dee .051
#2
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It has a lot of wear. It will poke through soon. The ball socket was likely not reset over the years, and/or there was not much oil in the fuel. You can get a replacement still from Cox International. An .049 one is fine too. The .051 piston is a bit heavier, and there is a bit more stress on things.
#3
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If you get a reset tool you can try a reset and it may flatten the head back allowing you to continue to run the stock piston. I am not sure they carry .051 pistons.
Sometimes they will get in old stock still in the package or will refurbish parts for resale.
Sometimes they will get in old stock still in the package or will refurbish parts for resale.
#4
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It might just be a bit poorly machined, in the Estes era anything would go out to customers...
The reset tool should have a recess in the center to allow for these kind of errors, and to avoid deformations to the piston itself.
The reset tool should have a recess in the center to allow for these kind of errors, and to avoid deformations to the piston itself.
#5
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I looked at the full-sized photo - it looks like the ball may be peeking through the top of the piston at this time. If that's the case, it's time for a new piston/rod/cylinder. I had a TD .049 many years ago that did that. I was out of Cox fuel so I went to the lhs and he sold me a jug of 25% racing fuel. He told me "Oh, yeah, it's got plenty of oil". After ruining a TD and a Queen Bee, I checked further and the fuel had 14% oil, mostly synthetic. Lesson learned the hard way - at least 20% oil, at least half of that castor.