FlooredCOBRA

I just got back from the field and had a bad day. I only took my dust out to fly today and was hoping for a fun day. It all ended when the engine burnt up.

I fueled up as normal and started to crank it up. It would not crank. I checked the plug and seen it was gone so i swapped it out for a new one. I cranked up again and found it was way to lean and would not run. I kept on richening until I got it running good. But I did not make a few turns on the rich side which was stupid cause I always do. I was in a hurry to fly since wife came with me and was ready to go home the second my foot touched the ground at field.

Anyways I cranked revved it up and launched out of my hand. It was running good for about 1 1/2 minutes or so then i noticed the power sagging off. I should of right the cut engine and landed. But I was being stubborn and kept on going.

I made a few more passes and then the engine finally got even slower and back down to what sounded like 1/4 throttle. I cut engine off and came in to land. This is where i got sick.

I got the plane back to the table and flipped the prop over....no compression. Not good! I pulled out the plug and it was definitely ran hot. The engine did not feel hot but the plug showed it ran hot.

I pulled the head off the engine and seen the head was covered in a nasty black colored smut. The head felt as if it was sand blasted with a black substance. The head was very coarse instead of smooth like before. The top of piston was the exact same way. And the engine had a nasty smell to it. I checked the sleeve and it looked okay I guess except that nasty dark black color at top of stroke. Not good once again.

To top it off I pulled my pipe off to leek through rear of exhaust. There is where I found the nasty piston. I am guessing that somehow the element from the plug burnt out and fell in between piston and sleeve. My piston has a huge gash on the side of it from top to bottom. Guess this is where I lost my compression.

Other than that my Dust flew great!

Well guess thats the last time I try to rush things. And what makes it worse about it I knew better!!!

FlooredCOBRA

I'll post some pics as soon as i get it apart.

Razor-RCU

My Feedback: (50)

I have one that needs bearings that I am trying to sell or trade- Would you be interested?

james

FlooredCOBRA

Razor, thanks but I already posted my order for a new sleeve rod and piston.

here are the pics

FlooredCOBRA

you can barely see the little dent on the sleeve. here is the piston

FlooredCOBRA

another

FlooredCOBRA

last one.

you can barely see the ding on top of piston. i dont have the best of digital cams but it works

Cactus.

My Feedback: (1)

i had a kinda good day too...
got Project magnum running at last, had the 9mm carb, and a 8x8 prop. took off, nice but slow.
Tried a 7.?x8 i made from a tipped 8x8 got the rpm from 14.8 to 15.6 but it was slower.
Gotta try the venturi and get a better prop, having a Leo 37 Funfighter over take you isnt fun

pdxpaul

My Feedback: (1)

I know how you feel. I had a TT40 eat a plug element in an APRA race, and it looked like that. Switched to McCoy 9s. So far, so good.

Paul

FlooredCOBRA

Since I got the engine I have been using McCoy 9s and they been working good.
Just lately I been swapping out plugs to find something different and then noticed burnt out plugs. The McCoy's never fully burnt out like others did.
I tried Hanger 9 medium heat plugs and K&B plugs also to find something different. This is when my problems started.

I think after my piston sleeve and con rod comes in I'll stick with McCoys again. Never had any problems with them before hand.