Grumpy Monkey

My Feedback: (7)

I have a brand new TTPro 46 fresh out of the box and noticed at TDC, it has about a quarter inch of play in it and what feels like a slight scrub. I took the head off to investigate and pulled the sleeve. At TDC, with the head off, the sleeve will raise about 3/8ths of an inch. There arent any scrub marks anywhere inside the engine. I pulled the back plate off and it seems when the rod gets to almost TDC is where the scrub feel starts(piston hangs in sleeve) and when it hits a few degrees aft of TDC, it stops and rotates freely. upon further investigation,The piston actually hangs at TDC and the crank rotates over TDC freely and "grabs" again and pulls the rod through. It almost seems like the rod is a little to long. Now the question is, will this correct itself during break in as the sleeve wears, or should i just get a replacement. I have another TTPro and dont remember that one doing this.

Thanks in advance,

Warren

ChuckAuger

My Feedback: (12)

Pretty much normal for turning a new engine over dry. The play (with the head on) is just the crank rocking back and forth with the piston all the way up. Normal. It does the same thing at BDC but you don't notice it as much since the piston is not as tight in the sleeve at the bottom.

The fact that the piston pushes the sleeve out at TDC with the head off means you have a good tight piston/sleeve fit. It is normal and even desirable in a new ABC/ABN engine.

Don't spin it over cold and dry any more than you absolutely have to..this isn't real good on what sounds like a very nice fitting engine.

Grumpy Monkey

My Feedback: (7)

Chuck,

Thanks for the reply, I just wanted to make sure all was well.

I am gonna break her in this weekend then.

Thanks again.

Warren

ChuckAuger

My Feedback: (12)

Warren, if you want a look at the other end of the spectrum, look at This Thread about a Loose TT46

After reading that, you should sleep very well knowing you have a dandy engine on your hands!

And I'm not being facetious..I really do think your engine is going to be a dandy..

DarZeelon

Warbird Fanatic,

As Chuck wrote, the "play" you are feeling is the oil clearance of the crank-pin, in the connecting-rod bottom end. It is felt easily because the piston is in a bind fit at TDC.
At BDC (piston at the very bottom of its stroke) the "play" is larger, but because the piston is loose, it is harder to feel.

When you break-in this engine, do it as described in this thread:

http://www.rcuniverse.com/showthread...59&forumid=145

Don't listen to anybody telling you to run it blubbering rich, four-cycle, or you could damage your new engine.

Sincerely,,