loose connecting rod to piston fit

Hi David,
Welcome to the forum!
Tons of info here and and lots
of helpful members.
To start, type in "piston reset" in the
search bar at the upper right.
Tried it myself after reading your post, and
it came up with plenty of good reading.
I'm sure some of the gang will chime in too, and
that's what it's all about.
Again, welcome!
Bob

Typically you want a ball socket fit with play of 0.002"-0.010". If it is any looser than that, I would suggest a reset tool.

Regards, Matt

Welcome to the forum

"Resetting" the piston is a normal maintenance practice on these motors. It takes a little practice, but you should set the piston so there is almost no play in the socket.

if the piston socket is left unchecked, it will start to hammer away at the top of the piston, and this happens:

(Picture from here)

There is a Piston reset tool blueprint on the Yahoo 049 collectors group if you don't want to buy anything and want to make your own.

daviddiag wrote: I have several old baby bee and golden bee engines that have loose piston to pin fit. They all well run in. How much looseness is acceptable? I have seen staking tool for sale. Is it worth it?

The above answers are right for where the rod and ball socket connect inside the piston. If by 'pin fit' you mean the drive pin on the crank is loose in the con rod at the bottom, that's a different story. But since there's not much you can do about that, if that's the case, just run them.If the pin breaks off the crankshaft, it most likely wouldn't bust anything else in the engine.

Welcome to CEF, glad you found us.
Rusty

I am truly impressed with this forum. My questions were all answered. I will be getting a reset tool. look forward to participating in the future. Thanks guys.....

daviddiag wrote:I am truly impressed with this forum. My questions were all answered. I will be getting a reset tool. look forward to participating in the future. Thanks guys.....

Glad you like it here.

Remember its: tap, tap, tap; not bang, oh, crap! lots of light taps and use a piece of glass for base, some of the anvils can distort the piston.

David, I agree that resetting the ball/socket should be routine maintenance.
However in the interest of full disclosure you should know that this is a controversial subject. One school claims that under normal operating conditions of our stock engines the piston is always forced downward against the rod, i.e., the rod never pulls the piston down and therefore the rod/piston slop has no effect on operation and is inconsequential. One fellow ran some rather convincing tests that seem to support this. He was investigating the effects of lube (synth/castor blends) and his measurements showed that even in the extreme failure illustrated in the above photo that all the wear was on the top side of the rod/piston interface and was caused by lack of lube. No wear was measured on the bottom side of the socket thus eliminating hammering as the cause.
On the other hand I know from experience that excessive slop WILL cause hard starting. (I believe this IS an accepted fact by both schools).
In regard to the reset tool, IMHO the anvil shape is more critical than the punch. The original Cox anvil has a ¼ in dia raised section in the center so that the piston is supported directly under the socket only. A flat bottom anvil (or any other flat surface used in lieu of an anvil) can cause the piston to mushroom unless you are very careful.
Al

Puffie40 wrote:"Resetting" the piston is a normal maintenance practice on these motors. It takes a little practice, but you should set the piston so there is almost no play in the socket.

if the piston socket is left unchecked, it will start to hammer away at the top of the piston, and this happens:

(Picture from here)

There is a Piston reset tool blueprint on the Yahoo 049 collectors group if you don't want to buy anything and want to make your own.

wow, looks like you shot it with a 'bb' at the piston

Please read:
http://coxengineforum.forumakers.com/t753-the-revised-2011-gibeault-mouse-race-program It's great info on performance as well as proper care and feeding of these cool little engines.

Here's what Paul says about resetting the socket:
"Using the wrong piston holding fixture can result in a mushroomed head piston (totally ruined), so I don’t use one. Clean the socket area with acetone or brake cleaner first to remove the oil. Then lay the piston on a heavy piece of ½” plate glass or flat thick piece of steel (something quite dense like a vice). With the tool in place, tap with a hammer, rotate a bit, tap again and continue, checking often until all excess play is removed."