On Wed, 31 Dec 2008 16:17:10 -0800, stryped wrote:

On Dec 31, 5:43Â*pm, Terry wrote:
On Wed, 31 Dec 2008 14:43:28 -0800, stryped wrote:
I have an old cast iron techumseh engine I am trying to rebuild. (The
rod broke). I am putting it back together. Â*At the bottom of the
stroke I can hear a sound and there seems to be some slight "play"
where the rod does not move the poston any. I think the same at the
top of the stroke.

Is this a problem or am I being overly cautious? This is my first
rebuild and have learned alot but wanted to get your opinion. I have
a video posted he

http://www.youtube.com/watch?v=WG_kcd9VV3Q

This does not sound normal to me. Did you check the rod bearing fit
with plastigage? Just a guess, I am no engine mechanic. Terry

This engine does not use a "bearing" per se. It is just an aluminum rod
on the crankshaft.

Any place where metal rubs metal is a bearing. Period. It may not have
a _separate_ bearing, but its still a bearing, and clearances still
matter.

A slight play top and bottom is not only to be expected, it's pretty much
essential -- no play would mean no clearance in the big and little end
bearings, which would mean a trashed engine in the near future. The
bearing play gets magnified A LOT by the fact that the piston moves not
at all at true top dead center and bottom dead center - that's where the
'dead' comes from. So the crank has to move enough into its curve to
start pulling on the piston.

There shouldn't be much clearance there -- I'm not even going to hazard a
guess at what is right, but it's in the single-digit or low double digit
thousandths for each bearing.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html