I have an old cast iron techumseh engine I am trying to rebuild. (The
rod broke). I am putting it back together. 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

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. 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

On Dec 31, 5:43*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. *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.

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

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

On Dec 31, 5:43 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. 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.

Probably on the order of .002-.004 on the big end - looser is better up to
a point with a splash lubrication system . Check the fit with plastigage
with the piston about halfway up the bore , if it's too loose the rod cap
can be filed or lightly sanded to close it up a bit . BE VERY CAUTIOUS if
you need to sand or file - a little bit goes a long ways when you're talking
thousandths . You must also be cautious to take an even amount off both
sides - the mating surfaces MUST be flat and parallel with each other .
--
Snag
every answer
leads to another
question

On Dec 31, 7:15*pm, "Terry Coombs" wrote:
Tim Wescott wrote:
On Wed, 31 Dec 2008 16:17:10 -0800, stryped wrote:

On Dec 31, 5:43 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. 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.

* Probably on the order of .002-.004 on the big end - looser is better up to
a point with a splash lubrication system . Check the fit with plastigage
with the piston about halfway up the bore *, if it's too loose the rod cap
can be filed or lightly sanded to close it up a bit . BE VERY CAUTIOUS if
you need to sand or file - a little bit goes a long ways when you're talking
thousandths . You must also be cautious to take an even amount off both
sides - the mating surfaces MUST be flat and parallel with each other .
--
* Snag
* every answer
* leads to another
* question- Hide quoted text -

- Show quoted text -

Sorry, I di dnot mean to infer that there was no bearing. It is just
that it seems alot of people mean a "main" bearing separate of the rod
when you say "rod bearing".

I measured the crank journal and it was within specs of my book. The
rod is brand new. I went ahead since my last post and put the cam in.
The sound is much less pronounced. Where do you think I should go from
here? I did not quite understand what you meant about "filing" the
bearing.