(OT?) small engine crankshaft end play

[George]

I'm trying to revive an old Lawn Boy 2-cycle mower. It runs, but has a
ticking sound in the engine. Investigating, I find that the crankshaft
has a lot (1/8"+) of (vertical) end play.

I opened the case on a 2nd Lawn Boy engine. (It has other problems.)
All I find to limit the crank movement is a shim, between the crank arm
and the lower bearing. That seems to limit how far the crank can move
down, but I see nothing to keep it from moving up, other than whatever
constraint the connecting rod creates.

Question: is this much end play normal for an engine like this? And, if
not, how is the movement supposed to be constrained. It seems a lot;
but, maybe it doesn't matter, as long as the engine is oriented
vertically?

Thanks,
George

[hls]

"George" <gbec...@verizon.net> wrote in message
news:6fs9c79o6rej0d08k...@4ax.com...

> I'm trying to revive an old Lawn Boy 2-cycle mower. It runs, but has a
> ticking sound in the engine. Investigating, I find that the crankshaft
> has a lot (1/8"+) of (vertical) end play.

If I understand your description, you have both endplay
and worn bearings.

Shims are used to limit crankshaft endplay.

But if you have looseness in the piston and connecting
rod, about the only thing I can think of that will give you
that is bearing wear, both or either wristpin wear and
main bearing wear.

Does this one have the roller crank bearing?

[George]

Update: it turns out that the 'shims' (in the 2nd engine) are actually a
thrust bearing, with cute little needle bearings in the thrust face.
And, that bearing is completely missing in the engine with the large end
play. I have no clue how that could be. I know enough of that mower's
history to be pretty sure that it wasn't removed. But, I don't find any
debris in the case.

Anyway, that seems like it could be the culprit.

George

[Scott Dorsey]

George <gbec...@verizon.net> wrote:
>
>Update: it turns out that the 'shims' (in the 2nd engine) are actually a
>thrust bearing, with cute little needle bearings in the thrust face.
>And, that bearing is completely missing in the engine with the large end
>play. I have no clue how that could be. I know enough of that mower's
>history to be pretty sure that it wasn't removed. But, I don't find any
>debris in the case.

Monday morning production quality.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[hls]

"George" <gbec...@verizon.net> wrote in message >

> Anyway, that seems like it could be the culprit.
>
> George

Sure could. Thrust bearing is the proper word. Sometimes
they are shim like, other times they can be of the needle
bearing types. (Speaking in general, for a lot of IC engines}

Once, I rebuilt a 2.5 l L4 Pontiac engine, and when putting it
back together, crankshaft endplay was out of spec (loose). I
called the machine shop that did the work, and asked them
what would be the consequence and how to fix it...No
consequence, they said, so I put it back together as was.
Worked fine.

If you have slack in the wrist pin or crankshaft bearing,
I think you need to deal with it.

[Nate Nagel]

hmm.

Once upon a time I had a '67 Dodge Dart, with the vaunted 225 slant six
engine. The car was a horrific heap which I paid less for than I likely
have in my pocket now, but the reason that I popped for it was that the
body was mostly rust-free, requiring only one minor repair around one of
the torsion bar sockets, being from either NC or SC (I forget which -
and when I say only one minor repair, I'm not counting dents!) and the
owner proudly told me that it had a recently installed remanufactured
engine. It did run well once I finally got it started. I proceeded to
change all the fluids, fix the wiring and the carburetor that kept it
from starting well, replaced the LF fender from when the PO had run it
into a parked car (possibly because the brakes were so shot that the
rear wheel cylinder pistons were loose in the drums!) completely rebuilt
the brakes and had new tires installed. The flexplate broke shortly
after :( I unloaded the car on an acquaintance for even less money
after the second transmission died due to a busted hose, thanks to the
mechanic that I paid to replace it not informing me that the cooler line
had been patched with fuel line down under the car where I couldn't see it.

The new owner of the car informed me that after she tore it down, she
found that the "recently remanufactured" engine had about 1/4" of crank
endplay. Hmm, ya think that might have been why the flexplate busted?

So anyway my assertion is that at least based on my personal experience,
keeping the endplay at least close to spec is important to having a
reliable vehicle. The sad thing is that had the PO not got boned by the
reman engine, I would have likely had good, cheap, durable (if
unsightly) transportation for as long as I felt like keeping the thing...

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[hls]

"Nate Nagel" <njn...@roosters.net> wrote in message > The new owner of the

car informed me that after she tore it down, she
> found that the "recently remanufactured" engine had about 1/4" of crank
> endplay. Hmm, ya think that might have been why the flexplate busted?
>

Sure could have been the reason.. A quarter inch is a LOT of
endplay. Mine was not so much, but it was outside of spec.

[jim]

Isn't the case where the intake air flows?
Anything loose in there gets
sucked into the cylinder and out the exhaust.

-jim

[George]

On Fri, 18 Nov 2011 11:09:49 -0600, jim <"sjedgingN0Sp"@m@mwt,net>
wrote:

Well, it would have to be ground pretty small.

On further inspection, I think the engine that didn't have a thrust
bearing never had one, that it was designed that way. The space between
the (top and bottom) thrust surfaces in that crankcase was a little less
in that engine than in the engine with the bearing.

George