ricobandito

I have a troy-bilt walk behind mower with a 9HP engine. model 28B702 type 1143-E1

I am looking for some information on replacing a broken piston rod.

A little history...

At one point, it was leaking fuel into the oil, I eventually tracked it down to some crud blocking the needle in the carb. Drained and replaced the oil and fuel. Ran it for about two hours during which is ran great and then as I was mere seconds from finishing, it made a large clank and an abrupt stop.
Eventually, got brave enough to tear the engine down and discovered that the piston rod had shattered. May have gotten overheated from some remaining fuel contamination, I don't know, but I digress. Other than the piston rod, everything looked fine. I ordered a new piston rod, gaskets, and oil flinger. However, as I reassemble it, when I tighten down the piston too the crankshaft, I cannot get it to turn any more. I don't see an remnants of any type of bearing and did not see one in the exploded view. Connections on the old rod pieces so not show any spacers or shims. It would seem like I shouldn't leave any play in this connection, but it is the only way I can get the shaft and flywheel to turn.

What am I missing, do I need to grease the crankshaft? If so, with what?
Or is there some type of adjustment or shim I should be using? Once I get past this, I think I can make a full repair or an stunning conversation piece.

manic

Im not a real whiz when it comes to this, let that be known up front.
Although ive tinkered with all kinds of motors. On a car there are inserts
that fit to the rod, like two halves,two half moons, ie inserts. That is
the actual material that meets the crank, I would think that would need
to be used for a mower motor. With those missing that would cause
a loose condition...and torque being all goofy.

octaneman

Hi Rocobandito

Are you sure that you did not install the new piston and rod back-wards ? I've seen it happen where the rod was installed incorrectly and the engine wouldn't spin. Remove the piston and rod check for proper positioning, size , and reinstall. Check the rings to see if they are the proper size for the piston, lubricate the walls of the cylinder to ensure a smooth fit.

post your findings.
Good luck !

Basementgeek

First I don't think small engine rods use a 2 piece "bearing", like cars. Yes put some kind of lube, oil, on the connecting rod before assembly to the crank.

Did you use a torque wrench to tighten rod cap bolts? That is important. You should have a little play from side to side, but really none top to bottom.

Oil the cylinder as already said to.

BG

k2skier

BG is correct, the rod itself is the bearing. If the rod bolts are different sizes, (the manual says on "some" 28ci models) the small bolt, 3/8 hex head MUST be torqued FIRST to 160" lbs, all the way, then torque the larger 1/2" hex head bolt to 260" lbs. I did this once a while ago and I think I was able to loosen both and follow the proper torque sequence and I didn't have to replace the rod.