Briggs Intec broken connecting rod

[Captn Cliffy]

I have a co-worker who ran his lawn tractor with low oil, and the connecting rod broke. B & S model-type 31C777-0226-E1; code 040319ZD. There is a fair amount of scoring on the crankshaft journal for the rod. The piston and cylinder bore don't appear to be damaged. My question is, how long do you think the engine would last if he just cleaned up the crank journal a little with emery paper and slapped a new rod on? I'm thinking since the rod is aluminum, any scoring on the crank journal would wear out the rod soon. There is no undersized rod available, so you can't turn down the crank. The only other option I see is replace both the crank and rod. Thanks for any thoughts!

 

[scott47429]

im going through the same thing with my parents John Deere how ever i didnt even take it apart to see how bad it is other then pulled the plug to make sure the piston wasnt moving and its not im just going to replace the engine for them but to answer your question if the crank is real bad it wont last very long i wouldnt think so if it was me i would replace both or replace the engine

 

[motoman]

I guess "do not repair" is common , at least with Briggs. I tried to buy a valve guide...NO ,must buy head. You cannot ignore oil and cooling on the Intek (and other Air cooled). They will fail. But if you understand and give TLC they will work. (Talking from experience only of my formerely troubled Intek)

 

[chance123]

DO NOT use emery cloth to clean! You do not want to remove "any" metal off the crank journal. You "might" find that the crank is not scored at all. Best thing to do is to take an old bottle that once contained oil. Cut it about half way down and cut V shapes on both ends. Fabricate it so you can rest "that" crank journal in it. Get yourself some Muratic acid (used for swimming pools). With that crank journal submerged in that bottle, fill the bottle with the acid so it completely covers the journal. The acid will eat the aluminum and leave the steel crank virtually untouched. These clearances are very critical and emery cloth might take some steel along with the aluminum. I have found more than once that using this method, the crank had no scoring whatsoever.

 

[Captn Cliffy]

Thanks, chance123! I'll definitely give it a try. The co-worker who was using the tractor pulled the engine off, drained the oil, removed the sump, and gave it to me. I haven't had time to disassemble any further, but from what I can see of the crank journal, I was wondering if the "scoring" was aluminum from the rod. How long should I soak the crank journal in the muratic acid?

 

[chance123]

Thanks, chance123! I'll definitely give it a try. The co-worker who was using the tractor pulled the engine off, drained the oil, removed the sump, and gave it to me. I haven't had time to disassemble any further, but from what I can see of the crank journal, I was wondering if the "scoring" was aluminum from the rod. How long should I soak the crank journal in the muratic acid?

The aluminum con rod is "much" softer than the steel crank. MANY times I have seen (after the acid treatment) the crank journal in perfect shape. It depends on how long it was abused.
I would soak it for an hour, pull it out and wipe it. If you still see some aluminum, repeat until it is gone. If the crank is scored, it will be very evident.

Am I spelling "aluminum" correctly? According to this board, I am not.

 

[motoman]

yes correct spelling and a good trick with the acid