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Fixer of Broken junk
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Connecting rod installed incorrectly or you forgot to install the oil slinger/dipper on the bottom of the connecting rod or both.

The oil hole in the big end of the connecting rod Always faces toward the Camshaft.


Go and buy a gallon of Muriatic Acid from your local hardware store. It usually costs $10-$15 for a gallon. Last time I bought some it was $12.99.

Important steps. Use Rubber Gloves when handling that stuff. Do this Outside.
Do NOT Breath the Vapor that comes off of it especially the strong vapor created by the Aluminum being disolved. It will not burn skin on contact but it will if you let it on for very long. Muriatic Acid is 100% Water Soluble so it can be rinsed off of skin with just plain tap water.



Pull the crank out of the engine and let it soak in the acid for about 1/2 of an hour. You might have to rinse it off and put it back in for another 10-20 minutes but it will not take long for the acid to completely desolve the aluminum.

After it is clean you will need to Neutralize the Acid on the crankshaft to prevent it from Flash Rusting which can happen Very fast. A minimum of 6 heaping tablespoons of Baking Soda desolved in 1/2 a gallon of warm water works good. Let the part soak in the Baking Soda solution for 15-20 minutes.

Then you can rinse it off and dry it and polish the journal with 2,000+ grit emery cloth cut into strips.

Since the rod did not break you have a very good chance of cleaning it up and reusing it. If a connecting rod breaks, the bolts can hit the journal which can easily destroy the journal.
 

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Fixer of Broken junk
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5,020 Posts
The strange thing is that the oil slinger was installed correctly. When last rebuilding the engine the rod would only go in one way with the oil hole facing away from the crankshaft. If I put it in with the oil hole facing the camshaft then the rod hits the camshaft. Also the Briggs and Stratton manual showed that the oil hole goes away from the camshaft and if installed incorrectly the rod will hit the camshaft. Am I missing something here? Thanks for the advice with the crank. I will definitely give it a try although the rod seems to be badly damaged is that still able to be cleaned up? Thanks for your help!
That makes no sense unless the connecting rod was bored off center. Sounds like a defective connecting rod was the fault.

The rods with the top hole should always face the camshaft. We had another member on here that rebuilt one and it blew up just a month ago. He also had the connecting rod installed the wrong way.


Here from the Briggs Shop manual. Alignment tabs face away from the Cam. Hole goes towards the cam.

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Bicycle part Font Auto part Metal Bumper
 

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Fixer of Broken junk
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Ya flat side has the oil hole.

Your Piston might be turned around the other way. Try rotating the piston if yours is not marked with the notch. It does make a slight difference because both the wrist pin in the piston and the main journal on the rod is slightly off centered away from the camshaft when they are install correctly.

I've had a bunch of tractors with those engines and completely rebuilt 2 and threw a fresh set of rings in another 1 but I'm no "Expert" on them.

I had an issue with an aftermarket piston that did not have the notch. Those are usually marked down by the wrist pin but I did buy a $89 cheap Chinese rebuild kit years ago that had no markings on the outside of the piston. It had an arrow cast into the bottom of 1 of the Wrist pin bosses on the bottom side of it. Didn't see it until after I tried to install it.🤬


Looked though part numbers in my old mid 1970s shop manual and Briggs doesn't list a .010 oversized rod in it. They do list a STD and a .020 oversized rod. Where did you find a .010 oversized rod? Do you have a part number for the rod?

Just curious because I have an old Sears SS15 tractor coming that is going to need a rebuild. It might need a bit of work on the crank because it has a load of hard earned hours on it. It's much easier and cheaper to polish .010 off of a journal than it is to machine and polish .020 off.

There was another thread about 2 months ago? on the forums that someone else installed the rod the wrong way. I looked for it last evening but could not find it. His rod seized and broke and screwed up the journal. I can't find the darn thread but his looked really nasty. Said that it ran fine and then started loosing power and it shut off abruptly.
 

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Fixer of Broken junk
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Just read in my service manual that if the Cam is out of time the rod will hit. Never considered that option but that is a possibility.

This is out of my older 1977 Briggs service and repair manual in the rebuild section.

Font Parallel Schematic Pattern Paper


Handwriting Book Font Writing Paper


Strange, with the piston installed with the notches like that the oil hole faces the Block.

This is the NOS Briggs .020 rod that I linked to just below. This is confusing the heck out of me. Alignment Notches on Both sides? Or is that Flash on the 1 side?

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Those are cheap Chinese aftermarket parts that Norman from isavetractors sells. He supposidly Cherry pics the parts that he sells but I've had fitament issues with his Rings and several of the carburators that I've got off of him were complete garbage. you can usually get the same exact parts directly from China off of ebay or amazon for 1/2 of what he charges.

Had to find an older parts manual because my newer parts catalog only lists the STD rod.

Parts manual here https://www.gardentractortalk.com/d3/downloads/monthly_03_2012/b937685c74a95406f09924925d760321-.pdf
#29 on page 11
.020 rod is Briggs & Stratton part# 390306

NOS .020 rod for $100

Aftermarket rod from someone that I've bought parts from. $48 never had a problem with his stuff even though they are all aftermarket parts. I rebuild a couple old saws and kohler engines using there parts.

My manuals do not say anything other than the 1.314" crank pin reject size for a STD crank.

AaaaaaHaaaaa. Just found this. For .020 crank grinding.

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Hope that helps. I may have been wrong about the oil hole facing the Camshaft?? At this point I am Very confused. It's been 8 years since I rebuilt the 16hp briggs in my old Montgomery Wards/Gilson and even longer since I had a crank out of 1.

In a Single Cylinder Kohler K series engine which I've literally rebuilt countless dozens of from a K161 to K341s , the oil hole Definitely faces the Camshaft, it even says to rite in any Kohler repair manual. Makes it ALOT simpler to rebuild an engine if you have Clear instructions.

They say that they will only fit on 1 way without hitting the Camshaft If the camshaft is timed correctly. I would go with that lol.

1 of the Teeth on the crank gear has a flat tip on it. Mark that tooth with a paint marker or something so that it is clearly visible. Line that tooth up with the Dot that is machined into in the Cam gear. Done.
 

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Fixer of Broken junk
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There is 1 used Crank on Ebay out of a Simplicity if you want but it's $100 and it is Just out of spec by .001 for a New STD crank. Should be fine to use with a new STD rod though. Journal looks nice and clean. It is out of a gear drive Simplicity so it has the 1" output shaft. Hydros used a 1 1/8" output shaft.


Would it be more cost effective to spend $100 on a usable crank and a new STD rod VS having your original crank machined again?
 
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