A strong mixture of Lye and water (or "Mr. Muscle" oven cleaner) works well too and is easier to obtain than hydrocloric acid. I've used it already with no effect; my crank journal is clean steel.
Tight Crank on New 10HP Briggs Rod
- Thread starter Go-Rebels
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A strong mixture of Lye and water (or "Mr. Muscle" oven cleaner) works well too and is easier to obtain than hydrocloric acid. I've used it already with no effect; my crank journal is clean steel.
Hydrochloric acid is sold as Muriatic Acid in any farm store, or Walmart, or Pool supply store.
bertsmobile1
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Plastic baking tray / dish with just enough acid in it to cover the journal by 1/2" left in the sunlight for a couple of hours to warm up then slip the crank in slowly
10 minutes to 1/2 hour will be fine wash very well with hot SOAPY water then rinse in hot water, boiling is best because the crank will dry quickly and it MUST BE OILED the second it is dry or it will rust.
Neutralize the HCl with chlorine.
Muriatic acid is a commercial grade of Hydrochloric acid before it is distilled in glass.
IT is generally pale green to yellow because of the residual iron left over from the production.
Getting rid of the iron is very expensive which is why Muriatic is dirt cheap & Hydrochloric is a lot more expensive
10 minutes to 1/2 hour will be fine wash very well with hot SOAPY water then rinse in hot water, boiling is best because the crank will dry quickly and it MUST BE OILED the second it is dry or it will rust.
Neutralize the HCl with chlorine.
Muriatic acid is a commercial grade of Hydrochloric acid before it is distilled in glass.
IT is generally pale green to yellow because of the residual iron left over from the production.
Getting rid of the iron is very expensive which is why Muriatic is dirt cheap & Hydrochloric is a lot more expensive
The problem is that my crank measures a little bigger than standard after being cleaned and that the original rod ID was obviously larger than the standard replacement rod ID that I can purchase today. I suspect that Briggs may have produced some out-of-spec cranks and had a batch of larger-than-normal rod bores produced to fit the cranks. It's certainly cheaper to ream out a connecting rod a little bigger than reset a crank in a centerless grinder and turn it down a little. Maybe Briggs always had a small supply of bigger rods at hand to build rather than rework.
I'm not entirely keen on shimming the rod cap mating surfaces because the surfaces are milled with a small step to center the cap over the rod. When I add a shim across both stepped surfaces I not only raise the cap relative to the rod (good) but I also create an interferance at the step and therefore slightly bend the cap putting the inside of the cap into tension (bad). Given that these connecting rods are marginal by design in the first place, I hate to add further stress to the cap but that might be the only way to get the clearance that I need.
I'm going to chemically clean the crank once again and polish using 1000 grit sandpaper then take it to a local machine shop and have them measure the journal OD again. Measuring with a 6" caliper is not the optimum method; I need a 1-2" micrometer which I do not have.
I'm not entirely keen on shimming the rod cap mating surfaces because the surfaces are milled with a small step to center the cap over the rod. When I add a shim across both stepped surfaces I not only raise the cap relative to the rod (good) but I also create an interferance at the step and therefore slightly bend the cap putting the inside of the cap into tension (bad). Given that these connecting rods are marginal by design in the first place, I hate to add further stress to the cap but that might be the only way to get the clearance that I need.
I'm going to chemically clean the crank once again and polish using 1000 grit sandpaper then take it to a local machine shop and have them measure the journal OD again. Measuring with a 6" caliper is not the optimum method; I need a 1-2" micrometer which I do not have.
bertsmobile1
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It does not take much alloy on a journal to make it tight so give it the acid treatment as others have suggested.
A single high spot will cause it to bind and dragging a bit of wet & dry over the journal does not work unless it is backed onto something flat & solid
It will just stretch over a 0.005 high spot.
I preferred the caustic soda bath over the acid bath , but both will strip any alloy off the journal.
After that a polish with a brass brush usually brings them up perfect.
A single high spot will cause it to bind and dragging a bit of wet & dry over the journal does not work unless it is backed onto something flat & solid
It will just stretch over a 0.005 high spot.
I preferred the caustic soda bath over the acid bath , but both will strip any alloy off the journal.
After that a polish with a brass brush usually brings them up perfect.
I will chemically clean the journal again this weekend and try to refit.
I don't think I can get past a 0.005" high spot. Did you mean 0.0005"?
I need enough clearance to get the rod to spin on the crank when cold, and tightened to spec, else I obviously can't pull start the motor.
I'm not keen on shimming the rod cap. If after chemically cleaning he crank I'm still tight then I'll just send the crank back and order another.
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I guess its to small for your local machinist to grind it to the correct size?