Briggs & Stratton Crank

[lefty]

Briggs

124T02 1227 B1

Code: 0811459

This is off of a craftsman mower. It was serviced by someone who forgot to put oil back in. The owner ran it and it seized. I took it apart and was shocked to find the piston and cylinder in good shape but the rod was messed up where it met the crank journal.

The machine has been given to me and I thought I'd get my first rebuild under my belt. It looks like the rod has been discontinued as a separate part but I can get the piston, rings and rod for about $50.

My question has to do with the crank. There is some obvious transfer of aluminum on the journal but it feels smooth. I can barely catch a nail in one spot. I saw some videos on youtube with people sanding out scratches with oil, fine sand paper and a long sneaker lace.

Is there a chance I can salvage this crank? A new one is about 70-90 bucks.

Thanks
Lefty

[Fulltilt]

Probably. Some have used straight muriatic acid dabbed on the aluminum transferred spots to remove it. The ol' stainless toothbrush helps things along.Then polish with some crocus cloth.

[Arkie]

I would think about checking the crank/rod clearance with plasti gauge in 4 90 degree places with the new rod.
If you have a micrometer check the crank to make sure it's round, but plasti
gauge will tell. You can do this with the crank and rod on the workbench out of the block.

[RoyM]

Plastiguage won't help much without a clearance spec. Briggs does give the minimum crank pin diameter, if it is still within spec, round and smooth you should be good to go.

[Fulltilt]

I would think about checking the crank/rod clearance with plasti gauge in 4 90 degree places with the new rod.
If you have a micrometer check the crank to make sure it's round, but plasti
gauge will tell. You can do this with the crank and rod on the workbench out of the block.

Plasti gage ? How is that going to work on a " messed up" rod big end and crank journal ?
Not to mention what Roy said.

[lefty]

Does anyone advise against fine grit sand paper, oil and a flat shoe lace?

[Arkie]

I would think about checking the crank/rod clearance with plasti gauge in 4 90 degree places with the new rod.
If you have a micrometer check the crank to make sure it's round, but plasti
gauge will tell. You can do this with the crank and rod on the workbench out of the block.

Plasti gage ? How is that going to work on a " messed up" rod big end and crank journal ?
Not to mention what Roy said.

He asked this: Is there a chance I can salvage this crank? A new one is about 70-90 bucks.

What I was referring too using plastigauge is to check the clearance with the new rod after he has tried to clean up his old crank rod journal.
He indicated he is trying to remove the aluminum transfer from the old crank journal and re-use the crank with a NEW rod.
I would check the crank throw with a micrometer and make sure it's not goose egged and check the clearance instead of just throwing a new rod on a cleaned up journal and hope for the best. Should be easy to check the rod clearance on the work bench. He did not mention if the end of the journals at the flywheel and output shaft ends of his crankshaft had aluminum transfer that transfer is from the block and he needs to abandon all. He mentioned the engine was operated with no oil in the crankcase.
He can read how to use plastigauge and check the clearances at 90 degrees to the first test for the second test to compare clearances and make sure the crank journal is round and with specs.
He can review how to use plastigauge on you tube. I use plastigauge quite often to check rod and main bearing clearances.

I'm wondering why you say that the new rod and old crank clearances CANNOT be checked using plastigauge after he attempts the aluminum transfer removal?
Its a single cylinder L head Briggs engine and no needle or roller bearing involved.
I would not touch it with a 10 ft pole to rebuild to sell unless I was going to sell it to a brother in law.



Respectfully.

[Fulltilt]

I would think about checking the crank/rod clearance with plasti gauge in 4 90 degree places with the new rod.
If you have a micrometer check the crank to make sure it's round, but plasti
gauge will tell. You can do this with the crank and rod on the workbench out of the block.

Plasti gage ? How is that going to work on a " messed up" rod big end and crank journal ?
Not to mention what Roy said.

He asked this: Is there a chance I can salvage this crank? A new one is about 70-90 bucks.

What I was referring too using plastigauge is to check the clearance with the new rod after he has tried to clean up his old crank rod journal.
He indicated he is trying to remove the aluminum transfer from the old crank journal and re-use the crank with a NEW rod.
I would check the crank throw with a micrometer and make sure it's not goose egged and check the clearance instead of just throwing a new rod on a cleaned up journal and hope for the best. Should be easy to check the rod clearance on the work bench. He did not mention if the end of the journals at the flywheel and output shaft ends of his crankshaft had aluminum transfer that transfer is from the block and he needs to abandon all. He mentioned the engine was operated with no oil in the crankcase.
He can read how to use plastigauge and check the clearances at 90 degrees to the first test for the second test to compare clearances and make sure the crank journal is round and with specs.
He can review how to use plastigauge on you tube. I use plastigauge quite often to check rod and main bearing clearances.

I'm wondering why you say that the new rod and old crank clearances CANNOT be checked using plastigauge after he attempts the aluminum transfer removal?
Its a single cylinder L head Briggs engine and no needle or roller bearing involved.

So, what you're saying is for the OP to BUY a new piston/rod a$$y to check out a suspect crank using plastigage. As that would be you preferred method, the OP would have to spend good money first, right? Not a particularly smart move, when the crankpin journal can be checked for dia. , egg, etc BEFORE spending any money, as was mentioned previously, correct?

And where did you read THAT at in my post ???
I said nothing about a new rod , I was clearly referring to the OPs OLD rod.

My take is the OP doesn't want to spend big bucks on a trashed motor.

Personally, I've never used plastigage on a lawnmower motor...never will. They don't use shell bearings, the rod/crank is either good or trashed, pretty simple, eh?

[KE4AVB]

Personally, I've never used plastigage on a lawnmower motor...never will. They don't use shell bearings, the rod/crank is either good or trashed, pretty simple, eh?

It isn't like it can't be done when the old nla rod is still intact but bearing area is worn. All you looking for is about .001"to .002" clearance. And btw that crankshaft journal can be turned to .020" under if needed.



This what you get when you're friends with a machinist. He just save me from having to buy a $350 JD carburetor that I got a bushing made for.

Personally I wouldn't be putting a lot funds towards this motor and instead obtain a new replacement for it.

[RoyM]

Briggs does not give a spec for rod clearance so what plastiguage would you use? The crank is either within spec or it isn't. If it is over the specified minimum install a new rod and be happy. If it isn't it's a new crank or engine. The L-head engines are no longer available from Briggs, adapting an ohv is probably not worthwhile unless you have a donor mower. If you really want the project replace the crank if garbaged.