I have a 5 hp Briggs seems the metal piece that keeps the connecting rod bolts tight didn't.It didn't come apart but it was loose wondering if is salvageable. Or if not are the 5hp cranks interchangeable ? This one is a 1978 I believe was hopin to use it for a minibike for the grandkids .
Is my crank toast ?
- Thread starter dshot59
- Start date
you can use 1000 grit wet or dry sandpaper cut in a strip the width of the crank's flat surface, oil it up and wrap it around the throw then wrap some shoestring around the paper about 3 turns then you can go back and forth to polish the surface. after a minute or two remove the paper and wipe it down then you can see if it is badly grooved or not.
If you can catch your fingernail in the scoring it is probably "toast". Ideally, You want the crankpin surface to be like a mirror finish. and ole4's technique is a good one to achieve that, however, you do not want to have to take off very much or the crankpin will be undersized. While scoring can be a concern, another one is checking to see if the crankpin is excessively worn (diameter). Get yourself some (red) "Plastigauge" (Google it and how to use it if you are not familiar) at your local auto parts store and check the crank to rod clearance. Anything in the .002-.004" range is acceptable with .003" being ideal.
Sidebar comment: Is that rod cap as badly scored as it appears in the photo? What does the other 1/2 look like?
Michael
Sidebar comment: Is that rod cap as badly scored as it appears in the photo? What does the other 1/2 look like?
Michael
Sure, that will solve THAT problem (at not much cost), but the bigger concern is your crank. By the looks of that rod cap the oil has been REAL dirty and the crankpin could be worn undersized. Briggs 5Hp cranks (with the "mini-bike" PTO end) are becoming hard to find. You really should check the rod to crank clearance as I mentioned above.
***EDIT- Another way you can check your crankpin for excessive wear (and if you have an ACCURATE micrometer) is to measure the diameter. If it is .9963" or less Briggs considers this as " reject" and you need a new crank. Make sure and measure it 2 ways at 90 degrees apart as cranks can wear oblong (egg shaped)
Michael
***EDIT- Another way you can check your crankpin for excessive wear (and if you have an ACCURATE micrometer) is to measure the diameter. If it is .9963" or less Briggs considers this as " reject" and you need a new crank. Make sure and measure it 2 ways at 90 degrees apart as cranks can wear oblong (egg shaped)
Michael
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After seeing the con rod and the end cap scoring, the discoloration and grooves seen on the crank journal might
actually be aluminum that was transferred or deposited there under extreme heat. A low oil situation is the likely
culprit or that and oil that has lost its lubrication qualities..(overly dirty oil that has turned to sludge).
If that is the case, one trick is to apply muriatic acid to the crank journal to remove or dissolve
the aluminum there instead of grinding or sanding it off. The acid will not harm the harder
steel of the crankshaft. After that, some light metal polish might be in order. You want it clean
and smooth.
Cleaning the crank journal and installing a new connecting rod assembly will get it operating again.
I second the motion of measuring it to be sure it is within Briggs specifications.
actually be aluminum that was transferred or deposited there under extreme heat. A low oil situation is the likely
culprit or that and oil that has lost its lubrication qualities..(overly dirty oil that has turned to sludge).
If that is the case, one trick is to apply muriatic acid to the crank journal to remove or dissolve
the aluminum there instead of grinding or sanding it off. The acid will not harm the harder
steel of the crankshaft. After that, some light metal polish might be in order. You want it clean
and smooth.
Cleaning the crank journal and installing a new connecting rod assembly will get it operating again.
I second the motion of measuring it to be sure it is within Briggs specifications.