OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Quantum crank

On this quantum I have the crank has end to end play of around .020(.5mm).On another block I have it has the same issue but more play by about 1mm.I pulled the second one down a couple of weeks ago and couldnt see what the cause was,no wear marks or such so put it into the too hard basket.But now that I have another with the same problem I would like to know what the problem is?

The crankshaft end float or play on the side valve Briggs engines is set by the position of the crankcase cover. Over time, the end of the main bearing (which is pressed into that cover) can wear, particularly on vertical engines, increasing the play. Briggs made more than one thickness of gasket, and required the overhauler to select a gasket to get an allowable end float. If there is too much wear to correct by reducing the gasket thickness, a special shim must be fitted to take up the slack. Here is the procedure for aluminium engines with plain PTO bearings:

Thanks grumpy,when I measured I used a digital venier caliper butted up to the end of the crank and crankcase just to get a ball park figure.So now knowing that it is a repairable problem in your opinion is it viable?The rest of the short block looks healthy but I am not keeping the mower for myself.

I don't know if the spacer washers are available in Australia. Though they certainly are in the US, the postage charges are ludicrously high:
http://www.ebay.com.au/itm/BRIGGS-A...M-PART-/400558048287?hash=item5d431ec41f

If I were trying to repair it for my own use, I would make a washer from steel sheet, reproducing the radius on the inside edge rather crudely. However I would not make such a cobbled repair if it were for anyone else's use. I rather enjoy making experiments and altering what I have made as often as necessary until it finally succeeds, but I would not subject anyone else to that process.

Fitting the washer is quite simple, it is just a matter of removing the crankcase cover and slipping the washer over the crankshaft then reinstalling the cover.

For what it is worth, there are many, many side valve Briggs engines operating satisfactorily with substantially more crankshaft end play than Briggs specifies.

Yep I am on the same line of thinking.I have re-assembled both the mowers (so I dont lose track) and put them in the think about it line.It seems that each of the Quantums I have has the same issue so I might try and get a more accurate measurement and see what i come up with.With a more accurate reading I might be happy with what I see.If I dont like what I see I'll play around a bit when time permits. Thanks grumpy

Thank you for raising it, wotwozthat. Excessive end-float of the crankshaft becomes a problem if it is greater than the lateral clearance between the connecting rod and the crankpin. Typically that lateral clearance is in the vicinity of 1.1 mm for a Honda engine, but I don't know the figure for a Briggs engine. Honda does not usually specify an allowable crankshaft end-float, but it does for one of their OHC engines, and the figure is 0.1 mm to 1.0 mm. So, if you are interested in researching what you can get away with on a Briggs engine, you can use a feeler gauge between the side of the connecting rod and the side of the crankpin's bearing area, with the connecting rod pushed as far as it will go toward the opposite side of the crankpin's bearing area.

I'll close this thread.