OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Remove blade boss & running engine with no weight

Hello all...

I was given a "Viking" mower with a Briggs & Straton Quantum 40 engine. The previous owner snapped the blade plate right off the boss, which sheared the head off one of the smaller bolts that anchor the plate to the boss.

I've removed the shattered blade plate. But I want to remove the boss so I can drill out and remove the sheared bolt. How do I remove the blade plate boss and the little keyway piece from the shaft? Do I hammer the boss upwards (towards the pull-start)? Or do I have to somehow "pull" the boss downwards (away from the pull-start)?

So what method do you guys use to remove the boss - and is there anything I should be aware of before I go belting it with a mallet? (And how do you refit it and its keyway?)

Also... I know you cannot run a two-stroke engine with the blade plate removed - ie. It needs a load to run/idle. Is this also true for a 4-stroke?

The reason I ask is, the engine is quite good and I'm thinking of making my kids a simple go kart. I was thinking I might just fit a small pulley onto the shaft. Then the kids pull down on a lever to tightens a fan belt against the pulley to move the car forward.

So would the 4-stroke engine idle with the belt loose until they pulled the lever to pull the fan belt tight?

Thanks for reading.

I understand Briggs & Stratton disapprove of running the engine without more of a flywheel than is provided by the magneto & fan assembly that is commonly called the flywheel. I think you'll have a bigger problem than that in trying to use a vertical crankshaft engine in a go-cart, though. You can't run the mower engine with its crankshaft horizontal - it wouldn't lubricate, and of course you'd have to redesign the fuel tank and carburetor.

You can remove the blade-plate mounting boss, but I wouldn't do it just to remove the broken bolt. I'd drain the oil, then set up the motor and baseplate upside down under the drill press so I could drill down the center of the broken bolt and remove it with an ezy-out. Before going to that trouble, though, I'd try just using a very small chisel or centerpunch to see if I could unscrew the broken bolt. Bolts that weren't bottomed in a thread usually require very little torque to unscrew them, unless they have rusted in.

One way to get the boss off I have found if you do not need it anymore is to start carving into it with a grinding disc (watch out for the crank shaft tough!

The heat from the grinding is usually enough to make it come off for me.

i done one similar a while back by cleaning above the boss with emery tape till the shaft was shiny clean, then knock the boss upwards onto the cleaned up bit, then emery up the the bottom piece, plenty of crc and hammer it down wards, all goes well it should come off cheers micka

A variation of Joe's method works for removing really tight or rusted-on inner rings of broken ballraces, too. Use the angle grinder carefully to groove the ring transversely as deeply as possible, then support the shaft, put a cold-chisel in the groove, and smack it once sharply with a heavy hammer. The ring is very hard, so it cracks through. Then you can pull it off easily with an ordinary gear puller. I have only had that fail on inner rings that had spun on the shaft so much they had blued up and friction-welded themselves to the shaft. In those cases I had to grind a second groove on the opposite side of the ring to the first one, and crack it through with a chisel there as well. Then I laboriously chiselled the welded-on pieces of ring off the shaft, and polished up the shaft as well as I could. Pretty desperate stuff, but necessary if the shaft is expensive or irreplaceable.

Micka, your method does work of course, but its a bit rough on the main bearing ballraces. I'd start by cleaning the shaft below the flange, then try to pull it downward with a gear puller.