OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines B&S blade boss removal from crank

Hi,

I've got a masport combo mower which had a damaged blade bar and boss carrier. I've removed the blade bar with ease but im having trouble removing the boss carrier. Any tips or advice on how to get the key out of the boss carrier?.

thanks

Hi romen, welcome to Outdoorking. Unless you post pictures of the blade boss and the shaft it's on, most of us will be guessing how it is attached. Best to show us what you are talking about.

A two leg puller and a long 3/8UNF bolt.

If it has busted the flange off it you could use a 3 leg puller.



Before you do anything, pull the plug out, get a helper, tip the mower over on the carby side, you watch, they pull away like mad, you are looking for a bent crankshaft.

If its bent, it is not worth fixing.

I used a car crankshaft pulley puller to remove the blade boss on my B & S, but I had threaded holes to screw into.

I found that if you wreck a main bearing and pull a ball out of the race, you can use this on the machined centre in the end of the crank. I found you can get heaps more pressure on the puller and it protects the end of the crank. Once you have a heap of pressure on; give the centre bolt a sharp hit with a hammer, if your lucky it will pop off! (if the boss is on a taper, as Grumpy says with out pic's we are guessing a bit....)

Fastgrass, I would prefer to avoid the process you have suggested. The ball bearing is very, very hard, and pushing against it will do horrible damage to the point on the end of the puller screw. Engines come and go, but tools last a lifetime if you treat them properly. If there is a centering recess in the end of the crankshaft, this fits the point on the puller screw and there should be no damage to either part. If there is no centering recess, just a plain flat end of the shaft, I prefer to use something along the lines of a piece of mild steel, with a drilled recess in it, between the puller and the crankshaft. If there is a tapped hole in the end of the crankshaft, I use a screw with a drilled recess in the head. Bottom the screw in the crankshaft, so there can be no damage to the crankshaft thread.

Ah Grumpy! we shall agree to differ a little here I think. I can and do understand your point of view (Re: quality tools etc.), I like your idea of the screw in the crank too (and can forsee trouble for the novice there too).

However, what prompted me was Rodeobob's Suggestion...

"A two leg puller and a long 3/8UNF bolt."

A bearing of "suitable size" not to damage threads / crank on the end of this will reduce friction considerably.
Friction is the enemy and limits the pressure that can be applied. (3/8" bolts are inexpensive and easily re-dressed if damaged, you will find that if you dress the end flat on a grinder the ball will bed in slightly) Although I use a 7/16" bolt myself...

Improving the pulling power (by reducing friction) of a home made set puller set up was where I was coming from..(and it makes a noticibly better)

I hope that qualifys my flippant suggestion a little better guy's.

Im not getting what you are on about.
Perhaps i did not explain propperly.


The shaft has a hole in it that is threaded to 3/8 unf. If its 7/8
If its 1" it will have a 7/16 unf thread in it.

The leading edge of the hole has a slight inwards taper too it.


The nose of the shaft on the puller will have some sort of point on it or a tapered insert.

Depending on your puller it may have a shaft thats fatter than the bore of the boss your are trying to remove.
Or in the case of my pullers, (a 4" stanley brand 3 leg & a no name 6" two/three leg) have a smaller shaft and a taper on the point that is too sharp to locate in the slight taper in the hole in the crank without posing a risk of damaging the thread.
I would rather avoid damaging the thread at all cost. Best way to do that is to fill it with a bolt.


So you then need a 3/8unf bolt of sufficent length that will thread a good distance into the hole in the crank to avoid thread damaging problems but then allow the full length of the boss to come off the crank.
Why the extra bolt length?, because if you want to reuse the bolt you need to avoid it bottoming in the hole and burring the thread on the end of the bolt and the best way to do this is too put a spanner on the head of the bolt and let it rest against a leg of the puller. Then when you wind the screw on the puller you can stop the bolt rotating.

That is then your friction point, where the taper on the screw shaft meets the bolt. Bearings still have friction points, and side loading a 'ball' bearing is not what it is designed to do. I think a torrington bearing is the one designed for this application.
Im not sure how you were using your one single ball bearing.


The bolt i have is about 2.5 or 3 inches in length and i have drilled a slight point into the top for the shaft of the puller to centre on. I would have easy used it 20+ times.
I used to use a 3/8 nut and hold the nut on the bolt head with the spanner, half on the bolt head, half on the nut. It worked ok but was a bit fiddly.


I have only ever had one boss that i could not get off with the puller. That was on a Rover super 4 20", the big boss with the 5/16 blade plate bolts. It was rusted solid. Im sure that was before i bought the pullers i have now.



Using a steering wheel type puller, You would need 3x long 1/4unf or 6mm bolts.
Im not so sure this would work on a tight one.


The other trick is to clean the shaft above the boss, lube it well then drift the boss up, clean the shaft where the boss was then slide it off.
This can work well.
Time wise, its easier to use a puller. Well thats what ive found.