lower steering stem bearing cup

[marky99925]

hi all
im doing the steering head bearings while my forks are away with maxton, all going fine until i came to drifting out the bottom bearing cup, the manual was fine up to this point but said there are recesses to get a drift on the edge of the bottom cup, well there isnt on my mk1 !
there was a slight lip all the way round the top and so i managed to tap that out ok. how did anyone else get the bottom cup out without buying/borrowing an expanding puller?
cheers
Marky

[Art]

I've never done steering head bearings on the SC58 but the ball race cup should protrude over its seating, never known them not to. Have you checked it with your finger tips? It may be the edge of your drift is rounded off or burred, it needs a good squared off edge to properly seat on the protruding edge of the cup.

[marky99925]

thanks Art
Yes, i felt for a lip both top and bottom with a finger once the stem was out, top was enough of a lip to knock it out okay with a round drift, on the  bottom i tried the round drift and felt for a lip with a blunt screwdriver also, just to get a start, there is a small gap where it seats and i read on an earlier post that someone used a washer on a long bolt with a couple of nuts to knock it out, presumably by getting the washer edge into that gap, now suitably refreshed by the beer fridge i'll have another look. I've got time as maxton will be another 2 weeks. i spoke to a local mobile bike mechanic of some repute who put me on to the expanding puller thing, worst case is he can stop by on tuesday and sort it out if no progress.
thanks again

[Art]

Now that you mention the washer trick I remember years ago having to remove a bearing cup using a length of M10 threaded bar as a drift with a pair of nuts holding washer, the washer was too thick until it was shown the grinding wheel to form a flat on one side.

Sounds as if you'll get this sorted, keep us posted on here.

[marky99925]

thanks Art, will do, luckily there's a great nut & bolt supplier 20 mins walk away, they have never failed to have what i needed, for the cost i'll buy the studding and bits and give it a go before paying the mobile guy. If it works i 'll try and post a pic of the resulting contraption.
Next is the getting the bearing off the stem without any butcherism !

[Art]

Here's what I have for use as a bearing press in conjunction with an appropriate sized ½" square drive socket. The specifications are M10 x 1.5 mm course pitch threaded bar, 4 off M10 x 1.5 mm course pitch full nuts and 4 off M10 x 1.5mm thick x 50 mm diameter washers. This set up should be good to press or drift the new bearings in place, add a M10 x 1.5 mm course pitch 30 mm connector nut in conjunction with a locking nut to protect the threaded bar at the end you're going to hammer if using as a drift. To double this set up as a bearing cup drift use a 20 mm diameter washer (get 2 or 3 so you have a spare) M10 nuts are 17 mm which means that a 20 mm washer will give you 3 mm to sit behind the bearing cup which should be enough to engage the cup without distorting the washer.

[marky99925]

Thanks for this detail Art, how do you use this set up as a bearing press? i was going to use the old cup and tap the new bearing down.

[Art]

That method works fine too.

Sorry for the confusion, I was trying to explain how that set up could be modified and used to drift the old lower cup out. I use that set up for press fitting the likes of wheel bearings and swinging arm bearings where you have access through the centre of the bearing. With the head stock bearings you can use it to fit the cups into the head stock tube but if you feel more comfortable drifting them in using the old cups go with that method. To get the bearing on the head stock stem use a drift against the inverted old cup.

[marky99925]

no problem Art, im pretty easily confused these days,  i saw a video of a guy using the drawbar method to fit the cups as you describe and i think im going to go with that, it looks easier to get a gradual level fit rather than tapping one side then the other. i suppose they will both work, each to his own etc.
 i think getting the old bearing off using the gradually thicker chisel down the sides of the stem idea  will be the more awkward bit.
Is that how you would get the inner race off? the ball bearing race itself just slid off.
Well that's monday taken care of !

[Art]

My preference is to drift off the old and where possible press on the new.

Wedging the old bearing off the stem by using thicker and thicker wedges with various flat bladed screwdrivers, cold chisels or whatever you have to hand is how I tackle the stem bearing. Use the 'wedges' in pairs one on each side of the bearing 180° apart to prevent the bearing rocking back on and to ensure all movement is coming off the stem, tap one side and then the other, then move both wedges a quarter turn 90° around the bearing circumference and repeat. The slower the progress the less likely you're going to damage anything, I've heard it said the difference between a professional and a grease monkey is how each wields their hammer.

I drift the new lower stem bearing on by placing the new bearing on the stem with the old cup above it so that the point of contact between the two is on the internal inside stem side of the bearing and use a drift and a light hammering action against the old cup to protect the new bearing and stem, think of this as a precision job with light taps of the hammer criss crossing your way around the circumference of the bearing to ensure it slides down evenly. There will be some rocking which can be kept to a minimum by only tapping the drift with light hammer blows just enough to move it fractionally.