Steering head bearings

[tomo]

Just in the process of replacing the head bearings on my 1979 GS750, but could use some advice. I ordered a set of All balls bearings, but have been scratching my head a bit !. I assumed the top and bottom races are the same, but the packaging for each bearing have different numbers. The set number is 22-1005, but one bearing pack has on it 99-3505-1 while the other is 99-3508. The dust seals both have the same number 33-1006. Just made me wonder if one bearing is for the top and the other the bottom, or whether they are the same. No instructions with the kit, but says info on installation on their website, could'nt access for some reason though. So, just wondered whether anyone has installed these and might be able to advise. Any help much appreciated. Oh, forgot to mention a PO had fitted tapered races before, pig of a job to get them out !.

[Redman]

I cant really say about your 750,
but on 1100G the lower set was noticeably larger diameter

(which also made it harder to knock out the lower one since was no edge accessible from the inside-top. Had to cut the inner race with a dremmel tool).

[Nessism]

Did you check ID and OD and compare to fitment on the bike? Sorry, obvious question.

[hampshirehog]

Bearings are different. I just googled and found the specs and for your bike they're listed as 27x48x14 and 25x48x15

[tomo]

Thanks guys. Just had a look at the old cups, seem to be the same outer diameter, but will have a good look at the new ones tomorrow. On my bike, there was no way to knock the cups out as at both top & bottom there is a bit of a radius of the headstock just before the bearing seats, so no way to get a screwdriver or chisel under the cups. I tried the dremel trick, cut the cup about two thirds deep then whacked with a chisel but no luck. So called a mate who is a mechanic and he came over, welded in a steel rod in the top cup then was able to knock out from below. Bottom one tried same but for some reason weld did,t hold, but he built up some weld blobs so he could knock it out using those !. So got there in the end. Anyway, I will have a good look at the bearings tomorrow, bit cold in the garage tonight, must be getting old !!. Thanks again, I,ll let you know how I get on. Any ideas on those sizes Hampshirehog, I,m guessing 48 is OD, 25 ID and the other depth ?.

[allojohn]

I believe the stem needs a modification for tapered bearings to fit. There is a ridge on the stem which must be lowered about 6mm for the top bearing to seat low enough to allow bottom bearing to be pulled up into the lower cup.

The Z1 site has the modification details, click on "view technical documents"

[allojohn]

Another way of removing the old bearing cups is to..... wait for it..... drill through the steering head at the angle point between the head and the cup seat. Then use a tiny drift to tap the cup out from behind. Fill the drill hole with a dab of silicon. No harm, no foul.

[tomo]

Thanks for all the advice everyone. Feeling a bit stupid this morning !. Took a look at the headstock this morning and a light clicked on in my excuse for a brain !. Pretty obvious as the stem thickens out in two places, 1" or so down from the top then at the base, the inside diameters of the bearings have to be different. So sorted out now, just have to fit them. Kept the old cups & centre piece of the old bearings to use as drifts. I read about the stem mod as well, think that must have been done by the PO as he had fitted tapered bearings. Thanks again everyone, I've been a bit dense on this one, posting before thinking things through !.

[kochic]

To remove the bearing cups without effort just weld a bead on it, the cup will fall by itself.
Marc

[Grimly]

To remove the bearing cups without effort just weld a bead on it, the cup will fall by itself.
Marc

And if keeping the bike long-term, grind an access slot into the shoulder above the bearing cup, so you can get a drift in there, next time you do them and don't have a welder to hand. I've had a couple of bikes that had two access slots cut from the factory, so it's not a new or dodgy idea.