bottom yoke bearing

[andypugh]

Nabz..dont try to part the stem from the bottom yoke!! That lot was assembled by Mr Hondas finest, with the idea that it didnt come apart again!.

For what it is worth, I disagree. The easiest way to get the bottom bearing inner race of is to press the stem out of the bottom yoke. It will just press back in again.

Now, imagine that the new press fit is looser than the old one (and, to be honest, I can't see why that would be, I would expect the same bits of metal to go together in exactly the same sort of way (and a PhD in materials science, maybe :-). What is going to be different? The stem can't drop out because of the way it is all assembled. It can't matter that there is less torsional grip, because there is precisely _no_ torsional grip between the top yoke (where you do the heaving on the handlebars thing) and the stem other than the friction on the washer due to the bearing preload.

As long as the steering stem isn't rattling in the bottom yoke, it will all work perfectly.

[fallenmikethebike]

Nabz..dont try to part the stem from the bottom yoke!! That lot was assembled by Mr Hondas finest, with the idea that it didnt come apart again!.

For what it is worth, I disagree. The easiest way to get the bottom bearing inner race of is to press the stem out of the bottom yoke. It will just press back in again.

Now, imagine that the new press fit is looser than the old one (and, to be honest, I can't see why that would be, I would expect the same bits of metal to go together in exactly the same sort of way (and a PhD in materials science, maybe . What is going to be different? The stem can't drop out because of the way it is all assembled. It can't matter that there is less torsional grip, because there is precisely _no_ torsional grip between the top yoke (where you do the heaving on the handlebars thing) and the stem other than the friction on the washer due to the bearing preload.

As long as the steering stem isn't rattling in the bottom yoke, it will all work perfectly.[/quote
Mmmmm yes i can sort of see and to some extent agree with your logical hypothesis ' i would still as an absolute last resort be inclined to disturb something that Mr H probably used something in the order of a 300ton pressure press to assemble.
One of my principle concerns would be that when i am tightening the bearings down, all i might be doing is pulling the stem out of its bottom yoke location[ only fractionally] i agree' and also once top clamp is re tightened this of course isn't an issue.
I can't recall seeing this tip elsewhere is it something you have done in practice? or a theory born of your learning ?
At the very least it would probably be a good idea to mark the the two items so that both marks could be realigned on reassembly yes?

[andypugh]

is it something you have done in practice? or a theory born of your learning ?
At the very least it would probably be a good idea to mark the the two items so that both marks could be realigned on reassembly yes?

As it happens, I have never approached the problem that way, but mainly through lack of a press. The stem itself will almost certainly have a shoulder on it, so it can't be pulled through the yoke (to answer a question that I deleted from the quote). It is a job I have only had to do a couple of times. I think that the last time I grooved the race with a dremel (or possibly an angle grinder) and split it off.
However, I know about the pressing-out-the-stem idea from discussions on rec.motorcycles years ago. I quick check through the R1 Haynes manual doesn't mention the approach though, suggesting levering it off with screwdrivers, then using a bearing puller, then using an angle grinder, then taking it to a Yamaha dealer. Amusingly the Official Yamaha Service manual suggests a cold chisel between the bearing race and the yoke, and a big hammer.

I suspect that the multiplicity of approaches to the task hints at what a pig of a job it is.

[kernow krusty]

Hi Andy,
What you say is, I suspect, pretty much true..but As mentioned, not that many of us have a 20 ton hydraulic press in the garage! My other concern would be getting the alignment right as you pressed the stem back in.
My mate has mixed and matched bottom yokes with other stems when fitting different front forks and yokes to different bikes ( the last one being a Honda C90 he uses for trialing - dont ask!),so its an option, but hes a bloody good engineer who presses cranks apart and back together for a living...
To be honest,i reckon Ive changed about 14 sets of head bearings in my time, and they all drifted off the conventional way, so I kinda thought nabz should persevere a bit longer!