neck bearings question

I'm building a new front end for my 750,('82 Maxim), and I've got a quick question. I want to use a 1" stem for convenience. The stock top bearing is 25x48x15.2, the bottom is 30x48x15. If I use a 1" stem I can use two 25x48x15.2's if that .2mm,(0.00787402) in height isn't critical. I really don't think it would even be an issue. Right or wrong?

 

I don't think the .2mm on the top and bottom will not matter but I feel that the .4mm will give you issues. The .4mm I am referring to is that 1 inch is equal to 25.4mm. That's quite the difference when it comes to lateral play in a bearing. If you head over to Allballsracing.com there is a fitment chart that allows you to input the bike you have and it will provide you with stem bearing that will allow you to convert to whatever you want (if you can find that bike).

-Chris

 

Clownman, thanks for the reply. I know the 25.4 thing, but as to looking up bearings for a certain bike I have NO idea what you are talking about.

 

Just go to the Allballs bearing site and at the top left just click on the drop down boxes until your bike is chosen, then click on the product in blue and there's your stuff.

 

I mean......Why would I want to look up bearings, I already know what bearings I need. I'm building a front end. I don't need bearings for my bike. I must not have written my question correctly, sorry.

 

OK, what is the size of the stem on the bike now?
If it is 25mm then that as you have already said is smaller than the 1" stem you want to use, so you will have to change the bearings to use the one inch stem.
That's what I get from your original post.
So the top would be too small and the bottom would be too big.
I hope that's the answer.

 

Ok, Here's the thing. I'm NOT using the stem in the Maxim. I'm building a whole new front end. Trees, legs, and all. I rounded off the new stem diameter to one inch in my OP. The stem will be 25.4mm from top to bottom. I will then use two 25x48x15.2 bearings. The bottom bearing on the neck now is 30x48x15 I just wondered how critical the .2mm is in hieght. That is my question. I have no idea where all this other bearing stuff came from. Sorry again for the confusion.

 

If your going to be making all new trees and everything, than making a 2mm spacer to take up that gap should not be a big deal if it is an issue. I say just do it, if the trees hit the neck, make the spacer. I have a 4mm spacer under my R6 triple lower bearing, and it works great.

 

It is not a matter of making up the difference. What the OP is talking about is the bottom bearing being .2mm taller than the original bearing.

To answer that question easily. No it will not be a problem. What it will do is space the lower tree that .2mm away from the neck tube. No need to make up any spacers for anything. That .2mm should not affect being able to torque the stem nuts correctly.

Ghost

 

Thank you MiGhost. I didn't think it would but I wanted to check with someone else in case I'd failed to consider something. Thanks to everyone for the replies. I return you now to your regular programming.