ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-11-2013, 02:41 PM   #1
Cdubs OP
made for adventure
 
Joined: May 2011
Location: SF, CA
Oddometer: 158
GS Stem and nut question

Guy is trying to machine some new stems for us in the group buy, does anyone know the answer to the bolded questions below?

Thanks!

Quote:
Originally Posted by HPMGuy View Post
I read up on the stem issue on the other thread. It looks like the old nut from KTM had 20mm of threads and then used a ~3mm washer leaving ~17mm of engagement. The replacement nut has 12mm of thread height but only 8mm of engagement because of the wide thread relief at the bottom. Either one is fine for a KTM, but apparently the different bearing taper of the BMW bearings requires significantly more torque than the KTM stem/nut were designed to take.

I don't know if this is really a huge problem, as I could only find one instance of it happening. Never-the-less, it seems like a good idea to address the issue at this time. I have cancelled the order for the KTM stems and have placed an order for 7075 stock to machine them from scratch. I will maximize the thread engagement on both the nut and the stem.

Since the parts are being machined from scratch, maybe it would be a good idea to copy the thread pitch of the BMW stem bolt so torque values would remain the same for the BMW bearings? This might eliminate some confusion regarding setup. Does anyone know offhand what the thread pitch is on the BMW P/N 31 42 1457859 "Screw" used on the '87-'91 R100GS?
Cdubs is offline   Reply With Quote
Old 06-12-2013, 04:26 AM   #2
AliBaba
Gnarly Adventurer
 
AliBaba's Avatar
 
Joined: May 2005
Location: Norway
Oddometer: 372
Maybe a bit off-topic but I changed head-bearings on my EXC the other day and had the same problem with the stem, but was able to clean up the threads a bit. The result was maybe okay for a slow enduro bike but I wouldn't used it on a fast and heavy GS.
Maybe increased weight and offset makes it worse?

There was also the same problem with the front wheel-axle, it works for now but a new one is ordered.
AliBaba is offline   Reply With Quote
Old 06-12-2013, 07:51 AM   #3
Pokie
Just plain Pokie.
 
Pokie's Avatar
 
Joined: Apr 2013
Location: Fort Collins, CO
Oddometer: 864
The thread size is 28mm x 1.5mm.
Pokie is offline   Reply With Quote
Old 06-13-2013, 12:48 PM   #4
Cdubs OP
made for adventure
 
Joined: May 2011
Location: SF, CA
Oddometer: 158
Thanks Pokie I passed this to HPMguy

Quote:
Originally Posted by Pokie View Post
The thread size is 28mm x 1.5mm.
Cdubs is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 06:52 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014