Steering head races

[farmer58za]

Hi again guys

While the frames are at the powdercoaters, I need to sort out the steering head bearings which are pretty well shot. Some things I observed are:
The lower race in the frame is loose on all the bikes. I epoxyed the race in on the 400 and want to do the same on the other bikes. Is this ok?
The races have a number 9937050 or 9937051 on them. Are they supposed to be in matching pairs? They all appear to be identical although the Penton parts book gives differing part numbers.

There's nothing in the Penton or KTM manual that covers the races.

Thanks in advance


Regards

David
'75 KTM GS175
'75 KTM GS250
'75 KTM GS400

[wildman]

I have epoxied my steering head bearings into one of my Penton frames and so far they are holding OK. I went to my industrial adhesive outlet and got the strongest 3M epoxy they had, supossed to be good for 190,000 psi., semms like enough, time will tell. The Penton manual says to replace the frame if the bearings are loose, not too practical today. Because the stock races are so short, it would be difficult to replace with modern tapered bearings, but I bet it could be done. I haven't heard of anyone matching up the original races with a modern equivalent.  
I sandblasted the frame neck where the bearings go to give the metal a little "tooth" for the epoxy to grab and used a threaded rod with washers and nuts to tightly hold the races in while the epoxy set. You might even try to cut some shim stock and wrap around the race before glueing the race in. Good luck. Dan Pagel


1975 250 Cross Country, 1974 175 Jackpiner, 1975 125

[farmer58za]

I sent the races to a local high accuracy machine shop to see if there is a possibility that they can turn up new ones which can then be heat treated. Interesting to see what comes up. If they can make the bottom race a hair bigger it may fit better. However, careful observation of the worn race indicates that the frame and race have not worn parallel so any larger bush will still not have a good interference fit.

As for the tapered roller bearing conversion, there is a size used on one of the jap bikes that will fit but the steering stem will have to be machined to suit the inner diameter. Any new tapered roller of the correct size will also be a sloppy fit in a worn frame.

Now, where's that darn epoxy.........

Regards

David
'75 KTM GS175
'75 KTM GS250
'75 KTM GS400

[farmer58za]

Got it!

The different part number bearing races must act together as a pair. On the 9937050 the balls contact the outside edge of the race and on the 9937051 the balls contact the inside edge (although they look the same). The axis through the ball contact surfaces is at an angle to the steering head axis which results in lateral as well as vertical support.

All that's well and good, provided that you have enough of each bearing race to make up a set. The previous owners saw fit to put whatever they could into the steering head and I'm left with an odd match.

Let's see what comes of the machine shop guys.  



Regards

David
'75 KTM GS175
'75 KTM GS250
'75 KTM GS400