Model D Torsion bar

[noel]

I am rebuilding my 150D and can't quite get the torsion bar right. I have fitted new bumpstop rubbers front and back. When I tried to set the torsion bar preload it is either barely 1/8 hole or on the next spline, its about 1 1/2 holes.
Anybody shed any light on this? Do I have to take out the rear bumpstop, set the preload without it and then compress the suspenion enough to get it back in. Or have I missed something? I don't think the torsion bar is twisted but I suppose it might be. Is there a way to check this? Thanks.

[Steve J]

The torsion bar has 21 splines on one end, and 22 splines on the other. This means that if the initial position is incorrect, it needs to be tapped out of engagement from the splines in both the frame and the torsion bar link, and rotated to a different position until the setting is correct. The best way to do it is to tap the bar out of engagement from both the frame and the link, rotate the bar forwards or back a spline at at time on the end that fits into the frame (the end with 22 splines), and then fit the link back on. Eventually, you will find a position to suit - the manual reckons on 5/16" preload, but I prefer a little more than that - around 3/8" (about 9.5mm).

[jbcollier]

The bar has two different splines. You're right that moving it one spline won't work but you should be able rotate it more than that and eventually find the correct position.

[noel]

Thanks guys. That makes sense. There must be an awful lot of wrong positions then. I've found one of them, the next one will be the right one. You've got to be positive about these things.

[Steve J]

There's 22 splines at one end of the torsion bar, 21 at the other - this theoretically means that over 360 degrees of rotation of the torsion bar link, there would be 21 x 22 = 462 possible positions, or one every 0.78 degree. Obviously, we're only interested in a very small section of that 360 degrees rotation where the hole in the torsion bar link is almost lined up with the holes in the engine case, but there will be one to suit, provided you've got enough patience to find it.....