Bmw R75/5 Fork Alignment

[lelocp]

So Im following Randy Glass fork alignment article and its going quite well, except when Im measuring the X- plane. Now from what I understand, if they are not with in spec, the forks should not properly work. When I'm measure the space between the forks the dial tends to move in a counter-clock wise direction. This got me thinking that the forks do not have to be spaced out but instead clamped, where the forces are pointing at each other. But from Glass's article and other articles they talk about tweaking the x plane by spreading the forks away from one another. Now could there be something wrong with my forks, they are not bent and are in good condition or should I clamp them so the force is squeezing the fork tubes?

[Duane Ausherman]

I don't understand your question. Do your fork tubes splay out or in at the bottom?

You also said, "Now from what I understand, if they are not with in spec, the forks should not properly work."

Read more carefully, you missed the logic. The fork tubes can be way out and work just fine. It is seldom, but we saw it a few times. To assure that your forks work without stiction, have it all in alignment. Any error can cause stiction. Notice I said "can" not "will" cause stiction.

If you get it together with everything in alignment, then there is no reason for stiction.

We had a wreck come in with the front forks shoved back so far that the wheel destroyed the fender when it slammed into the engine. It also wrecked the front cover and damaged the alternator. With the fender and cover removed the forks would just barely clear the engine. The forks worked perfectly with no stiction. Go figure. We each rode it down the road and it had zero stability, due to the trail change.

[lelocp]

My forks do splay out from the bottom.

[Duane Ausherman]

Are you saying that they splay out "AT" the bottom? That means that they are wider at the bottom.

[lelocp]

yes thats what it appears on the dial indicator

[lelocp]

well when i measure from the top of the fork and slide down the dial indicator tool, the needle goes counter clockwise indicating that the forks are being splayed. I might be holding the tool wrong but ive done it numerous times and continue to get the same results.

[ME 109]

You probably have your front end back together by now.....

What is the difference from top to bottom?

Tweak the forks in at the bottom until they are the same as the top and go for a ride.

[Duane Ausherman]

well when i measure from the top of the fork and slide down the dial indicator tool, the needle goes counter clockwise indicating that the forks are being splayed. I might be holding the tool wrong but ive done it numerous times and continue to get the same results.

As I am sure that you have noticed, one must hold the tool in a "neutral position" or the measurement isn't valid. The fork is so flexible that it is easy to shove it over a bit and get a bad number. That said, the usual error is to hold the tool shoved towards the other fork tube and that shows a taper, not a splay.

I actually suspect that those large nuts at the top were tightened up in such a way as to cause the tubes to splay. The fit of the nut in the top clamp is so poor that the tube can easily "walk" around and end up to be out of alignment. It is normal to need to file the two large holes in the top clamp to get alignment. Did you find that?

[lelocp]

do the top tops nuts have to be attached and torqued down when doing this type of measurement, because i have the them off. I also haven't mentioned that the bike has not been driven in 10 years. i'm thinking of just hooking everything up and riding it and seeing if i run into any type of problems.

[ME 109]

Measuring with the top nuts off will tell you the alignment of the triple tree, and/or the straightness of the forks.
But you wont know which is at fault until you have checked fork leg straightness by placing them together on a flat surface and while rolling them together, trying to fit a very thin feeler gauge in between them at several places along the length,and around in different places.

Ideally, if your legs are perfectly straight, you won't be able to fit a .05mm gauge in anywhere. That would indicate pretty darn straight.
Even more ideally would be if you had two rolling blocks and were able to assess straightness with your dial indicator.
The greatest gap, if there is one would most likely be at the point where the forks mount in the triple tree.

if the forks prove to be very straight, then the next step is straightening the triple tree.
There are more experienced with that procedure.....