Daniel, when you changed the push rod were the ends of the rod hardened and tempered? If not the ends could be wearing away especially at the lever end.
Ok, I rode a hundred km yesterday. You were right Rob, the nut was loose, but the real problem here is the pushrod. It shortened again even if I hardened and tempered it as suggested by Matty. I bought the rod in a DIY and i think that the quality of the steel was not appropriate.
Can someone advise what kind of steel I have to buy for this purpose in a Pro hardware?
The pushrod you are buying should be made from 'silver steel' and have the ends hardened. Silver Steel is a flame hardening high carbon steel and it is easy to make alterations to a pushrod made of this material if required.
First you will need to soften one end.
Heat the end to red and allow it to cool naturally in the air. This will soften or 'normalise' it.
Once cold shorten the rod to the desired length..but take care. Small reductions in length make a lot of difference. When you are happy the rod is correct and the clutch adjustment is correct with the rod fitted, remove it and heat the end you have altered to red, quenching it immediately in cold water.
This will re harden the end.
Then clean the end off with some emery cloth until you have a bright finish.
You will now have to 'temper' the end. (this softens it slightly and makes it less brittle.)
Place the end into a fairly gentle flame and allow it to slowly heat up. You will see the steel gradually change colour as it heats, first to a very pale yellow, then a darker yellow...then brown. This is an indicator of the changing temperature of the steel.
Allow it to go pale yellow and just as it starts to darken quench it very quickly in cold water. The rod is then ready to use.
If you go too far and the rod goes brown simply heat it to red, quench it again, clean it off and have another go. Lubricate the rod well with some light oil before refitting...stainless rod is not a suitable choice...the material is far too soft
The details in the posting are for a pushrod that is being shortened and has already been hardened...If you are starting with a new, 1/4" dia. standard length of silver steel (13" long) the first part about softening can be ignored as silver steel can easily be cut etc. in its raw form...Note a standard length is long enough to make the clutch pushrod for any BSA...
Personally I don't dimple the clutch operating arm end of the pushrod as the operating arm moves through an arc and I feel the ball should be free to move to avoid exerting a side load on the rod as it operates...However, there is a possibility I'm over thinking it!...Ian
