9 replies to this topic

[Covert]

so rebuilding tiny and the clutch arm was badly worn on the end as you can see, 

 

Got a brand new one from a chap on here but when trying to operate it , its really stiff to operate, ie i can barely move it then "clunk" it goes through the motion, put the old one back in and its fine.

 

Thought it was the pin at first so machined 0.5mm off it and its still the same so its not that

 

as you can see side by side the old one is worn on the hole where the pin goes through and on the end.

 

 

any help gratefully recived!

 

really dont want to go and buy another arm 

[Tupers]

Have you checked the plunger and release bearing? If the arm is that bad I can't imagine the bearing and plunger are in good nick. 

[Covert]

Plunger is as new. Haven't even tried it with the bearing on old one was scrap anyway. Need to buy a new one

[Covert]

Update , here is a pic of the Plunger, i cant see anything wrong with it , if anyone does please shout !
Here is a vid of my problem , first bit is the old arm , second bit is the new arm
http://vid1313.photo...zpstybnmndu.mp4

[Dan]

You say you got the arm from a chap on here, where from exactly? It's just it's not genuine, they are not made from that metal. It should be a dull grey/brown iron colour rather than shiny steel like that. Has it been plated or painted or something? This would change the dimensions of the part just as wear will but in the opposite direction so to speak. Normally it's quite apparent that they have been finish machined as you can see the tooling marks around the side faces and on the tapered cone leading to the ball, as well as the ball itself, and the bores are very accurate. Yours looks very smooth where it should show machining and looks to be quite a poor casting with lots of pitting and voids. I'm not saying for sure it's a bad part or the cause of the problem, but it's not original.

Have you greased the ball and pivots with graphite grease or is it assembled dry?

[Covert]

Thanks , its been plated by me as things tend to go rusty very quickly in my workshop
Here are some pics before it was plated


Ive no reason not to believe the chap that its brand new although no idea if its genuine or not.
Suppose i could take a dremel to it so ease it a bit !

[mk1leg]

Always replace both Items as they both ware at the same time so just putting a new arm in will not help...............

[Dan]

Well if you plated it you made the ball bigger as well as the drillings smaller. You have relieved the pins but the ball may be jamming, it also may not be round. What did you plate it with?

[Covert]

Zinc , cant see how it would have affected it myself as the plate is so thin but ho hum

[Dan]

Well this is only a suggestion of what might be the cause, given that all parts are new you shouldnt be having this difficulty. Without having it in our own hands all any of us can do is make suggestions. Zinc however is a bad choice for using here, the general rules for zinc plate are that it shouldnt be used where it may cause binding or used in moving parts. Zinc plating galls when used as a bearing surface, that means it essentially micro welds itself to anything, particularly other zinc parts, under pressure and friction. It's just something metals do, if there weren't oxygen in the atmosphere even steel would do it to the point that tightening a screw would be impossible. Yes the plating is probably only half a thou thick but that adds a thou to the diameter, and as the hole in the plunger is tapered the ball needs to be the right size to not get stuck. As the fit of the ball in the taper gets tighter and tigher through the range of movement it sounds a lot like it is galling up from your description. The plunger is plated with something like a gold passivate finish I seem to remember which is a zinc based plate so you may have accidentally made a zinc on zinc bearing there. As I said it's just a seggestion of the possible cause, but it's quite likely.