Hi all - new member here, first post, looking for my first bit of advice on my first shovel.
The bike is a late '79 4 speed and was originally (I believe) an FX; it's been modified by the previous owners to the extent that you see in the photo.
It It has some significant issues which I'm learning about and considering how to deal with (basically the engine is rumbly and a bit knocky - it's had a rear pot partial seizure at some point). All that I can deal with, however I've identified an issue with the clutch that has me stumped.
In this photo (apologies for poor quality) you can see that the clutch hub surface is scoring up really bad - it's actually wearing the hub material down, you can feel a step up to the unswept area. The (new) clutch friction plate in contact with the hub is also gouging and scoring - there's chunks getting torn out of the friction material. The wear that you see there and the debris lying in the drum occurred in just a few miles of riding. All the other plates look good; the clutch is adjusted right and it doesn't drag when the lever is pulled in (no wobble).
The only thing that I can think of is incompatibility between the friction material (which has sintered bronze in it) and the alloy hub material - maybe the bronze sintering is picking up the alloy, galling and then gouging the softer friction material. I don't know the plate manufacturer unfortunately - they were in the bike when I bought it.
Has anyone seen anything like this before, or have any idea of how to cure it? Do all friction plate materials contain sintered bronze? - I'd be happy to purchase another set of plates if that's the cure.

Thanks for any advice - I'll have lots of questions over the next few weeks, there's a lot to learn!

Cheers,

John

 

I have only owned a few bikes with the 4 speed clutch setup but I recall the drum was scored up pretty good when I ran wet plates dry. Looks like you are running a dry set up. I had good luck with the "police" clutch plate set..thicker...did not gouge my hub....

 

you might be onto something with the two metals. try red alto plates - they are organic. I also think I read somewhere that there is some kind of plate you can put in first to fix the damage to the drum.

 

the red altos are cheap enough to try but I found they were poor when run try...they blued the drum from heat. I have used a Nylatron ring before but that goes behind the drum. If there is plate to use to help with that scoring I'd like to try it....I do recall a 1/2 friction plate. Maybe that is it???

 

the original hub is steel that hub looks like an alloy one and if so a plain steel should have been used first in it so that does not happen --

dry clutches need dry clutch discs not wet ones like the original ones, a wet disc like the one in the picture cant be used on an alloy drum

 

Ah - thanks for the advice - makes sense. Yes, the primary is running dry and it is an alloy drum. So.. I'm going to try removing the first friction plate (the one currently against the drum) and see how well that works - of course that means that my overall clutch plate set thickness will be reduced by one disc - do you think that removing one plate will cause it to slip? If so i'll try and source alternative dry plates.
Unfortunately it's going to be some time until I get to try this, possibly months, as I have to rebuild the bottom end and get a rebore, etc.

 

There is an old trick for FX bikes to remove one fiber and one steel (won't work on heavy FLs) to have a lighter cluth lever