Clutch drag on 1938 Norton when hot

[garyhawksworth]

I have a 38 model 50 and since I have had the clutch out to do other work it drags once warm. Any ideas what I should check? I'm new to Brit bikes.

[33d6]

Aside from the usual suspects, general wear throughout the clutch, worn ears on the plates, worn slots in the basket, etc, etc, the standard trap for young players with this type of box is a worn thrust bearing inside the box on the mainshaft. When worn this allows some side movement of the mainshaft when you pull the clutch lever in so instead of the clutch releasing completely everything moves sideways a fraction and the clutch doesn't quite free.
The thrust bearing is merely a thick bronze washer, I can't remember the exact width off the top of my head. Replace this, end play goes back to minimum and the clutch releases fully.
Yours sounds as if any wear there is just starting to get to the irritating stage. It can only get worse. Its a common problem and well known.
Cheers,

[runesika]

Did you use a different type of oil after you worked on it ?   I use A T F 

[garyhawksworth]

Thanks for your tips

I have checked the basket and there is no wear. Some of the chaps in the vintage MCC suggest doing an adgustment on the bolts holding the clutch springs in place but I've seen in the "Book of Norton " that they should be fully tightend. Would there be an issue with loosening them? I have also cleaned all of the clutch plates.

I will have a look again if there is any play.

Regarding oil I have not been using any based on several peoples advise on the basis that the oil bath is likely to let it all leak out and modern chain lube looks after the primary chain. I'm I wrong?

[wetdog]

if this happens when things get warm it would surgest something is expanding , i have no idea what , but what  33d6 says sounds about right to me , is this the upright g/box ? is the cluch and main shaft nut tight both ends

[33d6]

An enclosed primary chain relies on the oil bath for both lubrication and cooling. Chain lube alone as used on the open and exposed rear chain is inadequate. It will overheat. Put oil in it.
If you ensure the faces of both the inner and outer chaincases are both flat and parallel you should have minimal leakage. You can also use a touch of silicone to eliminate remaining seepage.
These old bikes require a certain amount of careful fitting together to get just right but are very satisfying when you do.
Cheers,

[R]

Some of the chaps in the vintage MCC suggest doing an adgustment on the bolts holding the clutch springs in place but I've seen in the "Book of Norton " that they should be fully tightend. Would there be an issue with loosening them?

Are you reading that correctly ?  They should be ALMOST fully tightened - but then adjusted so the outer plate appears to lift squarely and evenly. If one has a bit  more or less spring strength than the others (not uncommon) then the plate doesn't lift evenly and clutch drag could well be the result. The spring pressure should prevent them from moving from where-ever you set them.  HTH.

[rosko]

with the outer case off, pull the clutch lever in and watch how the pressure plate lifts, use the K/S to turn the clutch, it should lift square, but it probably won't, it'll wobble a bit so adjust springs one at a time till it does; then start the engine, pull the clutch in if its lift as it should then the pressure plate will stop spinning.
done and dusted no drag, unless of course there are other problems as already said.

 use A nice thin oil in the case ATF or even 30 thinned with a bit of paraffin.

[garyhawksworth]

Thanks everyone for your advice - Since I removed the felt washer from behind the clutch it seems to run better. should this go in or outside the oilbath? I will try it with oil after the adjustments recommended.