Bike sorted

Yesterday Mark suggested putting the original, shorter spring cups back in to increase the pressure on the clutch plates. I wasn't too keen because the experts I'd spoken to in the past seem to think that the shorter cups were the cause of the clutch lever being so heavy - see the earlier post on this matter.

However, Roger Taylor from RTS Racing called me back yesterday and said he had seen C15's with both longer and shorter cups in. I said that I had read on various forums that people claim that "all British bikes' clutches slipped when they were new or rebored" but to be honest, nobody would ever have bought a bike if they slipped like mine was yesterday 'cos you can't get the damn thing to start - and without bragging, I'm good at kickstarting difficult bikes.

Roger also pointed out that the same clutch is used in the B40 which is much more powerful than my bike, so Mark came round today to put the old cups back in. I say "give me a hand", but from my stool I watched him:

1. drain the oil from the primary chaincase;
2. remove the footpeg, remembering that it is a left-hand thread!
3. remove the primary cover;

At that point, he kicked the bike over and we could see that while the chain was turning, the clutch wasn't. As Roger said, there's a good chance that with the longer cups in the clutch was maybe only gripping on the first plate.

I then watched him:

1. remove the four screws, springs, longer cups and pressure plate;
2. put the shorter cups in;
3. replace springs, screws and pressure plate;
4. adjust the screws so that the pressure plate was spinning evenly;
5. kickstart it over first time without the clutch slipping - huzzah!

Interestingly, the clutch lever is still lovely and light...

All that was left was for him to put it all back together and put my tools away while I put the kettle on.

New clutch plates in Mark's bike

As usual, click any image to zoom in.

Mark's clutch lever has been always been a bit heavy and noisy even after oiling it so he went to BSA Lightning Spares and splashed out this morning on four Surflex clutch plates, four new springs and four new clutch cups.

The photo on the right shows the old plates which didn't look too bad. The new Surflex ones are brown rather than black.

The cups that were already in were about 4mm too short - looked like they were out of a Bantam, maybe. All very reminiscent of the problem I had on my C15, documented here.

The slots in the blurred photo on the left looked like a set of gums with no teeth in from where the tangs on the plates had worn them away so we filed those smooth to allow the plates to separate freely and reduce drag.

It's all back together and not only is the clutch lever significantly lighter but the gearbox no longer clunks when changing down into either first or second gear.

Rebuilt engine back in!

As usual, click any image to zoom in.


It was a lovely, sunny day yesterday. Mark and I started work at 11am and by 8pm all the tools were away.

It wasn't too bad a job really - removed the seat, petrol tank, rear mudguard, chainguard, chain, carb, exhaust, engine and then put it all back together.






Once the new engine was in we filled up the oil tank and gearbox and Mark ran the bike up and down the road with the spark plug out and in gear to get the oil round the engine until we could see the oil return pumping oil.

The bike fired up first kick, which was nice!

We had a bit of trouble starting the bike a while later because the clutch needed adjusting (adjustment bolt was too tight).

I was sitting on the bike ready to ride home when it cut out and we couldn't get it started again.

I left it at Mark's overnight and we had another go this morning, adjusting the timing, and were fast running out of ideas when Mark suggested changing the spark plug. At that point he noticed that the rebuilt engine had a Champion N4C plug and not the recommended N5C. It started first time with the N5C plug in...

Heavy clutch lever

As usual, click any image to zoom in.





The clutch lever was VERY heavy and difficult to use without breaking a sweat or resorting to a can of spinach for every gear change.

Mark (his blog) came over to help me take the clutch apart. Turns out some dipstick had put spring cups in that were several millimetres too short which meant that the springs were highly compressed even before you pulled the lever in.














New cups and springs later and the clutch is lighter than a long-distance runner on a diet. Result!