Are we sitting comfortably children? Then I'll begin....
This is a tale of an evil motorbike and all the grief that it caused to it's innocent rider...
Ahem...
I did some research today and wandered over to the workshop with a lot of information about clutches and gearboxes and other wonderous things.
I'd read on the Andover Norton pages that they sometimes do compression checks when the engine is cold, so I thought I'd give that a go and see what the difference might be to hot.
SFA.
90psi again.
The follow up test is to pour some oil into the head, to see if that makes any difference: if it makes a significant difference, then it's likely that the rings are knackered.
Not really sure what to hope for...
But that isn't really much of a difference.
the next test is to confirm the valves aren't tight, which means taking the valve covers off, and the primary case so I can rotate the engine more easily.
Hmmm - those streaks look ominous....
I found TDC, and ... err...
That ain't tight.
The inlet valve has gone VERY loose, that's got to be affecting the timing, if nothing else!
The exhaust doesn't "look" too bad.
I reset the valve clearances to 0.002"
And gave it another 10 kicks
hmmmmmm.
Time for some prevarication. I decided to take the tank off to give me better access to the head, but in the meantime....
The oil tap lever has always bothered me, it's just too long and prone to getting caught on things.
So I took an inch or so off it...
Once I had the tank off I got a better look at the valves, they're definitely getting oil, which is a good thing.
So, while I pondered the lack of compression pressure....
I turned to the clutch and realised something.
I've always wondered exactly what the $%^&& this tool was for....
Clever!
Obviously, being one of my Dad's tools, it wasn't quite right, the gap between the prongs was too small, and I realised that it was actually damaging the thread on the clutch stud!!
So I performed some remedial work with a file, and it now fits a lot better.
I also realised that the effing big screwdriver I've got with a matching handle was ideal for quickly removing the clutch spring nuts once they're "up" enough to clear the studs
Do you even screwdrive bro?
yeah... not great
The first friction plate (which is one sided), is oily as feck
The innermost steel was gungy as feck, old congealed oil??
I realised that the primary chain would need to come off, so...
There's another one-sided friction plate which is the innermost part of the clutch assembly
I initially thought this was some sort of custom racing job from Mick Hemmings, but then realised I hadn't quite understood the diagrams of Norton clutches that I'd been looking at (it doesn't help that the manual I found online deals with BOTH the "heavy" twins (Dominators etc) AND the "light" twins (the 250-400s), which have a different clutch assembly. I think the manual is one that assumes a LOT of prior knowledge on the part of the reader....
The clutch push rod was lightly oily... I understand from my reading that this can happen, but shouldn't really be the case.
Apparently some people machine a slot or two into the push rod and fit o-rings... which might be a doable mod.
The disassembled clutch plates laid out in order. The innermost friction plates are dry (if a tad rusty :wtf: ) so I'm hoping that this oil issue is just a build up over time, rather than a bad leak. (I may have overfilled it...)
I pulled out the clutch holding tool I had stashed away...
but..
nope, that ain't gonna fly. Bah!
I borrowed some E5 from the tank to soak the springs and cups etc
Then made a start on cleaning the plates
But soon got very bored with that, and took another look at the cush drive assembly that was still on the bike.
These came out pretty easily...
and they're manky
The "cush drive" in situ
Eventually found a socket to fit (which I was surprised to find actually...), a 21mm "fitted", but that's a 13/16" spark plug socket.
Manky driveshaft and cog fitting
The clutch cush drive has a washer on the back
And a whacking great spring-washer under the nut, which was a LOT looser than I was expecting, I didn't need much effort to undo it...
I still need to get the "cush drive" apart, it's locked up solid, so it's been set to one side for now....
The nut on the gearbox sprocket is a left-hand thread, and was finger tight!
And there's a spacer behind the cog.
The cog is dished to push the chain run away from the gearbox body.
Wahay, I've got the right spanner!
I cleaned the cog and associated parts up and refitted them, more just so I remember where it all goes! (It's not all tight).
I still have to clean up the rest of the clutch, and then ponder the choice I now have.
Do I need to rebuild the fecking gearbox? I need to find out if the main seal can be replaced without splitting the box, and then decide whether or not to "live" with it for the rest of summer. IE, rebuild the clutch and get a short bit of riding before a full winter strip down, or do the strip down now, and miss the rest of the summer?? It could be just that I overfilled the oil somewhat and some has worked it's way down the push-rod tube. I haven't looked at that side of the gearbox yet, but that's probably something to do between clutch plates next time.
And then there's the lack of compression pressure in the engine itself. Is that a major issue that needs fixing? Has the head gasket gone?? That's basically the last option for a cause of the low pressure. (Well, assuming the valves are still sealing ok, another grinding of the valve seats presumably wouldn't hurt anything I suppose..)
My current thoughts are to sleep on it and make a decision over the next couple of days. Given the way the bike was riding
before yesterday, I suspect the compression pressure hasn't actually deteriorated since the first ride, that's just the way it is, so fundamentally, it would be ok for a few more rides, and I could then do another strip down over winter. It does seem like there's something fundamentally incorrect somewhere though. It just seems wrong to get less than 100 miles out of the bike between rebuilds!
I'll very likely order up a head gasket anyway (I don't have a spare), while I'm thinking about it and cleaning the clutch plates.
I WAS thinking of soaking them in petrol to get rid of the oil, (I'm sure of read of that being an old method for cleaning clutch plates), but I've not found anything yet about the best way to clean them.
