classic motorcycle forum

Good call. I've had a new valve guide pick up enough to grip the valve stem. Can you hear any chuff-chuff noises through the carb or silencer when it's kicked over?

Pride, as they say... Cometh before a fall.


I'd been quite chuffed with myself for the way things were going on the bike, so naturally it couldn't last.

Took it out for a longer ride to see how it behaved over 20 or 30 miles of continuous riding, not straying too far from home, riding around the local roads.   At first everything was tickty-boo, it loped along nicely, albeit the fuelling at low revs wasn't perfect: couple of backfires, but nothing worrying at all. Riding "at speed" was fine (tyre pressures were a tad low) but the engine felt good. Clutch and gearchanges were fine (even getting into first at standstill was a lot easier)

Then, while tazzing along nicely it suddenly just went "bleaerrrrrrrrrrrrrrrrrrrrrrrrrrr" and died.  I was on a quiet country road, and luckily a largeish driveway appeared so I rolled into that, safely off the road and stopped.

There was some swearing.

I pulled out the tools and checked the plug: Bit oily, but not overly so - running a tad rich I'd say. (and rolling off tests were indicating that too)


Yes there's sparks.  Yes there's petrol, yes the petrol is flowing into the carb.  Then when trying to kick it... I realised there was absolutely no compression whatsoever.  There is exactly the resistance on the kickstart that indicates the engine is turning over, (ie, it's not clutch slip) but no compression. In addition the head gasket wasn't "puffing" at all which would indicate failure of the gasket. (and there's no marking or blow-by staining to indicate gasket failure)

There was more swearing.

That's not a roadside fix.

I've broken down in worse places, and in worse conditions:




The fork weep is back...


Attempted artsy photo by headlight!




5 hours later:


Eventually got home at about midnight and threw the bike back in the workshop.

Mileage on the odo when I left:


Odo reading at breakdown:  It did nigh on exactly 30 miles!


Reference odo (from after approx 10-15 miles earlier this year)


so - it's done roughly 150 miles on this engine build...  :wtf: 

Still - more than I've done on either of the BMWs this year! :wtf:


Current thinking is the lack of compression is one of the following:
Burnt out valve - maybe that exhaust valve seat wasn't as ground in as well as possible?
Holed piston - messy
Failed piston ring  - that'll do the bore no end of good.
Valve-springs failure - outsider in terms of likelihood, but it would create the symptom.

I won't know until I get in there properly.   The "silver-lining" is that none of it is scary stuff any more and I feel more confident about figuring it out.

However - there's other projects that need to be done, so I'm going to park the JAPton for a month or so and get one or two other projects worked on.

Well - I needed something to keep me busy over winter....  :roll:

Difficulty finding neutral or 1st at a standstill is usually down to a dragging clutch, especially if the gears engage perfectly with a stopped engine.
The suggestion of halving the pushrod and fitting a clutch roller helps with this as the pushrod doesn't then spin with the pressure plate when the clutch is pulled, unlike a one-piece one, which can/does.
You'd get a little more thread to put your locknut on, too..

So, I did a  bit more research and bought a few bits from RGMNorton.


New push rod, longer adjuster screw, and a fancy new clutch lock nut with a built in oil seal around the push rod.


So this evening there was a blur of frenetic activity in the workshop!

This is the original push rod in place with the cable adjusters loosened off


This is the difference in length from the old push rod to the new one!



And this is new push rod in place!


It's a little too long tbh! :lol:


So I took some measurements to figure out how much I needed to take off it.








I think I'd need to take roughly half an inch off it too bring it down to a length where the pressure plate adjuster nut is usable.

So, in the spirit of investigating all options: I put the old rod back in and tried the longer adjuster screw.
Not bad!


That was with the adjuster pushed up against the end of the rod, with it retreated slightly to allow a gap, there's a decent amount of thread left for the lock nut


This is the play on the actuating lever:



I'm actually quite lucky with this bike because when I'm adjusting the clutch cable and lever, I can reach through the frame and get a finger onto the actuating lever so I can actually feel the movement of the push rod as the adjuster screw contacts it, so it's easy to get the adjuster screw "just" touching the rod, then back it off. If it was a normal Norton, there'd be a whacking great oil tank under the seat getting in the way.

I then continued putting everything back together


This is the "play" I ended up with on the clutch cable adjuster


Remembered to put the inspection cover back on


Then...errr ... there was just enough light left to take it out for 10 minutes!


Very very good run out! The clutch is behaving perfectly now!
I figured it was good when the bike was spinning up in the gravel, and pulling away in first felt like a modern bike!

First gear is still a pain to get into at standstill, but tbh I think a lot of that is the rear-sets, on the move the gear change is smooth as silk, up and down.


The only fly in the ointment was that the clutch lever play seemed to be opening up as I headed home,


So I need to pull the cover off again and see what's causing that. Possibilities are: the adjuster has loosened off, which is a simple fix.... Or the clutch main nut is loose, which is rather more scary!

Long term, I may cut down that new push rod and use the fancy new clutch nut, but for now the longer adjuster nut has made all the difference and seems to have solved the immediate issue. We'll have to see if the gearbox oil still contaminates the clutch and it that causes problems.

I did consider the fix of putting a bearing into the push rod, but tbh, I figured a longer adjusting screw was going to be the easiest fix, second only to a longer push rod, which may still happen eventually.

But it's all good otherwise, and I'm a happy bunny!

Cut the pushrod somewhere on it's length and put a 1/4" clutch roller in the middle. A bit of grease and good to go.