W/NG, loud metallic clang - Exhaust lifter?

[stevewhitt]

At tick over and low revs, engine running fine, but I noticed that if I revved the engine, there was an occasional nasty clang, particularly when the engine started slowing down.

Having read about the horrors of rocker boxes being destroyed, I focused on the adjustment (again) of the exhaust lifter lever. This time, there is barely 1/2" of free play before the lever hits the handlebar and the exhaust lifter opens. Ran the engine again, much improved but still the occasional clunk. So I removed the exhaust lifter mech completely, plugged the hole and the engine ran without any clunking; so I am 95% sure I know where the problem is.
When I purchased the bike, the exhaust lifter mech was missing. I assumed it just needed replacing. However, clearly it was taken out for good reason.

Not sure where to start really. I guess Ill have to take the rocker box off and check that the correct rocker arm has been used - How will I know?
I also was wondering if it might be fitted with an incorrect valve (stem too long perhaps?) Are the lengths published?

Another possibility is that the end of the tappet adjuster is hitting the inside of the adjuster cap; there might be a witness mark inside the cup! Not sure how removing the lifter mech would stop this happening, unless I am mistaken about that as the cause. I expect this is a red herring though.

Pictures attached taken today.

Any ideas/suggestions very welcome.

[will_curry]

First thought is that the adjuster seems to be screwed quite a long way out.

Have you checked how much end float there is on the spindle of the valve lifter?
Originally there was a spring to control the float but these don't seem to have
been available for ages. One of mine is packed out with washers and is prone
to leaking.

[stevewhitt]

It’s a brand new valve lifter assembly Will, zero end float.
Yes, I thought the adjuster is sitting high. I did wonder whether it was hitting the adjuster cap.

[stevewhitt]

To prove my theory that it is the valve lifter causing the problems, I put the rocker etc back without the valve leaver, engine runs just fine. I then put the valve lifter back with the cam at the furthest point from the rocker valve tab, engine ran fine. I then started moving the adjustment screw on the valve lifter clockwise a little at a time and trying the engine. I got to the 3 o'clock position with the screw and I could just start to feel the vibration through the lever as it came into contact with the rocker. The problem is that at any position before the 3 o'clock position, the lever on the handlebar does not rotate the valve lifter sufficiently for it to stop the engine!
I wonder if the valve lifter lever on the handlebar is not providing sufficient length of pull for me to adjust everything correctly. I have attached a picture of the lever that is fitted.

When I pull in my handlebar lever, the valve lifter lever rotates approximately 11/2 hrs, or about 0.35" measured at the tip of the valve lifter lever. The gap created at the handlebar lever is 0.5".

I am wondering whether my free length is correct.

Sorry if this seems like a ramble! I really appreciate the help and support I have found in this forum.

[simon.holyfield]

Interesting; a couple of points:

If you make sure the exhaust valve is shut when you adjust the decompressor, so the rocker is as high as it will go you shouldn't need much lever movement to lift the valve. Obviously you turn the screw clockwise to bring the peg onto the rocker pad.

Ariels normally use a double lever on the left bar - one for the magneto, the other for the valve lifter. I would guess these would give you a bit more than 1/2" on the cable, but as I say you don't have to move the lever much to lift the valve.

However, don't very late war W/NGs use the standardised handlebar layout with the trigger lifter, as you have here?

[stevewhitt]

Hi Simes
Yes, the late bikes did use the standard layout. I did make sure the valve was closed when I made the adjustment. I compared my cable with the spec on Drags site, they state 23"-26 5/8", mine measures 22 3/4" - 26 1/2", so 3 5/8" free length v 3 3/4", so mine has 1/8" more free length.

[will_curry]

How are you adjusting the setting of the valve lifter?

The external lever fits onto a taper on the spindle. I free the lever
from the taper, get the cable and spring in place and then turn the
spindle with a small screwdriver in the slot on the end of the lever
until the cam just touches the rocker arm with the valve fully closed.
I then back off the spindle slightly and tighten the lever onto the
taper. It can be a bit fiddly at times but it's always worked for me.

[simon.holyfield]

How are you adjusting the setting of the valve lifter?

The external lever fits onto a taper on the spindle. I free the lever
from the taper, get the cable and spring in place and then turn the
spindle with a small screwdriver in the slot on the end of the lever
until the cam just touches the rocker arm with the valve fully closed.
I then back off the spindle slightly and tighten the lever onto the
taper. It can be a bit fiddly at times but it's always worked for me.

Same method as I use.

[simon.holyfield]

Hi Simes
Yes, the late bikes did use the standard layout. I did make sure the valve was closed when I made the adjustment. I compared my cable with the spec on Drags site, they state 23"-26 5/8", mine measures 22 3/4" - 26 1/2", so 3 5/8" free length v 3 3/4", so mine has 1/8" more free length.

Hmm. Coming back to the free length - on my earlier version, the spring holds the cable in tension at all times. It struck me that if you have 0.35" movement at the end of the lever on the engine end and 0.5" cable showing at the handlebar end, you must have some slack in the cable at rest?

[stevewhitt]

I think my free length is part of the problem. Ill order a new cable and let you know. Thanks for your input Will, that is exactly how I tried to set it up.