Posted: Wed Jul 21, 2004 5:05 pm Post subject: I heard a tap, tap, tapping--and it wasn't the raven
I finally got my 72 Combat running last night and took it out for a spin. Commandos don't take a back seat to any other bike as far as a great sounding exhaust note! While I was riding, it dawned on me that I had never heard a Commando actually fired up, although I've lusted after one since my first trip to a Norton dealer in 1969. Anyway, on to my question. The the bike starts, idles!! and runs well. Once it was warmed up I noticed a rapid tapping noise above around 2,500 rpm, which was loud enough to cause me concern. Now, that may be normal valve clatter, but I wouldn't know what normal sounds like. While holding any steady speed in any gear, the noise is really noticeable, but it disappears upon acceleration and in not noticable while at idle. Valve adjustment clearances are spot on for a Combat. I know questions about sounds are difficult to answer but I would appreciate any suggestions. Kinda sounds like tapping a pencil point on the top of a metal desk. I've spent months working on this baby and would hate to blow it up due to my ignorance. So, is it normal or abbynormal?
Joined: 24 Dec 2003 Posts: 362 Location: Brisbane, Australia
Posted: Wed Jul 21, 2004 8:31 pm Post subject:
It would be nice if it was simply a worn alternator rotor key........
Just a thought, this is a bit hard without listening/experiencing as you have stated.
Joined: 14 Jun 2003 Posts: 667 Location: HOUSTON, TEXAS
Posted: Thu Jul 22, 2004 4:48 am Post subject:
Edgar,
Your Raven, er, tapping sounds abnormal to me. You should check for excessive valve clearances. However, sloppy valve clearances should be audible below the 2500 RPM threshold you mentioned.
Possibly a valve guide is tightening up with an increase in head temperature? Have you had any head work done lately?
Complete speculation here, but my guess I would be piston slap....
I had a '82 CB900F with a worn wrist (gudgeon) pin that produced a similar ominous sound. I have a nice piston/con rod paper weight...
I too am in the same boat as you - I have yet to hear my bike run... (oh the shame) In theroy I have a Norton, in reality I have a bunch of parts scattered throughout the basement (sigh)
Posted: Tue Jul 27, 2004 11:58 am Post subject: tapping noise
As you say diagnosis is pretty difficult by description. My '72 combat has what you describe. In my case it's a tappet noise probably due to the valve stem top hardening being worn or a worn valve tappet adjuster tip. I'm not worried about it since I know everything else is as it should be. Combats are probably prone to unusual valve tappet wear due to the weird angle caused when .040" was milled off the head the pushrods weren't shorted to match.
Joined: 24 Dec 2003 Posts: 362 Location: Brisbane, Australia
Posted: Tue Jul 27, 2004 12:30 pm Post subject:
I have had a layshaft 4th gear lose a tooth and make a sound that was difficult for me to trace.
You could "nurse" the bike along at first and not hear anything. It was because the one tooth was about to break off, but hadn't quite broken off. I had to get my bike home from a couple of hundred klms away & was lucky to do so. It did break off completely after I made it home.
3 of us, all "old" norton riders couldn't pick what is was until I finally pulled the geabox apart. We had been using the screwdriver trick to try & trace the sound & thought it was coming from the alternator area.
Once I got the gearbox apart, you could see where the tooth may have been "faulty" by the fracture line.
Posted: Sat Jul 31, 2004 8:23 pm Post subject: Norton Noise
nortonfan wrote:
It would be nice if it was simply a worn alternator rotor key........
Just a thought, this is a bit hard without listening/experiencing as you have stated.
Well I have a 71 Commando High Rider and I also was having the same sort of tap tap tap and even after adusting the valves it was still there. I pin pointed it to the left hand intake, so I decided to remove the head (which is a treat in itself) so low and behold I discover my left intake push rod was slightly bent, so I ordered a new head gasket and new push rods and now she purs like a brit kitten.
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At the end of 1967 the Norton Commando was announced.
The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.
It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.
Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.
It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.
The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.
