Heading for Bellvue

Good evening all, I have a frustrating issue with my mk III Commando.

I recently refurbished the head on my mk III Commando - new valve guides installed (courtesy of Mick Hemmings), new valves, seals etc. While I was about the workshop I also stripped and washed the clutch plates & replaced (the old) clutch cable. On re-assembly and riding to the National Rally in Norfolk I noticed what can only be described as an erratic clonk from somewhere 'in the engine' on the bike at tickover.

Suggestions from interested observers ranged from a pushrod not quite seated, to a sticky valve. I have just spent the day on the garage, stripped the head again, installed new exhaust valves (new inlets valves earlier with the new guides) replaced inlet springs (one side seemed to be binding slightly), and re-assembled. started up & initially all seemed fine, then the damned clonk again!. The bike runs fine at speed eager & responsive. This is a new erratic clonk, not audible when moving, only audible at tickover speeds, completely irregular no rhythm whatsoever (i.e not a rotating item hitting another at regular intervals). This is driving me nuts. As an aside I have also noticed that when switching the ignition off there seems to be a whirr from the sprag clutch area (red herring?).

At tickover in essence only the valves, pistons, camshaft, rotor & primary chain wil be moving. Final drive will be static. Does anybody have any idea what this noise could be? It seems to be totally random - will tickover e.g. for 5 minutes nothing, then 1 0r 2 clonks then 2 minutes & a clonk,53-4 minutes and nothong It's the randomness driving me nuts, I can't locate the sound in the engine, need to fix this before heading to Germany for the International Rally.

Cheers

Mike

Mk III Commando

Hi Mike

Chill out man, have a cup of tea step back! I remember john Carr telling me 3 mechanics spent two hours trying to find a ticking noise on a marina, only to discover it was the roof Ariel hitting the roof rack . Something is loose or broken maybe.

Best of luck happy days

Odd clonks and clunks at idle on MkIIIs often emanate from the hydraulic primary chain tensioner although the noise is often difficult to pinpoint. What type of oil is in the primary, and how much?

The sprag noise is not uncommon, as the engine comes to a stop, cylinder compression often forces the crank to rotate 'backwards' by a few degrees and this engages the sprag, but it's nothing to worry about.

L.A.B. said:

Odd clonks and clunks at idle on MkIIIs often emanate from the hydraulic primary chain tensioner although the noise is often difficult to pinpoint. What type of oil is in the primary, and how much?

The sprag noise is not uncommon, as the engine comes to a stop, cylinder compression often forces the crank to rotate 'backwards' by a few degrees and this engages the sprag, but it's nothing to worry about.

Click to expand...

My MkIII does exactly the same on occasions. I'm referring to the clonk at idle. Being a refugee from the 72 Combat debacle re main bearings, I was terrified that something very serious was happening. But then I figured if something real bad is going on in there, it will all be revealed sooner or later. Nothing more has ever happened and never is a noise to be heard above idle. And it is only very occasionally that it happens at all. I like it when L.A.B tells me all is okay. It helps me sleep at nights. Not that I sleep at nights regardless. There is ALWAYS something to worry about.

Phil

Normaly radom clonks is due to something loose?

Shot in the dark here, does the clonk happen when the engine is cold? if not the thicker oil may just be preventing a metal-metal contact. ie piston knock?

I had some clunk noises from idle to 1k rpms after i refurbished my MK3.. Gave me that gutted feeling (as we've all experience from time to time) for a while.. In the end it was timing.... yep..

It was toooo far advanced and was what we call it here "pinging/piston knock".. But wasnt really it was clunking/knocking.. In the end i Reset the timing (cos it was also chewing up my ankle) and the clunks dissappeared...

I dont think this style of Norton engine lends itself to very low idle speed (5-800)... and i dont know how accurate my tacho's are but things feel much sweeter at 1k-1.3 rpms at idle..

My clunks were intermitent in first 3 minutes (riding after that) of warm up , particularly at the 6-800prm range (idle) once timing was retarded it would idle at 6-800rpm range (just) but there was no clunk/knocks either cold, warm or hot.. Idled up to 1k+ and its all sweet...

I'm with LAB - look at the hydraulic tensioners. The bottom one was bent & jammed - don't know how that happened but it kept giving clunking noises as only the top one was working. Was running ATF - could be too thin - but now have put SAE 50 in - this keeps it a bit quieter.

Interesting observations, thank you.

Primary chain case contains manual recommended amount of oil i.e. until it stops flowing from the lower hole in the middle of the chain case cover (oil is Castrol 15/40 which I have used for the past 16 years). I manually tested tensioner & it seemed ok, there are some tram lines in the bottom of the primary cover, but I don't honestly know how old they are.

Just had a bunch of family check the noise (after cooking supper) which is so intermittent as to be really frustrating, (5 or 6 chimes in 15 minutes of running) sounds like the chime of something revolving hitting something stationary.
They did their best but... well, you know ... no really definitive feedback. Will run into work tomorrow & see if any of the other riders can help locate source of the sound,

Never had weird sounds like this before, really frustrating, if I can locate the source I can move forward!

Cheers

Mike

Mike Sullivan said:

Primary chain case contains manual recommended amount of oil i.e. until it stops flowing from the lower hole in the middle of the chain case cover (oil is Castrol 15/40 which I have used for the past 16 years).

Click to expand...

Well, you could try some 20w/50 and see if there's any improvement, after all, 20w/50 was the recommended oil for the MkIII primary chain case, and it stopped the clonks on my MkIII (ATF was the worst).

Mike Sullivan said:

there are some tram lines in the bottom of the primary cover, but I don't honestly know how old they are.

Click to expand...

If the primary chain is worn, then I think it can graze the inner primary case in a couple of places as it thrashes about at low speed, one area at the bottom of the inner cover and maybe also one of the stator outrigger pillars.

Mike Sullivan said:

I manually tested tensioner & it seemed ok,

Click to expand...

Tested in its 'primed' condition?

Good Afternoon: It could be that the rotor is starting to loosen. Not the nut, but the inner hub in breaking away from the magnets. My sons' bike had this problem and it became more frequent over time. Yes, it was frustrating to find. Set up a timing light. As the timing is checked and you hear the clunk the timing mark will move as the rotor is shifting back and forth on the hub. HTH frank

Problem solved, thanks to all for suggestions, the noise turned out to be from a badly located inlet pushrod.

Cheers

Mike

WoW thats different.!! Thanks for the update on resolution...

Hi mike

Glad you have your problem solved . One thing that puzzles me is that you heard the noise, then stripped the head put it back and still heard the noise. Was the pushrod defective when it wasn't located twice . Or am I missing something?

J

'One thing that puzzles me is that you heard the noise, then stripped the head put it back and still heard the noise'

I put it down to a stupid owner, we're never to old to cock it up!

I must have incorrectly located a pushrod each time I re-assembled, I spent a good 30-40 minutes checking the location and movement of every pushrods on Sunday as I tightened the centre bolt. I got my son to turn the engine as I watched with a torch & welding rod 'adjuster' & snugged the bolt down. Almost at the end of this process the same pushrod made a dive for freedom, then I noticed that the rocker adjuster was now very high on that inlet valve, running it down pushed the rocker arm into the cup & reduced the opportunity for wiggling around. What I surmise happened is that pushrod was trapped on the edge of the rocker or tappet (therefore slightly 'high') when I set the gap then when it dropped into correct position it had space enough to wiggle & then snap (the 'noise back into place (clearance must have been almost parsecs). I checked the rods that came out by rolling them on glass & they seemed to be straight, I had a spare set so put those in rather than run a further risk with possibly weakened rods.

I understand those things are moving fast so I consider I've had a lucky escape from serious damage.

Mike, (a very chagrined owner)

Mike

I find it hard to see in the head doing the pushrods , I think it can be down to luck ,unfortunately I have to do most on my Todd . But there is no way that I'm letting anybody, except the workshop dog, see me wearing that head torch!

Hope you have a good rally

J

I normally use heavy duty elastic bands on each rocker to maintain ball to pushrod cup contact once seated, unfortunately I only had wimpy ones (from bunches of spring onions) & they were just not strong enough & required more checking. Lesson (re-) learned... check, check, & check again! (& Once more for good measure )

Cheers, Mike

Mike
Think yourself lucky you don't live in my part of the world , cos if you had told the boys that story , they would have slagged you something rotten and you would be forever known as " pushrod Mike". In a year or two how you got the name would be long forgotten but they would still be calling you pushrod.

Glad to see you get you hands dirty.

Billy the fish

auldblue said:

Mike
In a year or two how you got the name would be long forgotten but they would still be calling you pushrod.

Billy the fish

Click to expand...

Alright, I'll "bite"; where did "Billy the Fish" come from? And don't cope out with any "long-forgotten" trash!

Nathan

Billy the fish , forgotten, no I don't think so. The billy the fish story has got everything ,hot women , jealous husbands, a Kawasaki 500. A fireblade , weekends in Dundee , only the kwaka was there, part time firemen, mechanics , small town mentality, old granny's giving you a piece of their minds and A good bit more, but no COMMANDOS.

So Nathan no way.