M600 ding ding ding

Riding along late last year, bike stutters and drops power, then picks up. "Old bike I thought, needs a bit of a run" and thought nothing else of it.

Then there was a slight knocking noise, nothing spectacular, but it was there. Either or, put her for her winter snooze with a trickle on and left her be. The weekly start up didn't give me any cause for concern.

Few weeks ago, decided to strip the carbs (and the were dirty), rejet as it had straight through and a pretty much open airbox, new belts, sparks and oil. Manually cranked to make sure I hadn't royally ****ed up the timing and all was good. So started her up and it ran like a dream........except the knocking.

And the knocking is still there two weeks after. Haven't been riding much in fear, but monitoring the noise and it's louder now. So she's off the road, drained the 150 mile old oil (with no metallic bits in it), checked the clutch but all is fine. So........I think the head and cylinder needs to come off

http://youtu.be/9n_ApQZxeLU

Any views people? Anything would be greatly appreciated as I'm currently thinking about the little end having bit the dust. Did think piston slap originally, and reading the comments. But it seems more than that now...

[Flip]

If you stripped the carbs did you balance them afterwards?

The hiccup could just have been the rubbish you found in the carbs partially blocking a jet while riding.

The 600's can be a little 'slappy' sounding (what mileage has it done?) but my first checks given what you've said about clean oil would be valve clearances and carb balancing.

Yes mate, balanced and she ticks over nicely. It's just hit 15k, not too high considering it's 17 years old I thought. Haven't done valve clearances yet, but I didn't think off limit clearances could make that noise?

[Dirty]

Originally Posted by Max724

Yes mate, balanced and she ticks over nicely. It's just hit 15k, not too high considering it's 17 years old I thought.

I wouldn't rev it that hard if I was you!

[Nasher]

Originally Posted by Dirty

I wouldn't rev it that hard if I was you!

Glad it's not just me who read it that way at first.

Nasher

[Mr Gazza]

Max, before you haul the heads off, check that the flywheel nut is tight on the left hand end of the crankshaft. It could be loose and knocking?
You'll need to pop the alternator cover off, which needs a simple puller. Make sure you have ALL the cover screws out before you apply the puller. There's a screw that hides in the chain goo, just in front of the sprocket... Clean it down and have a good look for it, it's often missed.

Also check the valve clearances and the condition of the timing belts, if you have not already done so.. Those should be changed every two years, regardless of mileage.

Get a stethoscope and see if you can narrow down the area that the knocking comes from.

If you need professional help we are lucky to have Carl Harrison over at Harleston, he comes recommended by many. 01379 852020

Originally Posted by Mr Gazza

Max, before you haul the heads off, check that the flywheel nut is tight on the left hand end of the crankshaft. It could be loose and knocking?
You'll need to pop the alternator cover off, which needs a simple puller. Make sure you have ALL the cover screws out before you apply the puller. There's a screw that hides in the chain goo, just in front of the sprocket... Clean it down and have a good look for it, it's often missed.

Also check the valve clearances and the condition of the timing belts, if you have not already done so.. Those should be changed every two years, regardless of mileage.

Get a stethoscope and see if you can narrow down the area that the knocking comes from.

If you need professional help we are lucky to have Carl Harrison over at Harleston, he comes recommended by many. 01379 852020

Cheers Gazza, I used the old screwdriver to the ear method (definitely got it the right way round) and it appears to be coming from the fwd cylinder, hence my concern. Didn't want to start pulling it apart any more than I already have, but hey, in for a penny and all that. Will have a look at the left hand side when I get a chance. Not being too optimistic though.

Originally Posted by Dirty

I wouldn't rev it that hard if I was you!

Damn......

[Darren69]

The 600's are well known for piston knocking on the front pot, but I'm guessing if that were the case it would be quieter when hot?

I have a very similar, albeit quieter, knock on my M750 so will be following this closely.

[Darren69]

Worth checking the alternator isn't loose as Gazza says. This is another common issue with the 2 phase bikes especially but not exclusively some 3 phase bikes suffer the same thing. My '97 748 had the same issue, apparently it was a service amendment that was issued when Ducati became aware of the problem but I think a lot of independant dealers didn't pick up on and nd if you don't catch it time it will make a mess of your crank and alternator. All for the sake of a 10p locking tab washer and some thread lock!

[Pedro]

600s are very prone to piston slap, almost sounds like ringing a bell, ours does it hot and cold, Motor is very sound, doesn't burn oil, runs very nicely

[utopia]

My 750 is mechanically noisy too.
Sounds "typical Ducati" despite it having a quiet, wet clutch.
Unless memory deceives me, it sounded exactly the same when I bought it with 2000 miles on the clock .. its now done 22,000.
Obviously mechanical noise still makes one whince a little, and its always worth investigating anything which catches your attention as being unusual, but maybe you don't need to fret overmuch in the meantime.

Presumably you verified that the belt roller bearings were all in good nick when you changed the belts.
Do you have the fixed belt pulleys (I would think so) or the adjustable ones ?
The latter could perhaps allow mis-timing but its hard to get it wrong with the fixed ones.

Valve clearances are reputed to remain pretty stable, but may be subject to a bedding in process over the first few thousand miles before they stabilise.
So maybe after 17k, they are due for some adjustment, which may contribute to the overall noise.
They're easy ..ish to check, but more complicated to actually adjust.
Might be worth checking in the first instance ?
How to vids here ....
https://www.youtube.com/watch?v=dIj3nSJGPZw
https://www.youtube.com/watch?v=3WQY1MRlmH4

Well, sorry about the delay, I've been busy with life.

Managed to have a look yesterday and this happened...













The alternator cover was cracked quite badly at the bearing circlip mount, I can only assume from a previous owner. But since I had the engine out I had to put my mind at rest by checking the top and bottom ends. Endfloat check seems fine with not much movement at all, the pistons are tight and the cylinders are smooths and still have their hone marks clearly visible.

But as I've torn it apart, things have become apparent which I never noticed before, so I've decided to bite the bullet and once I've found a replacement alternator cover, I'll powdercoat the frame, swingarm and hangers, clean the engine up, and basically, go for a full refurb...

[Dirty]

Yep, that's how most full restorations start