MRC Forum- brought to you by www.morini-riders-club.com

I have an annoying what I can only describe as bell ringing knocking noise from the clutch basket. This noise is always there when ticking over and revving and only disappears when the motor comes under load - in gear, clutch out. So far I have warmed up the bike and removed the clutch plates then started with E start but it’s still there. With the engine running, if I hold the clutch centre still with the basket rotating around it the noise is still there. The clutch basket look true as it rotates so no reason to suspect interference around its circumference. I have video’d the basket in slow-motion and can see no irregularities. This noise annoys the hell out of me and spoils what is a good engine. Has anyone experienced this problem before? Any help appreciated.

Is this not a characteristic of a dry clutch?

Hi Ming
I accept that dry clutches can be noisy but is has a destructive knocking noise which shouldn’t be there.

Should read distinctive not destructive

Ducati clutches are noisy, but my Morini clutches are not, not sure what is going on with yours Weevee, but it's not normal. Sorry not to be more helpful.

Hi Pedro
Thanks for your views. Do you know if the clutch basket should be balanced?

Hi weevee

First I have some questions:

Is this a problem that has always been there or has recently developed.
Does the clutch work normally and it has good feel meaning not harsh or grabby, slipping etc.
It should not be the case that the dry clutch is so loud to be annoying and then only when in gear and clutch disengaged is there any sound from the clutch.
When clutch is engaged there is nothing to be heard, whether in neutral or under load the entire assembly acts in unison.

I assume that all other causes of knock or drumming or ringing have been eliminated and that you are confident that the clutch is the problem?
Any knocking from clutch side then I would need to satisfy myself that the main bearing is OK.
Also there is a long standing worry among the Morinisti that the nut securing the primary drive gear could be loose.
And Indeed overly retarded ignition can give these kind of sounds.
But to help with the clutch because first you must be happy that all is well with the clutch.

To check the clutch:
With plates removed,
Please to check that there is not excessive rock of the clutch basket (by the way its called campana or bell in Italian !),
i.e outer aluminium part. Its hard to be precise here but i think already you say it appears to run true.
If the clutch basket is properly secured to the primary drive gear then any rocking here could be due to the centre bush of the gear being worn out.
With this problem there is likely to be oil inside the clutch cover.
If there is no rock then check the end float.
I assume the centre nut is tightened to the specified torque.
The clutch outer basket relative to inner centre end float should be between 0.02 and 0.08 mm , that is just perceptible float.
If there is a brushing sound as the clutch centre is rotated its OK but there should never be a knocking scraping or grinding
If there is excessive end float or binding at any point i suspect the special washer(bush) behind the clutch centre is failed.
Please say the age or engine number of the machine because there are three different types of special washer.
The clutch centre washer was on very early bikes made of steel but later replaced with bronze and finally with specially treated nylon
See picture: I think if all these points check out then you should compare the sound with another Morini to take the bike to a specialist. Where are you located?

Mark

Are you absolutely sure it's the clutch? My 500 has a similar ring to it. It gets more noticeable when idling on the sidestand. On mine it's the starter centrifugal clutch bits I'm sure. I've gone over it a week or two ago and couldn't see anything amiss. So I'm riding it and ignoring it-unless it develops!

I agree with Steve it may not be the clutch and the best way to check it's not normal is to compare with another Morini at a Morini club meeting.
but as ever you must judge whether there is a real fault or not.

Mark

Mark
Thanks for your in depth response. A lot of good info there. I am now convinced that the centre bush is worn which in turn has probably worn the oil seals as I have oil seeping slightly from the clutch cover. I have started the engine each time I removed a section until it disappeared. Only when the primary drive gear is removed does the noise stop - starting up momentarily with the outer case in place again and without the basket on the primary gear brings the noise straight back. FYI the special washer is the new plastic type. I will now change the bush and oil seals and retest.

Hi weevee,

The bush (350 part 25.03.05) within the primary driven gear is only operational when the clutch is disengaged and wear in this bush or the sleeve
is really only likely on very high mileage engines,
i have only ever needed to change this bush twice and on each occasion i also changed the sleeve (14.04.12) upon which it runs.
When changing both it was necessary , with original Morini parts, to ream the bush for a running clearance. I do not remember the clearance value.
So I wouldn't change the bush unless it is absolutely necessary and if you have removed the casing and have the sleeve and bush to hand you can check
the wear in any case. The sleeve will have a witness mark for the oil seal , when refitting it needs to be sealed to the shaft or there will be oil leaks.
The sealant recommended is Blue hylomar.
If i understand correctly you have removed the clutch outer basket from the primary driven gear and started the engine .. whoah!
It is good practice to replace all the seals when the case is removed.
Please take great care with the green seal on the oil pump gallery, the original type is not available and substitutes are of dubious quality.

Did you check the torque setting of the primary drive gear nut and confirm that all is well with the bearings.
Do not remove the nut as it should be replaced if removed.

Mark

Hi Weevee, It sounds like the problem is with the primary gears?

Check whether the crankshaft ring nut is tight and also check that there is no play in the shaft at the gearbox bearing/s.

On a 500 engine I had a problem with vibration linked with a slight chattering/ringing noise that increased with revs. When I removed the primary cover to check the crankshaft ring nut I found play in the gearbox input bearing (which couldn't be felt with the clutch basket/primary gear in place).

Hope you find the cause soon and the solution is straight forward, Ian

Listening to your comments looks like the sleeve is good condition after all. The crankshaft nut is definitely loose so will tighten and hope all comes right. Thanks for all your help.

Hi Weevee

The crankshaft nut is definitely loose so will tighten and hope all comes right

That make sense we thought of a loose nut. And as I said at the beginning,

Also there is a long standing worry among the Morinisti that the nut securing the primary drive gear could be loose.

Thought's of this nut coming loose keep long time morini riders awake at night, because the oil pump gear may slip on the shaft, and oil pressure is lost.
Some cannot stand it anymore and take the cover off to check

If your's has the ring nut with a yellow nylon insert then you need two special tools. Earlier 350s it was just a regular nut so only the holding tool is needed.
Many would replace the older plain nuts as a matter of course. If the nut looks in bad condition like its been beaten round with a chisel/screwdriver etc I would replace it.
Check the oil pumps gear has some backlash and adjust the fitting of the screws if it doesn't.
All these points are in the workshop manual in any case.
Torque 5.0 mKg
Mark

Hi Weevee

Please let us know how you get on. We are hoping for a simple fix

For help with the clutch assembly, shimming etc please see Paul Compton's You tube channel
https://www.youtube.com/watch?v=qZqksiAympg

Mark