Metallic scoring noise when clutch engaged

[allen3620]

Hi Guys
I have stripped the clutch and removed the left casing to be powder coated on my 78 350 Sport. Once rebuilt with the assistance of the workshop manual, parts catalogue and Paul Compton's videos I now have a disturbing scoring/grinding noise that only occurs when the clutch is engaged. It is important you know everything worked fine prior to this work. I have subsequently stripped it down again to investigate, taking care to check everything has been fitted correctly in the right sequence and for the life of me can't see I have done anything wrong. However my investigation has revealed traces of aluminium filings and scoring on the main crankcase around the primary shaft where the bevel washer fits against the bearing which could only be caused by the rear face of the black primary gear making contact with the case. There is what I believe a normal amount of end float in the primary shaft but no lateral movement so the bearing is fine. Why is this happening when all was fine before? Having spent 30 years in the motor trade, 10 of which on the tools I have a reasonable mechanical ability but this has got me stumped. I just hope it’s something silly I have overlooked. Please help.

[Steve Brown]

Not sure I'm thinking this through right, but have you missed out the thrust washer with the 4 ears between the clutch inner and outer drums? That is there to deal with the lateral movement of the primary gear and clutch outer drum assembly.

[allen3620]

Not sure I'm thinking this through right, but have you missed out the thrust washer with the 4 ears between the clutch inner and outer drums? That is there to deal with the lateral movement of the primary gear and clutch outer drum assembly.

Hi Steve
Thanks for the reply but the nylon thrust washer is in good order and in the correct place.

[norbert]

Are you sure that there is none of the studs loose?
The washer behind the primary is mounted the correct way, the reduced face towards the bearing?

[MickeyMoto]

Was the mating face powder coated? Might find the case sitting too far out. I removed the powder coat from mine before assembly.

[allen3620]

Are you sure that there is none of the studs loose?
The washer behind the primary is mounted the correct way, the reduced face towards the bearing?

Hi Norbert, the bevelled edge of the washer is definitely facing the bearing and no loose studs. Any further thoughts gratefully received. Thank you

[allen3620]

Was the mating face powder coated? Might find the case sitting too far out. I removed the powder coat from mine before assembly.

Hi Mickey, mating face is clean of powder coat. Thanks for your thoughts.

[mbmm350s]

Hi,
and used the correct fibre gasket? Using just sealant alone is not sufficient.
Mark

[allen3620]

Hi,
and used the correct fibre gasket? Using just sealant alone is not sufficient.
Mark

New gasket was fitted but thanks

[mbmm350s]

Hi
Between the clutch centre and the sleeve that fits over the primary shaft depending on combination of parts and type of thrust washer there should be either one washer or a number of shims or a combination.
However I cannot think how this could be the problem

The outer case itself has nothing to do with any end float
as the clutch outer basket passes through a single lip oil seal and is free to move in an out unless the oil seal that has no positive registration is incorrectly fitted. The clutch outer basket is screwed and dowelled to the driven gear. The entire clutch assembly can be fixed without the case present. This may help to diagnose the problem
With no plates present the outer basket end float relative to the centre should be set to perceptible float 0.02mm.
Too little float and the clutch will drag. Too much float and the clutch is rather binary.
most Morinisti set it by feel
I kind of went through what I would do apologies if you know all this already
Hopefully it will be something obvious
Mark

[mbmm350s]

Hi
If the clutch basket socket cap screws are too long it will cause the problem you described. They should be 22mm as measured on a dismantled engine of known provenance.
They must not protrude out of the driven gear.
M6 x22 is not DIN912 standard by the way. 20 or 25 are standard. Original screws are 8.8 black.
Also the dowells should not be loose or protrude.
Mark

[allen3620]

Hi
If the clutch basket socket cap screws are too long it will cause the problem you described. They should be 22mm as measured on a dismantled engine of known provenance.
They must not protrude out of the driven gear.
M6 x22 is not DIN912 standard by the way. 20 or 25 are standard.
Mark

Hi Mark
You make a very good point about putting it all back together without the casing on, this may help to see whats happening when the clutch lever is pulled, i will definitely do this tomorrow. Regarding shims & washers the set up from the primary shaft bearing was as follows; bevelled washer against bearing with chamfered edge facing the bearing, then the sleeve over the shaft with a smear of hylomar to seal it as per the manual, fit primary gear, then the case, then attach the clutch outer basket with dowels and bolt to the primary gear ( I have already checked the bolt lengths are correct as this also crossed my mind). fit the nylon thrust washer to the outer basket over the 4 bolt heads, then there were 2 shims on the shaft between the outer basket and clutch hub. finally fit the clutch hub torque it up fit plates etc. Thanks for the advice, very useful.
Craigh

[George 350]

While I am unable to add to what has already been said, re clutch, please make sure that the rubber seal between oil pump and case doesn't go astray with all the case off and ons. Easy to do if you are focusing on the other end!
Don't ask how I know this...

George.

[mbmm350s]

Hi, Craig,

The sequence of re assembly you quoted isn't the same as the manual, however the sequence you used
could be used when replacing the seals only to save removing the cover.
In the manual the primary driven gear and clutch outer basket are assembled together in the case first,
then the case is fitted and finally (for 350 ONLY) the sleeve is inserted (the 500 has a different sequence)
Anyway I cant think it would make any difference.
Could you post a picture of the wear please.

The primary driven gear has a central bush, excessive wear in the bush (or in the sleeve)
perhaps could cause rocking of the gear ONLY when clutch is disengaged, and only disengaged obviously
as all are locked together when clutch is engaged.
The sleeve usually has a witness mark showing the position of the lip seal.
The wear limit of these parts isn't quoted in the manual,
but i have only ever replaced the bush twice so wear here is rare,
I found the new part had to be reamed.

also if you check clearances and operation without the case you can eliminate any issue with the kickstart mechanism.

Mark

[allen3620]

While I am unable to add to what has already been said, re clutch, please make sure that the rubber seal between oil pump and case doesn't go astray with all the case off and ons. Easy to do if you are focusing on the other end!
Don't ask how I know this...
Noted, Thanks George

George.