48 replies to this topic

[Its a min]

The clutch plate can’t not be centred.

Ah, That's ok then. I only asked as I'd read not to tighten the flywheel/diaphragm/clutch, on verto clutch, until it was in place so as to allow the clutch to centre itself.

[imack]

Could be that the flywheel is going too far up the crank taper when torqued up and is pressing up against the C washer and thrust washer and pinching the primary gear preventing it from spinning freely on the crank.
Following up from your reply to my earlier comment, in my youth I replaced my gearbox and didn't shim the idler, it ended up too tight and I couldn't select or change gear with the engine running, it changed sweetly with the engine off though, it also wrecked the thrust face on the transfer case - lesson learnt!

[MIGLIACARS]

If the pressure plate had gone weak, would that not create a slipping clutch?

I would suspect primary gear too. If it has nipped up so it can’t spin freely on the crank then you effectively have no clutch mechanism.
Starting with the car in gear gives enough resistance to force the gear to turn (or actually not turn, whilst the crank rotates inside it).
However with the engine running and the car in neutral there isn’t enough resistance to overcome any nipping up so the primary gear rotates with the crank, effectively providing direct drive to the gearbox.

I have seen this with newly bushed primaries, and the ones using floating bushes.

Well i had a spi mini  doing exactly the same as this. exactly, replaced the fingered plate and hey presto like new so this is real. just my experience.

[Its a min]

Could be that the flywheel is going too far up the crank taper when torqued up and is pressing up against the C washer and thrust washer and pinching the primary gear preventing it from spinning freely on the crank.
 

Hi imack,

Thanks for the reply. Is there any way of testing/checking this once it's all assembled or is it trial and error?

[imack]

The only way to check it properly is with the crank removed or the transfer housing off, primary gear fitted and shimmed and then fit and torque flywheel and recheck primary gear end float.
Assuming the engine is in the car I think I'd fit the clutch plate to the primary gear and fit and torque the flywheel, leaving the clutch diaphragm and back plate off. You could then put you fingers through the starter motor hole and see if the primary gear spins freely by turning the clutch plate. You obviously can't check primary gear end float though.

[Its a min]

The only way to check it properly is with the crank removed or the transfer housing off, primary gear fitted and shimmed and then fit and torque flywheel and recheck primary gear end float.
Assuming the engine is in the car I think I'd fit the clutch plate to the primary gear and fit and torque the flywheel, leaving the clutch diaphragm and back plate off. You could then put you fingers through the starter motor hole and see if the primary gear spins freely by turning the clutch plate. You obviously can't check primary gear end float though.

Thanks for this.

 

You assume correctly in that the engine is still in the car. I'm a bit confused on how I could fit and torque up the flywheel and clutch plate without fitting the pressure plate. Do I need to remove the flywheel boss from the pressure plate? What would hold the flywheel in place as the pressure plate bolts to the flywheel and keeps it in position?

[KTS]

..sounds like that applies to a pre-verto type clutch

 

the equivalent for a verto type, *I think* would be to remove the flywheel only (..which takes the place of the pre-verto back plate..) and then refit the pressure plate and boss to check if it's binding on the primary gear?

 

i'd leave the clutch friction plate in place as well just in case that's being pushed back to far on its splines and causing the binding (..no idea if that's likely or even possible..unless you put the driven plate in backwards ?)

Edited by KTS, 18 December 2018 - 01:48 PM.

[imack]

Sorry, never dealt with verto clutches

[Its a min]

..sounds like that applies to a pre-verto type clutch

 

the equivalent for a verto type, *I think* would be to remove the flywheel only (..which takes the place of the pre-verto back plate..) and then refit the pressure plate and boss to check if it's binding on the primary gear?

 

i'd leave the clutch friction plate in place as well just in case that's being pushed back to far on its splines and causing the binding (..no idea if that's likely or even possible..unless you put the driven plate in backwards ?)

 

Thanks KTS, Something for the weekend.

 

Sorry, never dealt with verto clutches

imack, I starting to wish I hadn't!

[Its a min]

Quick question, does it matter which way round the C-clip fits? I only ask as I may have fitted it against the primary gear and has just dawned on me that it may not be perfectly flat fitted that way around where as, the backing ring would be. If that's the case, could this cause primary gear seize? Although, the primary gear was turning freely on the crankshaft.

 

Just a thought.

[DeadSquare]

The "backing ring" ,  that big washer with a lump on one side of it, goes on first, with the non lumpy side tight up against the primary gear, then, with the number 1 and 4 pistons at the top of the bore, the C washer is slid downwards into the grooves in the crank.

 

If you take out the spark plugs from 1 and 2, and drop in something soft like plastic straws, you can see which piston is coming up as you turn the crankshaft round.

[Its a min]

The "backing ring" ,  that big washer with a lump on one side of it, goes on first, with the non lumpy side tight up against the primary gear, then, with the number 1 and 4 pistons at the top of the bore, the C washer is slid downwards into the grooves in the crank.

 

If you take out the spark plugs from 1 and 2, and drop in something soft like plastic straws, you can see which piston is coming up as you turn the crankshaft round.

 

Cheers DeadSquare. Should the c-clip slide on easy? I only ask as I remember having to almost force it into the slot on the crank.

[DeadSquare]

NO.    If you remove the primary gear and then try the C washer in the crank slot, does it need forcing, if so, it or the slot are damaged.

 

You should not have to force it in,  it should slide in with what I call  "little finger pressure" / " very light thumb pressure".

 

Have you got a set of feeler gauges?  You should be able to slip a five thou feeler between the lumpy washer and the bronze thrust of the primary gear.  It should be no more than .0065" and no less than .0035".

 

The reason for making sure that 1 and 4 pistons are at the top of the bore before fitting the C washer, is that the next person to take the fly wheel off, knows that if they do the same, the C washer can not slide off the crank and become wedged behind the clutch, which could, under dire leverage, bend the C washer.  The clutch and flywheel then have to be dismantled.

[Its a min]

NO.    If you remove the primary gear and then try the C washer in the crank slot, does it need forcing, if so, it or the slot are damaged.

 

You should not have to force it in,  it should slide in with what I call  "little finger pressure" / " very light thumb pressure".

 

Have you got a set of feeler gauges?  You should be able to slip a five thou feeler between the lumpy washer and the bronze thrust of the primary gear.  It should be no more than .0065" and no less than .0035".

 

The reason for making sure that 1 and 4 pistons are at the top of the bore before fitting the C washer, is that the next person to take the fly wheel off, knows that if they do the same, the C washer can not slide off the crank and become wedged behind the clutch, which could, under dire leverage, bend the C washer.  The clutch and flywheel then have to be dismantled.

Cheers DeadSquare,

 

Something else to check at the weekend.

 

I'm starting to think this could be the cause of my problems. I bought new c-clip and backing washer and it was definitely tighter to get on than the old one to get off but put it down to wear. If this is the case, I've not seen different thickness c-clip/backing ring for sale so I'm assuming a flat surface, wet and dry and some elbow grease?

[DeadSquare]

As far as I know, the lumpy washer is a precision item.

 

Any differences in dimensions are taken care of, by a range of different thickness bronze washers that slide onto the crank before the primary gear is put on.

 

The bronze washer has an inside bevel on one side because the tail of the crank has a radius where it joins the rear main journal.  If it is on the wrong way, the radius does not let the bronze washer seat against the journal, which in turn means that the primary gear doesn't quite go far enough onto the crank etc: