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#Post#: 2908--------------------------------------------------
Clutch slip
By: Rob vW Date: August 18, 2021, 3:17 am
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Having been out and about a few times on the NF, unfortunately I
have discovered that it suffers from clutch slip in 4th (top)
gear. It is quite disconcerting, especially when you have built
up speed, to suddenly hear a sharp rise in engine revs.
Having read many posts about engine oil, clutch springs and
everything else, I decided it was time to delve back into the
engine to investigate.
The first problem to overcome, once the side of the engine was
removed (the engine is in the frame and the exhaust is still
connected) was a clutch compressor. It is quite simple to make
with a piece of 50x50mm 300mm long wood, some 40mm diameter
plumbing fittings and some M6 studding and some M6 nuts and
washers. Because the exhaust is still in place, you need to make
the studs long enough to allow the wooden compressor bar to
compress the clutch and still be clear of the exhaust.
You need to drill 2 holes in the wooden bar set at least 50mm in
from the end (to allow the wood to retain its integrity) and
200mm apart. The studs screw into crankcase holes diagonally
opposite each other so that the wooden bar goes over the centre
of the clutch.
I used 40mm plastic plumbing fittings as that is what I happened
to have lying around (in fact the M6 studding was the only part
I specifically bought) and put a screw on compression fitting on
the end to press onto the clutch. This means it sits nicely
into the centre of the clutch spring plate.
When you have set up the compressor, make sure you use some
penny washers under the nuts that will do the compression work
onto the wood. They spread the load and stop the nuts from
digging in. Gradually do up each nut equally to compress the
clutch spring plate to allow you to remove the big retaining
circlip. This is not difficult to remove once the pressure is
off, and then you can carefully back off the compressor nuts.
Once you have disassembled the compressor you can examine the
springs and clutch plates.
Here was my first problem. The springs were longer than
standard, by about 10mm. My guess is that they are Morini
springs. Secondly, neither Gutsibits or Stein Dinse had clutch
springs in stock. And Norton springs do not fit (diameter too
big).
Fortunately, I have a biker colleague in Germany whom I asked to
contact Pirner Guzzi. At first I just wanted springs, but Uwe
Pirner suggested that I should replace the friction plates as
well. The reason for this is that the original friction plates
were marginal at best, and of course the ones in my bike are
probably 50 years old, soaked in the wrong or old oil and they
splip and the wrong springs were fitted!
Therefore I made an executive decision to change the clutch for
Pirner's new improved clutch. This is where I have an advantage.
Since Brexit, Pirner like many other small business, will not
deal with the UK (it has become slightly more complicated).
However, my colleague ordered the parts which he received very
quickly. Unfortunately my colleague was unable to get the parts
into my weekly shipment from Germany (I work for a German
company) this week as they had suddenly become super efficient
and closed the weekly shipment early. So it will be at least 2
weeks before I get the new parts and can fit them! Updates in 2
weeks!
#Post#: 2909--------------------------------------------------
Re: Clutch slip
By: JamesNFalconaut Date: August 21, 2021, 8:14 pm
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Great write-up Rob.
Problem, analysis, method, solution.
Will be interesting to hear how the Pirner clutch goes.
#Post#: 2957--------------------------------------------------
Re: Clutch slip
By: cloggy Date: July 11, 2023, 12:04 pm
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I had the same problem. I changed the oil 3 times to get rid of
the car oil residue, and it stopped slipping. I was lucky.
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