NRS belt drive question.

[spondonash]

This question is directed to Richard Negus. Hi Richard, it's been a long time. I have a question regarding a slipper clutch I have for my NRS. Now to me the back plate has clearly been machined on the back, the triangular shaped strengthening ring has been machined flat and the centre boss has also been reduced in size.
Can you confirm that this has been modified please, it came with the belt drive from a very reliable source. ;)
Thank you.

[Richard Negus]

Hi Ash,
A long time indeed!
I may just be the camera angle, but your plate looks slightly different to either of the two I've got here.
If you put a rule across the back face, the machined area about 116mm diameter should be on the same level as the centre boss.
The splined centre boss should be about 14.1mm long.
Wayne's plate has some additional machining around the centre boss, presumably to give clearance on the drum bearing. I won't know for sure until I see the new clutch drums.
In 2006 at Rugeley, I did a proper scheme of the belt drive and made detail drawings of the drum and engine pulley. At that time, I was supplied with two different used clutch drums so I'd guess there has been more than one version of the slipper clutch.
R.

[spondonash]

Thanks very much Richard, yes 14.1mm spot on and yes absolutely level across the face so my assumption that it has been modified was correct. It makes sense as it was a complete clutch from a race bike. Fair to say different things would have been tried and the details lost in the ether. As the back face of the back plate doesn't contact the bearing in the clutch drum I assume there was a thing spacer between ?

[Richard Negus]

Ash,
14.1 and level is standard Kawasaki, just as Joe's new(ish) plate.
The 'NRS' modification is machining outside of the centre boss so that it does touch the bearing.
Bearing in mind that I last looked at the NRS clutch in 2006, I think the drum has a small lip at the outer side to retain the bearing and a circlip on the other side.
A close-up photo of each side of the drum bearing would help.
R.

[spondonash]

OK, well that's weird but this one has been machined and looks different to Wayne's for example as mine has LESS metal on it. Very strange.
I will post up a couple of photos but your memory is good as yes a circlip one side and a lip on the other.

[spondonash]

Here you go Richard. Do you recall how much needs to removed from the back plate to make it contact the bearing ?

[spondonash]

Richard, would it be possible to get some measurements please ? Am I right in assuming the centre boss remains the same at 14.1mm and it is just the material around it that needs machining ?

[Richard Negus]

Ash,
Thanks for the photos; I had imagined the circlip was at the back. Certainly Wayne's machined backplate wouldn't work with the circlip at the front like yours - unless there was also a stack of shims to get the clearance.
For your set of bits, I suggest you measure the drum and machine the backplate accordingly; 0.5 mm should be enough clearance. See attached sketch, where I assume a standard circlip, 2mm wide, is used and allow another 1mm for the outer lip on the circlip groove.
R.

2018-03-04 145320.jpg

[spondonash]

Thank you Richard, great drawing, it's very clear and easy to follow. 5 minutes on the lathe and job done. I've been in touch with Joe about having a centre nut and oil pump drive added to the batch if that's OK ?
Thanks again, brilliant.

[spondonash]

Job done, thanks very much Richard. Getting it set up in the 4 jaw chuck took the longest lol

[Richard Negus]

a centre nut and oil pump drive added to the batch if that's OK ?

You're on my list!
R

[spondonash]

a centre nut and oil pump drive added to the batch if that's OK ?

You're on my list!
R

Thanks Richard.

[Wayne]

Richard did Joe leave the oil pump bracket with you, i have the pressed in spacers that go with it. 2 are long to fit the nrs cutaway right hand end plate. The other which fits on the part of the std part of the right hand end plate is about 6mm long.

All the nrs with slipper clutch had A spaced off oil pump bracket. I cant confirm if Brians duckhams did. I have thought for A long time my slipper clutch had A spacer between the clutch drum and backplate

When the weather gets warmer i will mesure the spacers.

Regards Wayne

[Richard Negus]

Hi Wayne,
Confirming I have your oil pump bracket.
I'm hoping to have a clearer view of how it all assembles when the new drum arrives.
Rgds,
R.