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Newby Clutch Installation Report (G15-CS)

Discussion in 'Other Norton Motorcycles' started by AgentX, Nov 15, 2019.

  1. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    Hi, all-


    Wanted to share my experience so far putting a Bob Newby belt drive on my G15-CS.


    I chose the Newby unit because I was tired of the mess and repeated re-gasketing of the wet primary, having had it put together and needing to take it back apart a few too many times already. I also have a Newby clutch on my Enfield, and am very happy with it. I also took the opportunity to modify the inner plate a little to gain easier access to the magneto cap and the primary tensioner bolt, and to ease routing of/access to the stator wires.


    I spoke with Bob and he was encouraging, but warned that some work was necessary to fit the setup into the G15’s primary case; notably, the outer cover needs to be spaced away from the inner. He directed me to a Jampot article about installation in an AJS for reference, which noted:


    "Four modifications need to be made to the alternator chaincase of which only one is visible.

    1. The embossed circular ridge surrounding the gearbox mainshaft seal/tin slider on the
    inside of the inner chaincase needs to be ground flat, either with an angle grinder or a
    rotary file. In this manner the new clutch can sit comfortably on the gearbox mainshaft without fouling the chaincase at the rear.

    2. The lower section of the inner edge of the chaincase filler plug boss needs to ground
    down on the inside of the chaincase. Only a small portion of the bottom of the boss needs to be removed to allow the belt to clear the outer chaincase and the removal of metal should not affect the fitting and sealing of the chaincase plug.

    3. The standard inner/outer chaincase locating dowels (2) should be removed and
    replaced with new dowels made/inch longer.

    4. A spacer should be inserted between the two chaincase halves. I used black/inch
    thick hard Vitryl rubber on the prototype and torqued each chaincase screw to 5 lbs. If the screw clearance holes in the spacer gasket are punched out on the tight side, they'll stop the screws coming loose. Latterly, I intend to fashion an alloy spacer, probably in two parts and, I've noticed now that I can probably reduce the thickness to 1/8 inch (N.B.reduce the dowel lengths accordingly). The spacer is the only visible sign of the conversion as far as the chaincase is concerned."
     
  2. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    So I ordered the kit and got to work on preparing the primary. I had a machinist mill the chaincase flat per item 1. from the article, while cutting out what would become my access port for the magneto, primary case tension adjuster, and stator wires.

    I also ordered longer, hex-cap primary cover screws from British Fasteners.


    [​IMG]IMG_20191008_120419240 by Mick Doul, on Flickr


    I cut, dimpled, and re-hardened the clutch pushrod for use with a 6mm ceramic ball between the rod sections, with another at the clutch end to better engage the adjuster screw, which has a cupped shape. Newby recommends grinding the pushrod to a “bullet shape” but the ball has worked well for me on the Enfield and I stuck with it. I wanted it very close to flush with the end of the transmission shaft, as that position worked well for me on the Enfield.


    [​IMG]IMG_20191008_120845597 by Mick Doul, on Flickr


    Also did the initial grinding and smoothing on the chaincase filler boss using dremel, carbide bits, and a flap wheel. Without this grinding, the case will interfere with the belt path. As you can see, the plug itself could be a problem, but I figured I’d handle that once it was running.



    [​IMG]IMG_20191009_160348696 by Mick Doul, on Flickr


    Inner in place, with and without the access cover; later, I ended up getting some rubber edging and using a Dremel flap wheel to widen the kerf to accommodate its width. Still have some final fitting to do with that.

    [​IMG]IMG_20190923_100145376 by Mick Doul, on Flickr



    [​IMG]IMG_20191008_130525515 by Mick Doul, on Flickr
     
    Last edited: Nov 15, 2019
  3. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    I also had 1/2” longer locating dowels made; the Jampot article indicated the final spacing-out of the outer cover could be very narrow, but I figured I could cut these back down myself easily if needed.


    [​IMG]IMG_20191011_153957000 by Mick Doul, on Flickr


    When the kit arrived, it contained the pulley, clutch, belt, and spacer for the alternator rotor.


    [​IMG]IMG_20190922_134156845 by Mick Doul, on Flickr


    Unfortunately, Bob sent a splined pulley suitable for some Matchless engine, and not the Atlas tapered arrangement. He was quick with the replacement pulley and spacer, and I was able to get underway.


    I found the spacer didn’t like to work with the Woorduff key, but I simply trimmed a little off and it fit nicely.


    [​IMG]IMG_20191008_141827015 by Mick Doul, on Flickr


    [​IMG]IMG_20191008_142721057 by Mick Doul, on Flickr


    [​IMG]IMG_20191008_142956305 by Mick Doul, on Flickr


    Checked alignment of the belt path before putting the inner back on


    [​IMG]IMG_20191004_173233733_HDR by Mick Doul, on Flickr


    [​IMG]IMG_20191004_173223101_HDR by Mick Doul, on Flickr


    Mocked up and checked tension; loose with an easy twist to 90 degrees cold


    [​IMG]IMG_20191008_125905035 by Mick Doul, on Flickr


    And got it running as a test. You can see the clutch adjust screw is waaay out; I think I had an extra ball in the pushrod at this point, as I was dealing with some disconcerting clutch slip.


    [​IMG]IMG_20191008_153253935 by Mick Doul, on Flickr


    So after all this, the clutch really had some tremendous slip. After some flailing and thinking, I realized the clutch pressure plate was lightly riding on the transmission shaft. To fix it, I ground out just a tiny bit of metal from the center of the pressure plate which freed it to apply full pressure to the clutch pack. After talking with Bob, he said that with the “norton-type extended mainshaft,” this was always an issue, and he recommended taking 2mm off the mainshaft itself or adding another steel disc to the clutch. I may consider this if the clutch slips anymore in use after heating up fully, but for now my fix is working.
     
    Last edited: Nov 15, 2019
  4. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    To make my spacer, I found I needed at least 5/16-3/8" to feel comfortable the belt wouldn't foul on anything. 3/8" was about the max before the footrests would interfere, as well. I tried some aluminum spacers, but they were really awkward to install individually, so I got a strip of 3/8" wide silicone rubber and a 5/16" cutting punch from McMaster and got craftsy, making a spacer that fits most of the way round the perimeter. There's a gap on the bottom/rear for now, but this got me round the block.

    [​IMG]IMG_20191111_093506185 by Mick Doul, on Flickr

    [​IMG]IMG_20191111_093548288 by Mick Doul, on Flickr

    Once it was started, I used the punch to shape the inside to help it curve how I wanted from hole to hole. Looks rough from the inside but pretty good from the outside.

    [​IMG]IMG_20191111_100455424 by Mick Doul, on Flickr

    [​IMG]IMG_20191111_100459698 by Mick Doul, on Flickr

    [​IMG]IMG_20191111_150726608 by Mick Doul, on Flickr

    [​IMG]IMG_20191111_150737294 by Mick Doul, on Flickr

    [​IMG]IMG_20191111_162124938 by Mick Doul, on Flickr
     
    Last edited: Nov 15, 2019
  5. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    Next, I have located a slightly damaged spare inner primary cover. Planning on trimming out everything but the rim and milling it to make it into a solid 3/8" spacer. We'll see how that goes, but for the meantime, the proof of concept is working as-is.
     
  6. desmo

    desmo

    Joined:
    Aug 16, 2019
    superb work , all the british stock clutches were at best a compromise , they could have done better but unfortunately cost was the limiting factor

    early honda clutches must made the designers hang their heads in shame
     
  7. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Very nice step-out!

    Slick
     
  8. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    Thank you, guys.

    I also forgot to mention I stacked a few washers under each alternator stud to nudge it back towards the optimal location. This, however, has created my worst fear--trying to re-align the rotor and stator in this stupid, stupid arrangement. I'm pretty sure I have a very light rubbing going on. Best I can think (and after checking by PM with Grandpaul) is to slap some Prussian Blue on the stator and try to offset it based on any observed rubbing. This, of course, is a giant pain in the butt with all the assembly and disassembly going on to get at the primary cover. But it's easier without a gasket and fluid to deal with, so c'est la vie I suppose.

    Anyone have any tips on getting the alignment right? Honestly, it barely moves at all, as the cover limits the stator's ability to travel even with the nuts totally loosened, even after being spaced out from the original location deeper in the cover.
     
  9. Kelly

    Kelly VIP MEMBER

    Joined:
    Dec 18, 2018
    Very nicely done man. Great write up with pics too. Now I get what you were talking about on the cut out on the rear primary.
     
  10. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    I am going to take this to a machinist to skim it to 3/8" thick, which will eliminate all the remaining material aside from the rim and hopefully yield the best possible spacer.

    I might echo the cut-out on the backplate once it's mounted, or maybe just take it off whole along with the cover each time. I'll see what seems best when it's in place.

    [​IMG]spacer by Mick Doul, on Flickr
     
  11. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Remove all those sharp corners, notches, and cracks on that spacer plate, or vibration will make more!

    Slick
     
  12. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    Yeah, those will disappear when the milling is done. It will be just the rim of the piece with the bolt bosses.
     
  13. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    [​IMG]spacer by Mick Doul, on Flickr

    After taking this, used a hand drill with a 6mm bit to take the internal threads out of the screw holes.
     
  14. AgentX

    AgentX

    Joined:
    Jul 2, 2015
    I just had to take a little more material out of the dowel and screw holes to make everything fit easily by hand; didn't want it to become a struggle with the relatively fragile piece down the road and possibly bend something, plus I cleaned up the sharp edges left by machining.


    I also opened up the hole in the backplate where the wires pass through a little more, and also flap-wheeled that to super-smooth. The way the cutout is designed, I no longer have to fish wires and connectors out through that stupid hole...it's open to the top when the cutout is removed, and trapped in place in the little cavity I left once I put everything back in place.


    Drilled some little drain holes in the bottom of the spacer, too, since it's not weather-tight.


    Lastly, I need to take threads off the forward chaincase plug so that they don't interfere with the belt. Gonna mark the position it's in when it's tight and just grind away what little is needed for clearance.


    So I'm here now, and it's exciting!

    [​IMG]IMG_20191205_121309081_HDR by Mick Doul, on Flickr
     
  15. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    My method for the spacer was to get a sheet of aluminum, lay the cover on it and trace closely around the cover. It is also a good time to drill the screw holes. I used a band saw to cut it out and a disc sander to shape it. A mill was used for the interior.
     
  16. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    Very nice!

    Slick
     
  17. AgentX

    AgentX

    Joined:
    Jul 2, 2015

    Much less lazy (and destructive of old parts) than my way!
     

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