With renewed intent and a growing sense of urgency, the complete primary drive goes back on as an assembly, but not before making sure the splines on the crankshaft and mainshaft are clean. If you're wondering why the primary drive was off, you may want to refresh your memory here.
You absolutely need Loctite on their respective nuts, and the torque settings are not for the faint-hearted. I made use of the locking shoe once again and it worked very well:
At this point it would have been illogical not to take a look inside the clutch; especially because of the controversial "spring plate", essentially two metal plates riveted together, with some metal segments sandwiched in between, that sits halfway through the clutch pack. This is supposedly to give a more positive feel when disengaging the clutch, but there are horror stories of the rivets failing, and ending up as shrapnel in the clutch basket, primary or even the gearbox, with predictably disastrous consequences. I think you can appreciate how checking the condition of that plate would be a good idea at this point.
It should be noted that John Favill and his engineering team improved on the concept originally developed for the Norton Commando, and made it so that on the Evolution Sportster the entire clutch is fully self-contained and can be removed as a complete assembly (without having to remove the diaphragm spring and all the plates) if you just need to get at the gearbox, the shifter, the alternator or the starter mounting bolts. This was made possible primarily by using a different design for the diaphragm spring (one that lets you access the retaining mainshaft nut while leaving the plates and the spring itself undisturbed) and also by locating the clutch actuator outboard of the clutch assembly, instead of inside the gearbox as it is on the Commando, which then relies on a long pushrod through the hollow mainshaft to disengage the plates. But I digress.
In this case I actually inspected the clutch precisely as I would do on the Commando, more than anything because of workshop logistics. Many years ago I had bought a Motion Pro tool, and it has sat unused in its box until now. I think that qualifies this as a new-old-stock piece...
It takes considerable force to compress the Sportster diaphragm spring (it has to be very strong to withstand the phenomenal levels of torque and power coming from the crankshaft), but disassembly is very straightforward. I would recommend cleaning the threads on the tool and lubricating them with oil to aid operation.
Most of the plates were in good condition, worn as expected for the bike's mileage, and at least at first glance the spring plate seemed to be fine. I measured an overall stack height (including the spring plate) of 32mm exactly.
Closer inspection of the spring plate revealed a worrying tell-tale looseness, and I can definitely see how - in the long run - the soft brass rivets would get bashed and sheared off.
I don't want to run the risk of catastrophic failure, the resulting damage and repair cost (assuming it would be repairable) would be prohibitive.
Here is a third-party image of someone else's broken spring plate just to give you a sense of what can happen. No thank you:
So, I've decided to upgrade to a Barnett kit. I have one of their clutches on my Commando and I am very happy with it, so I trust this will work well in this application.
The extra plate kit (Part# 307-30-10011) comes with 9 Kevlar friction plates and 8 steel plates to compensate for doing away with the spring plate, otherwise the standard setup is made up of 8 friction and 6 steel. You could also argue that, if nothing else, this effectively gives you a larger clutch surface, which can't be a bad thing. The stack measures 32.5mm.
Just as a curiosity, the weight difference between the two "stacks" is 40 grams, with the Barnett being lighter at 869 grams and the stock being heavier at 909 grams.
Installation requires soaking the friction plates in transmission fluid (I left them for about 10 minutes and I use Harley-Davidson's original Formula+), then it's a very simple matter of alternating friction first, then steel, all the way until the pressure plate is ready to go back on.
There is a retaining circlip and a safety ring that seats the circlip in place (third photo down). Both must be fitted before the clutch compressor can be released. As usual with these things, it's a good idea to use a flat head screwdriver to check that everything has snapped into place properly; you don't want this failing when you're chasing Witold up the SS80...
It's finally time to refit the primary cover, so a new gasket goes on, then the cover (yes, this whole part is fiddly and you'll have to reach underneath with a couple of fingers to lift the triplex chain onto the slipper tensioner as you push the cover on) and each bolt.
Before installing the bolts, it's a good idea to clean out every threaded hole (as well as each bolt) just in case there's any residue of old Loctite or anything like that: that stuff can build up over time, and there have been instances where tightening a bolt against what is essentially an obstacle in the bottom of the blind hole results in a cracked crankcase (!). Best to avoid that.
Primary cover bolts get 9-12N⋅m; the service manual does not specify a tightening sequence to follow, and I'm aware that later models have one, however, for those it does not appear to be absolutely critical. Instead, I made my own and followed a star pattern to progressively tighten the bolts to avoid warping the cover. Common sense guys:
The LH footrest support bolts (numbers 2 and 5 in the image above) get 22-38N⋅m, but you get to that final torque only after all the other bolts have been fully tightened.
After that, the clutch actuator can be refitted and adjusted. With a small flat blade screwdriver you can feel where the adjustment screw seats; there is no need to force this to where it would begin to lift the clutch, instead, once you've identified the right spot, all you do is back it out by barely half a turn (though you may need a bit more or a bit less depending on your application and other factors such as temperatures, terrain, riding style...) and install the lockplate. Done.
I take a moment to pause and sit back, to go over all the various steps in my head and make sure I'm not forgetting anything. It's a quiet moment in the shed, it's cozy and there's a peaceful stillness to this whole scene that's somehow enhanced by the smell of oil and metal emanating from the motorcycle on the lift; it's glorious.
Time to get back to it; with everything reassembled, it is now time to check the primary chain tension. It's a good idea to check tension in a few places along the chain (let's say at least 4 different points, maybe 5), find the tightest spot and use that as a reference. Considering the triplex chain should have about a half inch of slack, a spanner of that size can work as a visual reference to see if you're in the right zone; this is a well known trick.
Items left on the checklist at this point are: fitting a new o-ring on the transmission drain plug, and installing it with 19-28N⋅m. Adding fresh transmission fluid (checking that the level reaches to just below the clutch basket), then adjusting the clutch cable (adjustment at the clutch itself was already done, as mentioned above).
I got some replacement screws for the derby cover from W&W Cycles in Germany, they're the exact same size (obviously) and button shape as the originals, only with a conventional socket/allen head instead of the confounded Torx.
2.5-4.5N⋅m for these ones
The shift lever pinch bolt gets 9-12N⋅m.
We are finally done with all things transmission, and even though it took far too long because of all the delays, this has been an extremely satisfying process from which I have gained a deeper knowledge of my motorcycle (now let's hope I got it right and everything works...).
0 comments:
Post a Comment