1200S: service time, part 11

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...).

Delays

Delays, shameful delays continue. I ordered a Barnett clutch kit on the 10th of September last year and received the worst after sale service of the past decade, easily, from the people at "parts europe" and a reseller in Italy by the name of "bikeinside", who was shoddy, detached from reality and completely disorganized. Both dealers were dismissive and just plain did not care that they'd left me hanging. Avoid these time wasters at all costs. 

After four months waiting, only to see a delivery date being pushed further and further into the future*, I ran out of patience and sourced the kit elsewhere, which cost a little more but at least I got it in just a couple of days. The first option might have been cheaper, but if it never materializes then it's no good. When I asked for my money back, the guy goes "oh if you want I have all these other clutch kits available right now"... Dude! You couldn't have told me that at the start of this whole thing? Instead you wasted four months of my time? What a dick.

I cannot accept delays and I cannot accept excuses: I have heard everything from COVID (really? still?) to the war in Ukraine, from labor shortages, to you-name-it. Supply chains are supposedly disrupted because of how complicated everything is, when in reality this is just the result of the usual "bankers" and their unchecked greed, ruining it for the rest of us. To hell with them all, better to think of more important things.

*You can check for yourselves at this link, bear in mind I first tried on the 10th of September and it had probably already been unavailable for who knows how long. What a joke.

The upgrade continues.

It's over to uncle Fester's garage to fabricate a new mounting for the oil tank (the one it has now has already cracked a couple of times). I think the problem is that having a flat bar (in green in the grainy shot below) welded across the frame to support the oil tank underneath, which is rather heavy, actually puts that bar under considerable vibration and torsional stress: it must be that at that particular point in the frame, stress is such that it can travel along the support bar and fracture it.

Much like the seat spring mounts and the rear fender brackets, this bar did not come with the frame but was added during the initial build of the Rising Star. It seemed perfectly sturdy at the time but there's obviously cause to revisit that. I believe the final solution will involve rubber mounting of some sort, but I'll let my friend figure that out.

Since the oil tank has to come off, this is a good opportunity to give it a thorough clean on the inside: doing this periodically is cheap insurance for the oil pump, in case there's any debris in the tank that could reach the engine, with predictably bad consequences. I also might as well strip the old paint and give it a fresh coat or two with good heat-resistant primer and paint, both available from Mr. White.

The seat mounts aren't the prettiest thing in the world and maybe there's something we can do about that as well, although this is a non-issue and up to uncle Fester's good taste.

With the engine properly hot, I also took the opportunity to go over the final adjustment of the idle/pilot circuit: this requires a slightly fast tickover to start, then adjusting the air screw to figure out where the engine runs faster; at that point the idle screw can be backed out (thus lowering idle speed) and the process repeated maybe once or twice more until you're sure you're at the best possible leanest mixture. Be prepared to re-adjust this depending on ambient temperature and riding conditions.

Riding this skinny, narrow bike after such a long time felt both familiar and a bit of a surprise at the same time: I had forgotten just how... distilled this bike is, and that somehow amplifies the whole experience. The handling of a properly built hardtail is something every rider should experience; the ability to set up a corner, drop the bike into it and feel it bite into the trajectory with total precision is truly a superior quality.

On the other hand, another thing we really must address is the front brake, because at the moment it's about as good as a strong headwind.

I did fit new brake shoes almost ten years ago, and at the time it seemed to make a difference compared with the original items it had when I got the front wheel for the initial build, but there has to be a way to skim/fix/true the assembly so it works better: OIF drum brakes are usually excellent.

The ride over was intense, no doubt because I had forgotten what the Rising Star is like to ride, but also because of the broken oil tank mount rattling underneath me. The air was definitely crisp, though thanks to global warming it wasn't freezing cold. While the exhaust is definitely too loud, I am once again surprised by the smoothness of the engine and how it delivers consistent torque all through the rev range. It may be relatively small but boy is it a blast to rip around on!

I'll update the blog as we go, I expect uncle Fester will keep me informed of progress, and I hope to be able to drop by once in a while to see how things are going.

Many thanks to Lele who helped out with logistics today, and also had a go at riding this contraption of ours (I need to get someone else into these British lamb chops so we can go on rides together!).

1200S: service time, part 10

You'd be forgiven for not remembering about the Sportster's ongoing overhaul. Since the last time I was able to work on it, almost FOUR MONTHS have passed as I waited for parts to arrive. These delays in the supply chain are infuriating and unjustifiable. Better to crack on with it:

CARBURETOR

The reason I'm getting into the carburetor is to improve what's already there and tune it keeping in mind this motorcycle now has a pretty unrestricted air filter and the wonderful Vance & Hines SS2R exhaust (fun fact: that exhaust system was developed for the AMA Harley-Davidson Super Twins class around the mid 90s, and debuted at Laguna Seca).

Before even getting started on this, it's a good idea to have a rebuild kit available, as you'll probably find that certain items will need replacement:

(Yes, if you look closely you'll notice that that brand-new-still-in-the-package gasket is torn. Great.)

It was during the Stealth Trip 2 that I had noticed the engine felt like it was running a bit lean, and the spark plugs would seem to indicate as much, as the electrodes look pretty white.

Nowadays with electronic fuel injection being ubiquitous, and general owner disinterest being prevalent, the concept of "tuning your machine for best performance" is somewhat of a moot topic, but those like me, who appreciate a carburetor and strong, simple air-cooled engines, still know what time it is, if you know what I mean.

I became a staunch Dynojet enthusiast after fitting one of their "stage 1" kits to my old Honda;
I was completely surprised by just what a big difference it made for such a (seemingly) simple modification, to the point that I can't help but wonder how much better my other bikes would run if they each had one fitted.
For example, I thought about the BMWs and how that would work; or would the little Yamaha gain some much needed horsepower and torque? In both cases I don't think a kit is available, though you could probably make your own if you reached out to Dynojet and asked for advice.
Now, what is available is a kit for the Sportster, and for pretty much any variant of the Sportster in every state of tune. Since I'm trying to make this bike be as good as it can be without compromising tractability and real-world usability, this is something I had been mulling over from the start.
First of all I checked what was actually in the carburetor (just in case it already had Dynojet components fitted) and what I found was a pretty stock set configuration, albeit without the welch plug over the idle fuel mixture screw. The latter had been turned way out, at just over two and a half turns from seated, which is extreme for a stock motor -if compared to the factory setting of 1&⅛ turns to comply with emissions regulations- and must have been an attempt at enriching the mixture after fitting the exhaust*. Obviously this does absolutely nothing where it counts, and only affects the idle. This is confirmed by the overall lean mixture I noticed.
The kit that suits my motorcycle is the E8103 and after an unacceptable delay of over three months, it finally came with definitely more stuff than what the Honda got: there is a comprehensive selection of main jets, the all-important needle, as well as a drill bit for the slide (how daring!), a spring, assorted clips and washers, and an emulsion tube.

Above: as per Dynojet's instructions, the 195 is appropriate for my bike, with an aftermarket exhaust and air filter. That said, I can go up to a 200 if needed, and I can raise or lower the needle as well, meaning I will get to optimal carburation no matter what.

Installation is very simple, you just have to be careful and use gentle hands; this is something that calls for finesse, not "Hulk smash!"...

I must admit that drilling out the slide made me a bit queasy, as it's obviously irreversible, but what the heck, no guts no glory!

A 1200S in stock/factory condition should make about 65bhp. With a good air filter, Dynojet stage 1 and the Vance & Hines, we should be looking at 72/73 real bhp (I am aware that this puts me squarely in the "danger zone" for the dreaded oil pump drive gear failure, I will discuss this with a competent mechanic and make a plan.).

Any work on the carburetor must be approached with extra caution, as you are dealing with small, delicate parts that can be very easily damaged. And damage here means lots of cash, so, you've been warned. I see one overall pitfall one could fall into when working on a carburetor, an involuntary misconception that "this is a small, self-contained component, therefore it's simple"; obviously it is precisely the opposite, this is complicated and delicate, and requires attention to minute details.

It is especially important to use properly fitting tools (such as the screwdrivers to remove the jets and float bowl screws, and the drift to remove the float spindle, although I wouldn't do that unless absolutely necessary) and to be very careful if using compressed air: it may seem like a good idea to blow 90psi down an air or fuel passage, but you might inadvertently blow some debris into it, with predictably bad results. It's better to carefully clean the outside before opening anything up, and always keep parts accounted for and safe from damage while on the workbench. The next photo serves to illustrate two things, the first being why you should clean the outside of the carburetor before opening it, the other is the serial number, which you'll need when ordering parts:

Make a note of all settings as found (air/fuel mixture screw, the idle position, needle position, and of course jet sizes) and don't assume that what you find is necessarily correct: some idiot might have been in there before you and forgotten a washer or reversed the order of some parts, inserted a needle seat upside down... you name it.

In my case this is what I found:

• air/fuel mixture screw set at 2.5 turns from seated, without original welch plug
• idle stop with 8.8mm of threads exposed
• stock non adjustable needle (pretty grimy)
• stock pilot jet (this is pressed in and not meant to be removable. It is also what meters fuel to the "enrichener" circuit and works in tandem with the small tapered needle that you actuate when starting the engine from cold)
• 42 slow (or intermediate) jet
• 195 main jet
• standard emulsion tube (filthy and crusty)
• standard float height 
• some dirt and impurities in the float bowl and related passages

The smallest, imperceivable defect could lead to an engine that's not running quite right, and you might have everything installed correctly, yet be unaware that a little bit of dirt left in a float bowl passage is causing that problem. Be thorough, be methodical and go over everything. 

While you're here, probably not a bad idea to thoroughly lubricate the throttle cables...

With the exception of checking that the accelerator pump nozzle is correctly oriented to shoot down the center of the bore, I wouldn't do any of this with the carburetor on the motorcycle, way too uncomfortable and too great a chance of damaging something. Bring this to the workbench and get comfy.

Above: stock needle at the top, Dynojet item below. Notice grooves to adjust mixture (with an 'e' clip, shown in the next photo).

Next, a look at the emulsion tubes, stock on the right, Dynojet on the left. It's easy to see there is a big difference and it results in two different types of acceleration. While the stock item probably delivers a smoother transition as the throttle is opened, the Dynojet delivers snappier response. Amal did something similar for the police model of the Triumph (nicknamed the "Saint"), in order to help officers quickly catch up to all sorts of troublemakers, agitators, communists and run of the mill lowlifes; it was a needle jet without the cross drillings, which supposedly gave brisker acceleration. Who knows.

Assorted notes:

You can check float height (after tilting the carburetor to the correct angle, see workshop manual), using a vernier caliper as a depth gauge.

If you need to remove the float pin, pay attention to the arrow cast in the carburetor body, as one end of the pin is larger than the other, and knurled.

Once reassembled, tip the carburetor to simulate position on parked motorcycle (kickstand test) and check for leaks. You need fuel in the bowl for that...

Obviously check the diaphragm and accelerator pump membranes: they must be supple, free of punctures or tears, and they should not be deformed in any way.

Above: properly clean and properly assembled. The two large bolts on the saddle are the breathers for the cylinder heads.

A note about marketing ploys, fools and their money (they're easily parted!): there are many products on the market that don't really do much of anything. Some call them "the answer to no question", others claim that something like a Dynojet kit is just expensive and unnecessary, and that you can get even better results with just a larger main jet that will only set you back a couple of bucks. Let me be clear: Dynojet kits really work as advertised, and if they seem expensive "because it's only a few small bits" then I must assume those people don't truly understand how carburetors work. I appreciate that I won't know for sure until I try it, but I am confident enough to bet on a noticeable gain in overall performance and throttle response. Watch this space, I'll write back to either confirm or eat humble pie.

Now, obviously any extra performance comes at a cost, and yes, gas mileage will suffer as a result... but not by much. And trust me when I say that when you're on the road enjoying the bike as it was meant to be, it really won't matter at all.

*remember, this screw meters fuel, not air.

Time for an upgrade

As Freddie Mercury quite rightly pointed out in the 1975 song I'm in love with my car: "rather buy me a new carburetor". Well, I almost certainly need to replace the carburetter on the Rising Star. Given infinite time and resources, I could try all sorts of remedies to fix the existing one*, but real-life constraints mean that's just not practical. As the 30mm item worked really well, I would be inclined to stick to that size, rather than "downgrade" to the original spec 26mm. I would normally consider nothing but an original Amal, but these have become seriously expensive and my pockets are only so deep, especially for a bike that I must admit I might use once or twice a year at the most if I'm lucky. So, against my own beliefs, I have decided to go for a much cheaper version and bought a Wassell "evolution carburettor"; this ended up being exactly £100 cheaper than an Amal. I did this only because quality of the actual carburetter body appears to be identical (aside from the finish) if not better. Fitment was hassle-free. The fact that any Amal parts actually interchange with it**, tells me these copies are made well enough and the difference in price is down to labor costs and a smaller overhead rather than quality. This is an important point, and I would consider using the words "alternative product" rather than "cheap knock-off" when describing the Wassell carburetters. This time, the Orient wins, sorry Britain.

I have to pay respect to this old carburetter, which I made up from a bunch of used parts in not-so-good condition to begin with, and yet it ran really well. This thing took a lot of abuse before it was finally time to replace it and I'm sure most other brands would not have been as sturdy as the Concentric.

Fitting the Wassell was very straightforward and presented no challenges. Starting at first was hard but more to do with fouled plugs (from previous monkeying around trying to get the bike to run) than anything else but, once running, throttle response is very smooth, consistent, crisp even. There seems to be no hesitation during pick up, and it idles fine just on a standard setting of the air screw (1&½ turns out) and with the idle stop so that you can just begin to see light through the slide. I am going to try it as is for now, with all Wassell parts and think about any changes to the jets and other components in the light of my next test run.

*In my attempt to free the blocked pilot jet bush, I ended up reaming it out of size, with the result that the whole thing now provides way too rich a mixture and is no longer tunable. My fault.

**With the exception of the slide: the Amal anodized slide that I already have does not fit in the Wassell, it is too tight a fit.