The 900SSie - at least - has the battery beneath the tank, forward of the rear rocker box. The battery tray is bolted to two lugs, left and right. The left one has an Allen bolt (or screw) with the head beneath the lug. The right one is missing. That one passes through the battery tray and the frame lug, into a bracket with a trapped nut, from which is mounted the starter relay. It was on removing the battery (for the first time) that I chanced to notice the relay resting on the rear cylinder fins (must have got pretty hot!) So, the fact the relay bracket precisely fits the underside of the frame lug and has a trapped nut seems pretty conclusive that that bolt points downwards, with the head in the battery tray recess (though it doesn't look very deep. Obviously it can't protrude into the tray or it'd wear a hole in the bottom of the battery. Guess I'll have to measure it, if I ever find my verniers). So I'm thinking logically someone, sometime, took the relay off, for whatever reason; took the battery out in order to remove the bolt. Then, when putting the relay back, either forgot to refit the bolt - or lost it and didn't think it mattered. And I'm laying in bed, expecting to fall asleep quickly, only I wonder if there's any other reason someone removed that bolt? Working on the head, say? Which simply wouldn't have occurred to me otherwise, because the bike has only done about 13,000 miles. In my lifelong experience with the internal combustion engine I can't imagine needing to work on the head within the first 13,000 miles! Or for that matter, would I have expected a coil to fail and a subframe lug to snap in less than twice that, as happened on the 999. So maybe the Ducati twin performance comes with a certain fragility? Which led me to think of cam belts needing replacement every handful of a thousand miles. When cam chains last ten times as long. As I recall, the critical weight in the typical valve train is everything below the spring. Is it that the drive becomes part of the critical mass in a desmo system? And that why the move to belt from bevel? Because it's all unsprung weight?
There are advantages and disadvantages of each system. Chains last a long time, but they also do stretch in use and need to be adjusted. Belts are more constant and don't change during use, but need to be replaced more often. Gears work great, but they are noisy, and they consume/waste energy and power compared to chains and belts. source: https://www.ducati.ms/threads/why-does-ducati-use-belts-and-not-chains-or-gears.728833/
Belts were a great step forward for ease and cost of assembly and maintenance, as well as precision in operation, and entirely appropriate for desmo valve gear in a 90 degree L twin. They are also intrinsically kinder to the “hard” parts in the valve train with some harmonic damping and “give” where needed. Bevels, whilst a lovely engineering solution of their time, are high precision and therefore high cost to make and maintain, and when worn introduce a variability to the timing that limits output and increases wear. Chains are reliable when you have sorted chain quality and tensioning, but are more effort and expense to install and maintain, and in a motorcycle better suited to sprung valve actuation. Don’t forget, in the same year as the Pantah was launched with belts, in 78, Honda was literally almost bankrupted by the CX500 camchain tenstioner recall. If Ducati had had the same, when they were already close to insolvent, there would be no Ducati.
Interesting. I haven't looked at that thread yet so don't know if it touches on this - but my only long-term cam chain experience is the Jota and the CB550F. You adjusted the Jota's by turning the adjuster in on tick over until it started whining, then backed off until it didn't. It had a split link. The Honda, though, had a Hyvo chain, metal, but with teeth on the inner run (and a spring loaded tensioner). It only now occurs to me that it was a belt! Just a metal belt. The Honda was the bike I built to go couriering on. I'd rewired a guy's Z650 and he paid me in most of 2 CB550s in bits. I built one bike from the two and spent £300 on new wearing parts. So, didn't cost me much and was basically a works hack - which is why I got rid of it when the Hyvo chain needed replacing. You had to split the crankcases to do that. It did last 50,000 miles though.
Interesting also! As I just replied to NineNineSix, I had a Honda with a Hyvo chain that I just realised was a metal belt. I think I can just about recall the CX recall. That was back when I simply didn't ride Jap if I could help it. I rode British pushrod singles and twins, lusted after a handful of Italian bikes that I couldn't afford. Then test rode a CB900F I'd rebuilt for someone and realised they're fun when they handle. So was then amenable to taking payment in dismantled CB550s. I still loathed the CX500. Even the guy I knew who had one wasn't very complementary about it.
I find myself agreeing with all of the above regarding why Belts are better suited to our engines than chains. I don't think they are a pain to change either. I've not done them on my 1260 Enduro yet, I know it will be longer on that, but on my M1000 after the first time it was a 1hr job to change a pair of belts. I need to do my 999 again in the next couple of months, but having already done it once before I'm expecting it to take just a little longer than the 2 valve engines purely due to the additional disassembly, although my fully faired 1000SS didn't take much longer than the M1000. The one point I don't think anyone has mentioned yet is a key one for me why Belts suit 'our' engines more than chains. Our cylinder/cylinder head assemblies grow in height quite a bit once they are hot, especially the rear/vertical one. A nice stretchy belt copes with that far better than a chain. And it's why the rear belt on an air-cooled engine is set looser than the front/horizontal one. .
Well that's something I'd never considered. Mostly I suppose what bugs me is the stuff you need to remove to even get at the engine*. Because my first three motorcycling decades were on - bar brief Kawasaki GTR ownership - unfaired bikes. Singles and parallel twins, triples and fours. Having to have any bike in the workshop without fail within half a dozen k or a couple of years, grates. Even though it isn't really that big a deal when I don't do the mileage I once did. I'd probably need extinction therapy to change that. I can get my head around a 20-year old bike with only 20k on the clock, let alone a 25-year old one with only 12k, because it seems to me the point must be to go fast whenever the opportunity arises, and that suits me fine. They're special tools. Like you don't use a torque wrench as a standard socket wrench. It's just damn hard to shake 30 years of ingrained assumptions. * And mostly because the knees these days object to getting on the floor to remove the bolts underneath. A bike lift being in no sense economically justifiable or there being room for one anyway.
External belts don't need lubrication, are (ahem) easily accessible for changing and, as above, can accomodate some movement. Chains - none of these...
I've said before on here that I think more bikes should have final drive belts instead of chains. Where width etc wouldn't be an issue like a cruiser or touring bike it would seem like a winner to save maintenance without going all the way to a shaft drive.
True, as far as it goes. But in the 1970s Ducati had launched the 350 and 500 parallel twins, which did have chain driven camshafts, and which were a failure. Dr Taglioni made sure not to make the same mistake with the 500SL Pantah.
Interesting thread. Much engineering development is driven by the materials/technology/production available at the time when attempts are made to resolve a particular issue. I'm willing to be corrected here, but I've always suspected the Desmo system was created to combat the inadequacies of valve springs to maintain the (exactness of) desired radical valve timing. Similarly for the bevel drive as belt material technology hadn't yet reached a useable level. Yes, these solutions required greater investment in production i.e. skilled manual labour, but that was reflected in the price of the product. But as production/machining technology improved to such a degree there was no need to have a guy spend a week shimming up an engine to take up the tolerances left by 1960s machine tools. One example I have heard on how bad some of those old bevel engines were, is having a rocker shaft's mounting holes in the head not drilled exactly (vertically) perpendicular to the valve.... What I don't fully understand is why cam belts on a car engine can go for much longer e.g. 60/70/80 K miles? Is it down to revs or perhaps belt size ? A quick story. My working career has being in the telecommunications industry and in the 1980s something called 'time division multiplexing' (TDM) was developed and implemented in a fully electronic computer controlled exchange (System X) which also allowed full time & space switching. It was pretty much a universal fitment into the entire UK telephone network. Now the concept of TDM was known about & understood for years and there was an attempt to build a similar exchange in the 50/60s that used valve technology. It was a non start primary because of the energy consumption and the massive quantities of heat it gave off. It was only when the transistor & silicon chips were developed that TDM became a viable proposition.
I think the reduced life for ducati cam belts compared to cars is down to the small pulley sizes, belts don't like tight bends. Belts on the air cooled engines fo get a hard time as there isn't much cooling around them. Do the belts snap if you don't change them ? Broke one on my 851 many years ago, and one broke on a monster I sold even though I warned the purchaser it was due . It's so easy and cheap to change them it's a no brainer to do them
That brings back some memories from my TTA / T2A / TOinT days.... always remembering to set your sample rate at twice the highest frequency in the transmitted analogue signal to ensure satisfactory reproduction when decoded. At least that's what sticks in my mind from almost 50 years ago
The TDM i.e. SS7 for telecomms was stringently defined and was 30 channels at 64 kbits/s giving a 2M bit stream. This was known as an E1 link for Europe and there was also the US (Bell Labs) defined 24 channel at the same rate giving 1.5M bit stream known as T1. Similarly the signalling for controlling the PCM voice channels was also stringently defined by ETSI & ANSI and was universally known as ISUP but came in a variety of country specific flavours e.g. ITU, US, Japan etc.
