Winter Layup - 1995 Ducati 900 Supersport

[OddDuck]

I had a quick go at getting the big seal out with generic hand tools and it became clear that all I'd do was to mess up the oil pump engine cover. There's no way to get enough force to bear without putting unacceptable loads through a relatively thin casting wall.

It seems that Ducati never got around to releasing a tool for this job. I've spent the last couple of days making up a dedicated, one-use tool for this job, something that could be used on the bench.

Hopefully the photos make it clear what's going on, if not, here's what it does.

Extraction of old seal: Pull plate fitted to rear of seal, grooved lip engages metal seal ring. Collar (so seal has some clearance to be pulled into) fitted over the top, then the threaded plate for the screws. 8 x M6 x 50 cap screws, tighten by hand, then go around every third screw and nip up to equal amounts. Ten minutes later the whole lot comes out, seal and all. No hammering, no gouging of the cover. Success.

[OddDuck]

... and insertion of the new seal, a generic SKF 95-75-10.

Free plate on top of seal, seal itself positioned on outer face of cover, threaded plate plain face on rear of cover. 8 x M6 x 25 / 30 cap screws and away, as before. No issues, I checked as I went and provided the screws are tightened small and equal amounts, moving around the perimeter in steps of 3, it doesn't skew.

The crankshaft bush oil seal original was 7mm thick - I've chosen to replace it with a 5mm seal, deliberately leaving a 2mm gap and lightly levering it back against its retaining washer and circlip. Not standard practice but oil pressure should keep it in place.

[OddDuck]

Gasket fitted, seals oiled, cover refitted. I put the clutch basket back in.

Loctite 510 is used on the 8 bolts securing the basket - this isn't only to keep the bolts from coming loose. The 510 also acts as a sealant. The threaded holes are open at the far end to oil.

One of the forum posts I'd seen about the cover's large diameter seal mentioned using the clutch basket as a driver to push the new seal in. Most of the way, at least. Sounds like a good idea, but this will axially load up the gearbox shaft bearing and possibly indent the ball bearing races. I wouldn't risk it myself, it's a lot easier to take the cover off and do this particular seal change on the bench than it is to replace that bearing.

Anyway... the basic clutch basket / hub locking tool shown here takes time to put on or take off, but it works. It's a lot cheaper than the two dedicated Ducati wrenches that would otherwise be needed. I keep its mounting bolts taped to it when it's not in use.

The numbers shown marked with Sharpie were done during disassembly so that plates and steels go back where they came from. It'll help with the clutch actually working properly, this time... I've had a lot of trouble with the clutch either refusing to release properly, or slipping under load. I think it's happening because things aren't sliding along splines properly. I'd taken the time to very carefully go over every steel's internal spline edge with a needle file earlier, but I'll only find out if that worked once things are running again.

The cover gasket gives approximately 4 mm of lift to the cover. Without this gasket, there's a pretty good chance of the spring cups scraping the inside of the cover (both cups and cover are marked from this).

My last note from tonight is a bit more general: I've been noticing that things wrapped in ziplock bags are coming out exactly as they went in. Stuff wrapped in rags, which was oily when it went into storage, is coming back dry. The oil's evaporating off even at room temperature. So far I've avoided rust, but that's luck - this has happened in about five months or so.

[OddDuck]

New rings fitted to pistons, via specialised piston ring pliers. I found it necessary to pull the spring out of the wiper ring, put this into the groove, then drop the ring in over the top. The other two rings were straightforward.

The cylinder bores were oiled and their pistons were then pushed into their barrels, via a ring compressor. There are much better ones than this - this is the generic Stanley tool - but it works. The trick is to wrap the compressor's ribbon of spring steel tight, fit it square and center to the barrel, and then shove the piston in fast. If you try to do it slow, the rings will catch on the 45 degree chamfer at the barrel's end and you'll have to try again.

Ducati's air and oil cooled V twin engines are unusual in that there's a cylinder base gasket, but no head gasket. The compression seal is achieved purely via a machined aluminium spigot on the cylinder and matching recess in the head. Oil seals between the two are done with O-rings. It's very easy to service, but these O-rings have a nasty habit of setting under compression and heat, so the heads have to come off again at fairly regular intervals.

I sealed the crankcase faces with a bead of Loctite 510, then the top surface of the base gasket with another bead, as per the manual. Barrel fitted, gudgeon pin connected and circlip fitted to piston, carefully. It's very easy to pop the oil control ring out if the piston slips out from the barrel. Then I found out that the new Nichols head studs are a bit of a tighter fit in the barrels than the normal Ducati studs. This got sorted out with a rubber mallet, careful tapping on alternate sides got the barrel to bed home.

[OddDuck]

A further note about the Nichols head studs... it's well worth while to check the base gaskets for fit (and take a chainsaw file to them where necessary) before final assembly. It looks like Ducati left fairly generous position tolerances for the holes in the base gasket, based on the their own studs using an 8mm diameter shaft. Those base gaskets aren't a perfect fit.

Barrels on, heads next. There's a little dowel with a neatly drilled hole placed between head and barrel, this must be to control oil flow to or from the head via restriction, by my guess. It requires precise positioning between head and barrel. I struggled a bit with alignment, again due to the new head studs. There was a fair bit of persuasion needed to get everything to close up, rubber mallet at first and then bit-by-bit tightening of the head nuts.

Ducati, and various aftermarket suppliers, sell wildly overpriced 15mm ring spanners with a half-circle cylinder head clearing hoop and 1/2" drive on the far end. These are for setting torque on the head nuts, since you can't get a straight shot at them with standard tools. Nice, but not really needed. I got a 3/8 drive set of crow's foot spanners, modified the 15mm to be a simple open ended spanner, and use this instead. The trick for setting accurate torques is to have the crow's foot sitting at exactly 90 degrees from the torque wrench. Another way of doing it is to purchase a 15mm ring spanner, a 1/2" drive socket (any size really), and weld the two together, then grind down the thickness of the 15mm ring so that you can get it in to the head.

Inlet stub pipes with stud bolt insulators were next, I needed to do a spot of filing on one insulator flange but other than that, they went straight on.

[ruaphu]

Wow, nice work OD, coming along beautifully, awesome read.


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[OddDuck]

Refitting the timing belts meant turning the engine over by hand. I'd bought a tool just for this and was very disappointed to find that whoever designed it must have never had the chance to test it... it screws in, you tighten up the nut on the collar, try to rotate your engine and instead simply unscrew the tool again. The only way it will work is if the engine is turned backwards, complete with the starter motor engaged and back spun.

The good designs use a couple of teeth to engage the small keyways left for this purpose at the left end of the crankshaft. I hacksawed and filed these in, then refitted and found that the tool still unscrewed itself. The big handle needs to be on the barrel, not the M6 nut. In the end a pair of vice grips on the barrel got the motor to turn over.

[OddDuck]

Timing marks on the drive pulleys aligned, I refitted the timing belts and checked timing marks with the belts pressed in where the tensioners go.

Something I've got to do on the next Stein Dinse order is have a look replacing at the pulley on the horizontal head... there are two different types of belt pulley used, one with a flange on the outer face and one without. It makes sense that the flanged ones are used on the timing shaft, but on the heads the flange prevents belts being fitted or removed. I think someone's managed to inadvertently swap a parts bin pulley around in a previous rebuild. In the end I had to undo the pulley and fit the belt in free air, after making sure which belt tooth fitted into which groove.

The next bit is setting belt tension. A few years ago I found this guide:

http://www.ducatisuite.com/belttension.html

There are a lot of methods of setting belt tension, ranging from the original 10 N pull tool, to sonic tools (belt resonates at 100 Hz or so), and the latest I've heard of is something to do with lasers, probably interferometry. If you're a pro or regularly redlining the engine then this is probably worth chasing up, but I've managed just fine for years with a pair of allen keys and setting belt tension by feel.

It's a simple enough method: use the allen key as a feeler gauge between the belt and the fixed idler pulley. 5mm on the horizontal cylinder, 6mm on the vertical. The problem with this method is that it's very dependent on 'feel', it's cheap but it's not precise. Tension has to be set with the motor cold.

Also at the timing position, one of the heads is under spring tension from the closing arms and it'll tension the belt. You have to slightly rotate the heads past the timing position to take this out. Have a play with belts and pulleys, you'll feel it if this tension is there or not.

The 8mm cap screws securing the tensioning pulleys are notorious for ripping their threads out. The metal used is very soft... it's not uncommon to find recoils have been installed. This is the case with all four on my bike. I used the generic M8 torque figure mentioned in the workshop manual, of between 23 and 27 Nm.

[OddDuck]

Motor now rebuilt, I set up for a lift off the stand and got it onto its feet again. Nearly had a whoopsie doing it - the slack chain for the hoist jammed into a corner between engine and U-bracket (at the rear) and started to tip the whole thing. It's a top heavy lift, the way I've done it, and if it starts to go it could get a bit dramatic. I noticed in time, relifted and got the chain clear, then I was away again.

Lifting: best done slow and with two people keeping an eye on it, from all angles. The chain bound up on the other side of the motor from me. This stuff is a pretty good reason to keep a pair of steel-capped boots around, too. The feet I've made for the engine are like guillotine blades. Very easy to stick toes or a foot under it - it's the kind of stuff you only notice once things start to go wrong.

Anyway, motor down safely, swingarm fitted. I wanted to put this in with no clutter in the way so that I could clearly see and feel what I was doing. Also, having nothing on the swingarm itself - no shock, no rear wheel - helped hugely. The swingarm axle needed a push and a twist to clear each of the four internal seal lips, but it would push all the way through by hand. I didn't need to use a drift or mallet.

There are shims used on each side of the swingarm, both to set axial clearance, and also to set alignment between the chain drive sprocket and rear wheel sprocket. These are supposed to be as close to perfectly aligned as possible, to give the longest possible chain life. This will have changed, after the engine rebuild, since I moved the position of the output shaft. I set the swingarm at the middle position, for now.

[OddDuck]

Something that I've taken to doing is putting a coating of grease over the engine bolts and both axles. There have been issues with these quietly rusting in place before - the black pitting is visible on the bolt shown - and once the rust gets stuck in, it makes very effective threadlock. I had a lot of fun and games getting the rear axle off for the last tyre change.

The frame is extremely easy to lift on or off. There are just two engine bolts, both long. Where it's possible to go wrong is that one has a fine M10 x 1.25 thread and the other a standard M10 x 1.5. The fine pitch thread screws into a threaded boss in the frame (RH rear). It'd be very easy get the bolts swapped and then to decide that it's just a bit stiff and beast the thing in... don't do this. If in doubt, try them with the frame sitting on the bench first.

The other thing about the frame is that a slender M14 socket is needed for the nut on the forward bolt. I ended up buying a 3/8th's drive socket specially for this job, my 1/2" drives just don't fit.

The next thing was getting the rear shock refitted. I'd had the swingarm powder coated, they'd managed to forget to cover a couple of the threaded holes, and I had to choose between forcing a bolt in or doing it right and clearing the threads first. A careful run-through with a M10 x 1.5 tap sorted it out.

The shock itself is shimmed at the top. This isn't in the official Ducati literature: the shock is on spherical bushings, with a reservoir mounted off-center. It tends to twist in its mountings. A pair of large diameter plastic shim washers on either side help with this. These washers are not clamped up by the pinch bolt, they just float around the central eyelet of the shock. Some people use O-rings, I've found that they don't last for decent mileages.

The other thing I did was to get a couple of high-tensile bolts to mount the shock on. Standard sized fasteners don't really work properly here - the shock's top hat bushings end up riding on the fastener threads. The bolts that I chose were sized for the correct length of plain shoulder - nearly to the welded-on nut on each mounting bracket - and excess threaded length was taken off the far ends.

Forks were fitted next, then I got the bike up on front and rear stands to get the engine stand plates off. Wheels and sidestand fitted next. The bike's now rolling stock and can be worked on semi-normally. From here it's mostly standard reassembly and fine detail.

[OddDuck]

A few more bits and bobs put back on. It looks like the PTFE tape I used on the carbie stub pipes last time mostly worked, in terms of sealing out dirt / maintaining vacuum seal. I had trouble refitting the stubs until I cut the tape back and exposed the first turn on the threads, then no probs.

The pod filters are a quick, cheap and dirty fix to get me going again for summer. Replacement airbox is still on the cards.

[OddDuck]

Chain's stuffed. One of the end links, now open that the joining link is off, has ovalled very badly. The joining link had a badly worn pin and I'd be surprised if it was the only one on the chain.

This one's going nowhere but the trash bin. I still had a play with it anyway... why not. There were a few stiff links in the thing and a couple that I needed pliers to force to move. I had a go with PB Blaster and flexing it, trying to work the lubricant in, but aside from very minor improvements it didn't seem to do much.

Granted, it's been sitting for nearly six months, and did seem to get better resting overnight after the dousing with PB. I became curious and took a stiff link apart. One side turns freely, the other was so jammed that I needed a pair of crescent wrenches to make it move. I'd been thinking I'd find rust inside. What was there was a nearly dry, tarry residue, with what looks like rust on the rivet pin underneath. The residue is quite sticky and tough, it's easy to see how it could bind a link up. The link (ruined now of course) freed up once the tar was softened with CRC and wiped off.

[OddDuck]

Getting the bike back on the road means going for a fresh WOF, the rear tyre was well and truly under the 1.5 mm minimum major groove depth, so I had to take the wheel off again for the new rubber. The chain sprocket carrier simply pulls out once the wheel is off the bike, there isn't a retainer used.

The torque pawl pins turned out to be quite badly rusted. The freshly greased rear axle came out filthy with rust. I took a closer look and realised that the entire core of the wheel is open to the weather. The axle, the spacers, the inside faces of all four bearings... it's all completely open to water ingression.

I've been thinking for a while that I should switch from washing the bike after a ride to washing it before - this tends to confirm that. Motion + heat + air movement will tend to dry it out while I ride. Putting it away post wash is putting it away with water trapped in gaps.

The pawls cleaned up fairly quickly with some wet'n'dry and CRC, then I used high-temp grease to try to cover them against rusting again. A quick squirt of chain lube at every chain re-lube should help too. I couldn't get at the rust on the internals so settled for a pass-through with a rag to get loose rust and old grease off.

While I was at it, I noticed the very careful re-weld job on the rear brake bracket - this has been perfectly smoothed over on the open side of the wheel. Looks like the bracket has snapped off completely at some point, cause unknown (folded disc maybe?). I don't have any issues riding with it - I've been doing that quite happily since I've had the bike - but it's interesting what comes up when the bike's stripped right down.

[OddDuck]

With the chain out of the way and the sprockets / swingarm etc cleaned up, I thought I'd have a check of the swingarm alignment. For best chain life, the sprockets are supposed to be perfectly in line. The adjustment is to change the shimming washers on the swingarm pivot axle, moving the entire swingarm to the left or the right.

The previous (now replaced) front sprocket retainer is pictured below. It's badly worn on one side, chewed out by the output shaft spline. I took the verniers to it and took a rough measurement of the wear: 0.4 mm on one side, 0.1 mm on the other.

Output shaft spline greased and new sprocket retainer fitted, I took a 1000 mm steel rule and had a play. The theory was that a straight edge between front and rear sprockets should clearly show any misalignment. What I found was that it's a good indicator but not definitive... the front sprocket floats on the splines, so it has to be rocked from one side to another, there's axial play as well, and also the rear sprocket misalignment shows up much more clearly than the front ever will. The swingarm is sprung open slightly so that the rear wheel will go in, this changes the rear wheel alignment as the axle is tightened, and this affects things too.

In the end the best answer I could come up with was that it looks OK as I'd set it by centering and guesswork. It's not clearly out, and that's about as good as this measurement gets.

I'd had the thought that alignment between front and rear wheels could be set by doing this and putting increment marks on the tensioner bolt heads, but that depends on the frame / headset being precisely matched to the engine.

Last note from the night was the replacement of the OEM Ducati side stand screws, with standard BZP 8.8 grade cap screws and flat washers. I've had to drill out two sets of the factory side stand screws due to their ludicrously undersized hex sockets and cooked-in loctite, that's quite enough. The side stand has to come off if you need to get in to the alternator cover, there's just enough interference for it to be a problem.

[OddDuck]

Most of the last week has been about details and the wiring loom. One of the things I've been meaning to get onto for a while has been adding a ground lead to the front subframe.

One of the things about chassis grounds is that they can can be tasked with carrying high currents. When continuity is checked with a multimeter (I did this before adding the lead) it can come back with a perfectly acceptable result, say less than an ohm. That's what happened here. This is tested at just a few milliamps, though. It may be a very different story when a headlight is being run. Current density vs small contact patches between bits of metal, that kind of thing.

So I've crimped a couple of ring terminals onto a 4mm piece of grounding wire and added this to the ground circuit. It can't hurt, apart from adding a few grams.

Crimp pliers come in two kinds: simple pliers with rounded 'squash' jaws, and the more expensive (or much more expensive) ratchet pliers shown. I like the ratchets. The crimp terminal is held on all sides and is always squashed to the same crimp - not too much, not too little.

The trouble with crimps is that the wire is open to moisture ingression and corrosion. That can be avoided by soldering the eyelet instead of crimping, but the trouble with solder is fatigue. The solder joint doesn't have any spring in it and will crack, unless the wire is supported immediately behind the joint. Swings and roundabouts, really. There's nothing wrong with either technique if done right, and anyway wiring tends to oil / dirt / corrode up after a while, no matter what you do.

The yellow leads shown in the picture are worth a mention: these are the leads from the stator to the rec-reg unit. I replaced the badly aged and loose Ducati OEM bullet connectors last summer, since apparently an intermittent contact on these bullet connectors can destroy a RR unit in short order. The gold-plated bullet connectors used are rated at roughly 40 amps, if memory serves. They're off a hobby modeller supplier, intended for RC helicopters, and were about $5 each. They don't lock, which is the only thing I don't like about them, but that's sortable by cable-tying both sides to the frame.

Reattaching tacho and speedo drive cables has to be done carefully - Ducati chose to use industrial plastic for the angle drive housing, not metal. The plastic is soft, while the thread on the cable retainer is reasonably fine pitch and in metal. It's very easy to skew the cable's retaining screw cap and cross-thread the thing. Once it's been done, it can be very difficult or impossible to get it to ever screw on straight again. It'll also rip a bit of the threads off the plastic drive housing every time it's done up or undone. Eventually it'll be impossible to get the cable to stay on because the angle drive thread will have been completely stripped. Make sure that the cable is fitted square and centered, and that the retainer cap is the same, and it'll be fine. Back-turn it to feel it click into the first thread if necessary.

Instruments refitted, I spent a while making sure that cable had enough flex length to deal with lock-to-lock turning. Same thing for throttle cables and the clutch hose. This can mean a lot of fit and try of course, it was most of a night to get the throttle cables right.

It's good to see it with the headlight back on again, but I'll test the wiring before refitting any body panels - too high a chance that I've missed a connector and have to get back in there again.