Winter Layup - 1995 Ducati 900 Supersport

[nzspokes]

... by getting another ride in the meantime.

Ducati ST2.

Went up today with a mate and did the deal, sorted insurance etc and then rode the new bike home. There are a couple of issues - I used these as bargaining leverage - and I'll cover these in a new thread. Nothing that'll keep it off the road right now though

Good to be riding again, I was having a great time on the test ride and then getting it home.

Nice. Now Pro tip, dont pull both bikes apart at the same time.

[OddDuck]

Nice. Now Pro tip, dont pull both bikes apart at the same time.

Yeah, everyone I know has been saying similar... don't know why!

[SVboy]

Well done that man! If anyone deserves a riding break, it is you!

[OddDuck]

In between going a bit OCD on the new ride and sorting out general holiday stuff, I managed to get onto (finally) getting the fuel tank squared away properly. It's been sitting on the garage floor, covered with an old towel.

It was just a matter of time before something got dropped on it or I managed to clip it with the car or something equally horrible and unnecessary happened. I decanted the petrol (very slowly and painfully) via the breather hole and got the tank into a stacking, rolling plastic clip lid box, with padding via rags, towel etc.

The breather hole thing took ages. I had self-sealing fuel hose quick releases on the other other lines and it's very difficult to get in underneath a full tank on the bench anyway, that's why I didn't use those, and I completely forgot about the drain plug on the tank. I noticed this again about three-quarters of the way through the job, thought about it, but didn't want to break a perfectly good seal.

Really wish I'd gone and bought one of the fuel siphon-pump things... but in the end it might have been a bit of a blessing. There was a lot of messing around with opening the filler cap so air could get in to let fuel get out, tipping, tilting, angles, mopping up minor fuel spills, getting petrol onto my hands and washing my hands and getting gloves on like I should have done first, and of course refitting the breather valve on its stub of hose when I was done.

The little breather valve didn't quite fit into the plastic box. OK, I took it off again, not a big deal. There was a very noticeable release of pressure from the tank when I did. Right. Breather valve's probably stuffed. It is pure chance that I noticed this.

It's a funny wee beast... it's supposed to do a few things. It lets pressure out of the tank. It stops fuel from sloshing out under braking (it's at the front upper of the fuel tank). It's also supposed to let air into the tank, to balance pressure again after a while running with an open throttle. There were a few failures of this valve on the 99 - 05 Supersports, and the high-pressure fuel pump managed to suck enough of a vacuum that the fuel tanks crumpled like a beer can as a result.

The valve is easy enough to test. Pull it off the bike - it's about the most accessible component on the entire bike - fit a clean piece of new hose, and try blowing through it from each end. Mark it or photograph it first. It's directional. It'll let flow through slowly but lock up at pressure, going one way, and it'll breathe freely the other way. There's a little rubber disc inside, held by two dissimilar springs, which acts as a valve. Mine had failed earlier via swelling of the rubber, probably from unleaded fuel over time. I just haven't been checking it.

As to why this is significant... I'd been having a lot of ongoing problems with carburettion and tuning, particularly a weird leaning-out effect while under sustained running.

I've spent ages thinking that the lean-out issue was thermal. I haven't been thinking about things like fuel delivery or liquid level in the carburettor bowls.

If this valve has jammed, then that directly affects delivery pressure to the fuel pump and thus the carburettor bowls. It wouldn't have to be a full jam to do it either. If air flow into the fuel tank doesn't keep up with fuel use then that could cause this.

If there's an issue with the carburettor floats or needle valves then that could do this too. The needle valves use spring plungers (against vibration) and it's possible that these springs introduce a proportional effect into fuel level versus required delivery volume to the bowls.

Another possibility is the fuel filter. I have never changed this. It's a pretty good bet that it's been ignored by a succession of owners. If the bike's running, why worry about it... filter clogging is gradual and would show up the most at high fuel demand.

The last possibility is the hosing and hose clips inside the tank itself. If there's something loose or perforated then I could be losing supply pressure there.

Anyway... they're all one hell of a lot easier to investigate and fix than installing dedicated temperature control. Simple things first.

[OddDuck]

Lapping the second cylinder head - this time it's the horizontal head.

This went very much as for the first, with a couple of differences. The head's a lot more warped, requiring more cutting with a rougher grade of paper, and the area where I think oil was leaking from has different features to the fretting damage I've seen on both heads.

The fretting follows diameters, as per the vertical head, with the worst area being by the exhaust port. The leakage paths (there are several of them in parallel close together) are radial, and look like grit has been cutting lines into the spigot's sealing face. I'm not sure of the mechanism for how the grit moves, but it took quite a while to cut the paths away with the paper.

I've stopped with a bit of the fretting damage still present. This is diminishing returns work and I'm OK with reassembling with it like this.

[OddDuck]

Lapping the cylinder spigots.

The guide disc was spaced outward from the paper with a couple of M8 flat washers. This was to try to avoid getting grit between the guide and the Alusil coating used inside the cylinder, although in the end this might not have been such a big issue. The guide is deliberately too thin to contact the cylinder at the top ring mark, if any damage occurs it will happen in an area that never sees contact during normal use anyway.

That said, I was still very careful with grit and oil moving from cutting face to the bore. Every time the lap was lifted off, I was careful to oil the paper (if needed), but to wipe the spigot itself down. This was to avoid carrying any grit into the bore when the lap and guide were refitted for the next stage of the cut.

The paper was buttered with oil every time there was a paper change. Silicone carbide is very hard but also very brittle and bits fall off the paper every time it gets flexed or worked... I didn't want loose particles falling into cylinder bores and sticking to the walls.

Initially I tried lapping with the lap on the bench and the cylinder inverted above it. The idea here was that excess oil would flow down and away. It didn't work, the cylinder tended to vibrate and chatter, even moving it by hand. In the end the lapping was done with the tool on top and the cylinder on the bench, as per the heads.

[OddDuck]

Things weren't quite so good with the horizontal cylinder... it's cracked across the spigot, close by the exhaust valve. The last photo is a crop of IMG_1392, with the hairline crack centered in the frame. I simply wouldn't have seen this without having cleaned the surface up and possibly it's been flying under the radar for some time. As far as I can tell, the crack runs down to the flat, machined surface under the spigot and stops there. I can't tell how far it goes inside the cylinder. The Alusil coating and the cylinder's wear and tear makes it confusing to try to track the fracture.

I think this has happened because of all the issues with the ignition and pre-fire during the compression stroke. This would have been putting huge strain on the cylinder, particularly with the piston near TDC. At the time of the highest pressure, the spigot is the part of the cylinder carrying the strain. It's also the thinnest part of the cylinder, there's only so much outer diameter available.

I'm going to gamble that the crack isn't going to either leak oil or get worse. If I can get the fuelling sorted out so that the bike doesn't run lean and hot, and with the ignition now sorted out, it might hold up as it is.

[OddDuck]

Stripping the engine case assembly back again for the crankshaft re-shimming, time to get back onto it. Oil evaporates, humidity moves in, I don't want to put this aside to find a rusty engine in a month or two. A few bits and bobs...

There's a pair of M4 cap screws holding the front sprocket's locking tab washer on. These are supposed to be loctited on with 222 and can be a pain to remove with the engine in this state - there's no compression to use as a countertorque, not with cylinders and pistons off. An oil filter wrench worked on a clean sprocket.

I deliberately didn't close the locking tab washers up flush to the entire relevant face of the securing nut. Each end was left curved and open. This was so that it was possible to get a screwdriver blade in later without having to chisel-tap the washer open. I don't want to put hammer-driven shock loads through bearings if I'm going to re-use them.

On a similar note, I've marked out the position of the locking tab, visible even once the nut's on again. It should be possible to bend the washer anywhere to lock it, but I'd prefer to avoid the tab to shaft area of the washer for this.

The timing gear (large) was a nightmare to remove earlier - there's almost but not quite enough room to get the legs of a gear puller onto it. Screwdrivers don't quite go in. A pair of allen keys can be sneaked into the holes and then levered against each other to bell-crank lever the gear off the shaft.

Removing loctite... I wanted a clean, properly locked reassembly. Old loctite either cracks and starts dropping into places it shouldn't go, or very efficiently wipes the new liquid loctite off when the screw threads are done up again. Best to have as close to bare, lightly oiled metal as possible. The use of a thread gauge as a scraper was probably a bit brutal (on the gauge) but I want to take loctite off, not metal. Chasing rolled threads with a button die can cut into the threads, weakening them.

It was a similar story with the M8 x 1.25 tap used to clean the clutch basket mounting threads, in the larger transmission gear. This time it wasn't loctite so much as accumulated engine ash. There was quite a bit of wiping with cotton buds, CRC 5.56, and then the 2:1 white spirits / isopropyl alcohol mixture afterwards. I had to wash the bearings out with the CRC, it's very hard to avoid ash moving around during this process.

[OddDuck]

I was surprised and disturbed to see what looks like corrosion damage to the clutch pressure plate. It looks like clutch dust has built up between this and the first steel disc. Either the dust has packed and then hammered dents into the pressure plate, or a galvanic corrosion pair has formed between aluminium pressure plate and steel disc. Possibly both, I can see both what look like burnished dents and also much rougher, jagged pits.

I've cleaned it up but sanding it out will take far longer than it's worth. The pressure plates aren't a particularly expensive component anyway. The more expensive anodised plates wouldn't have this problem.

Of passing interest... the clutch was locked up. Lightly, at least. This persisted even with the springs removed. It looks like the friction material will bond to the steels, given a period of sitting around.

Today has ended with the cases still together but everything else out of the engine, bagged and labelled.

[OddDuck]

Main bearings reshimmed, finally. This time I'm happy with the preload, I've gone for 0.18 mm. The crankshaft turns with some interference, as described in the workshop manual.

The gasket I've been working with so far, brand new, never fired up, has been stuffed by repeated refits. A few areas around the screw holes have become stretched and gone conical instead of flat. This is a problem, the last thing I need is distortions or wrinkles.

When I'd placed the parts order I'd ordered two gaskets, they were cheap enough and it was basic insurance. That decision has paid off. Ducati don't use enough locating bushes between the half cases and unless the mechanic is very careful with the gasket placement then misalignment and gasket damage is almost inevitable.

Didn't want this to happen again with the spare. The pin punch was used to feel where the gasket was placed and then adjust, if necessary - it's possible to use the nose of the punch to pick up the paper lip and then give it a sideways tweak, with the half-case above it lifted to allow movement. The case bolts and screws should go into their threads without any interference with the gasket.

I'd gone ahead and purchased my own dial gauge and stand, via Trade Tools:

http://tradetools.co.nz/products/4900120

For some reason the stand and gauge sets are buried in the micrometer section of the site, it took some scouting to find these.

I'd been worried about the resolution, hysteresis and accuracy of the 10 micron gauge but in the end it turned out to be perfectly appropriate for this level of work. I checked again with the 1 micron gauge from earlier and all this showed was that too much resolution can actually be a bad thing, it's possible to start chasing ghosts.

Crankshaft lifting was done with the main gear pin wrench, this turned out to be near perfect for this simple job. I'd gone and purchased a cheapo calculator for my shimming calculations, getting it wrong once was enough.

[pete376403]

No engine that I have worked on with vertically split cases (so, old Brits, slightly less old Jap trailies, English and Czech speedway motors and most recently my 08 KLR) has used a gasket between the halves. Even the old Matchless G50 didn't leak between the case halves (just everywhere else). Putting a gasket there seems like its just asking for trouble, adding a whole bunch of variables to what should be a fixed measurement. italians, eh?

[OddDuck]

Interesting. Ducati actually went away from gaskets a while ago and use sealant instead, probably to avoid crush / swelling issues as you say.

I prefer the PTFE-impregnated gaskets though, I find them a bit easier to work with in terms of cleaning up cases.

[OddDuck]

Going back into the pump case, to make certain the main drive gear was sitting on the crankshaft properly.

I'd been finding that this gear came off the tapered shaft very easily. The nut goes on with 107 to 117 Nm torque; it was loosening with about half this, then the gear would pull off the taper with maybe 20 Nm applied to the puller nut. Both of those are just by feel, I was using a breaker bar, but it was definitely lighter to take off than it had been to put on. It's supposed to be a beast to get off.

My experience with tapers has been that they go together easy but come apart again with difficulty. If otherwise, something's up. This is the main drive gear, it's transmitting nearly all of the engine's torque and power. It's an expensive component, mounted on a very expensive crankshaft, sitting in pricey and hard to get engine cases. Don't really want problems with this, especially since a consequence of failure could be an engine lockup while riding a corner or at speed.

It took about an hour to get in again, most of that comprising taking the clutch apart. I ended up being very glad I did. It turned out that the gear was sitting on the key, torqued up against the key's flat outer face on one side and the tapered shaft on the other. The bright raised ridge of metal on the key itself is where the key has been getting cut, while being jammed into its own keyway.

The Loctite 510 used to lock and seal the clutch basket screws has a habit of fragmenting and falling into the engine while the bolts are being withdrawn. Not a problem while the engine is in its normal orientation, bits and pieces will go down, end up in the sump and get filtered out. While it's on its flank, as pictured, bits of crumbly Loctite can fall into the gearbox input shaft's bearing races. This can be cleaned up with a cotton bud and some pushing around of the bearing, just don't force the thing through a jam. Use the range of motion available and lift fragments out of the bearing races.

The cut on the key itself is pictured. I've put a rag around the crankshaft main bearing, I didn't want anything falling into this during work.

[OddDuck]

Having a look at the key itself.

I took a file to the burr and removed this, then tried refitting the key and the main gear. Not much joy, something was still wrong.

I got vernier calipers onto both the key and the keyway, finding them very close in length but apparently still passable. The key kept refusing to go neatly into the slot machined into the crankshaft, though. It took a bit of close looking to see why, shown on the photo with the mirror.

The length matches fine. The corner radii on the key don't, so it jams into place. It goes in just far enough that it looks OK, but the key ends up sitting high enough to lift the main gear by the gear's keyway.

A spot of filing and using wet'n'dry and I had the key fitted into the crankshaft keyway properly - just loose enough to push home, not loose enough to rattle. The next step was to make sure that there weren't burrs or similar on the gear or the crankshaft. The edges of the keyway, on both components, were quickly radiused using a needle file and paper.

[OddDuck]

Testing for gear lift via key off the crankshaft... first check was using vernier calipers to see how far the gear was placed along the crankshaft, both with and without the key. It turned out that this does show lift, just not directly - it's not easy to measure how much height should come off the key by this method, if it's necessary to take some off.

While planing the key down in height a bit (from 5.00 mm to about 4.86 mm, on block and wet'n'dry paper, measuring via verniers) it occurred to me that what I really wanted was to look at the gap between key and gear, down the slot. Perhaps an easier and more direct method was using a bit of paper as a slim feeler gauge. This worked very well and showed a gap of at least 0.20 mm on an untightened gear. I can be certain that the main gear is now sitting on the taper, over the full surface.

I've refitted the lock washer and nut, applied clean engine oil to threads and nut face, and tightened up to torque. I haven't tested by attempting to pull the gear off again, there's a way a taper feels when it's being done up and this felt right so I've called it as done.

The base of the engine is now back together again, waiting on pistons, cylinders and heads to be refitted next.