Winter Layup - 1995 Ducati 900 Supersport

[OddDuck]

The MBP retainers and the EMS shims arrived earlier this week - turnaround was about a week, very prompt - so the last few nights have been about re-shimming valve clearances.

I'm very impressed with the MBP retainers. There has been some comment about them being a tight fit in OEM Ducati closing shims but they fit straight into the EMS ones. The EMS measuring tool for opening shims is also very good.

Closing shims are fussy bastards to fit for the first time. Lacking a shim kit (would have made life a lot easier) I ended up very carefully sanding these down, fitting, trying for play. Unfortunately it was a lot of work. Ducati recommend a 0.000" to 0.00079" clearance for all openers... there isn't much margin for sanding too far. If I'd bought the shim kit, I'd have found the closest loose size, measured the clearance, and then known what to sand the next biggest shim size down to. That could have been done on the bench with verniers and the EMS measuring tool, would have been a lot faster.

As it was, I found that the best way to test for fit wasn't to use feeler gauges but instead to fit and try turning the camshaft. If it was too tight then I could feel it very clearly, also I could feel the tightness easing off as I sanded it down until I finally had the right size.

Once that was done, opening shims were fitted, rocker arms slid across and retaining clips fitted. Something about these clips affects the opening shim clearances. There can be a difference of 0.003" or more if you take these off and then measure.

Lot of sanding, again. Nearly managed to order these right, in the end I had to take 0.10 mm off all of them in order to get the right running clearance.

I went around all valves with the feeler gauges when everything was done. Both opening and closing clearances are taken in the same place, between the opening rocker arm and the opening shim. First take the opening clearance, using the feeler gauge. Then push down on the closing rocker arm with a screwdriver, so you push against the spring and take up any slack, then measure with the feeler gauge again. Any increase is the closing arm clearance.

[pete376403]

Are the shims hardened right through or case hardened? In other words is there a risk of sanding/grinding off the hardening? I guess if valve clearances change very rapidly after running then they are not through hardened.

[OddDuck]

Are the shims hardened right through or case hardened? In other words is there a risk of sanding/grinding off the hardening? I guess if valve clearances change very rapidly after running then they are not through hardened.

They're through hardened - check this page:

http://emsduc.com/wp-content/uploads...ion-052915.pdf

Shouldn't be a problem. I have to admit that I'm concerned about the valves themselves bedding in a bit and clearances changing, I'll run the motor for a week or so and check clearances again.

[OddDuck]

Valve guide seals.

I've been trying a few things with the three types of aftermarket seals I'd ordered, trying to make them fit. The black seals pictured were initially very promising but I found three problems:

- they go oval with the spring clip fitted;
- they pull off easily;
- they just (only just) interfere with the closing rocker arm. I could see the rubber seal flex by using a mechanic's mirror.

Damn.

I tried another kind, part no. 761.389 (green, made by Elring, sourced from Mick's Garage) and found that it would actually work provided that I block-and-papered the metal outer ring down to a width of 5.0 mm. The cut-down M12 washer was used as a tool to help push the modified seal over the valve stem guide. I greased everything before pushing it on, it's possible to feel it pop into place. Once on, it needed screwdrivers to lever it off. I didn't have to modify the valve guide.

This worked very well on the exhaust valve guides but wouldn't fit on the inlet guides - these sit taller and there are interference problems with the closer arm. I've fitted the OEM Ducati seals (for now), these go on by using a small Allen key and stretching them over the guide boss.

They fit, obviously they work, but I have serious doubts about these over the long run. There's nothing backing the rubber up. Once they stretch or set, either at the valve stem or the guide boss, there'll be plenty of oil hitting that guide. Too much oil attracts carbon, which then grinds the valve stem and guide.

[OddDuck]

Finally, onto the frame top front triangle.

I cleaned the insert tube up and tacked in four points, then started to do the perimeters. This is a very slow process of turning the frame on the bench, trying for access and motion with the torch and filler rod, checking that the torch cable doesn't snag halfway through the pass, being sure before attempting to spark up.

I've bought a zero length back cap to help the torch navigate tight corners. Using this is easy: snap tungstens in half, resharpen and you're good to go.

Any tubing which has been bent will have thinned out through its wall on the positive side of the curve. Very easy to blow holes into, unfortunately. I should have trimmed the top wings of the fishmouths back a bit to avoid this - welding to the neutral axis of the bend and no further would have been a lot less tricky.

The first welds (about 2 / 5 ths of the perimeter covered so far) shown. The problems I'm encountering are difficulty getting the mask close enough to clearly see the weld zone and the rapid changes in weld current required progressing around the curve. Doing this is very different to welding up short little samples on the table - I had full hemispherical access with those and I could get the mask close. Doing this is making me really appreciate the skill level a professional frame repairer brings to the job.

[OddDuck]

I spent the week trying to complete welding the frame tube into place.

It's been an absolute bastard of a job. Lots of difficulty with either seeing the weld zone, handling the torch, or getting filler rod in. Or all three... TIG's really best with hemispherical access above the weld. I ended up purchasing a foot control last night and trying it this morning, would have helped earlier but didn't really achieve much today while trying to work in the most difficult part of the weld.

MIG would have been good, I think... it's possible to direct filler rod straight into a narrow gap. I think it might also be relatively easy to put a decent bead in without blowing holes in the thin frame tubes, but I'd have to try it for myself.

Very tired, have had enough of welding for now.

[OddDuck]

After a lot of thinking, I have decided to run with the welds as they are.

I've been painting. Went to a local body shop, left the frame with them, had them colour match and fill up some spray cans. I got some primer in the same paint system while I was at it. The lower front cross bar was starting to rust, so I took the chance to sand it back to bare metal and start on the paint again.

There's a slight colour mismatch between front (new paint) and rear halves of the frame. I could overcoat the whole thing (after properly washing the rear half), but it'd be good to keep the original colour. It's still possible to put another coat or two on without any problems, does anyone know the paint codes for the Ducati metallic silver used on the frame?

[pete376403]

Silver must be one of the hardest colours to match, even having the correct paint codes isn't going to help much when the original paint has 20 years of weathering.

[OddDuck]

Thanks Pete - those are words of wisdom, repaint the entire frame it is.

With that in mind I had a good long look at the custom mixed paint tonight... and I can't stand the stuff. It just looks cheap and nasty. It took a while to work out why. The original paint has a beautiful diffuse reflectance. It really isn't specular at all, while the new stuff has strong specular behaviour.

Diffuse: no direct reflections, any light on it bounces off over a full hemisphere

Specular: glossy, lots of direct bounce, the ultimate specular surface is a mirror.

The OEM stuff is luscious to the eye, even twenty years down the road. Good paint is very important in selling motorcycles and I want to keep that sort of look even if it's out of a rattle can.

So I did some checking around the web and I might have two possibilities. PPG make a close match to the original, sold through Bunnings, paint code 223.647 (Grigio Steel Ducati) or code 0011 (Grigio Metallic). So I'll see what they can do for me, I can certainly go over the front half of the frame again and see how it comes out.

[OddDuck]

Right, no luck whatever trying to get anything to a code from PPB. Off-shelf cans aren't any better than what I've got and usually are worse.

Fine, full overcoat with the colourmatched rattle cans it is... and on the off chance, I went and got a can of clearcoat as well. Colour and clear coats were sprayed top and bottom in two setups, with the frame normal and inverted positions on the table. The piece of alloy plate I'd used for a welding tble also serves as a carry tray, so I can move the frame to the bench, put the table away and get the car in for the night.

The clearcoat has tidied it up very well, I think... pictures below. This might have given some of the luminosity I'd seen in the original paint. I'm quite pleased with this, maybe it'll work after all. Engine shims arrived this week but I'll have to let this dry for at least a day first.

Just a couple of notes, from my mistakes...

First: yeah, the main tubes are chromoly. 4130 (or what the Italians call 25-Cro-Mo-4), as shown by the way it's rusted around where the seat and tank mounts have rubbed the paint off. Chromo rust looks quite different to low carbon steel rust, I should have guessed earlier that tabs, seat mount tubes etc are mild steel and are different to the main frame.

Second: any transition between old paint and bare metal needs to be tapered as carefully as possible, otherwise it'll show up clearly when painted. I'm not going to go back and do it again - there's a pretty good chance I'll be re-welding, and it's an old bike anyway - but it's worth remembering in future.

[OddDuck]

Got onto shimming the engine cases today.

It turns out that Ducati shim sizing can't be taken blindly off the packet: the sizes vary by as much as 25 microns from nominal and if you're stacking a few of them, it adds up. Also I found that one set of shims had the 0.3mm and 0.4mm shims swapped between their bags.

I was able to mix and match for most sizes, but some shimming involved taking an oversize shim and using paper and block to thin it down. I tried a few ways to do this - bye bye fingerprints - and in the end found that double-sided tape on a slightly under diameter socket was the best way to go. The double sided tape held up reasonably well against CRC 5.56 used on the paper (to keep it from loading up) and the undersize on the socket diameter meant that I could keep tabs on the shim thickness with vernier calipers. I did a lot of rotating the socket while sanding, this kept things parallel.

Assembly once shims were prepared was straightforward: all shafts fitted to one half, gasket placed, oil pump bypass valve and spring placed, other casing half fitted over the top. The oil seal for the timing shaft was pushed into place afterwards.

I checked end floats after torquing the screws up and found everything was what it should have been:

Shift drum: 0.20 mm
Gearbox shafts (both) 0.10 mm
Crankshaft: no play whatever, 0.15 mm preload used, shaft is a bit stiff to turn by hand once the crankcases are torqued up.

I did some checking on the 0.15mm preload and it's all summed up very nicely in this post:

http://www.ducati.ms/forums/77-sport...k-preload.html

Basically it comes down to the casings expanding more than the crankshaft. At operating temperature, there should be minimal to zero preload on the bearings, but no free play.

It's worth pointing out that the Ducati factory manual doesn't specify this, it just says "there should be no free play in the crankshaft". If I hadn't checked the Haynes manual and the forums, I'd have assumed correct shimming meant no preload but no free play at room temperature. The bearings would have been loose at operating temperature and probably suffered rapid failure.

[OddDuck]

Some more work, much simpler stuff - fitting a Nichols crankcase breather and rebuilding the goodies inside the oil pump cover. Timing belt pulleys and transmission gear both have to be locked with special wrenches and torqued up.

The transmission gear lock wrench isn't a Ducati item, it's aftermarket. It didn't quite fit but a spot of filing sorted that out.

Unfortunately I've missed a couple of seals... the big one that goes on the clutch drive gear's hub, and a smaller one that goes over the crankshaft end. Both fit into the oil pump cover and both are reasonably important - the big seal prevents clutch dust making its way into the engine, and the smaller seal controls the flow of oil into the crankshaft's center oilway. That'll be a couple of days delay but I should be able to get seals via the SKF distributor.

[OddDuck]

A bit more work today - alternator cover side, this time.

The oil seal (in the pump cover) for the crankshaft end has been installed the wrong way around, at least at first sight. Apparently they're all like this. Ducati did this until higher pressure oil pumps forced a switch to orthodox practise. I have no idea why - maybe they like controlled leakage - but that's the way it is, so that's the way I'll install the new seal. After I work out how to get the old one out... There's nothing to grip on and it's tight against the face below, so I can't lever it up. Never mind. Later. Move on.

I found out the reason that the timing shaft key had been such a pig to remove - it's a pig to install. The woodruff key just kept rotating in its semi-circular groove and then backing out, every time I attempted to install the timing gear. Very frustrating... The previous mechanic must have deliberately indented it so that it'd fix in place. In the end I found that using a pin aligned along the gear's key groove, keeping the key straight during installation, worked brilliantly. Hope that trick's useful for someone out there, but that said, use a pin, they'll bend if something goes wrong, where a needle might break and drop into an engine.

The driving gear for the timing was next, that was an easy drop in. Timing marks aligned, then spacer, collar, needle roller bearing and flywheel / starter clutch assembly were next. Alternator core and domed spring washer plus flange nut next, then I torqued them up. This is possibly the highest torque setting in the bike: 180 Nm. The easiest way to do it was to get the two handles close together and close them with by squeezing with both hands, rather than use arms.

The wrench for the alternator's permanent magnet core is worth a mention - it's a special made from machined aluminium. This is so that it's non-magnetic and won't stick.

Ignition trigger coils were next. These are supposed to be set on their bracket with 0.7 mm (+/- 0.1 mm) clearance to the flywheel rotor tooth, and aligned to the marks machined in the rotor with the horizontal piston at TDC.

A lot of judgement comes in here... Ducati didn't put any sort of absolute reference in for flywheel position relative to crankcase, despite keys / splines etc. You're down to judging what the conrod is doing relative to the barrel alignment pin, or similar. In the end I settled on a slightly conservative position, about 1 degree retarded from previous.

I suspect cheap and nasty attempts to bump up performance in the past... here's hoping it runs a bit smoother. I'm prepared to lose a few HP at the top end, I never need it on the road anyway.

[OddDuck]

I've had a problem with oil vapour and oil seepage getting out of the stator's wiring gland.

The original Ducati stator has a very nice high-temperature silicone rubber insulated twin-core lead. The lead itself is roughly 8mm diameter on the outside and seals with Ducati's trapezoidal-section O-ring and clamp gland. Mine had been in place for nearly twenty years, the rubber had crept under constant pressure, and the wiring inside had nearly touched. By the time I found that out, the stator wiring itself had failed (taking the reg/rec down with it) and the necking didn't matter anymore.

The aftermarket stator I replaced it with has turned out to work just fine in all particulars, except that the leads were covered with a loose PVC sleeve. PVC, oil, and engine heat just doesn't work. The PVC went brittle and hard. The sleeve was also open at both ends, meaning that even if gland-sealed on the outside, oil and vapour just walked straight along the inside. That's if it sealed on the outside. Mine didn't, it just collapsed under the O-ring. I had dirt and oil all over the lower left side of the engine. Nasty.

The smallish twin-core cylinder pictured is a home-made component machined out of high-temperature Tufnol. I've attempted to seal the wiring runs with silicone - we'll see how that goes - but the Ducati O-ring and gland actually do fit around the outside and tighten up OK. It's not perfect, it's skewed in the gland and there really should be a support boot for the wiring, but we'll see how it goes.

[OddDuck]

Oil seals in the case covering the oil pump.

These look easy... they aren't. The big one, 75-95-12, seems to need a press and a dedicated push tool. The small one has been inserted backwards. When it's twenty years old and it really is time to change it out, there's nothing to grip on.

The backwards thing seems to be standard practice on all Ducati 2V twins up until 1998 or so, from what I've read. If inserted normally, oil pressure would keep it tight on the crankshaft. If backwards, that seal lip would tend to float, lifted above the surface by oil pressure. Wear would be minimal, borne out by the complete lack of a seal wear mark on the crankshaft. The oil leakage would also mean that the bushing is continually cleaned, there's no risk of this turning into a sludge trap.

I tried a bearing puller on the bushing beneath - no joy. In the end I used the dremel to cut the seal wall out. A knife tip got the bend started, then the screwdriver went the rest of the way. I'll have to get every metal shaving washed out before reassembly. That's important anywhere in an engine, but doubly so here - this is the gallery feeding the conrod main bearing shells.