Winter Layup - 1995 Ducati 900 Supersport

[Voltaire]

I fell your pain, my BMW R90/S is still under a blanket after doing a top end rebuild and finding the RCA on the top end failure was no oil getting to rockers.

Quick flick thru your thread. Main Bearings SKF 72 (3)07 BEP?

I put that in a search with Ducati and only your thread comes up.

Tends to suggest no one has gone down this route before.

BMW have at least one BMW only bearing in their gear boxes, use generic at your peril.

People have used bearings that don't have enough clearance on them too, ends badly.

I'm not saying the ones you used are incorrect but some things IMHO are better sticking with OEM and engine/gearbox

internals are one of them.

Put the bike under a blanket, ride something else and enjoy the Summer.

Facebook is reminding me of " this time last year" just prior to the BMW shitting itself in Timaru.

[T.W.R]

TWR: thanks - have found this:

http://tradetools.co.nz/products/2845550

Unless you have another recommendation?

CRC 3109 is what a couple of the engineers used at work, same sort of 3pack item like the Rocol and about the same price.

You could probably take the bits you want to check into your local engineering shop and they'd do it for you while you wait for a fraction of the cost of buying
some that you would only use a portion of and turn it to a shelf ornament.

[OddDuck]

Tonight's effort (no pics sorry) was getting heads, barrels and pistons off in preparation for the casing split. Hopefully that's tomorrow. That's been covered in detail earlier, just a couple of things to say really... first, the workshop manual doesn't mention the gravel. Splitting the cases means that anything falling inside can be removed again easily but if it was just heads / barrels type work, you'd really want to avoid this happening.

The engine's more than a bit of a gravel trap. The stuff gets caught in fins, in the little gulleys that Ducati have thoughtfully engineered at the base of both cylinders, around belt covers etc. The engine stand's useful here, it's possible to put the relevant section of the motor upside down and then have at the gravel with pick / screwdriver / scrubbing brush etc. Gravity takes the gravel down and away from the motor. I wouldn't treat a nice new paint job this way though, it'd be strictly degreaser and light scrubbing with a paintbrush, also upside down or sideways if possible.

Second, it's going much faster the second time around. Most of the gear's here. I have made mistakes with my orders, though. Going through the exploded parts diagrams and picking out replacement bits by eye and memory isn't as good as a systematic approach, line by line ticking off of parts. Anything that's a seal, gasket, O-ring, or bend tab washer should get replaced. I've just found another such washer tonight that I don't yet have on order. Damn.

TWR: thanks, good advice.

Voltaire: Thanks mate. Yep, chancing it with non-Ducati main bearings was a bit dicey after all. They did work for around 12,000 miles, I wouldn't do it twice though... I've got the proper Ducati-supplied RHP bearings this time.

RHP 7207X2

RHP 7307X2ETN

I'd love to go bike shopping but have an issue with space, can't fit 2 bikes + car in garage and after car thefts in my street (my last car was one) there's no way I'm street parking my car at night any more. I've dabbled with the idea of an ST3 or ST4S. The 900SS is about a month away though, I just have to stay the course.

Facebook reminders... aargh

[OddDuck]

TWR - have purchased a 3-piece kit of the CRC Weldcheck 3109 stuff you'd mentioned - was in Twigg's buying a 46mm spanner and it was right there so why not.

Today's effort - splitting the cases and getting the crankshaft out.

The bearing puller was needed for getting the spacer sleeve off the shaft that carries the clutch hub. I'd notched this last time with a Dremel for exactly this operation. There's nothing to grip to otherwise.

The primary drive gear nut was an eye opener. This was torqued properly on assembly; it was only just more than finger-tight when I took it off today. The safety washer's there for good reason. The M6 and M8 cap screws holding the gearchange selector arm mechanism were dangerously easy to undo as well.

The nut holding the generator hub and flywheel on hadn't loosened at all. If anything it might have tightened. This was a rattlegun job to remove.

The 46mm spanner (got a 15" crescent in the end) was for counter-torquing the proper primary drive gear puller, which I'd bought a couple of weeks earlier. The puller is not cheap but worked like a charm, there were none of the dramas and delays that I had with the first pull while using a standard beam-and-leg 10-ton puller.

I noticed scoring on the oil supply end of the crankshaft - it looks like the shaft has been getting supported by the bushing pressed into the pump casing, since the main bearings weren't doing the job properly any more.

It feels like the shell bearings on the crankshaft journal are OK. There's minimal lateral play side-to-side on either conrod small end, and for now I'm going to call them as undamaged instead of disturbing the cap bolts to examine surfaces and take measurements.

With the casing split and the crankshaft out, I found something unexpected: only one main bearing seems to have failed, this the slightly smaller one on the alternator side. The photo doesn't show it clearly, but when the bearing came off the crankshaft, a lot of caked-on grey gunge was found over the spacing shims, the inner shoulder of the crankshaft, over the bearing inner race, etc etc... it was everywhere. In contrast the transmission side bearing is super clean.

Taking a closer look at the obviously damaged bearing showed occasional pits and spalling (if that's the right word for bits of the raceway surface where a flake has come off?) but this was hard to photograph. It wasn't the hammered, indented surface I was vaguely expecting, but I think that getting a clear view would involve breaking up the race cage and disassembling the bearing.

The oil gallery plug on the crankshaft itself has loosened, again. There are the beginnings of score marks on it, where it's been running on the bearing. I'm not sure what I can do about this aside from using loctite again.

[OddDuck]

I tried checking load ratings for the SKF bearings vs the RHP's... Curious as to why I've had an early failure. No definite numbers so far aside from angular contact angle.

Normal ball bearings have a contact angle of 0 degrees.
The RHP's are at 15 degrees.
The SKF's are running the more common angular contact angle of 40 degrees.

All else being equal - materials used, number and diameter of balls, raceway surface etc - the contact angle will be the biggest difference in the radial loading that the bearing can carry. The angle will be all about trading axial loading for radial loading.

Running some numbers and trigonometry, if F is the maximum force that can be applied through that contact angle before trouble:

40 degrees: allowable axial loading is 0.64 F, radial is 0.77 F

15 degrees: allowable axial is 0.26 F, radial is now 0.97 F

That's assuming a lot. The contact surface area used, raceway to ball to next raceway, will have a huge influence on load capacity, to name just one variable. But looking at the angle alone, if 0.97 F (on the normal 15 deg. bearing) could be considered 100% of the necessary radial load capacity, going to a 40 degree bearing means a drop in load capacity of

100 - (0.77 / 0.97) = 21% reduction

If the original design ran the bearings close to their raceway loading limit then this drop in capacity could be enough to go above the limit, even in an engine running properly. I've had bizarre ignition problems. It's anyone's guess just what's been getting shoved through the crankshaft. No wonder the SKF's didn't make it.

So yeah, I have to agree with Voltaire - even if it's not obvious at first, there's good reason to stay OEM when rebuilding. Not all angular contact bearings are the same.

[OddDuck]

Right, might have something useful for someone out there. DIY crankcase bake oven.

Simply chuck your case half into a cardboard box, wrap up the top with the box flaps / towel etc, and heat via hot air gun aimed inside through an open corner. Control is via kitchen digital thermometer, stuck through the cardboard. Works a treat, surprisingly.

It's actually better than a domestic oven in terms of warmup time and stability. It's also a lot more tolerant of used motor oil and dirt etc, you don't have to do exhaustive degreasing first.

The reason I was doing this was the bearing support cups. I had to get the transmission side one out and since the cylinder head studs are still in, the case halves don't fit into the oven any more.

Ducati use a steel cup pressed into the crankcase halves to support the main bearings. It's actually a pretty good idea I think - the cup is a very fine sliding fit on the bearing at any temperature, so bearing changes are possible quickly and easily, in theory at least. You don't have to heat cases, it's a careful pull and you're done.

The alternator side bearing change went without a hitch. The transmission side was another story, with much messing around with a bearing refusing to seat and a bearing cup apparently distorting, and finally I heated the case half and drove the replacement bearing and then the cup itself out to check components against damage properly.

The bearing cup has fractured. It looks like someone has taken a can opener to it. There's no way that this can be trusted to support a preload on the crankshaft main bearing, and it's possible that this cup has been this way for some time. There's a mark on the outer face of the cup where I think it's popped out of the casing and been rubbing on the transmission gear.

It's subtle. This actually looked OK while in the casing, it took a lot of messing around trying to get the bearing to seat before I twigged that something was wrong. The fracture is inside a groove, down in used engine oil etc and mostly closed - it is not obvious by eye. Long and short of it, if you've had a main bearing failure, I'd strongly recommend driving out the bearing cups for on-bench inspection instead of taking them on trust.

I had a think about the likely cause overnight and reckon there are two parts to this failure:

1) Ducati designed the cup with an internal groove at the base, to guarantee that the bearing end face sits flat and true. This groove has thinned out the cup wall, making the part weaker... the groove is standard practice when seating bearings and presumably is also there because the cup had to be ground to size to get such a fine tolerance. Grinding wheels don't tend to do sharp end radii very well, so the end of the diameter had to be undercut to finish it properly.

2) It's very possible that the cup was fractured during assembly by someone who fitted the bearing to the cup, then drove the whole lot home in one go. The bearing would have transmitted the push to the base of the cup. I think the correct sequence for this part is to drive the empty cup home, pushing from the top surface only, and fitting the bearing itself afterwards.

So it's now necessary for me to make up a specific push tool, my set of bearing drivers don't quite go to this diameter.

Stein Dinse order placed, 2 to 8 week wait on replacement parts. Voltaire, your advice is starting to sound pretty good right now.

[AllanB]

I like the hot box idea. A degree of risk the cardboard may start smoking?

Mrs B was unhappy this weekend at the smell coming from the oven as I cured heat resistant paint .............

[OddDuck]

Ta - 100 C was OK, I took care to direct the hot air into open space at the center of the box. So far the cardboard is looking a little dried out but that's about it.

Might be an idea to put the box on a concrete floor and well away from anything else though, I really should have thought of what I'd do if it started going wrong

[OddDuck]

Parts orders from Stein Dinse arrived last night. I'll be rebuilding the bike over the next couple of weeks.

It's been a fairly involved few weeks prior to this. With the bike possibly laid up right throughout summer I've been out looking for a second ride. I'd had the bright idea that I could go shopping with $5K-ish and get something basic, run that for a few months, then get the 900SS running again and move the second bike on. Treat the inevitable loss at sale as cheaper than renting and just ride, etc etc. I had this idea before I had any real experience of the current market.

Buying a second old bike which then broke down would have been a disaster. Cash is tight, legwork is cheap in bucks if not in time, it's cheaper to go looking at other bikes now than to fix this bike right here in front of me later, etc etc... it pays big time to be fussy at the front end while shopping. There's a lot of traps for the unwary out there. Let's just say that it's been an education. No wonder people get motorbikes brand new.

I've spent lots of hours looking at ads, getting out to see bikes in the real world has been a bit slower but much more valuable in terms of learning.

Bikes looked at so far: Honda VTR1000F (x2), Ducati ST2 (the Turner's job), Ducati ST4S. The Hondas just felt cheap (and both had serious issues), the ST2 felt perfect but didn't go, and the ST4S was a cautionary tale. This latter bike looked mint in the photos, OK in person, but turned out to have a twisted up front end during the test ride. It had been crashed. The handling had been destroyed. The engine was an absolute beast. I felt like Wile. E. Coyote riding his Acme rocket while chasing the Roadrunner... it's all fine until a wall comes along...

Anyway, I'm still shopping. The last six months have made it clear that it's a good idea to have a reserve bike and I'm appreciating now why serious riders either run brand new or have a stable. Or both, bucks permitting. Currently the first choice is an ST2 (not the higher powered 3 or 4 valver's) but I'll have to actually ride one to be sure.

[SVboy]

Was one of the VTRs TM listing. 1483862992? If so, could you PM me with what you found was wrong?

[OddDuck]

PM sent. BTW thanks Voltaire!

Carrying on, getting the new bearing cups into the cases... transmission side first. I used the hot box idea again, this time using a wristwatch to give a decent soak time of 10 minutes at just over 100 C.

I spent a while prepping for this five minute job, getting everything lined up... pulling the case dowels was really something that I should have done earlier. I don't want these getting caught on a bit of support 4x2 during the cup drive and maybe causing a problem with an engine case. Ezi-outs and a spot of CRC get the dowels straight out. There were no issues driving the replacement bearing cup in.

I didn't photograph this but I reckon that Ducati have updated the cup design. The new cups don't have the internal runout groove. I'm not sure how they're made (very high class CNC turning perhaps?) but it's a beautiful smooth internal wall, a fine base radius and then the internal flat. It's clearly much stronger than the old design.

Initially I'd been thinking about just leaving the original alternator side bearing cup in place - if it ain't broke, don't fix it - but after seeing this it might be a very good idea to replace this cup as well.

Wiping the gasket surface was done this time with a folded over rag and a good wipe with the brew (1 part isopropyl alcohol to 2 parts white spirits), this and some scrubbing seemed to work pretty well. Strongly suggest mechanic's gloves if anyone out there is going to start using this stuff.

[OddDuck]

Bits on the side... cleaning the swingarm, hugger and chain up before refitting. I can get all these onto the bench before refitting so why not.

It was water based degreaser for the swingarm and paintbrush / kitchen sponge plus bucket of water. I used kerosene and a paintbrush for the chain, with the bit being scrubbed semi-immersed in a parts tray. I haven't re-lubricated the chain yet, I should do this soon or else there's a risk of tearing the O-rings the next time the chain is flexed.

Cleaning everything up means that cracks, chewed up fasteners etc become apparent. The bit of semi-flexible plastic that guides the chain and protects the swingarm is cracked, I'll have to get this on order for replacement at some later time. The welds on the swingarm are fine, just shadowed in the photo.

Something I've been quite keen on for this rebuild is plain English labels on all the parts. Ducati don't put more than a part number onto the bag. Fine... if I'm in the garage and it's late at night, I really don't want to go through the exploded parts diagrams if I can help it. Much easier to bag and label when parts arrive.

The attached PDF is something I'm keen on trying for setting the preload on the main bearings. I think it's much simpler and more reliable than the method followed earlier from the Haynes manual. If you can't see it, it's a simple idea: assemble crankshaft into gasketed cases, leaving some open end float. Use a dial gauge or similar to assess the end float, zeroing the gauge and then lifting the crankshaft. The total shimming is then whatever the measured end float is plus 0.3 mm. Divide this shimming by 2 and you've got the shim stack needed on each side.

[OddDuck]

Tonight's effort: modify the engine stand / lift plates so that I've got a base for the dial gauge. I wanted these plates as close as possible to the four shafts which need shimming measurements. Since I'm doing the crankshaft, it makes sense to check the others and change shims out if necessary.

The photos make it look like the required screw holes were drilled in close proximity to the engine, maybe even using the casings as drill guides... nope. I marked out with a scriber and then got the engine well out of the way and covered it up before the power drill came out. Drilling was steel plate on bench with bits of 4x2 underneath, ruled and centerpunched drill positions, nothing fancy. Then I cleaned the workbench and the plates. I really don't need metal shavings caught in my case bearings.

The drill holes themselves were chamfered and then sanded as well, just to be certain. It'd be all too easy to have steel burrings carve up the gasket surfaces on the engine cases.

It's not possible to check all four shim clearances on one side: crankshaft, shift drum, input shaft, output shaft. I've ended up sorting out a plate for each side of the engine. There's going to be a fair bit of putting stuff on, taking stuff off, flipping the block, etc. It is heavy but it is possible for one reasonably strong person to do this on the bench.

[OddDuck]

Got the other bearing cup changed out. It was a hassle but in the end I was glad I did it... by eye, it looks like there's a crack in the groove, the same as the other side but not as advanced. If I'd left it I'd have had another failure. The photos show the old (polished) and new (black) cups and their grooves. I've tried to show the crack but the lens won't quite go that close. It's probably worthwhile trying the CRC Weldcheck stuff on it, just to have a play.

Having managed to borrow a dial indicator and a stand, I spent some time yesterday shimming the crankshaft and checking end float in the gearbox shafts and shift drum.

To my mind, this is the way to do this. It's a good way of taking a complex measurement and making it simple.

It does involve a fair amount of physical work and patience - the cases get turned over or split and re-joined a few times - and patience is needed for each measurement too. There was a fair bit of jigging of bits to get the dial indicator into position and rigid enough to be trustworthy.

I found out in the week that there are two kinds of dial: gauge and indicator. One's a lever (gauge), complete with corrections for angular deviation, and the other is a plunger (indicator). Either can be used for this kind of work but the indicator / plunger type is the most convenient.

The Ducati specification for 0.3mm preload turned out to be way too tight, in the end. That's purely my own opinion and going by feel: the bearings felt like they were grinding, on any motion of the crankshaft. Not good. A quick note here: if memory serves, the advice given in the Haynes manual is even tighter, 0.4mm preload, and if I did that last time around then that might be the reason for the bearing cup failure. A lot of force goes through those bearings with the motor running and failure by fatigue will happen at much lower stresses than sudden, catastrophic failure immediately after assembly... I'd get a few months down the road and then I'd be splitting the engine cases again.

I don't want to split the engine cases again. Time to get this one right.

I checked discussion of preload figures and found, courtesy of our American friends at ducati.ms, that 0.15mm is widely quoted. Further checking found a very interesting result: one of the guys did a controlled bake of his assembled engine cases, up to liquid-cooled and then air-cooled operating temperatures, and he found that 0.15 mm preload gave him 0.05 mm free play at air-cooled operating temperature. He was happy with that and full credit to him, I hope it's worked out. My own belief is that opposed contact bearings like these need some preload to maintain ball-to-raceway contact, at all operating temperatures. Without this there's the risk of the balls floating or skidding, leading to a rapid wear condition.

I ran my own calculation, simple linear thermal expansion of aluminium cases versus steel / iron crankshaft over a length of 100 mm and a temperature rise of 130 degrees (final operating temperature 150 C) and found an expansion of around 0.15mm. I've decided to go with 0.20 mm preload, making sure that there's still forced contact at normal operating temperature. This will settle with wear, of course.

An unwelcome surprise was end float on the gear shafts and shift drum: I'd thought I'd got this right the last time around... guess what, either the tolerance stacking or taking measurements over long distances with the verniers not quite at 90 degrees got me. They're all out of whack.

Shift drum: 0.15 mm end float (probably OK)
Output shaft: 0.15mm end float (outside the 0.10mm spec)
Input shaft: 0.03mm end float (way inside the 0.10mm spec)

The input shaft is a worry because the cylindrical roller bearing on one end doesn't really have the capacity to deal with axial loading. If that shaft warms up faster than the cases then it could go to a loaded condition. I'll have to open the cases again and sort out these shims before proceeding further.

[BMWST?]

any idea why the turners st2 didnt go??Were they up front about it not being a runner ?