Winter Layup - 1995 Ducati 900 Supersport

[OddDuck]

Some rebuilding and first go at re-shimming the valves.

Rubber shields and timing belt gears refitted to heads, then I refitted the valves. I packed the combustion chamber with a rag to stop the valves falling onto the bench with the heads placed flat, then put the opening shim into place on the valve stem.

Ducati use a pair of half-circle wire clips to retain the opening shim. These weren't Ducati's greatest design... they crush very slightly on the side under load, affecting the very tight closing clearance. You're supposed to refit them the same way. I've never worked out how to tell which side is which, so had to refit at random and hope. So far this hasn't been a problem, I've always struggled to get the closing clearance as tight as 0.000" to 0.001" anyway.

Refitting the clips is done by holding one against the valve stem, pushing the closing arm down against its spring with a screwdriver, persuading the clip into the valve stem groove, and letting the closing shim ride up against it to lock it into place. Then the other can be done the same way, while the first clip sits openly in the groove. A dab of motor oil helps.

Opening shims now ride far too tight. The valves don't close against their seats (well, the only one tried didn't, anyway). It's to be expected after valve seat cutting. I checked the gaps between rocker arm and valve stem head with a stack of feeler gauges, versus the existing shim spacing via micrometer, and it looks like I have to fit opening shims 0.10 mm to 0.20 mm shorter than current throughout.

[Kickaha]

Ducati use a pair of half-circle wire clips to retain the opening shim. These weren't Ducati's greatest design... they crush very slightly on the side under load, affecting the very tight closing clearance.

Have you looked at using the MBP collets instead?
https://store.bevelheaven.com/Engine...lt-Drive-Twin/

[Voltaire]

Have you looked at using the MBP collets instead?
https://store.bevelheaven.com/Engine...lt-Drive-Twin/

Liam at Fastbike Gear does them
http://www.fastbikegear.co.nz/index....23v9qth0mnkea3

He also has an interesting Frankencati 900ss FE as a test bench.

[OddDuck]

I'd managed to miss a bearing in the earlier list - this is the cylindrical roller bearing supporting the belt end of the timing shaft mounted transverse at the front of the crankcases. Here's the revised, full SKF bearing list for the engine cases and heads:

RNU202ECP x 1
16005 x 1
6005 x 1
6004-2RSC3 x 1
6305 x 2
2NUC3E0 x 2
35x47x7TC x 1 (seal)
25x52x7TC x 1 (seal)
22x35x7TC x 1 (seal)

Main Bearings
7207 BEP x 1
7307 BEP x 1

Swingarm Bearings
HK2016 x 4
4 x seals, Ducati 93041271A

Cylinder Head Bearings (per head, same for vertical and horizontal)
6004-2RSC3 x 1
6003-2RSC3 x 1
6202-2RSC3 x 1
22x35x7TC x 1 (seal)

Kickaha, Voltaire, yes, the MBP collets are definitely on the list. I have to do some shopping for replacement valve shims after getting some measurements, so there'll be some browsing before making a decision.

[OddDuck]

Just finished taking measurements for the new shims.

The normal method for checking clearances is to use a feeler gauge between opening rocker arm and opening shim. This gives the opening clearance. Then, taking a screwdriver and pressing down on the opening arm, the feeler gauge will now give the closing plus opening clearance. You have to rotate the camshaft to check that the valve is at the top of its motion, so it can help to take the belts off.

New shims: asssemble the valve, the closer and the collets, so the valve is positively retained and seated. Then take the feeler gauge, make a stack, and take various blades in and out until there's a nice fit between opening rocker arm and valve stem head. Take the operating clearance off this dimension and this is the new shim size.

The closing shim is similar. Fit the feeler gauge stack again, then take the screwdriver and press down on the opening arm to take up slack, then find the new stack thickness needed for a nice fit. The difference between loaded and unloaded is the current operating clearance. Then remove the opening collet and measure beween base flat and internal flat (where the half-circle clips go) with a micrometer. The micrometer will see the radius from the clips, take several goes and see what measurements come down to before the micrometer sees only the hole in the middle. Fiddly and a bit nasty but it works.

Something that initially concerned me was that opening shims are all around -0.10mm from current sizes, but closing shims are going to have to be +0.18 to +0.36 thicker. I think it's a legacy from my one and only track day. I revved the hell out of the engine and it's very likely that things got distorted.

Looks like the MBP collet retainers are going to be well worth it.

[actungbaby]

Check all load bearings for play, if in any doubt whatever then replace them. Photo everything, better, get the Sharpie out and label everything so you can rebuild it even if it's down loose bits all over the bench.

The 2 countershaft gears are probably loose on their freewheel bearings. Not a worry here unless it's massive free play permitting a mechanical collision of some kind.

Chipped gear dogs are a worry, your call on these but if there's a chance it'll pop out of gear under load then it'd be a good idea to replace these too.

Thanks mate great info yes it is the gears on there free wheel bearings so they benifit having support from gears to the side on engament.

yeah just only 3 gears are available out eh complate set new so be wait to find second hand replacments . wasint jumping out of gear.

That seems to be case on second third gears on blades that have been flogged wheelies etc wear am seeing must be lack of gearbox engine oil. that really pisses me of to see . whats a check of oil bloody slack lazy previous owners.

My bike had whine from what i thought was the gearbox was on that side (left the engine not the cam chain side. and thats more a rattle

at certian revs not a constant. sound as i have


On another forum was talk under cutting gears but o thought thats a term for the teeth face and is done for smooth opertion or

keep things quiet . also tlak of getting engineers to face the dogs . but then you have issues surely with lack harding and wear.

dunno only ametuer

just looking at my options for time and cost on very limited budget but like to a job well . no short cuts. as big job to take engine out. spli it

[pete376403]

Undercutting usually refers to the angle the gear dogs are shaped to - so that as soon as they start to engage the undercut pulls them into engagement

[OddDuck]

MBP retainers and valve shims ordered (direct from EMS), together with a closer shim measuring tool. I took a look at FastBikeGear's pricing and the retainers are significantly cheaper from EMS plus of course they've got their own shims. I've taken a risk and ordered as if my measurements were 100%. If I have to re-order then so be it, postage is $30 US for the budget option. There is a calculator for shim sizes on the site but I'm stuffed if I can make sense of it.

Now back on reassembling the engine case halves... Both casings heated, new bearings tapped in, then I found that the timing shaft is a light interference fit on the ball bearing side. Rather than use force I chose to reheat the entire casing half to expand the bearing's inner race and it went in without problems.

I put the circlip back in first and that's when I noticed a crack in the casing - take a close look at the photo and you can see it highlighted. Looks like Ducati have made a design mistake here. The metal above the circlip is very thin. I think that once the circlip groove gets packed with combustion ash, thermal expansion and contraction could break this open relatively easily. Unfortunately it simply can't be helped. Short of a new casing half, or attempting to weld it closed (greasy aluminium... hmm) I'll just have to live with it.

Bearing retainers were threadlocked with loctite 222. The folding table is going to be a useful working surface for manuals and the huge amount of bagged and numbered new spare parts.

[OddDuck]

Gearbox driven and lay shafts were next. Assembly lube was used on bearing inner races and seals, also the shims can be stuck down with this stuff, stopping them from falling off onto a grubby floor and so on. I'm going with the original shims and will have to try to check clearances after assembly with a new gasket. It should be OK, but with new bearings things could have shifted. It's also possible that I've made a mistake using assembly lube instead of new oil, but we'll see. The lube is basically a grease and it may affect measurements, since it'll tend to form a thicker layer between components.

The reassembly order is:

Driven and lay shaft assemblies refitted
Shift forks fitted (5-6 goes on the shaft with one collar, the 1-2-3-4 forks go on the shaft with two)
Shift drum fitted
Shift forks engaged into drum slots
Shift fork shafts inserted

... and that's it. It's actually pretty fast once confident.

[actungbaby]

Undercutting usually refers to the angle the gear dogs are shaped to - so that as soon as they start to engage the undercut pulls them into engagement

Thanks mate yeah that makes sence

[actungbaby]

[QUOTE=OddDuck;1130992776]Gearbox driven and lay shafts were next. Assembly lube was used on bearing inner races and seals, also the shims can be stuck down with this stuff, stopping them from falling off onto a grubby floor and so on. I'm going with the original shims and will have to try to check clearances after assembly with a new gasket. It should be OK, but with new bearings things could have shifted. It's also possible that I've made a mistake using assembly lube instead of new oil, but we'll see. The lube is basically a grease and it may affect measurements, since it'll tend to form a thicker layer between components.

Lube sounds good what did you use to clean your gears up so well look like new you can still see machine marks on the teeth
Some talk soaking gears in oil before installing them cant see how that work only make real mess everwhere not like there poreris

[OddDuck]

actungbaby - um, well, I didn't clean the gears at all. That's how they came out of the motor. All I've done is drain oil and wrap them in a rag. The photos are a bit over exposed so that details of the gear cluster are clear, that tends to make things like this look a bit cleaner than they really are. I've been running decent oil (Motul) so maybe that helps.

Further work: I fitted the crankshaft, then the oil bypass valve and spring (got it wrong with this when taking apart: there's a cap, which I didn't recognise and unscrew. It's still possible to reassemble by putting bits into the middle). Then I tried fitting the cases together (with gasket) and tightening all screws to final torque.

Very disappointed to find that the crankshaft bearings were loose. Also the gear shift drum had massive free play, of nearly a millimeter. Went and got the Haynes manual (thank you public library) and found a couple of things out...

First, whoever rebuilt this engine the first time around didn't use the right kind of crankshaft bearings. Normal ball bearings aren't supposed to be used. The main bearings are supposed to be opposed taper ball race bearings, and they're supposed to be preloaded via careful selection of shims to -0.15mm clearance. There isn't supposed to be any free play whatever.

With that in mind I've spent tonight measuring up to check shimming through the crankcase. Crankshaft, input shaft, output shaft, and selector drum all have to be shimmed correctly. I'd thought I'd have to assemble cases and then get in with a feeler gauge.

The procedure in the Haynes manual is a bit easier: use a straightedge over the case halves and take depth measurements to the bearing race or surface of interest, subtracting the width of the ruler afterwards. Take whatever shims are present off and then measure shafts end to end, then measure the shims themselves, then also measure the gasket thickness.

Having a look at the crankshaft shims:

Crankshaft length, bearing face to bearing face 87.96 mm
Left case bearing depth 69.14 - 25.10 = 44.04 mm (note that the bearing race has to be held level)
Right case bearing depth 69.80 - 25.10 = 44.70 mm
Gasket thickness 0.35mm

So, 44.04 + 0.35 + 44.70 = 89.09 mm

89.09 - 87.96 = 1.13 mm

With 0.15mm preload, required shimming is therefore 1.13 + 0.15 = 1.28 mm.

Existing shims are 0.62mm (alternator) and 0.35mm (transmission) = 0.97 mm, so this explains loose taper bearings.

So, from the manual, left shim thickness should be:

44.04 + 0.175 (half the gasket) + 0.075 (half the bearing pre-load) - (87.96 / 2) = 44.29 - 43.98

= 0.31 mm

It's not simply half, because to center the crankshaft in the crankcase, I have to compensate for different depths. Running this again for the right shim, to check that the answers add correctly:

44.70 + 0.175 + 0.075 - 43.98 = 0.97 mm

Total is 0.97 + 0.31 = 1.28 mm.

I'll have to go through the rest of the results later, then go shim shopping.

[actungbaby]

[QUOTE=OddDuck;1130992938]actungbaby - um, well, I didn't clean the gears at all. That's how they came out of the motor. All I've done is drain oil and wrap them in a rag. The photos are a bit over exposed so that details of the gear cluster are clear, that tends to make things like this look a bit cleaner than they really are. I've been running decent oil (Motul) so maybe that helps.

Further work: I fitted the crankshaft, then the oil bypass valve and spring (got it wrong with this when taking apart: there's a cap, which I didn't recognise and unscrew. It's still possible to reassemble by putting bits into the middle). Then I tried fitting the cases together (with gasket) and tightening all screws to final torque.

Very disappointed to find that the crankshaft bearings were loose. Also the gear shift drum had massive free play, of nearly a millimeter. Went and got the Haynes manual (thank you public library) and found a couple of things out...

Allways helps those haynes manualls are the best had factory honda ones but there more for professinal technican.

your photos are brillent amazed you got so far you must have gift for fixing things . so you duke nut i take it .people seem love these

bikes esp the air cooled ones . never ridden one myself for that matter on 3 non hondas in my life.yeah changing the oil is a must

pretty cool have sims for crankshaft i was looking on you tube on bmw with shims in the gearbox think that be

good to extend engine life . i thought these things think of the past in this build it to cost throw away world

[pete376403]

You can understand why modern (ie Japanese, Bloor Triumph, etc) use horizontally split cases. Vertically split cases introduce so many variables into engine assembly that virtually every single engine is a unique set of clearances. Plus its just asking for an oil leak.

[actungbaby]

[QUOTE=OddDuck;1130992771]MBP retainers and valve shims ordered (direct from EMS), together with a closer shim measuring tool. I took a look at FastBikeGear's pricing and the retainers are significantly cheaper from EMS plus of course they've got their own shims. I've taken a risk and ordered as if my measurements were 100%. If I have to re-order then so be it, postage is $30 US for the budget option. There is a calculator for shim sizes on the site but I'm stuffed if I can make sense of it.

30.00 nz for postage is great what puts me of ordering parts in small amounts as wack 70.00 nz just on few washers ;-)

I use you shop from nz post i have address in the uk and the usa and know china . cost me 300.00 to get two fork tubes for my vfr 750

They where heavy and long cant remember if was you shop or just sea freight from the states .

I only used them for plastic faring pannels and brake parts of ebay sellers but saves hassle bidding and then hoping they ship to nz

Most uk traders do then go 2 months or so once reachs the depo it shows up ever step of the way its great service.

They price refording postage to you and list each parcel .