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Thread: Winter Layup - 1995 Ducati 900 Supersport

  1. #571
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    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    797
    Fitting pistons to cylinders, fitting base gaskets to engine.

    The base gaskets are there to seal against oil leaks, they don't deal with gas pressure. Ducati use Loctite 510 as a sealant, that's the bright pink beads visible in the photograph. I've kept the assembly stock, with 0.4 mm gaskets used on both horizontal and vertical heads. It's possible to modify squish and marginally increase compression by omitting these gaskets or DIY'ing something out of thinner metal, but the price paid for that is vulnerability to impacting heads and pistons, if the engine has any coking due to running rich. Best restricted to race engines which are torn down frequently.

    Getting the pistons into the cylinders was a bit fiddly, until I learned the trick: slightly misalign the cheap Stanley piston ring compressor's leaves. This has to be done because Ducati left a generous 45 degree chamfer on entry to the cylinder bore. The rings like to pop out of the compressor and bind up on this chamfer during the push... it'd be very easy to try to force it and break a ring, carve up the cylinder, damage a piston ring land, or some horrible combination of all three.

    If it jams during assembly, just pull it, get it back into the compressor, take the time and set it up right. It'll go in once it's lined up, with those compressor leaves actually in the 45 degree chamfer but stopping short of the gentler taper leading into the main bore. Cylinder and compressor were wiped down and oiled before assembly, with ring gaps set at 120 degrees to each other in their lands, as per the workshop manual.

    It's not really possible to put pistons onto conrods and then lower the barrels over them, unless some kind of split-half ring compressor is available - something that can go in past the studs and come out again between them.
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  2. #572
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    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Heads onto barrels.

    Pretty simple really, fit whatever seals are needed, carefully fit the head square and flat onto the cylinder spigot, fit the head nuts and tighten these up in stages to full torque.

    One trap with this assembly is that it's possible to torque up with the head off-square, initially at least. The feeler gauge applied between flats on the cylinder and head was an attempt to make sure I had things nipped up square before the 1-2-3 torque sequence started. The torquing in stages should normally pull things straight, but I wanted to give the process the best possible start. This actually did work, after a rough sort of fashion. The stud bolts have a fair bit of spring in them, the fresh loctite sealant squashes a bit, etc etc... but it's better than squinting and guessing.

    The unusual black wrench pictured is a crows-foot, carefully ground out to a classic open-ended form. This grinding had to be done to get access for the torque wrench. With the heads overhanging the head nuts, it's not possible to take a straight shot with a traditional socket. It's also not possible to do this on a more recent engine, these use 12-point head nuts and unless a thin section 12-point crow's foot can be found, it's go looking for the very specific U-shaped spanner used for this job. Hdeusa make one at a decent price but it's payment via Paypal and probably freight via Youshop, they aren't a big outfit with a flash web sales frontage. Note that nut flanges and threads were greased prior to assembly, as per the manual.

    Something I didn't photo was running a swab through the horizontal cylinder's mounting holes. These were filthy with ingested road dirt and oil, there's access to these via the gap between head and barrel once the engine's assembled and they tend to trap gunge. I didn't want the studs to push muck out of the holes and then have this drop into the cylinder bore during assembly.
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  3. #573
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    28th January 2015 - 16:17
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    Timing belts.

    There are all sorts of arcance procedures and gear for setting timing belt tension. I've had success so far with the allen key as feeler gauge method, as outlined here:

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

    It can be difficult to fit the belts in the first place, though. Pulleys are supposed to be lined up with dots, but on the vertical head this happens at a point where the closing springs countertorque the camshaft. It'll want to spring back while the belt is being fitted to the pulley. The circlip pliers were being used to hold this pulley in position, they're narrow enough to drape the belt over them first.

    Belt tension was done with 5mm allen key horizontal cylinder, 6 mm vertical, as per the web page. The engine was turned by hand, putting the camshaft into an unloaded position to make sure that the belt was slack on both sides, before setting tension. I'd marked belts prior to taking them off, showing cylinder and running direction.

    I've made a change to the inlet manifold stud isolators. Time to see if the running rough and loud issue was thermal or electrical... the Tufnol insulators had an issue with crushing over time and needing the fasteners torqued up periodically. I've machined up some aluminium top hat washers to take their place. The manifolds will run hotter, but maybe that's desirable in terms of fuel not condensing on the manifolds during sustained running. Or maybe it's just small potatoes. The only way to be sure is to test it, once the bike's back together.
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  4. #574
    Join Date
    11th June 2011 - 16:30
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    Honda vfr 750 fn 1992 x2 90red
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    Quote Originally Posted by OddDuck View Post
    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.
    Dont drive yourself mad buddy your doing fine . you should see my cbr 900rr engine been on the bench over a year know .

    I tryed that clr stuff guy recommended it for alloy carby bodys . i had rusty steel clutch plates . wife droped the bottle and lost most of it. was tiny bit so i added
    so water sat the plates in and took the rust of real well . its only surface.

    I have a xr 200 crank that bearings have rusted and gone through the shiny stuff so know your frustraion. ;-) .

    glad your posting sorry for the butting in normal transmission ressumes .

  5. #575
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    11th June 2011 - 16:30
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    Quote Originally Posted by OddDuck View Post
    Fitting pistons to cylinders, fitting base gaskets to engine.

    The base gaskets are there to seal against oil leaks, they don't deal with gas pressure. Ducati use Loctite 510 as a sealant, that's the bright pink beads visible in the photograph. I've kept the assembly stock, with 0.4 mm gaskets used on both horizontal and vertical heads. It's possible to modify squish and marginally increase compression by omitting these gaskets or DIY'ing something out of thinner metal, but the price paid for that is vulnerability to impacting heads and pistons, if the engine has any coking due to running rich. Best restricted to race engines which are torn down frequently.

    Getting the pistons into the cylinders was a bit fiddly, until I learned the trick: slightly misalign the cheap Stanley piston ring compressor's leaves. This has to be done because Ducati left a generous 45 degree chamfer on entry to the cylinder bore. The rings like to pop out of the compressor and bind up on this chamfer during the push... it'd be very easy to try to force it and break a ring, carve up the cylinder, damage a piston ring land, or some horrible combination of all three.

    If it jams during assembly, just pull it, get it back into the compressor, take the time and set it up right. It'll go in once it's lined up, with those compressor leaves actually in the 45 degree chamfer but stopping short of the gentler taper leading into the main bore. Cylinder and compressor were wiped down and oiled before assembly, with ring gaps set at 120 degrees to each other in their lands, as per the workshop manual.

    It's not really possible to put pistons onto conrods and then lower the barrels over them, unless some kind of split-half ring compressor is available - something that can go in past the studs and come out again between them.
    Ive done with my fingers least on my xr 200 and xl 100 engines much

    easier when i had my dad to hold the cyclinder for me (not anymore)
    Unless he pops down from heaven.

    But even with your correct gear having someone keep cyclinder level is a god send. its just getting that first top ring . going . what stag 180 % on your ring gaps. cyclinders look very cool .

  6. #576
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    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    Quote Originally Posted by actungbaby View Post
    Ive done with my fingers least on my xr 200 and xl 100 engines much

    easier when i had my dad to hold the cyclinder for me (not anymore)
    Unless he pops down from heaven.

    But even with your correct gear having someone keep cyclinder level is a god send. its just getting that first top ring . going . what stag 180 % on your ring gaps. cyclinders look very cool .
    Thanks! For me, with this engine, it's the oil control ring. Strange but something about the narrow edges, the second edge always catches unless it's lined up just right.

    Ring gaps were set at 120 degree intervals, as per the workshop manual. That said 180 would probably work just as well.

    One thing about the rebuild: I didn't worry about this on the vertical, but on the horizontal I caught the oil control ring gap lined up almost exactly on the point where the cylinder and head had an oil leak. It might have been like that before. That's the lowest part of the cylinder, having the gap there really won't help with excess oil buildup. I've rotated all of those rings 90 degrees, so now the oil control ring's gap lines up with the gudgeon pin.

  7. #577
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    11th June 2011 - 16:30
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    Quote Originally Posted by OddDuck View Post
    Thanks! For me, with this engine, it's the oil control ring. Strange but something about the narrow edges, the second edge always catches unless it's lined up just right.

    Ring gaps were set at 120 degree intervals, as per the workshop manual. That said 180 would probably work just as well.

    One thing about the rebuild: I didn't worry about this on the vertical, but on the horizontal I caught the oil control ring gap lined up almost exactly on the point where the cylinder and head had an oil leak. It might have been like that before. That's the lowest part of the cylinder, having the gap there really won't help with excess oil buildup. I've rotated all of those rings 90 degrees, so now the oil control ring's gap lines up with the gudgeon pin.
    i use my finger nails sure is tedious but you can do it. i never had the right gear i be using that. i whouldint be too concerned cylinder are tapered . and with heat and the compession the rings get pushed more out. in two stokes some arent completly perfectly round . so they say i dobt u notice with the eye though.

    am not mechanic though . i only done one engine put toghter back in the day.

    gee reminded me i try get piston down and then u panic check the rings where still 120 % i think just go for it . i love to help where are you. ?

    patrick

    ps the pistons are slighty oval i meant not the rings yes from memory oil rings gave me issue too.

    Has the duke 3 rings oil scrapper and compression. oil more likey be forced up and any whould going down with be a design to keep crank bearings and con rod sweet.

  8. #578
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    28th January 2015 - 16:17
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    The Ducati uses 3 rings, compression, scraper and oil control, as is the usual pattern in a 4-stroke engine.

    Using fingernails to fit rings... yeah I can see that, but for me it's a 3 week wait on parts and I'd really rather not take the chance with a ring binding up and then breaking, or taking something out along with it. Tools are cheap these days, if the ring compressor costs less than one ring set then I know which way I'm going.

    The cylinder bore is parallel and circular over the working stroke of the rings. It isn't like that over the full length of the bore though. From the base, there's a 45 degree chamfer, then a much more gradual taper leading in to the parallel section. It's the chamfer that's the issue. The ring edges are razor sharp after they've worn a bit and they always bite in on entry, so they've got to be snuck in past the chamfer and allowed to contact the gradual taper. After that it's OK.

    Thanks for offer of help but I'll say no as politely as possible... working on this strictly solo means I can do things 100% my way, at my own pace.

  9. #579
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    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Getting into the fuel tank today, pulling the old fuel filter out.

    The way in is via the filler lid and the flange surrounding it. This is held in, ultimately, by a ring of grub screws engaging in a V-groove, and an O-ring. The grub screws come straight out, after all of them have been found (the heads are very small and if the flange has oxidised then they hide very well). The O-ring can jam. I had to lift the flange as far as I could, get some PB Blaster in the gap, and work the flange for a few minutes to get it out without putting a lot of force through the top of the tank.

    The arrangement inside the tank is:

    Mesh filter
    Fuel pump
    Fuel filter
    Metal pipeline to petcock and carburettor supply
    Metal pipeline for fuel return, terminating in an open end at nearly the highest point in the tank.

    The fuel pump is held in a twin spring C-clip, the fuel filter is connected to the metal pipeline via a very short section of 8mm ID fuel hose and hose clips. It's a five minute job to undo the hose clip and then pull these out as an assembly, after having lifted the filler cap and tank flange.
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  10. #580
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    28th January 2015 - 16:17
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    Next stage: check everything.

    The mesh filter is discoloured, its fitting ring is rusty, but otherwise it appears fine. No tears or holes, no obvious jamming, didn't have any issues pouring isopropyl alcohol through it during an attempt to clean it. I'll call it as probably OK, which is just as well. Stein Dinse indicate that this is a discontinued part. I've had a look at 600 / 750 engines (both Monster and Supersport) and no luck anywhere, if anyone knows a replacement pump inlet filter that'll fit, can they comment please?

    The pump itself was working just fine the last time the bike was running. It's not serviceable anyway, if anything's wrong it's a total replacement.

    The hoses ( 2 x 5cm lengths of 8mm ID fuel hose) have set over time but don't appear to have leaks or tears. It'd be a good idea to replace these.

    The filter, though... this is quite definitely a consumable. The maintenance schedule recommends a clean / change every 3,000 miles / 5,000 km's. I haven't changed it once and I purchased the bike at 32,000 miles. It's now got 62 K on the clock. Being curious, I sawed it in half for a look. Some sediment at the base, not much... the element's clearly used though. The filter uses paper and to the eye it looks quite badly loaded up. The two photos show the filter still wet and then after it had dried out.

    On reflection I really should have tried connecting a hose to it and seeing if I could blow through the thing first. I've got a brand new one to compare against. Too late now though.

    While I was at it, I changed the petcock out for a replacement. The old petcock wouldn't shut off properly, which was a pain when doing any work on the carburettors. I took it apart to see why this happened and how it worked. To do that, I had to force the cap unscrewed with a pair of vice grips. The end of the valve cap has been rolled, to prevent it coming undone (under vibration while running I guess).

    It's a simple design, two o-rings on two diameters. The larger O-ring controls fuel against leaking out of the base of the petcock. The smaller O-ring is the fuel on / off seal, working by insertion into a narrow, parallel bore. There's a very slight rounding off on the edges of the 90 degree entry, but there's nothing nice like a taper to guide the seal or anything. Yep, it gets guillotined every time it gets used, as shown by the damage to the seal in the photo. This petcock design really wasn't Ducati's finest moment, no wonder it wouldn't shut off properly.

    I've tried to photograph what I can see of the shut-off seal in the replacement (upgraded) spare part, shown here sitting on top of the old petcock. As far as I can tell, it's a similar O-ring, but pressing against a conical face in the manner of a needle valve.

    I also noticed that the hose barbs on the new petcock are slightly rounded off, they don't feature razor edges like the first one had originally. These edges cause problems with rubber shavings making their way into the carburettors if the hoses are reused, as would be normal after refitting carburettors post cleaning / adjustment.

    The attachment for both designs uses a 15mm hexagonal connecting bush, featuring a LH and RH thread starting from each end and meeting in the middle. It sounds fussy but it turned out to be good to use in practice, it means it's easy to set the petcock at any desired angle and then tighten up to seal to the tank.
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  11. #581
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    Reassembling the tank innards.

    I found out something useful while doing this - it's a good idea to get the verniers onto every hose fitting to confirm sizes, it's also good to check hose diameters once fitted to verify that the hose clamp chosen is within its size range.

    Doing this showed that Ducati have mixed and matched sizes through the tank. The pump outlet is 8mm, the filter (both ends) is 8mm, the piping used in the tank is 1/4". A close look at the old hoses (using verniers) showed that one hose was 8mm, the other was 1/4". They looked alike enough that I'd assumed they were both 8mm's, at a glance.

    It's not a good idea to use 8mm fuel hose on a 6.4mm pipe. It might seal over the pipe end, where it's been rolled to form a barb, but hose should really be tight over the entire diameter, the whole way along the rubber to pipe interface. I've tried using slightly loose hoses on pipe barbs etc before and it just never works out, the slightest wrinkle or opening and there'll be leakage, no matter how tightly the hose clamp is winched up.

    Post assembly, it occurs to me that the smart thing to do here is to use two bits of hose between filter and fuel tank, 8mm then 1/4", with a barb-to-barb size change adaptor and a couple of extra hose clips. Use a looped length in the hosing to get everything to fit in, if necessary. The fuel filter doesn't have to be in an exact position or orientation in order to work, just as long as it doesn't rattle or scrape too much.

    As it was, I've forced a piece of 1/4" hosing onto the fuel filter, stretching the hose a little with needle nose pliers, using bearing grease and then pressing it on with the help of a socket. This very nearly broke the fuel filter, it's not particularly strongly made.

    I've rebuilt using Jubilees, the more commonly available Tridons have a reputation for sharp edges and cutting into the hoses. My own experience with the Tridons (in stainless) suggests that they can come undone with time and vibration. I really don't want fuelling issues happening inside the tank, while on tour.

    The cable cutting pliers turned out to be a good purchase, making things a lot easier. Previously I've been cutting hoses with a box cutter knife, it's sharp but suffers from friction bindups with the rubber while the blade is passing through. The rubber then flexes and it becomes difficult to get a clean, neat cut.

    Reassembly of the tank fuelling flange was helped with some bearing grease. The weather seal gasket goes back on from outside, while slightly lifting the flange - it took a couple of goes to get this done.

    The fuelling flange carries a weather drain hose. This passes right through the fuel tank. If this comes off, either at top or bottom, rain will end up dripping into the fuel tank. It's a good idea to check for blockages in this piping (it does pick up road dirt etc) and also cracks, lack of securing clips etc. It's just 8mm outer diameter, I didn't have the relevant hose clip, so have improvised for now with a 20mm length of the 8mm ID fuel hose. It's a bit bodgy but the drain hose isn't pressurised, and anyway has been holding on by itself for over a year now.

    After this I took my first look at the carburettor floats in a while, I wanted to check spring tension on the needle valves. I found one tab slightly bent, with a 1mm difference in float heights. I don't know how this happened, unless I managed to force the floats upward while trying to refit the fuel bowls.
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