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Thread: Winter Layup - 1995 Ducati 900 Supersport

  1. #616
    Join Date
    4th October 2008 - 16:35
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    R100GSPD
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    Wellington
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    Quote Originally Posted by OddDuck View Post
    A very quick note - no photos sorry - filled tank with fresh petrol, made sure sump was full and tried the first start on the engine since rebuild.

    No issues. Gave it a few squirts of the accelerator and then a few turns on the starting motor. It caught and ran. The engine made oil pressure after a few seconds (go moly-based assembly lube!) and after that it was good to give it some revs just to hear the sound again.

    Very pleased. Miss my bike.
    is there a more pleasing exhaust/inlet/engine sound than a ducati V twin?

  2. #617
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
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    Lower Hutt
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    997

    yet more theoretical guff - this time it's dynos - nothing built though

    I've been laying low on things bike and garage for the last few months while clearing debt. It's been frustrating but necessary. Having time but little of anything else, I'd spent a few hours contemplating a home dyno setup and going through the details.

    Now, I want to be clear up front on this: I haven't built one, tested one, used one, hell I haven't even seen one properly. I saw a dyno setup being used once, on a car, from about twenty meters away. That's it, that's all the practical experience I've got here. Every word of what follows is old textbooks, pocket calculators, the internet, biros and refill, and more than a bit of OCD. I thought it was interesting and just possibly useful to someone, hence the post, but this really is just turning ideas over. The following is absolutely no substitute for practical experience.

    I'll also skip ahead to the conclusion, so we get the disappointment over with: it turned out that it really doesn't make sense to home build one, at least not for me.

    Estimated cost: $2000 and realistically my spare time for about half a year, that's if there aren't interruptions of course.

    I have one bike to tune. One. Once. And summer's coming. I could really use that $2K to actually ride with. It really does not make sense to take half a year and take on another project, to end up with a one-use tool that's been used and now clutters the place up, if this was successful at all anyway. It might make sense if I had many bikes to tune, or on going tuning, etc etc, but at this time I don't. Maybe later.

    So... the basics, apologies if I'm telling you stuff you already know:

    A dynamometer ('dyno') will let you take your engine to full throttle, while measuring output in terms of HP and torque, but also monitoring engine behaviours like air-fuel ratio, ignition timing and whatnot. It's basically the Holy Grail of things garage and engine tuning. This is not easy to do. As such, they aren't cheap.

    There are two basic types: Inertial and Brake.

    Inertial is simply a massive rotating mass. The bike accelerates the mass and by dint of cleverness, data can be extracted.

    Brake is the other type, capable of absorbing steady RPM and torque. It's way easier to read but much pricier.

    Some types of brake dyno:

    Friction - an axle with brake disc/s and brake caliper/s
    Eddy Current - an axle with discs and electromagnets
    Hydraulic Pump - a pump pushing oil through a needle valve
    Fan - basically the bike drives a giant air fan
    Water brake - a driven dished plate turns against a stationary dished plate, inside a flooded housing
    Force lubricated, oil shear friction brake - basically a wet multiplate clutch

    They've all got pros and cons but the most common is the Eddy Current.

    I became curious about the last type, the oil shear, so spent a while playing with the idea. The basic concept is that it's similar to a multiplate clutch: driven discs alternate with stationary discs. There's shear in a fluid wetting the disc surfaces. The assembly center is pressurised by an external pump so there's always a positive pressure gradient in the fluid between the center of the discs and the outer diameters.

    Basic formulae:

    For two plates, one moving relative to the other, with a fluid between them:

    shear stress = kinematic viscosity x plate velocity / plate separation

    Force between plates = shear stress x plate surface area

    Plates can be likened to discs, with an area and an average radius and velocity

    Torque per disc pair = force x radius

    Total torque = torque per surface pair x number of surface pairs

    and torque required to be absorbed, RPM, power etc can be readily determined via the bike's specifications for engine and gearbox.

    Of course it's basically just a clutch. I'd had the bright idea that I could make something that would replace the rear wheel. I'd counteract the torque via a handy through hole on the engine casings, with a spring balance measuring torque back to the body of the dyno. Presto, pop the bike up on a rear stand, remove rear wheel, fit dyno, take runs, success!

    Yeah... cutting a very long story short, after many, many calculations, it turned out that doing things this way means that the dyno has to cope with massive torque at full throttle. 540 Nm @ 1500 RPM, with my bike in 6th gear and the engine held at 6000 RPM. That's the lowest torque situation I could set up at peak output for the 900SS. There are space constraints of course, limiting the diameter and number of discs.

    The dyno's going to be absorbing between 60 to 80 kW of mechanical power. That's a lot of heating. I worked out that, to get around 10 C thermal regulation across the plate stack while under full load, I'd have to flow 2 litres of cooling water per second. That thermal control is needed because fluid viscosities tend to decrease significantly with temperature.

    After some work with disc diameters and spacings, the reason for the pump pressurising the center became clear: the only way to get acceptable torques is to run the discs at tiny gaps. 50 to 25 microns, or similar. They're basically in contact. The pump is necessary to make sure that discs stay lubricated and won't bind together, despite the conditions.

    Fluids: about the best I could find that was commonly available was 80-90W gear oil, with a viscosity of around 250 C.S. (centistokes), but it's rather temperature dependent. It gets slippy as things warm up. Golden syrup was contemplated (2000 C.S.) but again, same issue of temperature vs viscosity, and anyway I'd get a permanent ant infestation in the garage when the inevitable spills happened.

    Finally I did something I really should have done first: I took a pair of steel clutch plates and had a play, first with golden syrup, then with gear oil. It was messy but demonstrative.

    There is an effect. This idea does actually work. However it's a weak effect, even with something as heavy as room temperature golden syrup, the plates pretty much have to be ground into each other for there to be significant countertorque.

    Further calculation showed that the bike-mounted dyno is possible. With 21 plates around 500mm diameter, 80-90W gear oil, and cooling, this could (in theory) just work. However it's pretty marginal, the space constraints of replacing the rear wheel really limit what can be done (about 80 to maybe 100 HP). In the real world I'd say a roller system built into some kind of structure is far more realistic.

    Material: a full sheet each of steel and aluminium (as a bearing pair) would be needed for the plates, plus laser or water cutting, plus an axle, hub, housing, pressure plates at each end, seals, pressure pump, balance scale, RPM counter, etc etc... you'd be lucky to get away with $2K, or so I think.

    Noise: this is full throttle sustained running in suburbia. It's not going to happen for very long before I'd have conversations with officials, unless I can build some way to effectively muffle the bike's exhaust note while not changing the engine performance.

    Yep. Nice idea, good to play with, not going to happen. At least I didn't start spending money.

  3. #618
    Join Date
    14th July 2006 - 21:39
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    2015, Ducati Streetfighter
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    Christchurch
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    Pretty sure you could find a company with a Dyno and talk a deal well under that value to tune your bike.

    And the suburbia thing. Bugger em - run it during the week and make the bored housewives damp with the sound of a Ducati at revs

  4. #619
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
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    Lower Hutt
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    997
    Very late reply... apologies! Yep a series of Dyno runs would be cheaper than what I worked out. It'd make sense to build / buy something if there were a series of bikes to be tuned, otherwise it's just smarter and easier to pay the pro's.

    Just restarting work on the bike after taking a break. This time it's (finally) installing a brand new clutch basket.

    I'm going to nerd out over this. For me this is a huge deal - both the 900SS and the ST2 came with 30K+ clutches and I've just never had the coin to sort the baskets. I've never had a clutch running with anything like a proper clearance between basket fingers and friction plate tangs. It's always been rattly.

    The friction plates are getting replaced as well since there's not much point putting rattly old frictions into a nice new basket. It turns out that it's possible to buy friction-only plate sets - you keep the old steels and just sub in new frictions, which saves a bit of cash. Apparently this is possible on fibre / organic clutch plate sets. The friction material wears down but the steels don't. This particular plate set replacement wouldn't be possible if I was running sintered frictions, apparently these are a bit aggressive and take material off the steels over time.

    A couple of notes:

    The cheapo clutch locking tool works but could be dicey if dealing with a thoroughly dust-locked hub nut. Liam of Fastbikegear posted a while ago that these tools can damage the pump cover if too much torque goes through them... the pump cover is replaceable but not exactly cheap. The better versions of this tool use all four available screw holes. Neither is what a proper mechanic would use, since it takes a minute or two to fit the thing each time. I've got a proper clutch wrench on order from Oberon but it hasn't arrived yet.

    The tap and button die are being used to clean old Loctite 510 off threads, nothing else - I like to reassemble with components as clean as reasonably possible. I'd read somewhere that torque settings are based on fasteners as delivered to the factory, which means clean, straight threads, lightly oiled (liquid Loctite is supposed to have the same lubricity as a general light oil, for this reason). It pays to be careful and steady when doing this sort of work of course, a snapped off tap or a crossed thread would be a nightmare.

    The new basket is stock Ducati OEM. There's plenty of upgrade options around, in terms of performance, but stock is supposed to be the most durable. It's certainly the most affordable. Placing the two baskets side by side showed the difference between filed flat twice vs brand new.
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    Last edited by OddDuck; 23rd September 2018 at 09:51. Reason: clarity and spelling

  5. #620
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    ... and the result. It looks like the Newfrens are alloy plates, which I hadn't expected. They should be quieter than steel, but I don't know if they'll last as long or if they'll be kinder to the basket. It'd be good if these things happened of course.

    The gap's good though and that's the result I'd wanted. I imagine I'll have to ride the bike gently for a bit while the new plates bed in and settle down, Newfren left a note stating something along these lines.
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  6. #621
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    First run of the bike showed clutch issues, yet again. The bike's got clutch drag at standstill, choppy gearchanges and it's pretty much impossible to get it into neutral with the engine running.

    This was the reason for starting the thread about master cylinders going suddenly or degrading with time (general consensus was that they gradually lose performance due to corrosion and wear). Anyway, before going shopping, I tried a clutch system bleed to eliminate old clutch fluid as a variable. Earlier I'd purchased an ultracheap vacuum brake bleeder kit off TradeMe so took the opportunity to try this out.

    Well, it draws a vacuum. Let's leave it at that... it doesn't work properly with the bleed nipple, but that isn't the bleeder's fault. The threads on the nipple have to be sealed against air getting in, and on this assembly they aren't, so most of the vacuum is lost to a constant stream of air bubbles. I went back to the pump lever-loosen nipple-bleed-tighten nipple-release lever procedure and did the bleed that way.

    Fluid colour was good, didn't get any air bubbles out, slight improvement in clutch travel as measured via vernier caliper between spring cap and pressure plate. Travel went from 1.1 mm (!) to 1.3 mm.

    It was while doing this that I noticed that the spring caps themselves - which are supposed to be fixed rigidly to the clutch hub - are moving inward and outward with the clutch action, following the pressure plate. This is soaking up some of the clutch travel. Not good... the clutch hub is the two-piece OEM Ducati item with cush rubbers and it looks like the pushrod is somehow interacting with these cushings. I had a go at photographing this but it turned out to be tricky. The motion is on the order of 0.5 mm and the camera wasn't rigidly fixed to the bike, so any lean on the bike would affect the photos.
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  7. #622
    Join Date
    1st June 2014 - 21:23
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    Ducati 748R
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    nelson
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    79
    Quote Originally Posted by OddDuck View Post
    First run of the bike showed clutch issues, yet again. The bike's got clutch drag at standstill, choppy gearchanges and it's pretty much impossible to get it into neutral with the engine running.

    This was the reason for starting the thread about master cylinders going suddenly or degrading with time (general consensus was that they gradually lose performance due to corrosion and wear). Anyway, before going shopping, I tried a clutch system bleed to eliminate old clutch fluid as a variable. Earlier I'd purchased an ultracheap vacuum brake bleeder kit off TradeMe so took the opportunity to try this out.

    Well, it draws a vacuum. Let's leave it at that... it doesn't work properly with the bleed nipple, but that isn't the bleeder's fault. The threads on the nipple have to be sealed against air getting in, and on this assembly they aren't, so most of the vacuum is lost to a constant stream of air bubbles. I went back to the pump lever-loosen nipple-bleed-tighten nipple-release lever procedure and did the bleed that way.

    Fluid colour was good, didn't get any air bubbles out, slight improvement in clutch travel as measured via vernier caliper between spring cap and pressure plate. Travel went from 1.1 mm (!) to 1.3 mm.

    It was while doing this that I noticed that the spring caps themselves - which are supposed to be fixed rigidly to the clutch hub - are moving inward and outward with the clutch action, following the pressure plate. This is soaking up some of the clutch travel. Not good... the clutch hub is the two-piece OEM Ducati item with cush rubbers and it looks like the pushrod is somehow interacting with these cushings. I had a go at photographing this but it turned out to be tricky. The motion is on the order of 0.5 mm and the camera wasn't rigidly fixed to the bike, so any lean on the bike would affect the photos.

    i had a smiliar issue with a 900 monster, i ended up cleaning the hell out of the slave cylinder bleeding it several times adding an extra steel disc to the clutch pack right at the back( stops the rattle at idle) and adding some washers to the pressure plate springs. seemed to work for me, also check ur clutch lever is totally disengaging, do you have after market leavers? they can cause issues like that, sometimes a few strikes with a file sorts them out. clutch drag issues that is

  8. #623
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
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    Lower Hutt
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    997

    Worn shortie levers

    Thanks Layton - I do have aftermarket cheapo levers on the bike, these ones:

    https://www.trademe.co.nz/motors/mot...fa0515c416ee67

    Yeah they're a bit cheesy but they've worked alright for the last couple of years. I took the lever off and stripped it to find (unsurprisingly) that it's got obvious wear at the main pivot point and also the position adjustment pivot - this wasn't arranged properly. The screw threads bear directly on a brass bushing and the screw has cut its way into the brass.

    Both of these worn areas have affected the lever. Wear on the main pivot can be compensated by turning the spring loaded flat blade screw that drives the piston pushrod, but wear / cutting on the adjustor pivot directly reduces the lever-to-grip clearance and thus travel. It's possible to file the ball end of the lever flat and gain a couple of mm that way, this would mean roughly 0.07 mm more travel at the clutch slave but that's getting desperate.

    Looks like it's time to replace or upgrade. I'm thinking at least Brembos - the main pivot is properly bushed instead of just anodised aluminium used as a bearing surface - or possibly Oberons if I can afford them.

    No photos of this sorry - this was last thing last night and I was getting a bit tired - long day in the garage working out what was going on with the clutch hub and clutch pack.

  9. #624
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    997

    Measuring clutch pack, plate and hub movement

    Taking some proper measurements of what's going on with the clutch... I got the magnetic base and dial indicator out. One of the engine stand plates (from earlier) served to attach the base.

    This worked a treat. Results, for six springs:

    Pressure plate movement: 1.40 to 1.45 mm

    Hub movement: 0.18 to 0.19 mm

    I then took three springs off and remeasured. The point of this was to halve the clutch pressure force - if there's air etc in the hydraulic system, this test will show it up and it's possible to extrapolate back to zero clutch force, to what travel should ideally be.

    Pressure plate movement: 1.47 mm

    Hub movement: 0.17 mm

    Then I took all the springs off and tried the clutch pressure pack take-up movement, by hand (not photographed but very similar). This was a surprise: 0.80 to 0.95 mm. That's a lot of spring motion in the plate stack.

    Between the plate stack and the hub, almost all the slave cylinders travel is taken up. No wonder I'm getting clutch drag... 1.40 - 0.90 - 0.19 = just 0.31 mm nominal free play, and with plates rattling and bouncing there'd still be contact anyway... Hmm.

    The last photo shows the OEM Ducati clutch hub on the bench, stripped down. The system uses a pair of cush rubbers, two between each fin on the inner and outer halves.
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  10. #625
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    997

    Clutch Hub - axial free play

    Something I wanted to check was how much free play was natively available in the clutch hub. As supplied, without cush rubbers, how much does it move? What's happened, given that this was a worn hub?

    The hub was stripped and checked. Serious wear is visible on the inner flank, but curiously it's all on one side and only halfway down the diameter. A sideways look at a partial assembly shows that the cush rubbers don't set axial position - that would be set by the inner shoulder of the smaller locating diameter.

    I reassembled the hub without the rubbers and then tried checking how much it can slide on axis.

    2.75 mm

    Oh Ducati. What have you been doing??

    Yes, there's a bit of wear in the faces of the heavy cup washer, 6-point washer, all hub components etc... there isn't 2.75 mm worth of wear. Not a chance. Realistic figures for wear on the steel components are in the ballpark of 30 microns and the axial faces of the hub are similar. In short there's one hell of a lot of slack in the hub, I do not think that this is a good thing.

    Thinking about it, this was probably a result of the vertically split engine cases. The gearbox input shaft already has shims everywhere - Ducati may simply have wanted to avoid yet another collection of shims and critical tolerances. All that this component really has to do is come up to an end stop and then stay there, it doesn't have to be shimmed against moving toward the clutch slave. Still, I don't like it.

    The off-center wear on the outer hub's inner large diameter is also concerning. The hub's two main components, a cast steel inner and a soft cast aluminium outer, form a very basic dry bearing. They rotate a fraction of a turn against each other as the cushing does its work. If they're on center, the wear should be evenly distributed around the perimeter, not concentrated in a location. This indicates that it's been operating off center, skewed, and that would mean all sorts of clutch problems.

    I think that would have happened if a few of the cush rubbers had bound up and twisted during assembly, forcing the hubs off-center. Some shreds of torn rubber came out with the cushes... a quick look at the hub showed some sharp edges.
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    Last edited by OddDuck; 30th September 2018 at 20:04. Reason: notes about the 2.75mm slack

  11. #626
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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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    Reassembling the hub

    I cleaned the assembly up a bit before reassembly, trying to ensure that the cush rubbers would slide in straight this time.

    The inner hub is a cast steel component. The sand casting has left spikes, nodules etc over what should be smooth surfaces... cleaning this up took all of ten minutes, the steel isn't particularly hard and just getting the worst of the surface roughness off is enough. It's the same thing for the fin edges, just rounding these off a bit with a needle file will get the job done. Reassembly went fine.

    Making a washer to take up the axial slack took much longer than I'd hoped, though. It turned out that the 6-point washer wasn't flat. It is very slightly dished - approx. 1 degree - and my nicely lathed up washer turned out to need tapering. I don't have a lathe at home and had to improvise, see photo. The method is to sand it down against a flat plate, but with the washer skewed off horizontal via a long spacer under one side of the washer. Push up and down, rotate, repeat.

    Anyway, after much (way too much) sanding and trial-fitting of the hub, with cush rubbers removed, I had something I was OK with trying to fire up and ride on. The spacing is quite delicate: the hub shouldn't rattle, but shouldn't be nipped up either. To do its job, it still has to be able to turn. The 1 degree dishing would turn a perfectly flat washer into a bellville spring, which was exactly what I wanted to avoid, and a nightmare to size up accurately.

    I don't expect the washer to last. The original Ducati components appear to be hardened steel, presumably the only way to make anything last under the constant grinding from friction dust, while the washer is soft aluminium. It's a first trial. It's never going to be 100% first time; there's always a bit of try and learn and try again going on, and in this case the 1 degree dishing screwed my sizing measurements. I measured free play again once everything was reassembled - plate stack, pressure plate, springs etc - and it was a disappointing 0.10 mm. Maybe that's a now undersized washer, maybe that's slack being taken up on the input shaft. Whatever, I'll run with it and see how it goes. If I'd been trying to resize hardened steel I'd have been there for a week.

    The major benefit of this work may have been getting the cush rubbers to go into the assembly straight anyway. If memory serves, when I rotated the assembled clutch by hand, the friction tangs could be seen to wave in and out under rotation. They'd do that if the hub was skewed. Now they don't, they run steady. The clutch does appear to be releasing better when testing by hand with a shut down engine. This is good, but the acid test is to see how the bike goes while running.

    I have another issue to address unfortunately so testing is still a way off.
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  12. #627
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    997
    A couple of quick notes before I forget, starting with a better photo of tapering the washer - I really should get a lathe but space at home is an issue. The stainless steel strip to the side got marked by loose grit, I wouldn't recommend using anything precious here.

    It's a good idea to put something soft down on the floor while fiddling with clutch packs. I dropped one of the steels - from about 50 cm up onto concrete - and bowed the thing. It really didn't take much to knock it just enough that it shouldn't be reused.
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  13. #628
    Join Date
    3rd February 2004 - 08:11
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    1982 Suzuki GS1100GK, 2008 KLR650
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    Wallaceville, Upper hutt
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    Can you imagine how empty your life would seem if you had a japanese bike? You'd have to waste your time riding
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  14. #629
    Join Date
    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Lower Hutt
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    997
    Quote Originally Posted by pete376403 View Post
    Can you imagine how empty your life would seem if you had a japanese bike? You'd have to waste your time riding
    Bike Must Be Perfect

    PERFECT


    ...why don't people understand??

  15. #630
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
    Location
    Lower Hutt
    Posts
    997

    FCR41 carburettors - loose slides

    And now for some Japanese carburettors.

    I noticed while (briefly) riding the bike that the slides on the carburettors were rattling while the bike idled. They didn't do that before...

    Bike's still (still!) running rough. If the slides are loose, ie not under positive control, it'd be very possible to get quite different idle / part throttle openings between the two of them, particularly with the engine shaking and throwing things around.

    A quick look under the tank confirmed a loose slide - just testing it by hand showed free play of roughly half a millimeter, far more than was there with the carburettors new at roughly 25,000 miles ago.

    Clearly something's got a problem. Opening the carburettors up on the bench confirmed the free play (on both slides) and some close examination showed the source of this problem: the rivets holding the red idler wheels on the yoke which controls the slide motion. The rivets have loosened.

    There isn't much sign of wear through the carburettor bodies. The seals covering the vacuum plates are in good condition, so are the wheels carrying the slides themselves. The tracks those wheels run in are barely marked. Everything but these dinky little aluminium rivets looks fine.

    Options:

    1) get some sort of a clamp or vise onto the rivets and re-rivet them, all it'd take is nipping the thing up.
    2) buy a new yoke
    3) turn up some kind of threaded rivet replacement with a nut and loctite this into place.

    Thoughts about the options:

    1) piece of cake, get a suitable toolmaker's clamp and have at it. This time get a decent squish on the head, but try to avoid expanding the main diameter too much or bending / breaking the thing. The issue here is that the rivet came undone in the first place. There's a pretty good chance that it'll just do the same again.

    2) wait for a new part (could be six weeks plus) and then wait again for the new part to fail the same way the old part did... but it will work for the next few seasons.

    3) fiddly, time consuming, needs custom machining, but it's possible to match materials for things like thermal expansion. It's also possible to make it much stiffer than the original. Loctite obviously (might be hard to remove later if necessary), the big gotcha here is obtaining some sort of counter-torque feature on the inside side so that it can come apart again later. There just isn't much room.
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