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Thread: Winter Layup - 1995 Ducati 900 Supersport

  1. #481
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    28th January 2015 - 16:17
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    Quote Originally Posted by Voltaire View Post
    Is all this work from the original crack in the frame, leading to modified air box and flat slide carbs?
    Yeah, I never really stopped... there was always the next thing. I treat it as a chance to learn. Anyway, 'tis the season to wrench.

  2. #482
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    28th January 2015 - 16:17
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    A little bit of progress on a couple of fronts today... inlet manifold covers and the carburettor jacket.

    One of the issues with designing these components has been the difficulty of taking measurements. Things are at weird angles, there's no clear datum to work off, that kind of thing. The idea I had today was to use the aluminium plate and a set square. I'd place the item onto the plate, arrange it so it was silhouetted against the paper, then use the set square to help trace the outline. The square means that if things are 100mm or so up off the paper, it's still possible to get the outline right to within a millimeter or two.

    It's a bit laborious but it works. The major issue is holding the item (whatever it is) at the right plane, and fixed so that it doesn't move if I bump something with the square. The intercooler pipe is stuffed onto the inlet manifold insulator rubber boot for this reason - by a happy accident it fits on snugly and makes a perfect brace for the tracing.

    The aluminium tube is an 2.5" intercooler connector pipe with a 45 degree bend. I've used a large socket, wrapped in duct tape to match diameters, as a brace against crushing in the vise while it's being hacksawed. This will be the cover for the inlet manifold, now I need to make internal ribs to hold it in place.
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  3. #483
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    28th January 2015 - 16:17
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    Some brief work tonight convinced me that outlines traced onto paper aren't going to sort out the carburettor jacket. The carburettors are too complex to model this way easily.

    The rather boxy preliminary concept was modelled in card as just the front plate, and was promptly failed when I tried connecting a pod filter. It's just too far forward on the inlet trumpets and will get in the way, no matter how it's set up. I'll have to go under the forward brace bar if I want to clear the pod filters mounting points properly.

    The angled card has square holes - these roughly mark the position of the two air duct fans. I want to blow warm air onto each carburettor base and then use the jackets to direct the air over as much of the carburettor body as possible. There's got to be enough thermal conduction from the carburettor body into the throat to prevent icing.

    The playing with card did give me an idea, though... trial and cut-to-fit direct on the item does have possibilities. I want close fitting jackets, if possible. 5mm spacers and scissored card could be the way forward here. It may also be possible to mount panels via rubber box feet and external clamp or screws, but I'll have to see how I go.
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  4. #484
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    28th January 2015 - 16:17
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    Next try, change of method again, some progress with spacers and card. The spacers are paddle pop sticks, cut to length with a pair of engineer's pliers and stacked together with masking tape. Nice and easy to work with. These then set working planes and clearances from the carburettor body. I stuck a panel onto the side with double-sided tape and used that as a start plane. From there it's just a question of building up, trimming edges, and then getting panel shapes and sizes for the finished jacket.

    I've decided to try for two close-tolerance jackets instead of one larger wrap-around. A single jacket would leave a big gap between the two bodies and most of the ducted hot air would be blown straight through that, unless I use baffles. They'll be pretty boxy when they're done but first steps and all that... just as long as it improves the bike's behaviour on cold days.

    It occurred to me that this isn't the only way to design a jacket for a complicated object. 3D scanning and printing / casting offers options, so does clay and fibreglass, but both of these are out of my reach at the moment. This is the lowest resource base way to do it, it's just scissors, card, pop sticks, tape, pencil and ruler to design, then basic sheet metalwork for the actual build. I might need a lathe for the mechanical mounts, and it'd be nice to zip seams together with a TIG, but that's as involved as this gets.
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  5. #485
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    I would have thought glassfibre would be easier - wrap the carbs in gladwrap, build the shape directly onto them using clay / plasticene, and then lay the 'glass straight over that. Make two halves with a flange that can be screwed or clipped together

    Glass matting and resin is reasonably priced at Mitre10.
    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)

  6. #486
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    Quote Originally Posted by pete376403 View Post
    I would have thought glassfibre would be easier - wrap the carbs in gladwrap, build the shape directly onto them using clay / plasticene, and then lay the 'glass straight over that. Make two halves with a flange that can be screwed or clipped together

    Glass matting and resin is reasonably priced at Mitre10.
    Ta for that - still trying to work through ideas. I've spent way too much time and energy over the last couple of weeks trying to sort out the details.

    I had some time today to get back into the heat stove and weld the pieces up, the split into three sections was necessary because a normal 90 degree bend didn't quite fit. Not much to say here except that ensuring it'd fit on the vertical cylinder exhaust pipe meant doing the welding with it clamped to said exhaust pipe. The crocodile clips proved helpful while doing the tack welds.
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  7. #487
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    14th July 2006 - 21:39
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    Try Autobend for stainless bends etc.

    My lads old 1986 Ford Laser has a summer/winter preheat lever on the air cleaner inlet you flick over when colder. Which moves a flap to divert the incoming air off a tub over the exhaust manifold - same concept you are running. Works too - I had a 1980 SE Corolla years back with the same set up.

  8. #488
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    28th January 2015 - 16:17
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    Thanks Allan - had a look at Autobend and they look pretty good...

    Might have just found out a couple of useful bits of info:

    1) If you've got a sharp-edged barb on the fuel tap, there's a chance that it'll put rubber shavings into the fuel system if you have to put the hoses on and off a few times. These shavings can jam needle valves in carburettor floats, leading to fuel pouring into the inlet manifolds, etc etc... it was pure luck that I saw it before I put the pod filters back on.

    2) If you're smart-charging the battery over winter and it won't, for no obvious reason - before replacing the charger or the battery - disconnect everything off the battery and try charging directly with crocodile clips to the terminals. I've got quite a few add-ons running on the bike now and have been finding that both the Oxford Oximiser 9900 and the SCA general purpose smart charger wouldn't drive properly. My best guess as to what's happening is that the charger thinks that the battery is damaged, so follows its design and refuses to charge.

    For now I've put the bike back together as it had been for last summer, with the carb bowl heaters in place for cold starting. It's become clear that it'll take weeks or months to make the bits needed for winterisation, in the meantime it'd be good to have the bike for a sunny day.

  9. #489
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    20th January 2008 - 17:29
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    I finally got around to fixing the leak on the stock Mikunis today. I thought it was just a matter of taking the fairings off.....
    had to remove the battery/coils/ign and airbox. Fortunately having done this twice it does not take long but.
    Once the airbox was off took off the float bowls, replaced the float needles,float unit and bowl seals. also made up a drain so if it happens again does not drip on to hot bits.
    Full choke and it fired right up, choke off after about a minute and idled nicely.
    WOF next week and get out an ride the thing.
    For the rest of the weekend I shagged about with my F*&K'n Norton and its dragging clutch so as I can get it woffed and on the market.

    If they made a choke unit for the flat slide carbs they would work fine imho as once they warm up from engine to manifold conduction they are fine.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  10. #490
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    28th January 2015 - 16:17
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    Quote Originally Posted by Voltaire View Post
    I finally got around to fixing the leak on the stock Mikunis today. I thought it was just a matter of taking the fairings off.....
    had to remove the battery/coils/ign and airbox. Fortunately having done this twice it does not take long but.
    Once the airbox was off took off the float bowls, replaced the float needles,float unit and bowl seals. also made up a drain so if it happens again does not drip on to hot bits.
    Full choke and it fired right up, choke off after about a minute and idled nicely.
    WOF next week and get out an ride the thing.
    For the rest of the weekend I shagged about with my F*&K'n Norton and its dragging clutch so as I can get it woffed and on the market.

    If they made a choke unit for the flat slide carbs they would work fine imho as once they warm up from engine to manifold conduction they are fine.
    Yeah, been there many times with the stock Mikunis and now the FCRs in terms of getting them off the bike to be worked on. Surprising how much work is involved in removing carburettors with an L-twin. A transverse (Moto Guzzi) or flat (BMW) twin would be much easier, since the carburettors are out in the breeze and can be got at directly. Ditching the airbox, fabricating a battery box, and going to pods made maintenance quite a bit easier.

    I've started riding the bike again this week in preparation for summer, making sure any issues are sorted early. The electric heater system I trialled as an alternative to a choke is working - the bike starts first go and idles smoothly - but with one issue, it takes about three minutes for the system to heat to temperature. A choke butterfly is set to go in seconds.

    I'd seen pictures of a cold starting enrichment system on some Keihin carburettors. It seems to be an auxiliary fuel jet which is opened by a cable and needle valve, fittable as an accessory to single carburettors. It doesn't look like it's fittable on banked carburettors. It's truly bizarre that a carburettor as well thought out as the FCR series doesn't have provision for cold starting, but there we go... maybe that's a dedicated racetrack thing?

    Anyway, that brings me to a question that's been on my mind for a while now. I have a solution to the FCR cold starting issue. There are a few of these carburettors around globally. Are other people likely to be interested in this commercially, i.e. is it worthwhile bringing a product to market?

    For the record, I don't rate the odds of this happening, this is not a trivial undertaking. To go to market I have to design and make the thing to a much higher standard than has been built for prototyping. There'll have to be a company registration, I'll have to sort out deals with various online resellers, or start my own website and ordering service. Then there's tax, record keeping, trying to get this idea from it being just me working my arse off after hours from the day job to being something that other people do for me, etc etc... and under it all, the truth that this is an ultra-niche product with a tiny market, most of whom use the 3-squirts and crank the motor until it goes start method anyway.

    Anyway, thoughts from fellow KBers and experiences would be appreciated.

  11. #491
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    20th January 2008 - 17:29
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    The search for Ducati Perfection continues....

    The stock carbs are 38mm which is a good compromise between WOT performance and mid range response.

    Similar to old BMW Bing carbs in as much as you open a butterfly valve and the vacuum lifts the slide.

    Dellortos work well on BMW's but need a bit of choke or the few squirts of pump jet.

    Everytime I did that on the Sl I thought about the poor sprag clutch and starter motor.

    Facebook sent me a photo from last year and it was the SL with a pic of the speedo.....I had done about 60kms on it in a year

    Going to take it for a WOF this week and its been full choke and immediate start.

    Conclusion... running and not perfect is better than sitting in the shed

    A google search tend to suggest its been a problem for some years, yet others claim its not... mystery.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  12. #492
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    28th January 2015 - 16:17
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    Voltaire - Maybe the Sl-on-FCRs starting issues were some combination of bad idle tuning on the carbs and possibly a slightly weak ignition? I'd found that the slow fuel jet and slow air jet both wanted a tweak from as-supplied in order to start working properly.

    As to progress... design work on the carb jacket has stopped for now. Work work has gone nuts over the last couple of weeks, hopefully it'll ease up again soon.

    I did manage to get out for a tootle on Saturday. The bike started behaving badly, i.e. lots and lots of vibration. It was bad enough that I cancelled the ride, came back and took the exhaust system off again in case I'd left a rag stuffed inside. Nothing there, exhaust's fine, so I went looking.

    Exhaust pulses aren't smooth, at idle or at revs (tested by putting hand into outgoing gas stream). Lots of intermittent firing going on. Right... the spark plugs were showing clearly different combustion behaviour. One was super clean, the other borderline fouled.

    I finally (should have done this years ago) swapped the CDI units over and went for a ride. The vibration didn't get much better (it did, slightly), and on return, the fouled plug had started to clean up. The pristine one might have had the very beginnings of carbon buildup, but it was minor.

    That's the basic test for a sick CDI. However... in the interests of being sure (and keeping this post brief, and readable)

    Testing I did earlier:

    Compression: same on both cylinders, each OK
    Fuelling: identical settings on each carburettor
    Intake: no issues with either pod filter
    Pickup coils: gaps reset last summer, resistances OK, magnets seem fine
    Ignition coils: resistances tested OK, coils are new enough that there shouldn't be issues

    Testing I've done in the last few days:

    Pickup coils: resistances OK
    Ignition coils: voltage to each OK, between 11 to 13 V with engine running
    Carb synchronisation: off, readjusted to correct, no change in vibration

    and of course swapping the CDI's affected the condition of the plugs.

    It's really the last one that has clinched it for me. The bike's been fouling plugs on the vertical cylinder since I've bought it. It's been 22 years, it's not beyond belief that at least one of the CDI's is on the way out.

    It's possible to replace with OEM Ducati via Stein Dinse at reasonable money - approx $225 landed per each - I'll keep that as a reserve option, but for now I'm keen to give the Ignitech gear a try.

  13. #493
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    I suspected the ignition as my mate bought a 600ss semi runner and turned out to be one of the ignition units. I gather they are not highly thought of and now 20+ years old.
    Looked at Liams plug and play Ignitech but he said probably good to fit Nology coils too.....scope creep and about $600.00+
    I did try with the FCR's did all the research, set up and jet checks. Once it was started and warmed up was fine for the rest of the day but what a pita starting it.
    I'm happy with how it is now running stock bits.

    My 900ssie was a good starter and runner....have you thought about fitting fuel injection?
    As I mentioned I've got an Ignitech in the BMW, they are a nice bit of kit and liam is very helpful.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  14. #494
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    28th January 2015 - 16:17
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    Ignitech ordered... I went the whole hog and bought the Nology coils, the HT leads to go with them, the hall effect pulley mount sensor kit and the TPS plus bracket for the FCR carburettors. Spendy, but I want more vroom. Or at least a bike that goes nicely for summer.

    Liam did tell me that the CA Cycleworks coils will work with the Ignitechs, just not as well as the Nology coils will.

    Fuel injection, well... I'd looked at it a while ago. I have to admit that FI would solve a lot of problems. There wouldn't be any issues with fuel condensation inside manifolds, for one. The issue would be that I'd lose the long inlet manifolds. I reckon they're much of the bike's character - lots of punch midrange, gobs of torque with it, beautiful soundtrack... it just wouldn't be the same.

    Apparently similar happens if the bike is changed to split singles with short inlets, you get benefits higher up in the rev range, but lose the middle of the RPM range. Although I'd want comment from someone who's actually done it to be sure of that opinion, I'd thought pods would be bad but they turned out to be one of the best things ever!

    I had another start on the carburettor jacket tonight. The latest plan is to use the three bars holding the carburettor bodies together as mounting points. I'll fabricate a bracket that fits to these bars and then attach panels to that.

  15. #495
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    28th January 2015 - 16:17
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    Carrying on, after a breather (yeah, I got tired...) this time with the original Kokusan CDI units, because I was curious and why not. The workshop that I normally use is, ahem, in a state of renewal, and involved prototyping is going to have to take a back seat for a while. So, CDI's it is for now.

    What's inside? And what went wrong? And can it be fixed?

    Well, the first thing is to get in there. It's potted, thankfully not with epoxy. This one's sealed with a black silicone rubber. That's got to go before any sort of assessment or repair could be done.

    There are commercial de-potting compounds. Presumably these need some sort of heated bath and proper chemical disposal afterwards. I don't have any of this, hence the tweezers and doing it the cheap, impromptu, and laborious way. I got most of the way down before realising that I had to take a hacksaw to the case and peel that off, since it was blocking access to the sides and base of the unit.

    The photos below are nearly 8 hours painstaking work. One mistake and you'll break something off the board, too - I did that, bottom right corner. I think it's a resistor but can't be sure.

    Anyway... de-potting silicone. Basically nothing that you can buy at the local hardware shop will dissolve this stuff. A witches brew of 2 parts isopropyl alcohol and 1 part white spirits will slightly swell and soften it, though. Toothbrush scrubbing with this solvent mix removes the really fine bits of torn silicone. This helped (particularly in the final stages) but it's no substitute for bulk removal by getting in with the tweezers, push-cutting to get a jaw below the surface, and then yanking the silicone out in little chunks. It's the only way the stuff seems to come off. After a while, components started to unearth. A jeweller's flat bladed screwdriver was useful to push or chisel the last bits of silicone off. It was a bit like archaeology.

    As to the CDI itself, it seems to be a simple design featuring low voltages and the cheapest possible construction. It's made with a single layer PCB, surface mount components (mostly) and what looks like three carbon film resistors selected for trimming. There are technician's permanent marker notes on the heatsink - just some numbers, really. I presume that the square copper pads on the PCB are test points for use during manufacture and tuning.

    The underside has a thyristor (I think; three-pin TO220 package, no visible markings seen so far) attached to a heatsink plate, with three electrolytic capacitors beside it. If I was going for a repair, it's a pretty good bet that this is where to start.

    The heatsink mounted chip is directly connected to the ignition coil's primary winding, via the three-pin connector. It's clear that this chip carries a high loading, hence the heatsink. As to the electrolytics, well. They're cheap. They work. They're good for a while, but they're not stable forever.

    Electrolytic capacitors are basically guaranteed to fail. The capacitor is formed by two aluminium foil plates wound into a spiral, with an electrolyte paste squelched between them, and the plate surfaces insulated with carefully-generated aluminium oxide. This is then cased and sealed. The electrolyte can dry out, or the oxide can be dissolved off the plates if the capacitor isn't charged by use. They're also anything but accurate. Brand new capacitors can have tolerances of +/- 20%, straight out of the box.

    So, some very quick comments, based on what I see here:

    1) it's not possible to test the CDI with a multimeter. Any test path has to go through too many different components, since they're connected in a circuit. Testing can be done once it's been de-potted, though.

    2) components that are likely to fail can be replaced. That doesn't mean it's repairable. It looks like re-tuning is needed in order for it to run properly, at this stage I have no idea what this tuning would be.

    3) the capacitors are rated to +85 C. This is a common rating for electrolytics, and electrical components in general. If attempting to bake moisture out of an old CDI, it's probably a good idea to keep temperatures at around 60-ish.

    4) performance of this pattern of CDI will degrade with time. Components like film resistors and electrolytic capacitors aren't stable over the long term and values will shift by a few percent, possibly enough to affect ignition timing. YMMV of course. I have to confess that I've never tested the bike's timing with a strobe lamp.

    This dinky little unit is worth more than $600 NZ if bought at the dealer's. What a pain.
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