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Thread: Winter Layup - 1995 Ducati 900 Supersport

  1. #31
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    20th January 2008 - 17:29
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    I bought a 900ss off a mate, it had a new Nitron shock on it and other goodies, but I wanted to fit FCR's to it and carbon exhausts... you do the numbers and they start to add up.
    Then this came up a Jap import with about 27 K on it, for about $1500 more than I sold the SS for.
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    Already had FCRS and Termis on it, so did a bit of asset stripping on the SS as they don't add any value from a sellers perspective.
    I find its a bit hard to start with no chokes but goes really well. The Nitron is a great improvement over stock.
    Next job is bin the ignition and fit one of Fast Bike Gear's Ignitech systems. Had one on my race BMW for a few years and goes well.
    I haven't bought any parts for it since I've had it so a bit out of touch with Ducati's. I'm so used to buying parts on the net now I hardly buy anything here other than consumables.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  2. #32
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    28th January 2015 - 16:17
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    2000 Ducati ST2
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    Mint bike mate - envy!

    Concerning difficulty cold starting - I had this problem last winter and finally traced it to shitty CDI's. Cracked potting was letting moisture in to the electronics. Since bits of these operate at 150 Vdc or so, it doesn't take much moisture to lead to insulation breakdown and charge dissipation. I'd thought it was cold mornings and cold petrol, since it never seemed to happen in warm conditions. Baking the CDI's (gently) at 65 C for about 6 hours, and then coating the potting face in silicone seal grease, has worked wonders. Might be useful if you need a temporary fix before you can get your replacements.

    Carrying on with the layup...

    Here's what happened to the top front right frame rail. The crack goes a nearly equal distance under the gusset, tracing the same line. You can see weld beads from the earlier repair, close to the headstock.
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  3. #33
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    4th November 2003 - 13:00
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    Is that gusset factory? the 900SS I have in the garage doesn't have it

    I am sure the book I have on chassis designing/building by Tony Foale advises against welding across the ends
    "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough power."


    Quote Originally Posted by scracha View Post
    Even BP would shy away from cleaning up a sidecar oil spill.
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    Send Lawyers, guns and money, the shit has hit the fan

  4. #34
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    20th June 2011 - 20:27
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    Quote Originally Posted by Kickaha View Post
    Is that gusset factory? the 900SS I have in the garage doesn't have it

    I am sure the book I have on chassis designing/building by Tony Foale advises against welding across the ends
    Yeah he already said that its been fixed once by F1 engineering.
    Quote Originally Posted by Katman View Post
    but once again you proved me wrong.
    Quote Originally Posted by cassina View Post
    I was hit by one such driver while remaining in the view of their mirror.

  5. #35
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    28th January 2015 - 16:17
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    I've got the same book and you're right, Foale said to avoid this. He also said to weld at the neutral axis of the flexure, if possible on both sides of the frame member. This gusset has been welded on the highest stress plane. The ideal gusset would have been a piece of channel shaped and placed like the gusset, welded top and bottom straight edges, but not over the curves around the tube's circumference. It's not intuitive at all.

    So far my thinking is - weld the crack up, leave a decent bead, and install a cross member to complete the triangle, as the bottom part of the frame has been made. The gusset can then stay as is.

    The snag is that the airbox then doesn't go in. Even if I modify it, it'll be a pig to get into place.

    Removable frame element, maybe?

  6. #36
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    28th January 2015 - 16:17
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    Back to the engine... Got the horizontal head off, then both barrels and pistons. It turned out that water and winter had attacked the horizontal cylinder head studs and nuts - they'd rusted on. I tried using the open end of a 15mm combination spanner, nearly ripped a nut up, then ground the ring end down until it'd sneak into place under the camshaft housing.

    Barrels were taken off with the motor inverted so that gravel chips wouldn't fall into the cases... just as well, had quite a few stones come off. I'll have to take an hour and go around the cases with a screwdriver, might do that later tonight.

    There's what looks like powdered aluminium clumped up in the squish zone of the head. Not good. Really not good. The spigot faces are showing fretting damage (both cylinders, worst on the horizontal), and it's pretty obvious that the horizontal cylinder has been running very lean. Both heads are showing nasty oiling. The rings actually look OK, there doesn't seem to be any gunking in the oil control ring or either of the seal rings. What I've seen of the valves shows oiling on both the combustion and port sides, so chances are that it's oil leakage along the stem and guide.

    Cylinders actually look alright. Minor scoring on the horizontal, nothing major, and the vertical looks just the same as the last time I'd had the heads off.

    O-rings throughout have squashed and set. Clear evidence of oil leaks on the return oil line in the horizontal cylinder.

    Conrod bearings actually seem OK, no excessive play, and I noticed a 'B' engraved into the horizontal conrod, as well as '530' engraved into the underside of the engine case. Someone's rebuilt this before.
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  7. #37
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    28th January 2015 - 16:17
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    Looks like I only get 6 pics a time. Here's a couple that should have gone with the previous post.

    Cylinder head studs are quite a picture... vertical looks mint, horizontal looks like salvage from a junkyard. Ducati's design leaves a gap between head and cylinder, so the water kicked up from the front wheel gets in... not the best really.

    Right, off to get stones off the cases and out of the head and barrel fins.
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  8. #38
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    28th January 2015 - 16:17
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    Got into it again last night and got thinking - I'd value contributions.

    1) Ducati OEM valve guide seals really aren't all that good. This is the second time I've had the heads off and both times the valves have been oiled, piston crowns and combustion chambers carboned up. The seal is just a rubber teat, basically. There's no positive clamp around the guide head beyond the rubber's own tension.
    Every car valve seal I've ever seen has a metal body over the rubber for the guide head, a spring for the valve stem, and has to be punched into place with a socket. Am placing an order for these:

    http://www.athenaparts.com/eng/produ...stem-seals-kit

    As soon as I can figure out their diabolical website... it is a cunt of a thing. Try shopping on it and you'll see what I mean. Gasket quality looks top notch though.

    2) It's probably worth making and installing an insulator between the cylinder head and the inlet stub pipes. Currently these are directly coupled to the head and so conduct engine heat to the incoming fuel-air mix, before induction and compression. There were several times over the summer where I got stuck in traffic on very warm days and the bike got seriously loud - it quietened again once we were rolling and had some slipstream to work with. Can't speak for power. The effect got quite worrying, if it's that hot going in then how hot is combustion and exhaust becoming? The inlet stubs seemed to vary in temperature quite a bit, although I didn't take measurements.

  9. #39
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    20th January 2008 - 17:29
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    The early to mid 90's head studs are known to snap, are you going to get new ones?
    How important are valve guide seals? Air cooled BMW's don't have them.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  10. #40
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    28th January 2015 - 16:17
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    Quote Originally Posted by Voltaire View Post
    The early to mid 90's head studs are known to snap, are you going to get new ones?
    How important are valve guide seals? Air cooled BMW's don't have them.
    OK, I hadn't known that about the head studs. Given the corrosion and overheating that's been going on, it's probably a good idea to replace them.

    Valve guide seals are needed on this bike, Ducati screwed up in the head design (again), the vertical cylinder seems to have permanent puddles of oil at both inlet and exhaust seals.

  11. #41
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    28th January 2015 - 16:17
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    Scraping the carbon deposits off the piston crowns, using a relatively soft, smooth-edged knife blade and turpentine as a working fluid. The snag with doing this is that fragments of carbon will have washed down to the ring grooves, I'll have to clean those later. The rings have to come off to be checked for wear anyway - the technique is to fit them to their bore, at the lower part of the stroke, and measure end gap with a feeler gauge.

    There are a lot of scratches on the piston at left. I made a mistake and used a brass wire brush on the carbon at first, before trying the knife.
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  12. #42
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    20th June 2011 - 20:27
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    You would not just fit new rings anyway?
    Quote Originally Posted by Katman View Post
    but once again you proved me wrong.
    Quote Originally Posted by cassina View Post
    I was hit by one such driver while remaining in the view of their mirror.

  13. #43
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    28th January 2015 - 16:17
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    Pulling the valves out of the heads, prior to scrubbing valve faces, combustion chambers and ports.

    I've got the rag balled up under the head, to fill the combustion chamber and support the valve. Sequence is:

    Pull clip, using 2mm Allen key

    Find spot in camshaft rotation where rocker arm will slide across

    Lift off opening shim

    Slide rocker arm back into place, rotate camshaft again to lower rocker arms (lower arm won't move; the closing spring holds it up)

    Push down on lower arm using flat screwdriver, to lower closing shim on valve stem and open up closing shim collets

    Pull these off with either fingers (best) or magnetic pickup tool (probably a crappy idea).

    Pull closing shim off, valve should now pull free.

    I had to lever the closing shim off with needle-nosed pliers wrapped in a rag, though. The closing shims have been working a ridge of metal out into the inner diameter. The shims themselves are supposed to be re-inserted the same way up that they came off, but I'm stuffed if I know how to spot that.
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  14. #44
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    Quote Originally Posted by nzspokes View Post
    You would not just fit new rings anyway?
    Weeellll... Curious, more than anything else. But you're right, it's the smart thing to do.

  15. #45
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    20th June 2011 - 20:27
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    Quote Originally Posted by OddDuck View Post
    Weeellll... Curious, more than anything else. But you're right, it's the smart thing to do.
    Fair call, I would be checking the gap etc of the old ones as well.
    Quote Originally Posted by Katman View Post
    but once again you proved me wrong.
    Quote Originally Posted by cassina View Post
    I was hit by one such driver while remaining in the view of their mirror.

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