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Screw In Rear Cylinder - 750 Ss Carby

Discussion in 'Supersport (1974-2007)' started by Ronald, Jun 20, 2020.

  1. Hi all,

    Last year I bought a 750 Supersport from 1992 (= wet clutch), which I'm working on now. Currently the engine just needs a service and some minorities and the bike is up and running again (and IMHO way better looking than when I bought it). One of those minorities is the screw next to the spark plug on the rear cylinder. What is the function of this screw and why isn't it on the parts list? The issue in my case is that I think there's oil leaking / sweating from behind the screw. Further, one of the former owners did not do the screw any good by molesting it with poor tools or excessive violence, so I'd like to replace it anyway.

    1.) What is the function of this screw?
    2.) Why isn't it on the parts list and exploded view? Or am I missing something and is it item number three? (See image). If not, does anyone know the right parts number so I can order it?
    3.) Can I take it out without anything which is held by it falling into the engine?
    4.) I suppose that applying a heat resistant thread locker (eg Loctite 243) or silicon gasketing product would be enough to resolve the oil leaking problem.

    Thank you for some clarification and advice!

    Duc 750 SS_before.png

    Ducati 750 SS_now.JPG

    Duc 750 SS_Rear cylinder.png

    Ducati 750 SS_parts list.JPG
    • Like Like x 1
  2. A good question to which I do not know the answer, although no doubt someone will be along shortly to explain.
  3. my thought as a complete guess would be a blanking screw for an oilway drilling
    but that's just a guess al is probably the one who would know
    • Agree Agree x 2
  4. As far as I'm aware, this is correct. I too have has this screw leak before. From memory it has a copper washer behind it. As you suggest, some high temp loctite should resolve the issue. It appeared to be a drilled hole for oil when I looked at it, Ive also got one on my ST2 barrels so check that micro fiche too. Nothing fell into the engine when I took it out.
  5. Checked the ST2 micro fiche and its not there either
  6. Just noticed yours is a grub screw, mines a bolt with washer.
  7. I'd agree with johnboy, looking at it's position in relation to the head nut I'd suggest it's to allow oil to drain back out of the head, down the side of that stud & into the sump or it's how oil gets up into the head & valve gear.
    #7 CAT3, Jun 20, 2020
    Last edited: Jun 20, 2020
  8. id say, louigi, forgot why he drilled the hole and decided he better cover his tracks by adding a screw... maybe he was on the grappa?
    • Funny Funny x 1
  9. cigar to johnboy. :upyeah: I believe the reason it's not listed as a separate part is that it would normally be included in the cylinder head "finished item" assy number.
  10. Yes it’s just a blank for a drilling, they do tend to weep, I put some high temperature silicone on the last few threads (the threads next to the head of the Allen screw/bolt/grub screw, whatever’s been put in there, the idea being we want to seal the threads but not get silicone into the oilways), anyway it’s never leaked since.
    • Agree Agree x 2
  11. Thank you all for your thoughts and advice! Highly appreciated.
  12. Yup, I also hated the yellow wheels when I bought the bike. But looking through I saw a decent Supersport underneath :) And having the wheels powder coated is not that expensive (BTW took color code RAL 9016 - Traffic white).
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