valve clearance problem

[kmev]

(and the bevel-twins use the same shim-caps!)

As do single valve rubber band motors (8mm valves).

[jbcollier]

What is the size of the shim that will give correct clearance?

Wild cams will often causing shimming to go outside the normal range, especially with desmo cams.

[DewCatTea-Bob]

" As do single valve rubber band motors (8mm valves). "

____ That's also of use to know of ! _ I-myself didn't know of THAT 'first-hand', (as my interest in those newer type Ducati-models began fading back then when the DUCATI-name got taken-over by Cagiva).
__ I now wonder if the range in available shim-cap sizes then became any different at all from the established range (which was available back when only the Duke-singles were being produced) !?


" What is the size of the shim that will give correct clearance?
Wild cams will often causing shimming to go outside the normal range, "

____ In this case (for which this thread was started), a replacement shim-cap slightly less than 1.8mm thicker than the particular existing/fitted shim is what's sought-after for this particular project-fitment.
So guessing that the currently fitted shim is likely near the original standard expected size for the n-c 250-Scr, then a shim-cap somewhere around 200-thousandths thick, ought be close to what's needed for this project. _ And that means that only the thickest Ducati shim-caps I've ever known of, will possibly be of any use in this extreme case.
To be sure, we need to know the exact thickness of the shim-cap that's already in place, (and of course the desired valve-clearance that's expected for use with the unknown cam involved), so as to know (considerably less roughly) what size shim-cap is going to possibly work properly.
So hopefully, we'll soon be given the needed info that's been omitted so far.
__ If the thickest shim-cap ever made available (near .190"), is still too thin, then hopefully some layers of aluminum-foil will fill-up any remaining excess-clearance...
It's relatively easy to use a valve-cap & cork to cut dots of such metal-foil, to then be inserted up-into the inside-top of a slightly insufficiently-thick shim-cap, so as to thicken it up just enough to get the desired valve-clearance, (for otherwise merely 'close' clearance-settings).

____ Now waiting for the additional needed info, so further help-advice can be offered.


Hopeful-Cheers,
-Bob

[Jordan]

Postby DewCatTea-Bob »
__ If the thickest shim-cap ever made available (near .190"), is still too thin, then hopefully some layers of aluminum-foil will fill-up any remaining excess-clearance...

I'm afraid that'll almost certainly not work, Bob. I've used pieces of hardened steel shim from feeler gauges in the past, and even those got mashed up after a while.

Jordan

[DewCatTea-Bob]

" I'm afraid that'll almost certainly not work "

____ I'm glad that you brought-up this bit of doubt ! ...
That backyard-mechanic idea was never my-own ! ... I'm sure I first read of that suggested temp.trick in a cycle-mag of the late-60s. _ And I-myself have never had to try that adjustment-method, as I've most-always had a good shim-cap selection to choose from.
But I do know for sure that doing that method was (at least) once a fairly widespread practice performed by many who had to mess with adjusting Duke valve-clearances,, as I've come-across a fairly great number of the otherwise stock valve-shims which had as many as 7-layers of metal-foil well compressed into the top-inside of the cap ! _ And I'll bet that any others of us who happen to have a fair sized collection of old/used v.shim-caps could find that they have at least one cap with some foil stuck within. _ As they look just like any other used shim-cap inside, except that if ya pay extra-close attention, the foil's surface looks ever so slightly shinier (than a used-cap's inside-surface without any installed foil).
Sometimes the caps with foil look so very much like a well-used unmodified/stock-cap, that ya doubt that there's any foil at all stuck within,, and-so if ya ever have a v.shim-cap that seems too thick for your particular need, then before considering to stone it down, first try using a scribe-pin to see if ya might find that ya can dig-out any layers of foil (from off the inside-top). _ I-myself have done-so many,many times !
__ I never meant to indicate that such shimming-practice offers a permanent v.clearance fix, but it does seem to at least temporarily help fill-up slightly-excessive v.clearance.
I wish I could reproduce here the old cycle-mag.article I once read, however I believe it directed using a shim-cap & a sheet of thick aluminum-foil along-with a piece of flat cork, all pressed together within a vice,, and also I believe it mentioned to expect up to 60% eventual compression of the metal-foil after it's extended use, and-so recommended avoiding the use of more than 2 or 3 layers of such foil-shimming.
____ So I'm fairly confident to say that this (temp) shimming-method indeed must be of some legitimate use (if not "work" downright-outwardly) !


Dukaddy-DUKEs,
-Bob

[jbcollier]

I do not have a parts book in front of me but I seem to recall 8 mm valve openers are available up to 7 mm or more. Measure the shim and check with a dealer. The factory supplies shims in a much broader range than the aftermarket.

[kevin]

Yikes! I didn't know I was opening up such a can of worms! I appreciate all the advice I've received and will let you know if I come up with a solution to this specific problem. You guys have been more than helpful. Bob, I totally understand your concern over the site and keeping it specific. I am a recent member of this forum and have included a couple of pics of my Ducatis and a narative of my introduction to the Ducati world in my profile. I would think just being on the site and relating my experience with Ducati would qualify me as "Ducati related" and the photo of the 305 was never meant to steer this forum in another direction, just a note on my experience with restorations. Just having this site is so important for keeping the singles alive and I applaud your efforts in this endeavor.

[DewCatTea-Bob]

" I didn't know I was opening up such a can of worms! "

____ Please don't be concerned, as it's not really looked at as merely "a can of worms", cuz getting so widely detailed into such stuff here is our way of more often providing food-for-thought for those of us who're always hungry for such.


" Bob, I totally understand your concern over the site and keeping it specific.
the photo of the 305 was never meant to steer this forum in another direction, "

____ Of course Kevin,, I was already pretty-sure that YOU-yourself had quite innocent-intentions when you posted your off-topic pic... It's just that I had realized the likely need to somewhat nip-it-at-the-butt before any others came-around to possibly take the ball & run-off with it still further-onward, thus-then possibly creating a series of off-topic posts (which really ought to be deleted, but no-one really wants to be so heavy-handed as to throw-out any of that which others thought had been legitimately worth posting).
Such running-off is simply naturally a common issue with forums, which rather needs to be kept in-check, as here at this w.site we really wish to keep OUR-own DUCATI-w.site totally dedicated to just DUCATI-Singles ONLY, as well as is reasonable to keep maintained.
(If you had posted something completely unacceptable, then it would've been deleted and you possibly would've been given a warning of some sort... So, no actual worries to speak-of here really, (so far) !


Hopeful-Cheers,
-Bob

[DewCatTea-Bob]

By: jbcollier...
" I do not have a parts book in front of me but I seem to recall 8 mm valve openers are available up to 7 mm or more. "

____ Wow, "7mm",, that's rather surprising (if the shim-range for those newer Ducati-engines ALSO range-downard to under 2mm) !
Is that actually 7mm in 'shim-thickness', or could that figure actually be simply the total-height including skirt of the valve-cap (for an overall-length dimension) ?
__ Before, (back when I was still active with DUCATIs), I never knew of any shim-caps 'thicker' than 5mm !


" The factory supplies shims in a much broader range than the aftermarket. "

____ Well it's about time ! ... I've been unaware of ANY shim-caps made by any aftermarket sources (which fit DUCATI-singles).


Hopeful-Cheers,
-Bob

[jbcollier]

!!??

Google: 8 mm Ducati opening shims

I looked a wee bit more and found 6.3 mm openers. Have not checked at the dealer.