160 Camshaft Shimming Question

[Winter]

Hello.
In the "Assembling the Timing Shaft" section of the manual it states,
"Lubricate the cam lobes and insert the shaft in the head bearing (put in existing shims, if any)
Fit the woodruff key
Insert bevel gear

A dry run assembly of the camshaft with the end cap in place yielded some play. Should the cam be shimmed tight as it sits between the two bearings, or will the shims, bevel, washer and nut on the bevel end of the camshaft snug it up so that the play is removed? The manual says to insert shims with the cam, but tolerances aren't indicated. Maybe I have answered my own question because I am leaning toward shimming both the cam between the bearings and the bevel gear as is required.

Thanks in advance.

Best,
Andrew

[LaceyDucati]

Hello Andrew

The shims referred to in the manual are the bevel shims between the retained bearing and the bevel gear. The cam is held in place in the bearing via the gear and retaining nut and the bearing cannot move as it is held in place by the circlip. There is always quite a lot of play at the end of the cam to the bearing in the end cap, some 2mm or so in most cases. In theory this is no issue as the 15mm diameter of the cam is long enough to extend fully into the bearing for support. However in practice sometimes due to manufacturing alignment issues between the cam bearing recess and the tunnel/face on the other side, the bearing can sometimes walk out of the cap. This doesn't always happen and when it does it doesn't really cause any issues. You can place bevel shims on the cam at the cap end to restrict movement it certainly won't do any harm, but I would leave at least 10 thou (0.25mm) freeplay.

Hope this helps with your question

Nigel

[DewCatTea-Bob]

____ Firstly, I must mention that I find Nigel's post-wording/response to be not-only un-faulted, but also very quite complete as well ! _ So-thus there's really no need for any further post-replies, (in attempt to answer the inquiry any better),, but I'm doing so anyhow, as it never hurts to have things discussed in other-words, as well,, (cuz even-though Nigel's thoughtful wording makes good-sense to ME, a newbie may still possibly desire to have his-own interpretation confirmed with an alternate view-point).



[quote= Winter ...
" In the "Assembling the Timing Shaft" section of the manual it states,
insert the shaft in the head bearing (put in existing shims, if any)
A dry run assembly of the camshaft with the end cap in place yielded some play. "

____ Since the camshaft's unfinished-length is slightly shorter than the space between the inner-sides of the two camshaft-support bearing-races, there's then of-course some right-&-left free-play which the camshaft can slide back & forth in between, (which could possibly be noticed as you've found, only when the camshaft is left merely-just installed into it's place between it's support-bearings) !



" Should the cam be shimmed tight as it sits between the two bearings, "

____ No, not really,, as Ducati has never been concerned with restraining THAT slop-play, as that play is eliminated once the camshaft-nut has tightly secured the camshaft against the right-side support-bearing (that's locked to the head). _ Although, that previously detected slop-space still remains, it finally becomes relegated between the shaft & the left-side support-bearing, where it's relatively unimportant.



" or will the shims, bevel, washer and nut on the bevel end of the camshaft snug it up so that the play is removed?
Maybe I have answered my own question "

____ It seems that you must actually understand what's-what, but that the stated wording you've interpreted from your manual has allowed you to consider more than just one place where the shims may be meant to be placed at.



" The manual says to insert shims with the cam, but tolerances aren't indicated. "

____ If any shims were actually meant to be placed anywhere between the two support-bearings, THEN you would indeed expect to find a related tolerance-range to be listed in a workshop-manual,, but now you understand why none are indicated.



" I am leaning toward shimming both the cam between the bearings and the bevel gear as is required. "

____ You should now well understand that shimming of the camshaft between the IN-sides of the two support-bearings, is UNnecessary ! _ As the shim-work in question is only in concern with just the space on the OUT-side of the right-side support-bearing.
__ If you still have the original factory-installed bevel-shims, then you're probably good-to-go, (unless perhaps you've replaced your original right-side support-bearing with another that's not the exact-same thickness,, in which case, you'd then have-to adjust the shimming accordingly).
But if you're starting from scratch and-thus have-to re-shim the upper bevel-gears, then you may wish to read-through a related thread, of which here's a link to it - viewtopic.php?f=3&t=1663


Hopeful-Cheers,
-Bob

[Winter]

Thank you very much for the responses.
After placing a dial indicator on the end of the cam with the cap installed it yielded 19 thou in "slop" but that seems to be okay since it will snug-up
Yes, I did replace both of the bearings, BUT, I erred in not measuring the raceways to determine exact difference between the old and new bearings. SO, there may need to be shimming beyond the existing two (2) that were behind the bevel gear when dismantled. (.004 and .008 according to my calipers)

I have researched the link to bevel shimming and have already used it to match the lower set. The grind marks are quite telling. I used the back of my fingernail across the mesh to see if it would catch and indicate alternate planes for the gears. Nothing to be found. Maybe the fingernail method is my contribution to the topic.

All the Best and I will carry on and keep calm.

Best,
Andrew

[DewCatTea-Bob]

[quote= Winter ...
" it yielded 19 thou in "slop" but that seems to be okay since it will snug-up "

____ Right,, as regardless of the amount of camshaft slop-clearance, it won't be left in play after the camshaft-nut has tightened-up the shaft against the right-side support-bearing.



" I did replace both of the bearings, BUT, I erred in not measuring the raceways to determine exact difference between the old and new bearings. "

____ All such bearings as those #6202-units, really ought-to have their raceways manufactured to be the EXACT-same width of precisely 11.0mm, but unfortunately such consistency can't always be depended upon (to consistently be exactly .4331"). _ And-so it's always a good-idea to mike such bearings to make-sure that there's no measurable width-difference between original & replacement bearings, especially of-course whenever they are to be used in conjunction with any shimming, (since any difference in bearing width-thickness is of-course combined-together [within the total-thickness] along-with any included shims).



" SO, there may need to be shimming beyond the existing two (2) that were behind the bevel gear when dismantled. "

____ If your replacement-bearings happen to be the exact-same width (as those which were replaced), then of-course your bevel-gear mesh-lash should be unchanged (and-thus your original-shims should be all that's needed).
However, if your new/replacement-bearings happen to be more than .0005" thicker or thinner (than the originals), then your previously factory-set bevel-gear mesh-setting would-be somewhat significantly disturbed, thusly causing either tighter or looser tooth-meshing. ...
So, (for example),, if your new 6202-bearing (that's installed on the right-side), just-happens to be .0015" thicker (than the original), then you'd probably need to stone-off 1 or 2 thousandths off-from your thickest shim.
OR, in the case of a thinner replacement-bearing,, an extra-added shim (of likely the thinnest made), may then need to be included (along-with the original-shims).



" I have researched the link to bevel shimming and have already used it to match the lower set. "

____ Do you mean you had already done that, before I posted the link (to that other related thread) ?



" I used the back of my fingernail across the mesh to see if it would catch and indicate alternate planes for the gears.
Maybe the fingernail method is my contribution to the topic. "

____ That's probably good enough of a method to check for any hard to see steps (in level-difference), but it's fairly doubtful that you're the first to try that.


Hopeful-Cheers,
-Bob

[Winter]

"____ Do you mean you had already done that, before I posted the link (to that other related thread) ? "

Yes. It was very helpful in determining the difference between the alignment/timing marks struck into each gear and the ground patch 2-3 teeth away which show the mating plane. However, I focused only on the lower set at the time. Now I see the upper set reassembled (dry run) I see the grind marks on the inside radius. Clever really.

Thanks,
Andrew