Vento 350

[DewCatTea-Bob]

By: Jordon...
" Is it possible to work out how much cam timing clearance should be used, if you didn't know? "

____ Probably but, it seems that it wouldn't be a very easy thing to fully work-out simply. ...
__ From Ducati's own various recommended clearance-settings for their various cam.models, it seems that different cam-lobe profile-designs are matched-up with varying 'clearance-ramp' parameters.
Clearance-ramps must be at-least designed to take-up the 'running valve-clearance' just prior to the cam-lobe's lift-ramp actually becoming encountered by the cam-follower, so as to more gently activate the valve-train so that it's not subjected to being shocked & KNOCKED-open (by the otherwise suddenly encountered abrupt lift-ramp of the lobe).
And since different cyl.head-models have varied running valve-clearance settings matched with varied cam-lobe parameters, it then must be that the required clearance-ramps need to have their-own varied parameters to best suit each particular combination of such combined clearance & cam-lobe parameters.
So while clearance-ramps seem to be largely insignificant compared to the rest of the cam-lobe, they do after-all exist and have a relatively important function to perform.
__ If it weren't all so seemingly complex, I'd then expect that simply resetting the valve-clearance to double that of whatever the regular recommended normal running-clearance is supposed to be, would then be that which is all that's required (in order to measure correct v.timing readings), but it doesn't always seem to work-out that simple way (for some reason).


" could an abrupt change in contour signify the "real" opening point? "

____ No-doubt so. _ Cuz in comparison to the actual lift-ramp, the clearance-ramp has a far gentler rate of lift,, so once the lift-ramp takes-over (from the clearance-ramp), the lift-rate would then vastly change (to a much increased rate).
However it would take some very detailed dial-gauge work to detect the exact point of change. ... With a proper high-quality dial-gauge setup set to be extremely delicate for monitoring any relatively minute changes, the exact geometry (such as the beginning & end points, the duration, and lift-rate) of the clearance-ramp could then possibly be detected & mapped-out (onto some sort of graph). _ But that tedious job would be difficult to properly accomplish and would probably need to be done by experts who use very expensive & very finely graduated dial-gauges, not to mention extremely well controlled rotation of the camshaft within the test holding-jig.
__ But yes, there's no-doubt that there exists a certain point where the clearance-ramp hands-off the lifting-chore over-to the lift-ramp, but determining exactly where that particular point is actually located (and therefore how tall it may actually be), is the real-trick. - (So the Japanese have attempted to make it easier for us all, [by introducing their 1mm lift-point standard, for start & end reading-points].)


Dukaddy-DUKEs,
-Bob

[Ventodue]

However I really don't read Spanish too well ...

Me neither, Bob ! But I'm pretty sure that the running clearances are 0.05-0.07. Jon P. would quickly put me right , but this is what the manual says:

"El juego de funcionamiento entre vulvlas y balancines, con el motor frio, es de 0,05- 0,07 mm."

Which I translate as:

"The running clearance between valves and rockers, with the engine cold, is 0.05 to 0.07 mm."

(Which is in the same field as a Bologna valve-spring wide-case, I think?)

Ciao/un saludo

Craig

[Jordan]

By: Jordon...
" Is it possible to work out how much cam timing clearance should be used, if you didn't know? "

__ From Ducati's own various recommended clearance-settings for their various cam.models, it seems that different cam-lobe profile-designs are matched-up with varying 'clearance-ramp' parameters.
-Bob

Thanks Bob. The problem is when you have a camshaft but not its identity, so lack the specified checking clearance.
Triumph used to call this feature "silencing ramps" that were supposed to limit noise by gently taking up clearance.


Jordan

[Muzz350]

there is something odd about the timing figures .

on my degree wheel it goes from zero to 90 degrees and then back to zero again



Eldert

Hi Eldert
Your timing wheel is set up to make it easier to read especially for valve timing. eg Starting from zero at top dead centre(TDC) after combustion the exhaust may open 80deg before bottom dead centre. If the degree wheel reads from zero to 360deg that would show 100 degrees on the wheel and you would have to count backwards from BDC. Not too hard when its 80 but when they start reading 73 deg BBDC and 67 degBTDC it is easy to make a mistake. (See diagram)
Muz

[Muzz350]

Hi Craig
I fitted a conti replica from Road & Race but seemed alot louder than my old 750ss especially starting it early to go to work. I would like to know where I could get a replica similar but better than the original.
The plug looks rich so heading back to a 150main jet.
The valve timing is the Lento but not the figures on the diagram but the figures in the chart. I have one difference which is my exhaust closes 70 deg ATDC not 78deg?
I also have the option of changing the cam to something milder and better suited to a street muffler.
Is your Vento right hand gear change like mine? (My old 750 was right hand gear change as well)
Muz

[DewCatTea-Bob]

By: Jordan...
" Is it possible to work out how much cam timing clearance should be used, if you didn't know? "

" The problem is when you have a camshaft but not its identity, so lack the specified checking clearance. "

____ Okay Jordan, I was not clear before as to exactly what you had particularly meant by "if you didn't know" , so I elaborated enough that I had hoped I had covered everything well enough,, but now I better understand what you had meant by your chosen wording. ...
__ If ya don't know which cam.model ya have to start-out with , then ya can't be sure of the valve-clearance that it's normally intended to be set with, and so thus ya also can't figure how much added-clearance the valve-clearance is supposed to be set to, so as to then be able to properly measure the intended valve-timing (for hopefully then learning which cam.model the outcome-results would match).
__ Fortunately, (other than a lot of trial & error guess-work), determination of the intended valve-timing is not the only way to identify any particular cam-model ! _ As most-all models of Duke-camshafts have a unique combination of intake & exhaust cam-lobe max.lift . _ So if ya mike both the base-circle with lobe max.size, and also the base-circle min.size,, ya can then figure-out the lift-size of the cam-lobe (and thus-then the cam-model [along-with help from me] ).
I have a collection of all but 3 or 4 of all the various camshafts employed in every Duke-model, (not including the Vento-models unfortunately), and have recorded all their cam-lobe lift-heights.
Having lots of experience with many copies of the various cam.models, I've come to be able to identify most of them by on-sight alone, but still, it's good to confirm the cam.model by miked-measurements.


" Triumph used to call this feature "silencing ramps" that were supposed to limit noise by gently taking up clearance. "

____ Yes that's no-doubt the same-thing as 'clearance-ramps', but probably just given that designation-name by their sales-department (so as to make a standard-technique sound like some new trick they came-up with). _ But yes, the otherwise insignificant ramps do indeed cut valve-train noise, (not to mention make life easier for the valve-train).


Dukaddy-DUKEs,
-Bob

[Jordan]

That's good to know, Bob.
A unique valve lift combination would be good evidence for identifying Ducati single camshafts. Then we could set the correct checking clearance, and check away.
What would induce you to let us in on your valve lift data?

Jordan

[Ventodue]

I would like to know where I could get a replica similar but better than the original.

Jon Peglar got some stainless ones made by Armours in the UK. Looks like this:



Best would be to contact Jon for more details. You should be able to find his e-mail on the list of Forum members.

The valve timing is the Lento but not the figures on the diagram but the figures in the chart.

Yeh, as Bob picked up, the figures in the chart are wonky!

Is your Vento right hand gear change like mine?

Yup - as far as I know, all were. It is a Ducati single after all! This does give raise to a small problem - the lever tends to hit the silencer on the down shift. Again, Jon came up with a simple solution - he re-made his gear lever so it sits outside the silencer.

[DewCatTea-Bob]

____ Just as often happens, this thread has developed a number of differing/associated topic off-shoots, so it's too bad that when such order-disorganization is apt to begin, that it can't instead be avoided by having new-posts which respond directly to any entered off-shoot, rather become attached HORIZONTALLY (towards the right-side), instead of having all the various new off-shoots all attached vertically (like they have to be order-listed here). _ That way, a thread-reader could more easily skip-through past thread-post off-shoots and easily stick to just those of direct interest.
Currently as posts get order-listed, the only help for a thread-reader to stick with just the original thread topic-line, is to take note of a new post's sub-thread topic-title,, but unfortunately, very few others besides myself ever bother to helpfully re-title their new-post (away-from the default thread-title).
__ I've mentioned something about this issue once before, and for a short while afterwords, posters began paying-attention to their post's title, but that good-trend unfortunately didn't last for long.
Anyhow, forward-on to THIS post's topic-title.....




By: Muzz350...
I fitted a conti replica from Road & Race but seemed alot louder than my old 750ss "

____ I've seen some Conti replica-mufflers, which on their OUTside appeared very similar quite well enough,, however on their INside, they were certainly NOT a very fair replication of the Conti muffling-design ! ... As the internal louver-flutes were faced in the OPPOSITE direction, which no-doubt was the main reason why the ex.sound wasn't quite the same pleasing note of the genuine Conti-productions.
__ It's too bad that (it seems) none of the good-looking replica-mufflers can't be repacked with glass-packing, cuz then such a muffler could enjoy the straight-through exhaust-outlet performance, yet also with very good sound-volume control.


" The valve timing is the Lento "

____ Exactly how did you go-about determining that, so definitely ?


" I have one difference which is my exhaust closes 70 deg ATDC not 78deg? "

____ Did you carefully check all the other three v.timing-points ? ...
There's a possible +/- 5-degree tolerance, so if your other readings were also similarly advanced, then it could be that your camshaft needs to be retarded (in relation to the crankshaft), or maybe you don't have an original-stock camshaft.


" I also have the option of changing the cam to something milder and better suited to a street muffler. "

____ If you don't intend to go racing on a track which keeps the engine constantly revved-out (and makes no use of 1st.gear), then a considerably milder cam would make your Duke more FUN to ride !
I'm sure most thrumper-single/Duke-riders would agree that a 350-Duke provides a better/more pleasing ride when fitted with a Mach-I/Gray-camshaft.
However with a straight-through type muffler, the 350Mark-3/G&W.cam provides the best performance. _ But don't confuse that Green & White camshaft with the 250F1/G&W.cam, as the F1-cam is a RACING-cam that's TOO wild for regular street-use.
To help tell those two G&W.cams apart, the LIFT-figure/amounts for the 350M3-cam is 10.0mm & 8.50mm, (intake & exhaust respectively), while the 250F1-cam's is (rather more roughly) about 9.85mm & 8.35mm . - (These figures are roughly +/- .1mm /.004" tolerance, [while those of every 350M3-cam I've ever checked were all right-on the stated-figure, +/- under .001"] ).


Duke-Cheers,
-Bob

[Jon Pegler]

Having been away from home lately, I seem to have missed this thread.
Craig seems to have covered most aspects of the cam timing.
One thing that has not been mentioned is that most Ventos have two timing dots on the bottom bevel gears.
The Vento should be timed to the left hand of these dots, not the one that aligns with the keyway.
This was covered in another thread a year or two ago and I think Eldert included some photos.
I will try and include a couple of phots of a part worn orange and white cam.
Note the orange and white paint dots on the body of the cam, possibly a Mototrans peculiarity.
On my own Vento I replaced the double coil springs in the head with standard hairpin springs.
This was mainly to avoid too much cam wear.
I think the coil spring set up is too stiff for road use.
I have spoken to Nigel Lacey on this topic in the past, and he considers coil springs fine for racing, where the revs are kept high at all times. However, on the road the motor keeps having to return to tick over to allow for traffic lights etc so I think the double coil springs are a bit too stiff.
(If new coil springs are needed, the outers are 750/860 ones and the inner springs are from the 350/500 GTL)

Jon