My first Duke (and my 1st post)

[kaysystems]

Hi to all

I've read posts on this forum for some time now, but finally as it looks like I'll be able to work on my little Duke I trout I should join.
So here is my first post and a short story of my sweetheart.

I bought my Duke in the UK in 1974 when I was 16. It was advertised and registered as a 250 Mark 3. As a teenager having limited resources I didn't know better, or much about Ducati's - except that I wanted one.
My father loaned me the money and it was mine. It had a round style tank, a Mark 3 seat, said Mark 3 on the steering head sticker, and had triangular tool boxes. The fact that it had square style fenders meant nothing to me.
It even had a Vic Camp fairing, but wasn't too fast.
After talking to the local 'experts' I soon learned how to make a Ducati go faster - install a 30mm Amal carb and instal a hi lift cam.
Done. The cam came from Wittey Ducati.

Base circle is 20.9mm with an inlet lift of 10.34mm and an exhaust of 9.68mm.

Surprisingly it ran and idled. It ran pretty well. I soon learned that it had a small valve head and lower compression piston.
My Duke wasn't what I thought. It was a 'Bill Hanna' 250 Monza' that was surplus to requirements and went to the UK an long with a few thousand more, but was registered as a Mark 3.
After a friend crashed his wide case 250 I inherited the piston and head, which I grafted onto the bottom end, changed the cam to my 'special' one and used the 30mm carb.
Now it was quite fast and a lot of fun.

I'm now rebuilding it. I decided to continue the Mark 3 route. I picked up genuine fenders from a dealer that didn't appreciate what he had. Less than $150 for the pair. Just need to get the chrome off. The front is the correct narrow one.

Don't want to make this very long story too long, so I'll ask for help now.

I have 2 more cams that I'd like identified.
One has white & green paint
Base circle is 20.8 mm and 9.95mm lift on the inlet - 20.98mm and 8.53mm lift on the exhaust
Sounds like a white & green one to me.
The other that I was told is a gray cam is
Base circle of 22.9mm and 9.04 lift on the inlet -23.2mm and 8.31mm lift on the exhaust

Is this a gray one?

My final question for today. What is the barrel height for a narrow case Mach1/Mark3 ?

Regards

[DewCatTea-Bob]

" So here is my first post "

____ Welcome-aboard (finally), David !
__ Where are you located ? _ G.B. ?



" It had a round style tank, a Mark 3 seat, said Mark 3 on the steering head sticker, and had triangular tool boxes. The fact that it had square style fenders meant nothing to me. "

____ Got any pix of it to share ?



" The cam came from Wittey Ducati.
Base circle is 20.9mm with an inlet lift of 10.34mm and an exhaust of 9.68mm. "

____ Who produced that camshaft ?
Too bad that Ducati didn't make any n-c.cams with that much lift,
(I don't know why they didn't).
Do you have any valve-timing specs for that non-Ducati cam ?



" After a friend crashed his wide case 250 I inherited the piston and head, "

____ Which w-c.250-model was it ?



" One has white & green paint
Base circle is 20.8 mm and 9.95mm lift on the inlet - 20.98mm and 8.53mm lift on the exhaust
Sounds like a white & green one to me. "

____ I guess there's no-doubt about that ! ... Trouble-is though that there were two different cam.models with that same color-code. _ Their model-names are the '250F1' cam, and the '350M3' -(350 Mark 3) cam. ...
Your given lift-figures indicate the M3.version. _ (The F1.version has roughly 9.85 & 9.35mm lifts.)



" The other that I was told is a gray cam is
Base circle of 22.9mm and 9.04 lift on the inlet -23.2mm and 8.31mm lift on the exhaust
Is this a gray one? "

____ You weren't misinformed ! _ There's no other Ducati-cam.model which it could be (other than the Gray/M1.cam).
Is it used ? _ If so, did you take your mic.reading on the center (as opposed to the unworn edge) of the ex.lobe ? - (As I suspect that it's somewhat worn.)

____ Anyhow, I have to congratulate you for somehow obtaining for yourself the two most desirable std.production Duke camshaft-models !
__ I-myself already have those two cam.models in my-own cam.collection.
Do you have any plans for either of them ?



" What is the barrel height for a narrow case Mach1/Mark3 ? "

____ That's something which I don't recall from memory, and-so will have to look it up later for you.
UPDATE - I've since checked my n-c.parts-book, and here follows the cyl.jug heights of the various 250-models...
Mark-III/Mach-I = 94.5mm
Scrambler = 95.6mm
Monza/GT = 96.1mm



Duke-Cheers,
-Bob

[Thevin]

Welcome to the forum lots of info Bob is the cam expert....

[kaysystems]

" So here is my first post "

____ Welcome-aboard (finally), David !
__ Where are you located ? _ G.B. ?

I'm now in Canada (Quebec) so have a relatively short riding season

" It had a round style tank, a Mark 3 seat, said Mark 3 on the steering head sticker, and had triangular tool boxes. The fact that it had square style fenders meant nothing to me. "

____ Got any pix of it to share ?

Somewhere. I'm moving house, but I'll post something when I find it

" The cam came from Wittey Ducati.
Base circle is 20.9mm with an inlet lift of 10.34mm and an exhaust of 9.68mm. "

____ Who produced that camshaft ?
Too bad that Ducati didn't make any n-c.cams with that much lift,
(I don't know why they didn't).
Do you have any valve-timing specs for that non-Ducati cam ?

I wish I knew who made it. I had to bore out the cam tunnel to get it in!!!

" After a friend crashed his wide case 250 I inherited the piston and head, "

____ Which w-c.250-model was it ?

250 mk3

" One has white & green paint
Base circle is 20.8 mm and 9.95mm lift on the inlet - 20.98mm and 8.53mm lift on the exhaust
Sounds like a white & green one to me. "

____ I guess there's no-doubt about that ! ... Trouble-is though that there were two different cam.models with that same color-code. _ Their model-names are the '250F1' cam, and the '350M3' -(350 Mark 3) cam. ...
Your given lift-figures indicate the M3.version. _ (The F1.version has roughly 9.85 & 9.35mm lifts.)



" The other that I was told is a gray cam is
Base circle of 22.9mm and 9.04 lift on the inlet -23.2mm and 8.31mm lift on the exhaust
Is this a gray one? "

____ You weren't misinformed ! _ There's no other Ducati-cam.model which it could be (other than the Gray/M1.cam).
Is it used ? _ If so, did you take your mic.reading on the center (as opposed to the unworn edge) of the ex.lobe ? - (As I suspect that it's somewhat worn.)

____ Anyhow, I have to congratulate you for somehow obtaining for yourself the two most desirable std.production Duke camshaft-models !
__ I-myself already have those two cam.models in my-own cam.collection.
Do you have any plans for either of them ?

I will use the gray one on the street after my resto is finished.. I'll try the white/green too for comarison

[Ventodue]

" The cam came from Wittey Ducati.
Base circle is 20.9mm with an inlet lift of 10.34mm and an exhaust of 9.68mm. "

____ Who produced that camshaft ?
-Bob

Hi Bob,

Witty Ducati was John Wittman, a well-known British singles racer and tuner. He re-built my Scrambler engine for me. Nice guy, very knowledgeable. Last heard of living in Spain.

Photo of him in action on page 145 of Mick Walker's Ducati Singles.

Ciao

Craig

[DewCatTea-Bob]

____ Firstly, thanks for the info in your response-post, Craig !



By: kaysystems/David...
" I had to bore out the cam tunnel to get it in!!! "

____ I don't understand why you'd need to do that, as I believe the cam-tunnel is 42mm, and the dimensions you've given for your special-cam make it no wider than 31.5mm, so that leaves over 10mm-clearance to slide the camshaft in-through,, and even when the threaded-end of the shaft reaches-in to the point where it then HAS to also fit-into/within the bevel-end shaft-bearing, your given measurement-figures result with a base-circle radius + lobe-height dimension which leaves .2mm of clearance within the cam-tunnel's 21mm-radius ! _ And that's about what would be expected by a cam.designer, so as to take full advantage of the available space within there.
__ Anyhow, if something didn't turn-out right so that you actually did indeed NEED to increase the cam-tunnel's radius, then how did you go-about coping with the resulting gap for the oil-line's passageway-connection between the head & the camshaft bearing-support/cap-cover ? - (If that resulting gap wasn't properly dealt with, then your camshaft would-not have been fed with oil !)

____ Which w-c.250-model was it ?

" 250 mk3 "

____ I've heard tale that the WideCase 250Mark-3 may've come with either the large-valve
or a small-valve cyl.head-type... so which did you find that-one to have ?



" I will use the gray one on the street after my resto is finished.. I'll try the white/green too for comarison "

____ Neither of those two cam.models is as wild as a 250DESMO-cam. _ The M1-cam would be best for running with a muffler,, while with a straight-through exhaust, the 350M3-cam should allow your-250 to outperform a 250-DESMO overall -(meaning that the DESMO would only be able to match it's performance just at the top RPM-range).
OVERALL, in a 250-engine, the 350M3-cam will outperform the M1-cam with or without a muffler (especially without !). _ The only advantage the M1-cam would provide (over the 350M3-cam) is a slight power-advantage at the lower RPM-range when running a muffler.
__ I'm unsure as to how your special/non-Ducati cam would compare, but considering it's lift-figures, I'd assume that it's valve-timing is likely as wild as a DESMO-cam, and as such would thus-then not work well with a muffler,, and also, (without muffler) would only produce just a slight power-advantage at top-RPM (at the great expense of low-end power), and thus provide an inferior OVERALL power-output.
But if it's valve-timing isn't too much wilder than the M1-cam, THEN it could be your best cam.


____ I've now updated my previous-post with the cyl.jug-height data which you had asked for.


Duke-Cheers,
-Bob

[kaysystems]

Thanks Bob

You asked why I had to open the cam tunnel. This was in a Monza head and it rubbed. Even my current narrowcase big valve head would be tight.
The timing on this special cam is wilder than the Mach1. When I get home tonight I'll try to get a picture of both cams & post them.

(forgot to mention that I ran the special cam with a Dunstall muffler. Geez - it was fun)

regards

David

[kaysystems]

____ I've heard tale that the WideCase 250Mark-3 may've come with either the large-valve
or a small-valve cyl.head-type... so which did you find that-one to have ?

I had the large valve. I think the sleeved down cylinder version for Europe may have been small valve.

David

[DewCatTea-Bob]

" You asked why I had to open the cam tunnel. This was in a Monza head and it rubbed. Even my current narrowcase big valve head would be tight. "

____ Those two head-models (and all others), have the same 42mm cam-tunnel size !
__ If the tip of the intake-lobe rubbed in contact anywhere within the original bore, then rather than bore-out the entire tunnel-length (and therefore run-into the oil-passage issue), you could've instead simply ground-away a little of the tunnel-wall (just at the point where the clearance-problem existed).
__ How many different cyl.heads do you actually have ?



" The timing on this special cam is wilder than the Mach1. "

____ That's no-doubt the actual case ! _ I'd expect that it could possibly be even wilder than the 250F1 or std.DESMO cam-models. _ And if so, it'd be much better suited for a 450-Duke.



" When I get home tonight I'll try to get a picture of both cams & post them. "

____ That would be quite interesting & much appreciated !
Do you think you could possibly get a pic.shot which shoots directly through the shaft's center-hole ? - (As that would perfectly profile the the cam-lobes !)



" I think the sleeved down cylinder version for Europe may have been small valve."

____ What "sleeved down" cylinder ?
The only sleeved-down cylinder I know of on any Duke-model was the late-175 model, (which was used for in 200-cyl.jugs).
__ If you're actually meaning to refer to the Mototrans (69x66)-250, THAT was actually a bored-out 200,, and yes that model would've employed the small-valves.


Duke-Cheers,
-Bob

[kaysystems]

You asked why I had to open the cam tunnel. This was in a Monza head and it rubbed. Even my current narrowcase big valve head would be tight.

____ Those two head-models and all others, have the same 42mm cam-tunnel size !
__ If the tip of the intake-lobe rubbed in contact anywhere within the original bore, then rather than bore-out the entire tunnel-length (and therefore run-into the oil-passage issue), you could've instead simply ground-away a little of the tunnel-wall (just at the point where the clearance-problem existed).

If I have a base diameter of 21mm and add 10mm lift, that's 10 on the radius - so the diameter is 41.

When I get home tonight I'll try to get a picture of both cams & post them.

______ That would be quite interesting & much appreciated !
__Do you think you could possibly get a pic.shot which shoots directly through the shaft's center-hole ? - (As that would perfectly profile the the cam-lobes !)

I'm sure I can do that. That's an interesting challenge for me. I'll post it as well as the Mach1, just for everyone's reference

David