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Mark. III Camies in `53 Shadow - What is right timing?

Sebastian Huber

Well Known and Active Forum Website User
VOC Member
Ask for Advice
What is right timing for camy and timed breather?
Tried to follow advices of Paul Richardson but realised, that camy of cyl.1 (rear) is marked twice
-twin dot and 5 cogs later with single dot.
Camy cyl.2 (front) has twin dot, 11cogs later "B" and again 3 cogs later slash.

Should I follow recomended timing at 0.12mm valve stroke
(inlet opens 40-42° before TDC, close 60-64° after BDC, exhaust opens 72-70° before BDC, close 28-33° after TDC) or should I give priority to advice of valve stroke?
(inlet open TDC 2.79mm, close BDC 4.82; exhaust open at TDC 5.58mm, close at BDC 1.65mm)
What position has timed breather in correlation to Cylc.1 ?
In which position is breather fully open?

Hope for advice this way.
I´m not afraid of this job but feel threat of exhaust pipe Cyl.2 won`t survive a second time!
 

Black Flash

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VOC Member
Hallo Sebastian,
alles was du wisssen musst steht unter diesem thread: Timing a Comet using a Degree Disc - what does everyone do?
Falls Du es noch genauer brauchst ruf mich einfach an:06442 23113 abends,
Bernd
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
The timing is right when both valves have equal lift at about 4 degrees BTDC. It needs the right equipment (in English "a dial test indicator") to measure it, although as a rough check done by eye it is still useful. The lift is about 3.5 mm. There is an article about the method in MPH 648 (January 2003). I like the method because it looks at the critical part of the four-stroke cycle - the overlap. Get that right, and most of the other numbers don't matter. In fact I timed my Garry Robinson 105 cams that way, then checked the opening and closing figures which were both where they should have been. Unfortunately I don't have any figures for Mark III cams, which (I think) came in with the Series D bikes.
 

Sebastian Huber

Well Known and Active Forum Website User
VOC Member
Hallo Bernd,
vielen Dank, werde versuchen, den thread zu finden, andernfalls mich bei dir melden, wenn`s bezgl. breather, etc. noch Fragen gibt.
War mir schon klar, dass es diese Frage wohl schon dutzende Male gab, wollte aber doch auf Nummer sicher gehen.
(bin zwar schon etwas angegraut, aber in der Vincent Community noch absoluter "Frischling"; habe die Shadow erst seit 59 Wochen)

Grüße nach Solms
Sebastian
 

Sebastian Huber

Well Known and Active Forum Website User
VOC Member
Hello Tom,

thanks a lot for quick repley!
It`s Friday evening, wife is out for dinner and whole evening free for workshop where lady "Black Shadow" is waiting.
As already answered to Bernd it was clear that I´m not the first posting this question but I want to do it right straight away, especially with timed breather where I lost original timing when opening chamber.
Position "B" of cam gear to "B" of breather gear looks very strange. Would mean due to gas dynamic it works on paraphase.
... and why not to ask the experts with years of Vincent Experience?
I think I have the right equiment due to riding old bikes pre 1930 for more than 40 years. But I`m aware Vincent is a little bit different.
This forum is simply great, isn`t it?

Have a nice weekend
Sebastian, the Bavarian
 

davidd

Well Known and Active Forum Website User
VOC Member
For the breather you can do the check with a clean plastic tube attached to the breather pipe. With the rear cylinder at TDC you should not be able to blow in the pipe. As you turn the engine with the dergree wheel in place the you should be able to blow in the pipe at 70 ATDC. The breather will remain open until 30 degrees ABDC (rear cylinder still). If it is way off, pull the breather and move a tooth and repeat. This was the advice that Neville Higgins gave in MPH 608 at page 23.

David
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
I used the 4 deg BTDC method with my Andrews (now Megacycle) cams, but was told to use .050" lift to get past the quieting ramps that Mk3's also have.
 

Sebastian Huber

Well Known and Active Forum Website User
VOC Member
For the breather you can do the check with a clean plastic tube attached to the breather pipe. With the rear cylinder at TDC you should not be able to blow in the pipe. As you turn the engine with the dergree wheel in place the you should be able to blow in the pipe at 70 ATDC. The breather will remain open until 30 degrees ABDC (rear cylinder still). If it is way off, pull the breather and move a tooth and repeat. This was the advice that Neville Higgins gave in MPH 608 at page 23.

David

Thanks David,
this info was still missing. I though of delay in closing because of gas dynamic, but wonder how much it may be.
Local Bavarian time is 6:35, Saturday morning starts good!
Will Go straight away in workshop for to finish timing.

Have a nice weekend,
Sebastian, the Bavarian
 

Sebastian Huber

Well Known and Active Forum Website User
VOC Member
I used the 4 deg BTDC method with my Andrews (now Megacycle) cams, but was told to use .050" lift to get past the quieting ramps that Mk3's also have.

Hi Bruce,
thanks for feedback. Have to sort out details today. See that quieting ramps when measuring starting point. Reduced freeplay at this point new and wondering now if I`ve eliminated quieting ramps this way. Certainly, with new adjustment following advices I´ve got during last 20 hours I`ll get best timing.
Thanks to all guys who spent their time in helping me on my first post!

Have a nice weekend in Apple Valley!
Sebastian, the Bavarian
 

timetraveller

Well Known and Active Forum Website User
VOC Member
Has anyone ever measured quieting ramps on a Mk III cam? The only Mk III cam I have ever measured up properly was a brand new one lent to me by Colin Jenner. It had just been manufactured by Gary Robinson and it timed up perfectly so I have no reason to think that the cam was in any way defective. There was nothing that could be considered quieting ramps on either the start or end of either of the lift profiles and calculating valve velocity and acceleration also did not show any difference from a Mk I. I have been told, but whether it is correct or just another Vincent myth, that the way in which the quieting ramps were produced was to grind the base circle 15 thou undersized and then to blend the new base circle into the original lift profiles over 20 degrees at the start and end of each cam lobe. Remember that this might be myth but if it is correct then it would not have been a quieting ramp and it would have been an incompetent modification. A proper quieting ramp would have had a slow lead in on the acceleration curve and it was just not there. If anyone has another Mk III cam which they think has a quieting ramp I would be happy to do the measurements again but the one example already measured did not have detectable ramps.
 
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