Cam Timing

[Duc906]

romus
It's great to here you got the job done. I appreciate your feedback and kind words. I rode with the cams at 106 deg for a few weeks and I was happy with how the bike was running and, like you, I found the bike was great around town. It also performed well on the open road,160kmh was what I took it up to and it felt smooth all the way, no sign of pinging. I changed the timing to 110 deg a couple of weeks ago. So far the only noticeable difference is at the higher end rpm, above 6500rpm. The weather is starting to turn colder so the desire to go for rides is fading.I want to try the timing at 114 deg before winter gets here, but I would be happy to set it back at 106 deg,to be cont.........

[higgy]

No noticeable difference to air fuel mixture (AFM). I have a gauge showing AFM as I ride and it seems to be reading the same, but I need more driving to be sure.

Hey Warwick,out of curiosity have you tried to adjust your air mixture screws since doing your cams. Wondering if you still have the difference as before or if they can be adjusted in a more balanced fashion ?
Higgy

[higgy]

Ken
Your impressions on the different cam timings would make a nice addition to your Timing doc

[romus]

No noticeable difference to air fuel mixture (AFM)...

Hey Warwick,out of curiosity have you tried to adjust your air mixture screws since doing your cams. Wondering if you still have the difference as before or if they can be adjusted in a more balanced fashion ?
Higgy

Yes, I am almost the same adjustment for both air mixture screws, now that the cams are timed together. Just a 1/4 more turn for the rear cylinder to account for the bend in the rear manifold.

[paso750]

Hi,

a friend of mine is prepairing to optimize his ignition. He would like to correct the ignition timing of the rear cylinder also to improve the engine`s smoothness (which is only possible with some modification). Appearently the ignition timing of the rear cylinder is by 2° less advanced than the front cylinder to reduce thermal load. The pick up bracket seems to indicate this, too. The strange thing is that noone, incl. some Ducati mechanics seem to know about this.
Anyone out there know something ?


G.

[higgy]

Hey G
Seems to me I remember an article at a tech site about fixing this. I'll take a look tonight to see if I can find it again
If I remember it was an Italian site with a guy using the modified Two plug heads in his cart

[paso750]

higgy, if you find it let me know

[higgy]

Still looking G

[romus]

Still looking G

This is an interesting question. I was wondering about ignition timing.

So far I have done the good improvements on the carb and cam timing. I understand that ignition timing is one of the other factors that should be adjusted right.

What is this thermal load anyway, that they would want to fix it by retard ignition timing for the rear cylinder? Why would it be a mistake to be fixed?

[duc907]

Still looking G

This is an interesting question. I was wondering about ignition timing.

So far I have done the good improvements on the carb and cam timing. I understand that ignition timing is one of the other factors that should be adjusted right.

What is this thermal load anyway, that they would want to fix it by retard ignition timing for the rear cylinder? Why would it be a mistake to be fixed?

I have only heard of this being done on air cooled vee twins that do not get enough air over the rear cylinder to cool it. Is there some one out there with more info?

[paso750]

It`s not a mistake that has to be fixed. The engine should run smoother when removing this though. The question is how much thermal load will change.
Some random thoughts: if the timing is not set correctly the rear cylinder may be more than 2° off. Causing the engine to run rough. Some guys report that the engine runs better when the carbs are not perfectly synchronized but adjusted slightly towards the rear cylinder.
A friend measured the degree marks on the flywheel and they are accurate. Hence due to one pickup being 2° off the marks on pick-ups and flywheel don`t perfectly match. Only one mark can. So how do shops adjust the pick up (bracket) ? Considering that noone asked knew about this they probably set the pickup bracket to the "middle" meaning they try to match front and rear marks which in the end causes both cylinders to be more off correct timing.
Btw anyone used a TDC finder to precisely measure if the TDC marks are accurate ?

G.

[higgy]

Btw anyone used a TDC finder to precisely measure if the TDC marks are accurate ?

I still have my old two cycle dial indicator set .When I do finally get around to doing my cam timing I'll let you know what I find
Was planning to work on the bikes today,wife had other ideas

[Tamburinifan]

Btw anyone used a TDC finder to precisely measure if the TDC marks are accurate ?

Engineer friend did this on a DB2. TDC mark was just 1-2 degrees off.

[paso750]

It`s mentioned in the file:

BE VERY,VERY GENTLE WHEN ROTATING THE ENGINE WITH THE
PISTON STOP IN AS YOU DON'T WANT TO PUT THE STOP THROUGH
THE TOP OF THE PISTON.ALSO, DO NOT ROTATE THE CRANK A FULL
360 DEGREES WITH THE STOP IN AS THERE IS A CHANCE THAT THE
VALVES MAY MAKE CONTACT WITH THE STOP.

This is specially the case if larger valves are installed or cams with increased lift or like in my case both.

[paso750]

A couple of years ago I tried to learn more about cam & valve timings and collected lots of info from numerous sources. I meshed up many texts into one file. Most sources were in english so the file is, too. At a certain point or depth of an engine topic most sources begin with mathematical formulas. Tbh since that is when I begin to lose interest there isn't any of that. It was intended as a sort of work of reference for myself while trying to keep things understandable. If somebody is interested, here it is:
https://app.box.com/s/pst9p706lhf9nvrf8kzpm6kcr5zefayb

G.