Misc: Everything Else how easy is it time the mag on shadow
- Thread starter Roslyn
- Start date
More info here: https://www.vincentownersclub.co.uk/index.php?threads/timing-a-rapide.8994/#post-83186
And Here: https://www.vincentownersclub.co.uk/index.php?threads/rod-to-hold-the-timing-disc.8184/#post-70858 My 34 deg tool mentioned in #11 is
More: https://www.vincentownersclub.co.uk...met-series-c-ignition-timing.7493/#post-62767
https://www.vincentownersclub.co.uk/index.php?threads/wont-idle-low-too-much-timing.6548/#post-48811
And Here: https://www.vincentownersclub.co.uk/index.php?threads/rod-to-hold-the-timing-disc.8184/#post-70858 My 34 deg tool mentioned in #11 is
More: https://www.vincentownersclub.co.uk...met-series-c-ignition-timing.7493/#post-62767
https://www.vincentownersclub.co.uk/index.php?threads/wont-idle-low-too-much-timing.6548/#post-48811
Well I have not got on well with timing the shadow so far as the plastic degree disc broke in two and I have ordered a new one for next week and will give it yet another attempt sort things out in damp cramped shed.
As for putting a bolt in the plug hole to hold the piston in place I used to do with a triumph twin and in the end had piston failure on the timing side??
As for putting a bolt in the plug hole to hold the piston in place I used to do with a triumph twin and in the end had piston failure on the timing side??
You can buy a little cheap tool that screws into the plug hole, That slides up and down.
You don't need a degree disc, The book gives you how much before TDC in inches I think it's about 11/16 ".
Good Luck. Bill.
Bill, that seems to be a questionable method: The spark plug thread is at an angle so the clock reading depends on the piston top shape. I would definitely use the degree disc - at least once, and after that you can get the clock reading at that orientation for later use , for these pistons.
Vic
Vic
I agree you need to degree is once and the piston crown shape matters. On my Shadow it is a 1/2 in down from TDC for 35 recommended for the BT-H I have fitted. I've marked the point on the tool as well as the scale is rather difficult to read.
Steven
Yes you are right Vic, But we are talking old Vincents here, No two are the same, When we go into a Petrol Station in U.K. We get all kinds of rubbish, I think 11/16" will be fine, There is lots of slop on the fibre Pinion,
ATD, There has to be or you will have trouble, And if you use a fag paper or as I do, Look and see when the heal of the points gets to the lump of the cam, There are so many ways, All + or -.
Most Vincents will run a few degrees out and most people would not know.
Cheers Bill.
I use the simple device Bill mentioned above. The upper end of the rod is larger than the hole through its spark-plug like body so the rod, which is graduated in mm can't fall into the cylinder. The rod is graduated in mm and also has a small o-ring and you can tell from the psst sounds what stroke you are on.
I don't believe the piston shape matters though. The rod will contact the piston at a given point and that point will rise and fall consistently. What can easily be done is compensate for the angle. The rod is moving as the hypotenuse of a right angle triangle and we are interested in the vertical side. If you know the angle of the plug-hole, simple trig. gives the compensation factor. For example it's 90% of the rod movement if the angle is 60 degrees and 70% if the angle is 45 degrees.
I fitted a manual advance to my twin when I had it, and this made timing even easier as it ran slack wire advance. From memory, 34 degrees advance is approx. 3/8", remembering to rotate the engine backwards first to take up all the backlash in the gears.
I have to admit I used a pencil for most of my life. Funny what you are shown as a teenager sticks - I guess that's because it worked!
Gerry
I don't believe the piston shape matters though. The rod will contact the piston at a given point and that point will rise and fall consistently. What can easily be done is compensate for the angle. The rod is moving as the hypotenuse of a right angle triangle and we are interested in the vertical side. If you know the angle of the plug-hole, simple trig. gives the compensation factor. For example it's 90% of the rod movement if the angle is 60 degrees and 70% if the angle is 45 degrees.
I fitted a manual advance to my twin when I had it, and this made timing even easier as it ran slack wire advance. From memory, 34 degrees advance is approx. 3/8", remembering to rotate the engine backwards first to take up all the backlash in the gears.
I have to admit I used a pencil for most of my life. Funny what you are shown as a teenager sticks - I guess that's because it worked!
Gerry
£9.95p www.fekedcom Cheers Bill.
The piston shape will influence the position of the rod. Especially if you have some kind of lumpy piston. In my drawing, which I admit is extreme, the vertical line represents the cylinder wall. The angled line represents the line of action of the plunger in the tool. The horizontal lines represent the crown of a flat top piston, the arcs a domed piston. As the flat top piston descends 0.25 inches the tip of the move horizontally 0.25 inches. The total movement of the tip of the plunger is 0.354 inches. If say the crown of the piston has some shape to it. In this example a simple arc. The upper arc is centered on the upper horizontal line. The bottom arc is centered on the lower horizontal line. So the vertical distance is still the 0.25 inches. The total plunger movement is 0.089 inches. Unless you know cross section of the crown, I would degree is at least once.
Steven
Steven