Can’t Get Timing Correct

Ralph Dill

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I can not seem to get the ignition timing correct on my 1974 Commando. I am detailing the process I am using to see if any of you can help me locate what might be wrong or what I am doing wrong. When I do what I describe below, bike will not start and inspection reveals timing way off. Observing profile of timing cam, it appears that cam will open points at either of two places along its circumference which seems to me to correct since it rotates at 1/2 crankshaft speed; but does it matter which of the two timing cam lobes I use to set either set of points? Constructive reply’s much appreciated.
1. Rotate engine until one piston is at TDC.
2. Remove all valve rocker covers
3. Identify which cylinder is firing by physically feeling valve lash on both intake and exhaust rocker arms.
4. Identify primary wire feeding voltage to coil of aforementioned firing cylinder (b/w or b/y).
5. Follow said wire to identify which set of points are firing said cylinder. These are the points to be timed.
6. Reverse engine slightly to position timing mark on primary scale at 28 degrees.
7. With timing cam locked in full advance position (fully CCW) and points gap set at 0.015 inches and whole advance mechanism sliding fit on exhaust camshaft taper, rotate timing cam until said points are just beginning to open.
8. Repeat steps 3 to 8 with other cylinder.
9. Remove timing cam locking device.
 
Ralph Dill said:
7. With timing cam locked in full advance position (fully CCW) and points gap set at 0.015 inches and whole advance mechanism sliding fit on exhaust camshaft taper, rotate timing cam until said points are just beginning to open.
Click to expand...

No, you unlock the AAU from the taper if both sets of points cannot be set within the length of the backplate and sub plate slots.


Ralph Dill said:
8. Repeat steps 3 to 8 with other cylinder.
Click to expand...

You obviously can't do '7' again once you have set the first set of points which is why you need to fit the AAU in a position where both sets of points can be set within the limits of the back plate and both sub plates.

Ralph Dill said:
Observing profile of timing cam, it appears that cam will open points at either of two places along its circumference which seems to me to correct since it rotates at 1/2 crankshaft speed; but does it matter which of the two timing cam lobes I use to set either set of points?
Click to expand...

No, there should only be one opening point on the points cam used by both sets of points.
 
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Also, One of the mistakes that people commonly make is they connect the trigger wires on the points under the insulator so instead of sending a pulse to the coil, the points are grounded. It may not be your issue, but it's such a simple mistake that it's overlooked when it's done.
 
o0norton0o said:
Also, One of the mistakes that people commonly make is they connect the trigger wires on the points under the insulator so instead of sending a pulse to the coil, the points are grounded. It may not be your issue, but it's such a simple mistake that it's overlooked when it's done.
Click to expand...
Yes, I understand that the first set of points can be timed by moving either the cam plate or the points, but once that is done, the second set of points must be timed by moving that set of points only. My trigger wire orientation, in order is, nut, insulator, trigger wire connector. I think this puts the trigger wire in contact with the looped end of the insulated points spring.
 
Ralph Dill said:
My trigger wire orientation, in order is, nut, insulator, trigger wire connector. I think this puts the trigger wire in contact with the looped end of the insulated points spring.
Click to expand...
Correct.
Can’t Get Timing Correct
 
Your points cam should look like this (possibly what you are seeing as a second opening is the closing ramp?).
Can’t Get Timing Correct
 
L.A.B. said:
Your points cam should look like this (possibly what you are seeing as a second opening is the closing ramp?).
Can’t Get Timing Correct
Click to expand...
I will check. Thanks for the picture. Then, where is the OPENING ramp? Is it just to the left of the scribe mark in this picture? Is that the point on the cam supposed to be just opening the points on the correct timing? What is the purpose of the larger slot to the left of the scribe on the face of the cam? So from the looks of the cam, it appears that the points would be open for about 180 degrees of cam rotation; is that correct? Sorry for all the questions. I am trying to get a better understanding of what I am dealing with here.
 
Ralph Dill said:
Then, where is the OPENING ramp? Is it just to the left of the scribe mark in this picture?
Click to expand...

Yes, that should be the opening ramp.

Ralph Dill said:
What is the purpose of the larger slot to the left of the scribe on the face of the cam?
Click to expand...

You can use it to move the cam to full advance if you don't use the washer (or even if you do).

Ralph Dill said:
So from the looks of the cam, it appears that the points would be open for about 180 degrees of cam rotation; is that correct?
Click to expand...

Yes.
Note that the scribe mark is only used for setting the points gap, it is not used to set the timing.
 
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L.A.B. said:
Yes, that should be the opening ramp.



You can use it to move the cam to full advance if you don't use the washer.



Yes.
Note that the scribe mark is only used for setting the points gap, it is not used to set the timing.
Click to expand...
Thank you for your responses. I understand more now about how I approach this. Appreciate it.
 
hybridracer said:
That is wrong. Owing to the backlash in the drive to the points you must always rotate the engine forwards to the 28 degree mark.
Click to expand...
Interesting. Will do. I suspect you are referring to the potential slop of the exhaust cam drive chain.
 
Ralph Dill said:
I can not seem to get the ignition timing correct on my 1974 Commando.
Click to expand...
1. Was the bike running normally "before" you started working on the timing?
2. What occurred to elicit the work on the ignition timing?
3. By any chance, did you also work on the carburettors?
4. Is there spark at the plug(s)?
 
grandpaul said:
1. Was the bike running normally "before" you started working on the timing?
2. What occurred to elicit the work on the ignition timing?
3. By any chance, did you also work on the carburettors?
4. Is there spark at the plug(s)?
Click to expand...
Long story. Much work over the last year. Memory now confused over what happened when. Bought bike 8 years ago and it ran well for 7 of those years. About a year ago it started to run poorly and became difficult to start. PO had installed a Boyer ignition which after much work I suspected it was failing, so after having had so much success with the installation of a TriSpark ignition in my Triumph Trident, I installed one in the Commando. It ran well for a time, but then began exhibiting the same aforementioned faults. I ran the TriSpark diagnostics which indicated it was OK, so I then focused on carburation and installed a new set of Amal Premiers which did not solve problem, so I am back to ignition. I also have a Truimph Bonneville that I bought new in 1974 that always runs well and still has points for ignition, so I thought that since I can not diagnose electronic faults and points are mechanical, I would convert to points so eliminate ignition as the source of my issues, but I have struggled in getting the set properly. Various attempts have resulted in total inability to start, or a violent explosions seemingly coming from the left exhaust. That is where I am now. Have yet to apply any of the learnings from the forum. Maybe tomorrow or Monday. Thank you for your interest. And yes, I am now getting spark at the plugs.
 
Ralph Dill said:
Long story. Much work over the last year. Memory now confused over what happened when. Bought bike 8 years ago and it ran well for 7 of those years. About a year ago it started to run poorly and became difficult to start. PO had installed a Boyer ignition which after much work I suspected it was failing, so after having had so much success with the installation of a TriSpark ignition in my Triumph Trident, I installed one in the Commando. It ran well for a time, but then began exhibiting the same aforementioned faults. I ran the TriSpark diagnostics which indicated it was OK, so I then focused on carburation and installed a new set of Amal Premiers which did not solve problem, so I am back to ignition. I also have a Truimph Bonneville that I bought new in 1974 that always runs well and still has points for ignition, so I thought that since I can not diagnose electronic faults and points are mechanical, I would convert to points so eliminate ignition as the source of my issues, but I have struggled in getting the set properly. Various attempts have resulted in total inability to start, or a violent explosions seemingly coming from the left exhaust. That is where I am now. Have yet to apply any of the learnings from the forum. Maybe tomorrow or Monday. Thank you for your interest. And yes, I am now getting spark at the plugs.
Click to expand...
WHAT are the symptoms?

"About a year ago it started to run poorly and became difficult to start"

Expand on this, as that is quite general.

Timing chest been open yet? Chain in good order?
Properly tensioned?
Wiring properly done when switching from the EI units and points?
 
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Ralph Dill said:
PO had installed a Boyer ignition which after much work I suspected SNIP...
Click to expand...

Your problem is that you are guessing instead of testing... Where's the "test, don't guess" guy when you need him?? I'm doing his job now... 🤣

You guessed and changed the boyer to tri-spark, then you guessed and changed the carbs to premiers, then you guessed and changed to points..... I see a pattern :rolleyes:
 
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OP, if the advance mechanism is worn out you will assume a new set of problems to troubleshoot, one of which is that the engine won't idle down as the advance won't return to 0 till shutoff. Look for slop in all the moving parts of the advance mechanism. Also the springs can get weak or the pins they hook on can get bent out of position affecting the start of advance and full-advance RPM.

Slightly OT but are advance mechanisms available once again? I have several worn-out ones I saved for some reason I no longer remember but should my Boyer ever go bad I might be tempted to go back to the factory setup. I don't think the Boyer advance curve is spot on.
 
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o0norton0o said:
Your problem is that you are guessing instead of testing... Where's the "test, don't guess" guy when you need him?? I'm doing his job now... 🤣

You guessed and changed the boyer to tri-spark, then you guessed and changed the carbs to premiers, then you guessed and changed to points..... I see a pattern :rolleyes:
Click to expand...
Before we can test, we need to know more information.🗣️

Otherwise, the hypothesis we create, will be as vague (and large) as the general symptom description. 💡
 
Ralph Dill said:
I also have a Truimph Bonneville that I bought new in 1974 that always runs well and still has points for ignition, so I thought that since I can not diagnose electronic faults and points are mechanical, I would convert to points so eliminate ignition as the source of my issues, but I have struggled in getting the set properly.
Click to expand...

If you are used to setting Triumph twin points then the Norton is basically the same except for the points cam that rotates in the opposite direction so the auto advance units are different, the Norton one having no peg location.
 
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