Cause for timing to be advanced beyond adjustability

[mandm]

Hello,

I've searched this forum and the internet and have not found my answer yet. My bike is running Pamco, E-Advancer, PMA, Normal Battery. It's a '73. I've been slowly tuning it up to sell it. When I got it, it had a standard ignition/points. Before doing anything, I followed the advice of: Adjust valves, timing chain, points gap, etc... There were no timing marks on the PMA, so I removed the valve covers and used a TDC tool to find TDC and that correlated with the camshaft pins, etc... I then marked TDC to check timing. I used both a test lightbulb and a strobe light and saw that the engine was firing approx. 30 degrees beyond what I'd found to be normal timing position. I've added a Pamco with E-Advancer and still see the same firing position. When revved up, the timing advances as it should. It runs ok and does not kick back or seem to be running as it's indicated. I'm going to re-check my timing marks again.

A stretched cam chain would retard timing, correct? I thought about a skipped tooth on the cam chain, but the cam position matches piston @ TDC when I checked.

A big thank you to this forum for all the help I've already found through reading here.
Any ideas?

 

[pamcopete]

mandm,

Keep in mind that the timing at idle (1,200 RPM) is 15 degrees BTDC, not TDC. Also, the dual output coil produces a negative voltage on one of the spark plug wires and a positive voltage on the other. Most timing lights work best with the negative voltage wire, but there is no easy way to determine which that is, so if you are unknowingly using the positive wire, you may experience erratic timing light action, including an indication that the timing is late, assuming you mean retarded timing with "30 degrees beyond what I'd found to be normal timing position" The word beyond to me means after the desired point. So, try the other spark plug wire to see if the results are different.
Also, it's important to check the timing at 1,200 RPM or less because any faster than that will cause the advancer to introduce some advance which means there is less available for full advance, if in fact you mean the advance is "beyond" where it is supposed to be. The tach on the bike may not be accurate at 1,200 RPM, so either use another test tach or set the idle at less than 1,200 RPM while setting the timing.

So, I think to help you any further, you will have to help us by describing what you mean by the word "beyond".

 

[mandm]

Thanks for your input. I plan to take some better photos later. I've checked timing on both spark plug leads with same results. I've attached a photo of what I'm calling 30 dig beyond BTDC. It fires on the arrow at slow idle and advances beyond that arrow when revved up.

 

[wherearewe]

You certain you got your timing mark in the correct place? You use a piston stop and degree wheel?

 

[pamcopete]

Thanks for your input. I plan to take some better photos later. I've checked timing on both spark plug leads with same results. I've attached a photo of what I'm calling 30 dig beyond BTDC. It fires on the arrow at slow idle and advances beyond that arrow when revved up.

I'm sorry, but I am still confused by your term "beyond" especially with "30 dig beyond BTDC" The "B" in BTDC means Before, so you are saying beyond before? Please try to explain what you mean without using the word "beyond".

And for others who are reading this post, this is why I always recommend that you install the PAMCO, or whatever ignition you are going to use, before you remove the stock rotor with its timing mark or else you may end up with a situation beyond your ken.

 

[mandm]

Pamcopete - I bought this bike with the PMA rotor installed and no marks. By "30 degress beyond" i mean that spark occurs at the point where I've drawn the arrow - which I'm assuming as 30 degrees advanced from what it should be. I'm also assuming that there are 3 marks that should be made for timing reference. 1 is TDC, 2 is where timing should fire on idle and 3 is the advance range for 3k rpm? There was no change in condition between stock points and the Pamco/e-advance. I'm in no way thinking the Pamco is the cause.

I did use a piston stop and a degree wheel. I'm not certain of anything at this point and I'll be re-checking and take photos as I do. Thanks again for the input, it's much appreciated.

 

[pamcopete]

mandm,

OK. No problem. We'll still be here to help you once you have verified the information but we just need an unambiguous description of the problem.

 

[barncat]

these motors of course spin counterclockwise so this is apparently firing too far "before" TDC as Pete points out, as opposed to "after" or beyond.

i've heard some PO's install the rotors without woodruff keys, which is a bad idea. you did find TDC but perhaps the rotor slipped on the crankshaft? just a thought... no way to tell without pulling it.

modifying and installing a key is IMO the hardest part of a PMA swap. tight tolerances and the magnet pulls it out of position. grease to stick it in place and luck are required.

 

[wherearewe]

these motors of course spin counterclockwise so this is apparently firing too far "before" TDC as Pete points out, as opposed to "after" or beyond.

i've heard some PO's install the rotors without woodruff keys, which is a bad idea. you did find TDC but perhaps the rotor slipped on the crankshaft? just a thought... no way to tell without pulling it.

modifying and installing a key is IMO the hardest part of a PMA swap. tight tolerances and the magnet pulls it out of position. grease to stick it in place and luck are required.

Good suggestion. That did occur to me. It might have slipped but he would be pretty unlucky for it to slip from when he marked it to when he tested his timing. A lot of people have run these without woodruff keys without to much problem. In fact Hugh specifically says dont use one on his install blog (yes i know there have been a few epic arguments over the wisdom of this but its worth pointing out - and yes i think use a key). Is the nut tight on the crank i wonder?

There are a couple of good videos by IAMCARBON (i think) on using a degree wheel and piston stop. Maybe watch them and double check the correct procedure was followed so that can be ruled out.

 

[peanut]

And for others who are reading this post, this is why I always recommend that you install the PAMCO, or whatever ignition you are going to use, before you remove the stock rotor with its timing mark or else you may end up with a situation beyond your ken.

pete what happens if your electronic advance system is installed with reversed leads ?
On the Boyer it apparently defaults to permanently full advance ,which is how some racer use it .

I also read somewhere that a reduced battery voltage /charging output can effect the advance curve on the Boyer not sure how that would effect yours ?

 

[pamcopete]

pete what happens if your electronic advance system is installed with reversed leads ?
On the Boyer it apparently defaults to permanently full advance ,which is how some racer use it .

I also read somewhere that a reduced battery voltage /charging output can effect the advance curve on the Boyer not sure how that would effect yours ?

There aren't any leads on the PAMCO that can be reversed without causing some damage.

The battery voltage would have to be less than 8 Volts to cause a problem with the E-Advancer. Less than 6 Volts for the standard non E-Advancer model.

 

[peanut]

thanks pete. I thought it worth mentioning as I am unfamiliar with your pamco and recently was made aware of the reverse polarity function and low voltage effect on the Boyer operation