Pamco Ignition causing backfire through carbs.

[KlubFoot]

KlubFoot,

Well, that picture of the rotor above clearly shows one magnet missing. I'm not sure what happened since that. Is it possible that you replaced the missing magnet? If so, the magnets have a particular polarity. Opposite magnets are the same polarity.

The rotor that is on the bike does have all 4 magnets in place. As I mentioned above, the backside of the rotor (or the side facing the motor) has different exposures of each magnet. What I mean by that is, 2 magnets are completely exposed, 1 magnet is covered by the aluminum and 1 magnet is half way covered.

Is this correct, or are all 4 magnets supposed to be completely exposed?

 

[KlubFoot]

You mean there's physically no exhaust on the RH side? Have you checked the valves on that side? Maybe a valve/rocker arm issue?

I am going to check the cam chain tension and the valves this evening. This is what I suspect as well... however the motor was running well when pulled and the same issue has now occurred on 2 different motors with the same Pamco unit, so I was trying to make sure everything was set up properly first.

I still have not pulled the whole assembly out to make sure the advance was set up correctly either.

 

[KlubFoot]

I have a general question... the motor in question is a 72. Is there anything different about the advance set up between this motor and later years? If so, what changed?

 

[pamcopete]

KlubFoot,

The magnets will work with any of the positions that you describe.

 

[dckareem]

one thing it also does. I dont know if anyone has said this before. The right side of engine chirps when it is idling.

The advance isn't binding. Click just like in your video, but didn't know if we should file down the pin just in case.

 

[XSLeo]

Chirping indicates a vaccum leak. It could be at the carb holders or the throttle shaft seals.
Check for vaccum leaks. It's pssible that the carbs need cleaning. 99% of the time when one cylinder runs ok and the other won't carbs are the issue.
Leo

 

[KlubFoot]

The "chirping" sound DCKareem is referring to is more of a pinging noise due to the off timed detonation.

XSLEO... I swapped my set of carbs on to his bike and it still did the same thing. I have another Pamco unit that I should have in my possession this evening. I am going to throw that on his bike just to double check the ignition. From there, we are going to run a leak down test and check the valves.

 

[dckareem]

here is a video of the bike running

 

[COOPERB27]

Sounds like a stuck exh valve to me, pull the inspection caps & roll the motor over & check the valves. just my 2 cents

 

[dckareem]

going to run a leak down test and check for air leaks.

 

[dckareem]

I was thinking bad cam chain if not the exhuast valve. Maybe?

 

[pamcopete]

dckareem,

Could I ask you a favor? It looks like the problem may not be the PAMCO, so, could I ask you to change the title of this thread? If you still think the PAMCO may be causing the problem, what else can I do for you?

Thanks,

Pete

 

[Fatman]

dckareem,

Could I ask you a favor? It looks like the problem may not be the PAMCO, so, could I ask you to change the title of this thread? If you still think the PAMCO may be causing the problem, what else can I do for you?

Thanks,

Pete

The title is what got me reading this thread, I wanted to see how a simple system could make it back fire through the carbs. Think I would look into valve gap then carbs. What I have seen and played with on the Pamco system it should work or not, not much gray area. Do let us know the fix.

 

[pamcopete]

Fatman,

Yes, that is essentially correct. The PAMCO is just a switch. Turns the coil on and off in response to the position of the magnets on its rotor. The advance mechanism can create some unique symptoms due to loose springs, worn out weight tabs, binding advance rod etc. I have had a couple of cases where the locating pin for the advance plate was missing and that did create a lot of misfiring for obvious reasons.

So, might be a good opportunity to list the main causes of a PAMCO failure:

1. Bad voltage regulator. Especially the old relay type that can fail and cause the alternator to produce a very high voltage.
2. Bad contacts on the kill switch or ignition switch. The kill switch especially may have not have had its contacts cleaned since the bike left the factory 40 years ago.
3. Binding advance rod bushings, especially with the later '80 to '83 models that did not have the bushings from the factory. Pressing them in by hand can result in them being cock eyed and binding the rod.
4. Missing locating pin for the advancer. This usually happens with a new advancer.
5. Plug wires not making contact with the coil internally. Do a resistance check from cap to cap to ensure all is making contact. The Ultimate coil will actually jump a 1" gap, so you can have plug wires that are not connected to anything and the coil will produce enough voltage to jump the gap, but you will get a very poor spark that could result in poor starting backfiring, missing etc.
6. Bad spark plugs. It's amazing how a badly fouled plug can really screw with your mind. I had one the other day on my CB450 with a PAMCO and I just about had the whole ignition system torn apart because I was not getting any action on my strobe light. Finally, I just changed the plug on the offending cylinder and the lights came back on.
7. Bad plug wires and plug caps. The plug caps especially self destruct over time. Just replace them, or start with new ones when you install your PAMCO.

So, I hate to admit this, but in many cases people buy a PAMCO because their stock ignition system has some of the problems listed above. After they install the PAMCO,they still have the problem, so check these items first before you decide to replace your stock ignition. (What? What did I just say? Huh?.... )

 

[motor650b]

So, I hate to admit this, but in many cases people buy a PAMCO because their stock ignition system has some of the problems listed above. After they install the PAMCO,they still have the problem, so check these items first before you decide to replace your stock ignition. (What? What did I just say? Huh?.... )

That's what I was thinking. My bikes only 37 years old, is there something else wearing out also? My bike backfired before the PAMCO and backfires now also.

Pete, my newly installed EI is great, and I enjoy the minor 'throttle off' backfire.
Another, not as good site (Wikipedia) suggested that some backfiring, or afterfiring through the exhaust system, is part of changing the exhaust system which affects gas flow through the system.

Dan

 

[Marvelicious]

Did this ever get resolved? The reason I ask is because I was reading this thread and came up with a scenario that might create the symptoms described.

Bear with me, Pete, what would happen if the unit were missing a weight? Seems that perhaps it could still fire half as often as necessary. Since this is a wasted spark system, one cylinder would see spark when it wanted it and run just fine, only losing the extra spark. The other cylinder would only see spark at the end of the exhaust stroke, perhaps feebly igniting an uncompressed mixture that begins to burn as the intake valves open...

 

[pamcopete]

Marvel....,

Yes, you are correct. With a wasted spark system you still get a spark on both cylinders with a missing magnet but only one of the cylinders is getting the spark at the right time.

 

[Atxrider]

Hey guys,

Dunno what was found on this one and what resolved it but I have a similar issue with mine.

I found that in turning the advanced rod 180º the firing cylinder went from being the right, to now the left.

So I know that both cylinders are getting the right amount of fuel and compression, but something is going on with the ignition.

Sounds exactly like what Marvel was saying. One side will fire and the other will miss it's perfect igniting point, even though both have a fat spark.

I have the 60º dwell with the Pamco and it appears to have all of the magnets.

What else could cause this?

 

[pamcopete]

Hey guys,

Dunno what was found on this one and what resolved it but I have a similar issue with mine.

I found that in turning the advanced rod 180º the firing cylinder went from being the right, to now the left.

So I know that both cylinders are getting the right amount of fuel and compression, but something is going on with the ignition.

Sounds exactly like what Marvel was saying. One side will fire and the other will miss it's perfect igniting point, even though both have a fat spark.

I have the 60º dwell with the Pamco and it appears to have all of the magnets.

What else could cause this?

Could be a weak magnet in the rotor which would have the same effect as a missing magnet. PM your address and I will send you a new one.

 

[Atxrider]

Awesome! Thanks Pete!

I will PM ya here