robtg wrote:Path of least resistance may be a clue.
Do you think a dodgy jumper wire connection between the two coils could be the culprit? Would that change how the right coil fires too?
Any resistance in the circuit including the points could lower the voltage/current in the primary and allow one coil over the other to fire. That is what I have observed, or as least what I thought it was, Or it just smoke leaks from the wires.
Garnet wrote:I agree with all your theory Ken. I also agree with your other secert thought about 2 12V coils in parallel should work like 2 6V coils in series. But they don't, and I can't tell you why.
I think that I am ready to put this problem to bed and draw some conclusions.
Tonight, I took the bike for a ride and adjusted the carburetors. In doing so, I realized that there is a problem there too, but it is not related to the initial problem.
The right side carburetor idle speed cannot be brought down low enough to bring the bike to a normal idle speed. If the other side is adjusted to balance out this carburetor, then the bike idles at over 2k rpms. So, one can basically shut the air intake (butterfly) down on the left side and the bike idles at about normal speed, a little out of balance. The left is still working, but not as hard as the right. It is subtle enough that you can almost believe that it is normal. But you can also pull the left side ignition lead and the bike continues to run on the right side. My conclusion here is that the right side butterfly is not closing far enough to adjust the idle down. I imagine the left carburetor is fine.
Other than an out of balance idle (slight side to side motion), the bike pulls and runs great.
Once at this stage, I decided to put the original (suspect) coils back in. I went for a ride and confirmed that they are working fine.
I then reinstalled the original ignition leads and suddenly the bike idled very poorly and missed at all rpms.
So here is my conclusion:
1. The coils were fine
2. The ignition leads were bad
3. There may have been a grounding issue
4. The right side carburetor is letting too much air in at idle.
For those of you who may not have read all of my steps, you may not understand why I suspect that there was a grounding issue. I had previously solved the stuttering left side ignition by swapping out both coils for some good used ones. In my latest test, I also found out that the original coils were actually good. So the only thing that I had done was to disturb their mounting, improving their connection to their bracket/frame. I also followed this by adding a grounding wire from battery to coil mount to diode board. This insured that the frame had a good ground.
The carburetor repair will have to wait for another day, as I have other projects to tend to.
Thanks again
Last edited by Frog on Mon Feb 07, 2011 12:38 pm, edited 1 time in total.
It was the "other" possibility that we considered at the end of the evening. By swapping out the coil and finding it fixed, we discussed if it was the coil or the grounding. That is why I suggested putting the "bad" coil back in to check it out.
I nearly always had to perform that test to confirm that I had really found it. Too many times those slight possibilities came back to bite me in the A$$.
Still, I think it a good idea to replace those coils.
My tinkering with the carbs wasn't really possible until the ignition issue was first solved. I too was noticing that it didn't appear that the right side responded correctly. I would check the idle jet and expect to find it partially plugged up. It certainly could be the butterfly.
Many owners are riding bikes that run no better than what I found when we started. Frog is just very particular and insists on things being perfect. I highly appreciate that attitude. In my day, it was very few that even knew the difference, or cared.
I do plan to be working in your area again next week. I would enjoy spending some more time on the bike. From memory, I think that it will be Thursday and Friday. I will know later today or tomorrow. Depends upon when I feel like doing up my reports. Maybe I will just take care of household issues. Linda is gone for 10 days and this is a good time to work on "her list." The list of things to not do.
By the by, you should see just how big of a wrinkle is in one coil from the mounting strap. They all do some of it, but this one is one of the more squeezed up coils. It doesn't seem to damage them though.
Ask the Indians what happens when you don't control immigration.
I must now go down and check how I have mounted the coils on my conversion. I have a Boyer ignition and a pair of the above coils. When I installed them last summer, they where completly isloated from ground, mounted to a clamp around the battery, but I think that I ran a ground wire to them, I don't remeber. I ran the bike on points first, then installed the Boyer, an it ran great In both cases.
This winter I moved the coils to a better looking place under the seat. This time I am sure I left out the ground wire, and I am sure that the mounting bracket is isolated from ground, and it runs fine.
Now I must go and find out what's up. I, like Ken, love these discussions.
I do agree that it would be wise to replace these coils as preventative care. The carburetors also need some attention to get the idle right.
But, I am not the owner of the bike and was just there to do the frame swap. I could not give it back to him without it running at least as well as it did when I got it.
I will recommend that he replace the coils in the near future and find some good used carbs for the parts that his will need.
But his bike is ready for some riding enjoyment.
Thanks Duane, I look forward to our next visit. I will surely have another project in the works, but not that same bike.
I am glad you have a resolution for your customer.
Sorry to further hyjack your thread, but hey, that's what we do around here.
I just checked out my conversion and the coils are deninatly NOT grounded. I have only had it running for about 5 min while I checked the timming, so I'm not sure what will happen when it get's hot, but the bike ran nice and settled down to a smooth idle and had good throttle response. That does not tell me what will happen under laod.
I sure wish I could remeber if I had a ground wire on them last fall.
The can of the coil does not need to be grounded. It is not internally connected (check it yourself if you don't believe me... you only need an ohmeter) and grounding it will make no difference whatsoever. If you need any further evidence, just look at all of the car applications where the coil was rubber mounted. There are coils made for use in CD type ignition systems that are grounded but these will not work with standard 'Kettering' type systems... especially if the can is grounded.
The can of the coil does not need to be grounded. It is not internally connected (check it yourself if you don't believe me... you only need an ohmeter) and grounding it will make no difference whatsoever. If you need any further evidence, just look at all of the car applications where the coil was rubber mounted. There are coils made for use in CD type ignition systems that are grounded but these will not work with standard 'Kettering' type systems... especially if the can is grounded.
Rob
Thank you Rob.
Well then, I am not sure when swapping out the coils helped. Maybe his old coils are acting up intermittently.
PS-I edited my conclusion post a bit...as I don't want the next guy to be misled by my conclusions.
