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Discussion Starter #1
I've done some searches but am still a bit confused as to how to test both the primary and secondary coil resistance. The Scrambler is a 270 degree, two coil engine. I think I've tested the primary properly - using my meter to the + and - leads into each coil - the reading is 6 ohms. I'm not sure how to test the secondary coil resistance. I have used my meter's probes to touch the + and the coil output (spike?) and get a reading of 2.22K ohms on each coil... Is this the right way to test the secondary coil resistance and what reading should I be getting. I also tried to test the continuity of the spark plug wires - but don't get a reading, perhaps because of some built in resistance, not sure of that. I have checked that the spark plug cap is solidly screwed into the wire, it is.

This bike has begun to miss on one cylinder or the other once the bike is nice and hot. My last two rides - one very short one of 15-20 mi exhibited this miss for a good portion of that ride, the other ride was 50-60 miles and it exhibited the miss in the last few minutes of that ride. The bike seems to start and run fine when cold. I don't want to jump to a conclusion that the coils should be replaced, if, in fact they are ok.

I had earlier replaced the plugs - with the same NGK as were in the bike and that the manual calls for, checked that they were gapped at .9mm, put some antisieze on the threads and put them back in - I think my problems started after I changed the plugs...oh, oh...

thank you,
Tom
 

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You can check the gap on the crank position sensor ("pickup coil"), should be no more than 0.8mm. And you can check the sensor itself, documented in other posts. It's been known to fail when it heats up.

Ignition system problems two years ago with my bike ended up being from a gradually failing ignitor.
 

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I've done some searches but am still a bit confused as to how to test both the primary and secondary coil resistance. The Scrambler is a 270 degree, two coil engine. I think I've tested the primary properly - using my meter to the + and - leads into each coil - the reading is 6 ohms. I'm not sure how to test the secondary coil resistance. I have used my meter's probes to touch the + and the coil output (spike?) and get a reading of 2.22K ohms on each coil... Is this the right way to test the secondary coil resistance and what reading should I be getting. I also tried to test the continuity of the spark plug wires - but don't get a reading, perhaps because of some built in resistance, not sure of that. I have checked that the spark plug cap is solidly screwed into the wire, it is.

This bike has begun to miss on one cylinder or the other once the bike is nice and hot. My last two rides - one very short one of 15-20 mi exhibited this miss for a good portion of that ride, the other ride was 50-60 miles and it exhibited the miss in the last few minutes of that ride. The bike seems to start and run fine when cold. I don't want to jump to a conclusion that the coils should be replaced, if, in fact they are ok.

I had earlier replaced the plugs - with the same NGK as were in the bike and that the manual calls for, checked that they were gapped at .9mm, put some antisieze on the threads and put them back in - I think my problems started after I changed the plugs...oh, oh...

thank you,
Tom
You are checking secondary resistance correctly, primary positive to plug wire ( coil out put) post on the K ohm scale. According to the Haynes manual the reading from the primary + post to the spark plug end of the coil wire should be about 15K-ohms, with 5 ohms of that being in the plug wire. If the plug wires are showing no reading as you say, open circuit, they need replacing before moving on.
 

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The bike seems to start and run fine when cold. I don't want to jump to a conclusion that the coils should be replaced, if, in fact they are ok.
Indeed. Firstly if, as you say, the bike is missing on random cylinders, the likelihood of both coils developing the same fault simultaneously is very slim. The problem therefore is most likely to be from something common to both cylinders.

At this point I would normally advise checking out the pickup coil as these are known for breaking down when hot then working fine when allowed to cool off. Testing the pickup coil involves removal and taking a resistance reading when heated up in boiling water, and since this also requires replacement of the alternator cover gasket, it is quicker and easier just to replace the coil as a process of elimination. Besides, in your case the problem sounds too intermittent to get any definitive answers by testing and the coil is one of the cheaper components in the ignition system.

However, before considering anything else I would advise doing some research on the anti-seize compound that you are using on the plugs. Since your ignition coils are single fire they would require a good ground to the cylinder head via the plug's thread. I'm not saying that the compound is the cause but it may be that when warmed up it achieves a melting point and loses connectivity. Try cleaning the compound off the plugs and head, and running for a while without it. If the problem does not go away then you can start looking at the pickup coil. At least, this won't cost anything to do.
 

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Discussion Starter #6 (Edited)
Thanks for your comments. I've had a dealer check the coil, plug wire, cap and plugs and all are working as they should - I am told. This leaves the pick-up coil and the ECU. I'm told by the dealer that the pick-up coil either works or doesn't work - which I take at face value and that, the then most likely problem is with the ignitor/ECU - and that there is no test procedure or piece of equipment that is able to test this component (which is a bit expensive). Both Haynes and the dealer confirm this. In the states, the OEM part is $360 to replace and is currently on back order (mine is a carb'd '06 Scrambler as I mentioned)...there is an aftermarket ECU available through Triumph Twin Power (UK) - they have companies in the U.S. (BellaCorse, T&J Cycle & others) that sell their product ( a bit less $ than a non-available OEM part).

So, after returning the coils/wires/caps/plugs to their respective places on the bike, the bike runs again as before when cold and I intend to perform a test ride to confirm my original diagnosis of missing on one cylinder before spending the dosh for a new ignitor...and then will then spend it on the TTP aftermarket part. And if after that, it still runs poorly, I will be bummed out and replace the pick-up coil as Ripper told me to do. A bit backasswards, I know. Doh!
 

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Procom also has a replacement ignitor with selectable configurations, including the stock setting. I paid about $260 for mine about two years ago, from Newbonneville.com.
 

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This leaves the pick-up coil and the ECU. I'm told by the dealer that the pick-up coil either works or doesn't work - which I take at face value and that, the then most likely problem is with the igniter/ECU - and that there is no test procedure or piece of equipment that is able to test this component (which is a bit expensive). Both Haynes and the dealer confirm this.
What your dealer told you is incorrect. I have been on this forum for 10 years and seen bad pickup coils spring up on almost a daily basis. Very few of those have just quit suddenly, they normally cause running problems anywhere between a misfire and total loss of ignition. The pickup coil is a well known troublesome item on here, as is the ignition switch, which could also be a contender for the cause of your problem, but the pickup coil is the cheapest item in the ignition system so it makes sense to start there. The coil can be checked out with a meter, but when it is intermittent as your problem is (the engine doesn't actually die), it is easier to just replace it, since removing the original for checking involves taking off the alternator cover and new gasket anyway, so you may as well just renew the coil and eliminate it from your testing. That way you don't lose much if the bike still runs bad after.

If your bike is a carbed model it doesn't have an ECU, these are only on EFI models. Your bike will have an igniter. That should be the very last thing to be tested after all the other components in the system because of the expense. However, there is one check you can do which won't cost anything:

Take off the seat and look at the underside. Are there any rub/scuff marks where the seat pan has been hitting the igniter? This is another common problem with carbed bikes that your dealer will know nothing about. Especially with a passenger, the seat puts pressure on the igniter connector and causes poor connectivity which gets worse over time. This in turn produces running problems. Some on here who have had this problem have solved it by either raising the seat a few millimetres by fitting larger frame rubbers or cutting a hole in the seat pan. Do your homework before pulling the trigger on a new igniter as it could be an expensive mistake.
 

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Discussion Starter #9 (Edited)
Ripper, thanks! Will do! I've been using the terms ECU and igniter interchangeably, never too old to learn. Thanks again...
 

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Discussion Starter #10
Follow-up to my original post...

After my post #6 and the comments of Ripper above, I did the following:
1. Added a bit of hard rubber (about 1/4") to two of the underseat rubber bumpers to provide some additional space for the igniter to clear the seat pan. I did take the bike out for a ride, hoping that, that might make enough of a difference - in my case it did nothing, bike still ran poorly off and on, on one cylinder.
2. I decided to skip changing out the pickup sensor for the moment, although I did place an order for one along with an alternator gasket. While it wasn't on back order, it did ultimately take a couple of weeks to arrive at my dealer.
3. In the meantime, I decided to order a Triumph Twin Power "Fire Starter Performance Ignition Unit", stage 1. Well the U.S. dealer mistakenly sent me one for a 360 degree engine (i.e. T100), so that got returned and then the correct one arrived a week later, yesterday.

I installed the TTP igniter this morning and took the bike out for a little ride. This seems to have corrected the problem that I had. The bike is running smoothly, better than before, very few if any decel pops. I had it up to 70mph and maybe at some points in the ride up to 5K rpm. Seems to have done the trick. So, while I will have a spare pickup sensor that will work either on this '06 Scrambler or my '08 T100 - it will remain as a spare for right now. The new igniter was the ticket that seems to have done the trick for me with this problem.

Thanks to those of you that responded to my original post. And my thanks to A&J Cycle for having the patience to do a return on the TTP igniter for the correct one that would work properly on my bike!
 

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Thanks for closing off this thread, grebmrof, with a happy conclusion!
 

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Unfortunately, the only way to find out that the problem is the failing ignitor is to put in another ignitor and see what happens.

I'm glad that this fixed it for you.
 
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