My previously ultra reliable [well since complete restoration 4 years ago, anyway] 1974, Interstate stranded me a few weeks ago with complete loss of power. It was towed home and, after evaluation, I found that the TriSpark module was faulty. I contacted Colorado Norton
works who very kindly agreed to switch the module for no charge even though it was three and a half years old. Since installing the new module, [statically and dynamically timing it] I'm having a puzzling problem. It is severely misfiring on the left cylinder.
The bike starts easily with both cylinders firing smoothly [for the most part] in idle. As I slowly twist the throttle just off idle, the left cylinder cuts out. If I increase throttle it starts to fire again though with lots of popping and banging in the exhaust. At full throttle both cylinders fire but with intermittent misfiring. Suspecting carb problems (I have twin AMAL Concentrics
, new with the rebuild) I took them both apart and cleaned them in an ultrasonic cleaner, even though they looked pristine. I have also done the following:
1. Measured the needle jets with gauge - perfect
2. Cleaned out the idle passageways with a #78 drill - twice
3. Checked both float bowl heights
4. Both slides move up and down synchronously and smoothly
5. Both choke slides are up and out of the way – i.e. not sticking
6. Swapped the high tension leads left to right - no difference
7. Changed both hypertension leads - no difference
8. Changed spark plugs probably 10 times
9. Added new bullet connectors to the black/yellow and black/white wires in the timing cover. These are heavier gauge marine wires, by the way.
10. I removed and disconnected the ignition switch and checked all connectors and cleaned them.
11. I pulled the handlebar module containing the kill switch apart and cleaned all contacts
12. Checked compression in both cylinders, and show 150 on the right and 147 on the left
I plan to have a jump lead from the battery
directly to the Trispark module. However, I do not understand why only one cylinder should be a problem. The bike also has a hot coil from Colorado Norton
works - could there be some false in this which is causing misfiring on one cylinder only? Any and all help would be greatly received.
Thanks in advance,