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Interesting Solution for Miss
I've been pushed to the edge of insanity and back by this intermittent miss. I am fairly certain that I've finally licked it.
Symptoms:
Number three runs well from startup until startup+five minutes.
Number three becomes a dead miss five minutes after startup.
Miss may disappear intermittently during riding; no known correlation to driving conditions.
Actions taken:
Sync'd carbs.
Replaced plugs with one range hotter.
Cleaned carbs.
Removed petcock and checked for obstructions in tank and at screens.
Cleaned duck-filter at carbs.
Installed aux. fuel filter between carbs and tank.
Cleaned carbs again.
Re-set float height to 14-15mm.
Metered out all coils, spark wires, and associated wiring.
Metered out ignition pickup.
Igniter swap with used spare.
Igniter harness disassembly.
The carbs were clean as a whistle. My tank and petcock were also clean. The floats were set to about 17-18mm. I set them to 14-15mm. I also never realized that the carb vent tubes need to be routed in such a way as to prevent kinks.
I discovered that my #1 and #2 spark leads were running at 5K Ohms. #3 measured 8M Ohms. Yes, that's 8 million Ohms. I ordered some replacement Nology leads. Triumph wanted ~120 for one wire. Nology sold me three very fancy wires for about the same. They were plug and play with my existing Nology coils. The new wires were all the same length and caused me mild grief trying to route them. Luckily, the tank hides the mess.
I thought the absurdly high resistance lead was my issue. After replacing the leads, #3 still dropped out.
I did the usual musical coil dance and metered them. I found nothing of interest. The pickup metered good ( 600Ohms ) cold and hot. The low side of all coils also measured good ( 0.6Ohms ). The harness between the coils and igniter metered good for resistance; plenty of continuity.
I started jostling the harness around while the miss was present. It wasn't until I started jostling the igniter modular connector that the miss disappeared. I hooked up a spare lead to #3 and a plug. Sure enough, I was loosing spark. I was able to correlate the absence and reappearance of spark with my jostling of the igniter connector.
I disassembled the connector. The white face place pops off if you wedge your finger nail under it. The terminals are held in place by small plastic clips directly above them. I used a set of tweezers from my swiss army knife to push the little clips up. Just ram it in the hole and apply gentle pressure. I then pushed the terminal back into the plug with a small screw driver. This allowed me to remove the connector completely and inspect the terminals. Remember to jot down your pin out before disassembly.
I then, one by one, wired up my spare igniter to the dangling leads. I noticed several of the terminals were EXTREMELY loose after plugging them into the igniter. I gently crushed each terminal with my swiss knife. This put much more pressure between the terminal socket and the male pin on the igniter.
I reassembled the connector and went for a 30 mile shake down run. No issues so far. The miss was reproducible every time while the bike was stationary. Thirty-miles without an issue is a good indicator that I've probably fixed it.
However, I don't want to announce success prematurely. If the miss doesn't reappear in about a week, I'll know for sure I've fixed it. I'll keep you apprised.
--Avatar
PS - In addition to the igniter plug, I found a duff spark lead, crap in the duck-filter, kinked carb vent tubes, and incorrect float heights. I am amazed with how nicely this bike runs now. I suppose there's no substitute for tender love and care.
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