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Carnbonized Rotor

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RJS

RJS

Jedi Warrior
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Hey All,

I started noticing a miss or stumble in the engine when pulling away from a stop sign. A quick inspection turned up a slightly carbonized ignition rotor. I was able to quickly clean it off with a scotch pad and all is well again.

However, just curious if this was a symptom of some other malady? I've never had this issue in 11 years. I should note the engine has been running cooler this year from what I strongly suspect is a thermostat stuck open - could that be the cause?

Bob
 
It was likely just a bit of an oily finger print left on the rotor. I can't think of any way the temp could have been a player. If you figure out how to make these run cooler I'd like to know!

John
 
Wouldn't hurt to check out the resistance of the plug wires, from the terminal inside the cap to the terminal at the plug. Last time I saw a rotor fail (on a friend's 4A IRS no less), one of his spark plug boots had come apart inside and was allowing the voltage to go way high when firing that cylinder.

Your symptoms don't quite match, but I would check it anyway.
 
Its not likely that that bit of carbon was your real problem. I'd scrape at the inner cap terminals to clean off corrosion, and Ohm the cap/wires as Randall suggested. Remove and visually inspect all LT and HT electrical connections from the coil to the distributor. Measure for 12V at the coil, no less!
 
Thanks guys. I will try your suggested tests this weekend. Perhaps I can take the TR out for a final drive before putting to sleep for the winter.
Bob
 
BTW, when I ohm the cap and wires, what is an acceptable reading?

I'll also look to see if one contact in the cap looks different from the others or if they are all consistent. That may tell me if I have a problem with one single wire.

Bob
 
Maybe the center carbon contact worn?

Cheers
Chris
 
RJS said:
BTW, when I ohm the cap and wires, what is an acceptable reading?
Click to expand...

That depends on the type of wires you are using. Resistor wires may measure somewhere between 5000 to 10,000 Ohms depending on length. Wires with metal conductors will typically measure close to zero Ohms.

As a footnote to that, the resistor wires are used with "standard" spark plugs while the metal core wires are typically used with resistor plugs.
 
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