> My TR3A just started running rough like it was missing. Not being an
> experienced mechanic I thought I would seek some advice on
> how to track down the source of the problem
Could be lots of things. First of course is just a visual inspection for
any obvious problems: dripping fuel, loose wires, etc. Poke the throttle
linkage and check that the rear carb opens too.
If it hasn't had a major tune-up recently, I would probably do that next.
Otherwise, try to identify which cylinder is missing and swap it's spark
plug with another cylinder. If the problem follows the plug, obviously the
plug is bad (even new plugs can sometimes fail).
I would also check the "end to end" resistance of the spark plug wires (from
terminal inside dizzy cap to plug terminal). The value itself isn't
important, only that all of the wires are roughly the same resistance. IOW
if three of them are in the 8K to 12K range, and one is 25K, the 25K one is
probably bad.
A quick mixture test is appropriate too, just lift the "diddle pin" on each
carb and see what the idle rpm does. If it rises a bit and then falls back
to where it was, the mixture is good.
There is more, but that's where I would start.
FWIW, although I would rate it low on the list of likely suspects; last time
this happened to me it turned out to be a failed ignition coil. Crappy
Lucas part only lasted 53 years!
<G>
Randall
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