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mostlyxs
10-17-2017, 09:50 AM
Spark intermittent, not dependable, OK one day, won't start the next, thus I began investigation:
My YTM225 and YFM225 both have the plug wire molded into the coil itself, and entering the slip-on spark plug connector as if possibly molded into place.
Inside, the clip that attaches to the plug electrode is contained in a brass segment that is slotted, and was found to be loose. I carefully removed it using
big screwdriver, to find a 1/2" long segment of 1/8" solid wire, with a spring beneath it, slightly compressed when everything is snugged up.
I suspect this junction is inconsistent, and I cannot determine how the wire is so tightly bound to the plug connector, nor how the electrical connection is actually made.
I recently saw a picture of a coil offered for sale that had the plug connector unattached, presumably to allow buyer to cut long plug wire to proper length for the
application, so I suspect it is NOT molded in place.
I have confirmed everything up to the plug is working, proper resistance, etc.. Have swapped out coil assemblies with success, only to again experience issues.
One used assembly was received without the spring or wire segment inside, and when I ohmed out the secondary, using a long scribe, it checked OK, but there
was no connection to the plug clip. I made the missing parts, and it functioned well on a third machine.
It is frustrating when one is forced to use all these old parts, that some previous owner jimmied with, reassembled improperly, forgot their issue, then sold on-line.
If you can shed some light on how Yamaha designed these parts to interface, I sure could use the help. Right now, I can't trust either machine to get me back home!
I have this dream of stumbling upon an unused YTM225 in the back of a local dairyman's barn, that was a spare, never having fuel poured into the tank!
Thanks in advance,
John

YamaBoss
10-19-2017, 12:26 PM
If your having problems with used coils just buy a new one and you won’t have issues again.

mostlyxs
10-19-2017, 12:41 PM
Thanks!
The last new coil assembly I bought had an open secondary. While I wait for another, I decided to dis-assemble an old one. I find the plug connector
is NOT molded on, but after removing the weather cap on the wire end, you can unscrew the connector from the wire. It has a molded in screw that
threads into the core of the wire. I cut 1/2" off the wire, reassembled the connector and cap, and was back in business. Moisture had entered that
connection and corrosion interrupted the circuit. If at first you don't succeed .........
John