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Lucas K2FC magneto trouble help

9416 Views 17 Replies 9 Participants Last post by  Tony the torch
This is not a call for help, but rather a tech tip that may help you with your K2Fc magneto if you are having trouble with a poor/no run condition. The time this happened to me, it was on a fresh build, complete motor build, complete mag rebuild. And the bike ran like a champ for two weeks before this issue reared its ugly head.

Backfiring out exhaust, stalling out, and eventually a "no-run" condition, only occasional firing of either cylinder. It was much like having very fouled plugs, and having the kill switch "on".

Upon further trouble shooting, it began to run, but only with the cap off (even without the kill wire connected).

The issue turned out to be a slightly loose (not rattling loose, just not completely cranked down) center stud. After tightening the stud, it ran like a champ again, instantly.

I hope this info helps another one of us fools who are addicted to old British iron.

Cheers, Dan.

This is not the mag in question, but it is a K2FC...
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Yep. it's often the intermittent problems that are the toughest ones to solve, and this one was pretty random. BTW, since you are too American for those Lucas mags, you can ship 'em all to me. It's my way of helping you maintain your high level of American-ness :D You're welcome!;)

I'll have to get all these Lucas mags out of the drawer where I throw them to see if that stud is loose! hahaha

Good tip, that's one of those things that could drive a guy nuts.

Clay Rathburn; Too American for Lucas Products since June 7 1974.
Thanks Tony! That makes perfect sense.

More magneto tips....
On all mags (Hunt, Lucas or BT&H) we use a buzz box to set the static timing for an initial setting point, but we always check that static timing setting by clamping the spark plugs to the cylinder fins and kicking the engine over with the timing light pointed to a degree wheel.
make sure you have the advance unit locked in full advance,
If you don't verify where where it's firing this way at you are just assuming the timing is ok.

Many times on Lucas mags you will get a different firing point and point gap on each cylinder and it is necessary to "tap" that center bolt sideways to correct the centering point and thus correcting the gap and each firing point.
Yep, the product mentioned above definitely works. See this thread for more info on the EasyCap
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