Lucas K2FC magneto trouble help

9419 Views 17 Replies 9 Participants Last post by Tony the torch, Feb 3, 2013

supercrouton

Discussion Starter · Jun 6, 2012

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.

Symptoms:
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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Mr.Pete

· #8 · Jun 7, 2012

Tony the torch said:
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.

Tapping the centrebolt will only change the radius of the points heel,and it will make the same change on both cam lobes.The gap will increase or decrease the same amount on both lobes.
It will not correct any differences in points gap or timing.
You need to move the cam lobes to correct timing difference.The easiest way is fit a shim on one side,between the cam housing and main body.Even a 0.003" shim can make a big change to timing differences.

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Mr.Pete

· #10 · Jun 7, 2012

Ducbsa said:
Do you mean that you wedge a shim between the OD of the cam ring and the bore it fits in?

No,don't try to shim the OD of the cam ring.
Put the shim into the faces between the cam housing and main body.It will tip the cam ring slightly on an angle (or straighten it up,if it was at an angle).If you put the shim near the cam lobe with less point-gap,the gap will increase and the timing changes.

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