Refitting magneto

[magnusk750]

I'm refitting the kK2F on my 55 G9 after having it serviced by a specialist in Sweden. Can't get the cable and manual advance -retard to work, and no real info on the subject in manuals and writings, probably too easy... About a year since I took it away from the bike and aither I don't remember how the cable was fitted, or the guy who serviced it has made a mistake somehow.

I think I found the correct slot for the mushrom shaped plunger into the camring, and the camring goes nicely into it's seat, flush with the housing. But, nothing moves. the cable is stuck, moves max1-2 millimeters when I draw the cable end, and the same stuck if I try to push it. The spring is present in the magneto side off the cable.

Is everything that should be there present in the seat for the camring?

Any help appreciated! So little left now before I can try to start the bike.

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[Groily]

The plunger is in the correct slot. If the cable is adjusted properly the cable and plunger will move smoothly when you operate the lever at the 'bars (with the cable detached from the magneto).
I can't see in the 2nd picture, but does the camring have a bigger slot, about 10-11mm wide, at 6 o'clock as you look at it fitted to the magneto? That notch goes over the little stop pin at 6 o'clock in the housing and is what allows the movement. The arc of movement should be about 18° on the camring.
In the first picture, it looks to me as if the cam is maybe positioned a bit too far 'clockwise' in the housing - but it's hard to tell and may be an illusion. If it IS positioned wrongly, then the notch won't be aligned with the pin - but in that case the cam would probably be sitting proud of the housing. The pin is actually an eccentric 'nose' on a screw, which can be adjusted to fine-tune the internal timing of the magneto (the moment at which the points open relative to the position of the armature / magnet). The pin needs to be so positioned that the nose can actually act as a stop - ie it mustn't be turned so far in towards the magneto body that it doesn't engage with the notch in the camring.

If by any chance the camring fitted is one for a magneto designed to run with an auto advance unit, there won't be a wide slot, just a narrow one that registers closely with the stop pin and therefore does not allow movement.
It would be odd if the chap who repaired the magneto fitted the wrong sort of cam, but funny things can happen.

If the camring has the wide slot, it should move if you rotate it back and forth by hand in its housing with the cable disconnected. If it doesn't, there's something jamming it. If it moves freely disconnected from the cable, then the problem is with the cable and / or plunger and / or its adjustment.

If the camring is the wrong type with just a narrow notch, it's not a huge problem as the notch can be ground (carefully and respecting the need only to allow it to retard from its fixed position - metal has to come off one side only of the small notch to avoid the risk of over-advancing).

(Don't omit to put the retaining blade back into position on the opening contact breaker point when all is ready to run!)

[magnusk750]

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The slot at 6 o clock is a little more than 3/8 wide, 9,8 mm. I suppose that's the correct one?

[Groily]

Yup, that's fine. 9.8mm is perfectly adequate.
I'm guessing it moves through its small arc if you push it by hand when it's on the housing with the plunger and cable not fitted (as I can't see any reason why it shouldn't) . . . so the issue is probably plunger and cable related.
It can be a fiddle to get the plunger to engage when fitting the camring - and sometimes due to wear, the plunger slips out and jams at full advance or full retard. I suspect that is what might be happening.
Often a change of plunger will cure that (not that there's anything obviously wrong with the one you have got mind you), or it can be controlled by careful cable adjustment so that the plunger is never pulled or pushed so far that it can slide out of its notch.

[magnusk750]

Wit a new cable, a smear of oil, thin, on the outside of the cam ring and some fettling it's now in it's its right position. Sometimes it's great help just when someone basically says: nothing wrong here, just keep fettling. But, when we're at it, I followed the excellent article by John Allen on twin timming, where it's said that with the right hand cylinder on compression phase rotate the magneto armature "until the contact breaker is about to be opening on the bottom ramp of the cam ring." LIke in the photo? (I know it's not important, one can always switch the HT leads, but never hurts to eliminate every possible confusion.) And, is there a better way of keeping the armature in position when tightening the nut on the timing gear than just holding it with my hand?

Tomorrow I'll try to start the bike, if nothing dramatic occurs!

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[Duncan]

You probably already know that you need to move the spring arm over the pivot nipple on the side of the points that move, it engages with the indent in the spring arm to locate it, the little nipple can fall out and is a swine to find if it does.

[magnusk750]

I can see it now, but I probably hadn't if you hadn't pointed it out Duncan, thanks.

[Groily]

A very good way to hold an armature still is to remove the earth brush from the flange end (it unscrews) and screw in something of the same thread (it's BSF), preferably with a softish nose or pad between it and the brass armature. (I use a nylon one, or brass in emergency).

It will hold the armature firmly enough not to rotate when you (carefully!) do up the pinion nut (having not omitted to put that blade retaining clip back in place!). You don't want to screw it in hard - just enough to prevent movement for that all-important moment when you seat the gear on its taper.
This is a far better way than holding the armature by the points centre screw with a socket.

Bottom ramp 'like in the photo' - Yes. The lower lobe of the camring fires the REAR pick up, the gearbox side one.

If you are being very picky, you might want to check the timing on BOTH cylinders; to see that the points open near-enough the same, in relation to the pistons, on both sides. WIth luck (and a rebuilt mag), it could be perfect - or, with used parts, less than. In which case you could split the difference when setting the timing. Usually, with a manual camring and used parts there'll be a difference of a couple of degrees, but if it's much more, then it can be a problem for smooth running. (1° error on the magneto = 2° on the crankshaft . . .)

[clive]

My thought was that the cable adjuster is turned fully home, meaning a long amount of it is inside the housing. Could this be what is preventing the plunger from moving? I have a faint recollection of running into this some time.

[magnusk750]

It's been running! For like ten seconds, several times... I think it doesn't get fuel after running for a few seconds. For the moment it's got a period Monobloc. I have a brand new Wassell Concentric knock off, will try that one.