K2F POINTS GAP

[robin rose]

Can some one let me know the points gap for a K2F mag as I am about to have my first ever dealings with one, points look burnt and are at about .008". I assume everything comes out on the brass carrier when you take the centre bolt out and that it is indexed into position somehow. cheers Rob.

[pete.collings]

The brass points carrier has a protruding spur that engages with the slot in the armature. It is a common problem for the protruding part to be damaged or break off (trying to refit without aligning with armature slot!). This will allow the timing to slip.
The points gap is around 12 thou, but this can vary between cylinders dependent on how worn the slip ring is. Buying a new one does not necessarly solve the problem, I have found a new one worse than an original worn one!
When rebuilding a K2F, I used a home made degree disc and pointer to check the difference in points opening position, if it was 2 degrees or less, the motor usually ran OK. I have found a new camring with 5 degrees difference. Remember this will double with actual crankshaft rotation. It is possible to carefully grind the cam by hand (I used a round emerystone) to even up the opening point, competition motors usually had this done to improve performance.
Another problem can be a big difference in points gap between the opposing ramps, if the bearing end housing has worn due to a bearing working loose and spinning the insulating washer. I have previously rectified this by shimming under the bottom of the bearing outer to raise the height of the armature, an old feeler gauge is good for this if you don't have any shim material.
A later (cheaper?) type of points block used non brass and a points setup similar to that used for coil ignition bikes, setting the gap by an eccentric on the points base plate.
If replacing the points in a brass backplate, the screws are fine pitch and easy to damage, especially the one into the points themselves (which can corrode in place), it is also easy to loose the screws when refitting into the spring hole, one slip and they fly into distant parts of the workshop! Modern replacement points are designed for either clockwise or anticlock fitting, don't loose the small plastic pip that fit on top of the points arm and is secured by the swiveling spring retaing arm.
In general, take great care in dismantling and reassembling the points assembly, they are easily damaged and expensive to repair/replace.

[robin rose]

Thanks Pete for your response. The plastic pip you mention appears not to be in place, is it an insulation feature?

[pete.collings]

The plastic pip is to hold the points heel assembly in place on the mounting pin, and prevent it moving upwards and downwards.
It can easily get lost if the spring retaining arm is moved away from the points, and usually the bike will still run with it missing. Although not vital, it helps keep the two points faces in alignment, and as far as I am aware doesn't provide any insulation. The main insulation is between the central tower section (where the tapered securing screw fits) and the base of the block, but this should not need to be disturbed unless there is an obvious problem. There is also an earthing brush that fits in the recess on the back face of the block, and runs against the alloy of the magneto end plate. The bike will still run without this, but presumably it earths through the bearings, something that can cause pitting in the running faces.