D7 Magneto

is the cam set correctly to open the points? is it the correct points? have the points worn too much? is it the right rotor button?

Hi trainzkid88, thanks for the reply
I will ask the mag man to check your comments on the points, not sure how we would know if the rotor button was correct or not? I will ask him to check if there is a part number stamped on the back.
When I look at the MJK parts book (https://oldcroak.com/mjk-edition-c-d-parts-list/) there only appears to be 1 part # for the ROTOR, distributor RT52154PA and it is the same for both 360 deg and 180 deg versions 

I think (could be wrong) that there are multiple caps that would physically fit the MJK and your hunch might be correct, that the one you currently have is not the correct cap. I know this is the case for Wico so perhaps A-B also had that arrangement.
I just checked the manual you posted and there are at least four different distributor plate part numbers listed (item #71). For your C109 magneto, the part # listed is DP 52471, but first you'd want to confirm that the C109 model is the correct one for your tractor

The 109 is the correct replacement. You may have the wrong cap. 180 deg. uses DP52471, the 360 deg. uses a DP52442.

yes check all the part numbers are correct for the application. bosch,wico and lucas are the 3 most popular brands of mag in the world and there were versions within versions. robert bosch gmbh developed a lot of automotive technology and many companies licenced that tech. and it continues today.

I think (could be wrong) that there are multiple caps that would physically fit the MJK and your hunch might be correct, that the one you currently have is not the correct cap. I know this is the case for Wico so perhaps A-B also had that arrangement.
I just checked the manual you posted and there are at least four different distributor plate part numbers listed (item #71). For your C109 magneto, the part # listed is DP 52471, but first you'd want to confirm that the C109 model is the correct one for your tractor

Hi Perkinsengineer,
The Magneto cap you have pictured is true and correct for the MJK 4/2 180, the lower/centre brush contacts the centre of the rotor and the upper left and right brushes are in the 10 o'clock 2 o'clock arrangement to provide the odd firing of the earlier pilot motor firing pattern. The later even firing pattern on the MJK 4/2 360 magneto on the later engines is obtained by a 10 o'clock 4 o'clock arrangement. Those caps are still available. I hope this helps,
Darren