Matchless lives again

Replacement mag bolted straight on. Only difference was setting the timing up. On my original NR1 competition mag it was pull lever inwards to retard the ignition i.e fully advanced is on a slack cable. But on this replacement N1 mag its pull lever in to advance i.e fully advanced on tight cable. A fairly critical difference to consider when setting the ignition timing up you would agree!!

Started second kick and ticked over ok, however what is that smoke I see - ht lead touching the exhaust and burning through so not exactly a trouble free exercise - next job replacing ht lead and routing it away from hot things!

 

My mag is now with Armoto near Chesterfield who are going to repair and return within 10 days.

It's definitely goosed

Rigged up this Heath Robinson arrangement to confirm what I already know - primary winding and/or capacitor failed open circuit. Good news is that Kev from Boston has a spare N1 mag that he's willing to lend me whilst mine away getting refurbished.

The spark has gone......

.......from the Matchless ignition system.
The magneto is poorly I think. Went to take it out for a spin and it wouldn't start. Fuel checked o.k,
points checked and opening/closing o.k. Spark plug out and no spark. Changed the HT lead then the spark plug and still no spark. Pick up brush checked and o.k but the slip ring and the brush are covered in oil/grease.
Off with the mag for a closer look. Mag drive cover off and its packed with grease - chain o.k etc but you touch anything and you're covered in it. Drive sprocket tight and resorted to small two leg puller.
Then the front mounting bolt is seized in its spacer so patience, WD40 and jiggling instead of battering it with a drift - 45 minutes later its free and the mag is off.

All greased up

 

Off at last

 The magneto is a 1952 Lucas model NR1 42179 - a competition type. Rang around a few repairers and they were all stacked out with work for up to 6 weeks or more!!

 

Decide to strip it down to check what I could - Earth brush, contact breaker assembly, HT winding continuity, LT continuity, bearing insulation, and also to clean everything up whilst its in bits. The condenser which is the favourite culprit for failure is buried in the armature.

No safety gap screw fitted so its simply a matter of undoing the screws securing the contact breaker housing to the magneto body and pulling the armature out.

 

The bearings feel o.k, but the insulating washers on the bearings are totally goosed, plus the presence of oil/grease means the drive end shaft seal is not too good either. The capacitors don't look original - certainly not 1952 vintage plus theres a pair of them instead of one so I reckon its already had  a 'condensectomy' in the past.

 

Brightspark Magnetos has info on checking, troubleshooting and maintaining magnetos . Checked the HT winding continuity between the slip ring and the armature shaft and its 6300 ohms which is acceptable. The LT circuit measured across the contact breaker points with them open was 0.6 ohms, again o.k.

 

The windings appear ok, so I'll change the insulating washers, brushes and oil seal and if it works, it works otherwise its off to Dave Lindsley for him to sort it.

Drive end outer race & insulating washer

Contact breaker end outer race & remains of insulating washer



NR1 magneto in 'kit form'