40 plus Magneto

[Hugz]

hi, Picked up a '61 40plus (SJP) and pulled off the flywheel cover to give the points a once over and found the key floating around inside... that's no problem as I have removed the flywheel and reinserted but what does cause me concern is the magneto base plate moves around. I can see a screw in the side which tightens it up but how do you know what position the base plate should be? Does the screw locate into fixed slot? (it doesn't seem to) If it doesn't then presumably we can alter the timing.

Apart from that she seems to have had very little use.

Cheers Hugo

[charlesp]

Timing is fixed on these. If you pull the baseplate off you'll see a dimple drilled into the crankcase - that's where the screw should locate. When that's all done up tight the baseplate can't move.

Good luck

[Hugz]

Excellent, I assumed that was the case. Be interesting to move it around under various loads to see if there is much change in performance. Did I read somewhere that you can change the timing on the Marstons?

Thanks.

[charlesp]

Some of the Marstons - those designated 'Special' - did indeed have an advance /retard lever. It didn't later the timing by very much, but I'm sure it helped at low revs, for instance.

[Hugz]

This little lady is turning out to be a stubborn one! I have a nice juicy spark, excellent compression and the plug is fuel damp. She hasn't fired once! Still not 100% sure that I've got the flywheel plate in the right position. This dimple seems hard to locate. Tried quite a few different positions. Looking at my other seagulls the location screw seems to line up with the centre of the carby head.

Never fear I shall persevere.

Hugo.

[charlesp]

Whip the flywheel off, and remove the baseplate - then you'll see the dimple.

[Hugz]

Aaaha! here is something a little unusual. Whilst positioning the piston at it's lowest point I noticed that this is the position that the points close. I'm assuming that this when it energizes the spark plug. A spark at this time is definately not going motivate 'missy' into life!

Something has got to be 180% out.

Anyone know what % btdc this should be? Its a villiers magneto. My century (that runs like a dream) seems to be about 25% which surprised me.

[charlesp]

Ignition timing is at 23 1/2 degrees - and as many on this board will confirm that's not critical. In fact there are numerous examples that are way out..

If you don't have a protractor, then fold a bit of paper on one corner, that'll give you 45 degrees. Fold again and you have 22 1/2. Perfect.

The ONLY way that this can be 'wrongly timed' - assuming the screw is in the dimple - is if you've got a Century crankshaft by mistake!

Let us know...

[Hugz]

Yaaaay!!!

Had to wait for my primary girlfriend to come and cook me dinner... we are 180% below tdc downunder <grin> and with her help just lifted the flywheel off and sure enough the dimple (bluudy big hole actually!) was 135% away from where I was expecting..... directly at the front of the motor unlike 102's and Centuries. It confused me as the Ht lead was positioned to go around the port side when it should have been starboard.

Bet this frustrated the previous owner!

I'll fire her up in the morning.

Hugo

[Vic]

Had to wait for my primary girlfriend ............. I'll fire her up in the morning.

[charlesp]

Primary girlfriend - love it!!!

So much better than 'Significant Other'

[Hugz]

A little frustration setting in... Well for the seagull anyway <wink>. She still won't fire up. I'm pretty convinced the electrics are ok. Good spark, new plug. Points cleaned and set at 20thou, also plug. Pulled carby apart and cleaned. All jets are clear, Centre piece was a little hard to remove and reinsert, changed fuel... no water, looks good..

Had a couple of backfires and that was it. Put a bit of juice straight into spark plug entry but still no sign of life. At this stage I'm confused.

I might need to take the head/barrel off and a have a look/see.

I tried it in water and out... no luck.

Thanks Charles for your support on this.

Hugo.

[Hugz]

Next edition... this is like an online maintenance course! I've separated the cylinder from the crankcase and all looks in order in fact there is hardly any carbon deposit on the piston at all. I'm getting the suspicion that someone has been here before me as it fell apart far too easily. As the forty plus only has two studs holding the cylinder in place it strikes me that it is critical that this seals properly. There is no evindence of gasket sealant (the gasket came off intact.. surprise surprise) so I'm thinking that maybe it was sucking in air here.

I'll seal her up and fire her up tomorrow. (deja-vu?)

Never say die!

Hugo.

ps How much should I expect to pay for a pair of century piston rings?

Got to go, secondary girlfriend is on her way!

[Hugz]

Success!! Purring like a little kitten. She didn't go at first so it was back to the drawing board. I was checking the points again and noticed there was a little bit of movement with the magneto base plate which was causing a fluctuation in the points gap. I solved this by using a strip of adhesive copper foil and wrapping it half around the casing that the plate slides onto creating a tight fit. It worked a treat but whether it can take the gruelling punishment this little missy was designed for only time will tell.

I've got the odd drip of fuel so I'll make some washers from kangaroo hide to give it an aussie flavour.

Hugo.

[charlesp]

Glad to see her running.

Kangaroo hide, now that's one I've never thought of...