Spark?

[Nick]

I stalled my bike late last year and couldn't restart it. Got busy with another bike and left it!
I have finally got round to fitting a new head gasket but have no spark at plugs.
I have a friend who has checked there is power to the electronic ignition unit so I have removed the oil pump to check the optical trigger. It has oil in there too.  He feels that it should send a spark if something is placed between the beam,
He feels the only thing to do is change parts to work out what isn't working?

There is no sign of a beam? do these stop can this be renewed?

My bikes been a great starter over the last 7/8 years, any help greatly received ?

[hendred]

Have you tried cleaning the lenses of the light source and photo diode?  Could be covered in oil/dirt.  Do you have a drain pipe from the oil pump area and is it clear?  If it is an original Luminition system new spares are not available.  The latest Luminition parts are not compatible with the system originally fitted to Silks.  Smokey Paul may be able to help as he has acquired a lot of Lumention parts or you may be lucky on eBay - I was. Also check the connector block between the optical trigger and the ignition block.  The system works on very low voltages and any dirt/corrosion in the connector block will stop the unit from working.
The manuals say don't try the trigger in a well lit area, it can give false results.
Hope this helps.

[Nick]

Thanks will try cleaning first and get back to you either way.

[hendred]

I think the beam is infra red so you won't see it.

[hendred]

The Silk handbook has more information on testing the Lumenition system if you have a multimeter.  It's in Section E.  If you don't have the handbook it is in the Downloads area on this site, see Silk mkIi part2.

[Nick]

After 46 years I think its wise to change both unit and trigger.
There are a few units on line but how do I know what model fits, the only markings on the back of my unit are 164877 which doesnt seem like a part number when goggled and all the units look the same.

[hendred]

A new Lumenition system can be fitted but it is not straight foreward.  The control box fits in the same position as the old one but the new optical sensors have a different hole spacing which requires modification of the base plate.  Also the leads come out out on the opposite side of the optical sensor which requires a new hole for them in the casing.  Tony Donnithorne has fitted one to his Silk and he kindly sent me the information on how he did it.  The system he used was a Lumenition PMA 50 which is quite expensive new.  Probably why many have gone down the Boyer Bransden/Pazzon route.  I can send you the fitting details for a new PMA 50 if you want.  Personally I would check out the system you have as detailed in the manual before bining it.  Keeps life simple if all it needs is a good clean of the optical sensor and the connector block.

[Nick]

Very grateful for your time and detailed response.
I will check it first, there are some new old stock examples for sale too.

My bike has always been reasonably good at ticking over in the 8 years I've had it.
But had become erratic on the last few runs and on the last would stall if revs dropped anywhere near tick over.. My friend who has some electrical experience thinks this could indicate the units starting to fail as he feels the advance and retard is electronic and it wasn't working properly prior to failure.


But first step check unit.

[hendred]

The advance and retard is mechanical.  It sits inboard of the optical switch and the "chopper plate".  The Lumenition system acts like a contactless points system with no built-in advance and retard.

[Chris Exelby]

Hi Nick, I had an issue with my Silk earlier this year. At higher revs the engine missed and spluttered, working fine at lower rpm. The issue was the battery voltage which was borderline and at high rpm with the higher currents required the Luminition system struggled. I use one on my MGB and its well known that the module does not work well at low voltages. The static voltage was fine, but under load dropped significantly. A new battery fixed the problem for me.

[Smokey_Paul]

Nick I have spares if you can seen me a picture of the pick up you have ?

[Nick]

Finally -I had a friend check the system today.
He says the voltage from the sensor is not what the manual says but feels it is working.
Wiring out the sensor as per the book still gives no spark- so he feels its the electronic module

[Nick]

[Nick]

there is only a patent number on the back 164877


Anyone know what the original part number is?

[Chris Exelby]

Hi Nick, I found this simple test procedure. I have been using the Luminition system for many years and have yet to have a module fail on me. Might just be worth checking once more:-

''To test a Lumenition module (Optronic), unplug the distributor connector, then short the blue and black wires at the module's plug to produce a spark at the HT lead (if none, module/coil suspect). For the optical sensor, block the light beam in the distributor with black card to see if it creates a spark; if not, test the sensor's voltage (around 7.5V on blue/black with beam open, drops to 1V when blocked). Always ensure good earth, 12V power, and handle HT leads carefully.''

[hendred]

I think the voltages given by Chris are for the later Lumention systems.  The ignition section in the handbook for the voltages on the original system fitted to Silks.  They are much lower but the test procedure is the same.  Any corrosion on the contacts in the connector can cause problems due to the low voltages.
This is an obvious one but it caught me out, are the spade connectors at the coils making good contact?  The wiring is a bit tight in that area on my bike.