variable timing

[IanA]

I have a 1975 widecase 350, fitted with standard motoplat ignition.
When i first got the bike it started and ran a treat but a few months ago the fibre timing gear shattered. (Yes, i know this probably means its a Spanish engine) and i sourced a metal replacement from Spain.
On first assembly all is good, the timing dots line up, the bike starts easily, but eventually seems to stall. it will then refuse to restart or backfires/kicks back so badly that it sprung the circlip off the swivel head of the kickstarter and shot the head onto my lovely paintwork, chipping it!!

On inspection, if i reset everything with the dots aligned, it looks good but after a few revolutions the dots no longer align and it takes 20-30 (sorry havent counted exact number) revolutions before the dots once again align, so depending where the engine stops decides what the timing is for restarting, hence my kick back issues. I believe. To get it to start after it stops, i have to re-adjust the timing stator, so something is moving somewhere.

I'm assuming the shattered timing gear has something to do with it but the replacement was an exact match. It's driving me to despair, especially as the warmer weather is approaching and want to use this bike regularly. Would convert to Electrexworld via Lacey's but it takes it ignition signal off the same timing shaft and i fear i need to solve this issue first before investing.

[Duccout]

Hi Ian,

The dots not lining up after rotating the engine is normal, it is due to the hunting tooth principle. I'm guessing that something is able to move out of adjustment in your Motoplat ignition. Any ideas anyone?

Colin

[IanA]

well of course!!
Today she is starting and running like a kitten, first kick every kick after it is partially warm, using the indicator timing is pretty smack on the dot on the crankcase. Ahhhhhhhhh!!!!! Thanks Colin, i did try a different search and found a thread about the dots only aligning every 10th cycle.

Think you are right Colin. I was going to fit the electrexworld combined ignition and alternator, and they have just come back in stock, but didn't want to until i was happy timing gear etc was correct. Perhaps this is the right course of action now she is playing ball, as it may be a Motoplat issue, the bike stood for over 10 years and electronically the timing is moving, alas i don't have a strobe to try.

i will spend the rest of the week, periodically starting to see if it has finally settled, before investing £400.

Any further views greatly appreciated. Cheers Ian

[Duccout]

Hi Ian,

I am no expert, but I don't think that the Motoplat system was rated very highly when it was new, and now after nearly 50 years it must be suspect. The Electrex World system is easy to fit and time (apart from the difficulty in overcoming the alternator magnets, which try to move the crankshaft. It may be better to adjust the ignition timing with the alternator off, before fitting the new one).

Let us know how you get on.

Colin

[blethermaskite]

I also have a widecase 350 which had motoplat electronic ignition, over time the ignition system produced an ever weaker spark until it just completely died, before it went "phut" I was getting rogue timing issues and kickbacks (sometimes) I replaced it with a period Lucas Rita system which has performed perfectly ever since.
Cheers,
George

[IanA]

Thanks for your responses.
It now starts ok and runs sweetly once started, so im guessing it is a dying motoplat and will invest in the electrexworld system now i know its not a mechanical issue, shattering fibre gear was obviously a red herring.