40 minus will not start

[High tide drifter]

Hi all
I recently acquired a 40 minus non runner.
It had compression so I figured it might run.
I have managed to get her sparking . I also cleaned the carb and petrol tank. Put some new fuel in but can't get her to fire up. I did pour a little 2 stroke in the plug hole and air intake to oil the piston. Also tried some easy start all to no avail. Any ideas would be appreciated thanks.

[Charles uk]

Post the full engine number, from the bottom of the crankcase, so we know exactly what you've got.

[High tide drifter]

Hi sorry I didn't put it in yhe original post
SJM 830 C6

[Journeyman]

You seem to have covered all the usual things you need to do to get them running.
Some times you will get a spark when you try with the plug in the open.
But the spark will fail when the plug is under compression in the cylinder.
This is because compressed air has a higher resistence and the spark will find the easiest way to earth.
So if you have a faulty HT lead or cap the spark will find it’s way to earth before reaching the plug.
Also a faulty plug can short to earth internally rather than arcing across the electrodes.

Dave.

[High tide drifter]

Thanks Dave
I will try changing the HT lead

[High tide drifter]

Hi Dave
Sound advice I replaced the ht lead and sure enough she fired up for me. Very pleased indeed.
Thanks again for taking the time to share your knowledge.
Regards

[Journeyman]

Glad it worked out for you, always feels good when they come to life, sort of a hint of adventures to come.

What part of Ireland are you from, I know the Irish cost quite well?

Dave.

[african imp]

Hi all
I recently acquired a 40 minus non runner.
It had compression so I figured it might run.
I have managed to get her sparking . I also cleaned the carb and petrol tank. Put some new fuel in but can't get her to fire up. I did pour a little 2 stroke in the plug hole and air intake to oil the piston. Also tried some easy start all to no avail. Any ideas would be appreciated thanks.

I had the same problem on a forty series and gave up trying to get it to run.

A couple of years later I tried once more, same story, this time I changed the plug and the HT lead, no change, then I cranked the motor over with the spark plug removed and grounded, the spark would start then as soon as some speed on the flywheel got going, the spark at the plug stopped.

I removed the flywheel and changed the Wipac2 coil and the motor ran perfectly after that

[Pinger]

But the spark will fail when the plug is under compression in the cylinder.
This is because compressed air has a higher resistence and the spark will find the easiest way to earth.
.

Cheers!
I always understood it but resorted to a 'harder to introduce a spark in the higher pressure environment' analogy. Nice to have the proper technical explanation.

[Raya]

The compressed air resistance theory sounds good but is not quiet right. In reality, the resistance of air is so high, it is practicaly infinite. The spark plug works because of the dielectric property of air called the breakdown voltage. This is the voltage at which an electric arc will start. This voltage is a function of both the pressure and the distance between the two arc points. This relationship was investigated by Friedrich Pashen in 1889 who tabulated the relationship between breakdown voltage and pressure for various gases. Look up Paschen's law if you want to explore this further.

So what is happening with the seagull in this case, is that the voltage being produced is suffient to reach the breakdown voltage at atmospheric pressure but insufficent to reach it at higher pressures.

[Charles uk]

Seagull coils in good condition, depending on the ignition type, produce between 13,000 & 20,000 volts.

Thanks Raya

[Journeyman]

Back in the day if you had a National Licence a lot of manufacturers would service their components for free, this included Lodge. Toward the end of the season you could hand your plugs to a Rep or send your plugs to them.
They removed the side electrode, cleaned the plug fitted a new electrode and then tested them. This included testing the resistance and then testing the plug under pressure. Any plugs that passed the test would be returned with new washers.
When I asked the Rep at one of the meetings why they tested them under pressure he told me the resistance was higher under pressure and as the spark would take the easiest route to earth a defective plug would be shown up when the spark tracked to earth internally. The tester had all the voltage necessary the pressure just showed up the defective plug insulation?

[High tide drifter]

Glad it worked out for you, always feels good when they come to life, sort of a hint of adventures to come.

What part of Ireland are you from, I know the Irish cost quite well?

Dave.

Hi Dave
Sorry for the delayed response to your question
I live in County Kilkenny on the banks of the river suir above Waterford city.

[Journeyman]

Hi Dave
Sorry for the delayed response to your question
I live in County Kilkenny on the banks of the river suir above Waterford city.

Hi yes, sounds like a great area to explore with a Seagull how far up the rivers are you allowed to go with a boat? Passage East is the furthest I’ve been, have always meant to get up to Waterford, some day.
Dunmore East is a regular port very convenient when sailing from South West Wales, though the Kittiwakes can be very noisy in there.
Dave.

[High tide drifter]

Hi Dave
it is possible to navigate up river as far as Carrick on Suir.Tidal waters reach as far as the wear in Carrick.
It is possible to reach Clonmel from above the wear.
The river rises in a place called the Devil's bit in Tipperary. Most of my enjoyment is taken from the waters between Waterford and Carrick
Regards