No spark from Villiers coil

[atoyot]

Well, it sounds like you're on the right road toward getting compression back. About that ignition though - others much more experienced than I, have cautioned that one avoid applying motorbike ignition parts standards & measurements to these marine engines. I'd take their word on it.

Here's a resistance spec for what I think you'd have in a '65 Seagull outboard engine:

4.78 ohms HT lead disc to nut.
4.78 ohms HT lead disc to small screw on coil.
0.2 ohms Nut to small screw on coil. (Points Closed)
1.12 ohms Nut to small screw on coil. (Points Open)

Is your flywheel bronze in color (or it was originally so)?

[one_riff_brian]

It's a grey flywheel- I've seen bronze ones, but it's not one of them. Re: the coil resistances, you domean 4.78 kilohms- don't you? It's a moot point, the HT winding is open circuit, but I checked with an oscilloscope, and I am getting volts out of the LT winding. For now, I'll use a spark from a 12 battery and a Lucas coil to get it moving, but getting a spark from an external coil at a quarter of the price of a Villiers replacement seems like a worthy road to explore.

[atoyot]

My source gave those specs for the Mark-I gray flywheeled ignition systems, not for the Mark-II as I first suggested. That being the case, those specs are correct in this case. My mistake in copying the data from the book for the earlier post. The measurements are in Ohms, not K-ohms.

If it is a Mark-I, it would look like this:

Mark I ignition plate.jpg (30.88 KiB) Viewed 2338 times

If you're getting an open circuit as you describe, then you have an open in the HT windings that doesn't belong there in the Villers ignitions that Seagull commissioned. Let us know how the rebuild goes.


-Ted

[phil]

Actually you will find that the coil secondary reading is K ohms, people often state just ohms, the scale range on the VOM is often disregarded. Consider that the ratio of primary ohms to secondary ohms determines the ratio of primary volts to secondary volts. As secondary volts need to be in the 15 kilo volt range to properly fire the plug, the ratio for this example would be 15,000/ 3 volts or 5000:1 If we work backwards from a known value of 3.6 k ohms secondary we get 3600ohms/5000 = 0.72 ohm primary. Note this is just an example, using ohms figures that may be close to reality.

[atoyot]

Point taken. If I'd thought about the windings and ratios, the error would have become apparent. I'm not accustomed to working with manuals that fail to mention that its figures are assumed to be in K ohms.

Yet another series of corrections to be made in the manual written by that nice fellow out in Victoria.

[one_riff_brian]

Actually you will find that the coil secondary reading is K ohms, people often state just ohms, the scale range on the VOM is often disregarded. Consider that the ratio of primary ohms to secondary ohms determines the ratio of primary volts to secondary volts. As secondary volts need to be in the 15 kilo volt range to properly fire the plug, the ratio for this example would be 15,000/ 3 volts or 5000:1 If we work backwards from a known value of 3.6 k ohms secondary we get 3600ohms/5000 = 0.72 ohm primary. Note this is just an example, using ohms figures that may be close to reality.

Careful! I'd expect the primary windings to be of much heavier wire, and I'd have limited faith in the average multimeter at the lower ranges, so I'm not sure that the measured resistance ratios would mean much. I'm more interested in the volts and amps in the primary coil when I get it running.

The rings, head gasket and base gasket are on order- they might or might not be here for the weekend. Do I hone or abrade the inside of the cylinder before I fit new rings? I never really understood if or why it makes a difference.

[atoyot]

Do I hone or abrade the inside of the cylinder before I fit new rings? I never really understood if or why it makes a difference.

Good advice, consistent with repair techniques on small (land) engines & autos. It has to do with making sure the rings seat in.

http://www.saving-old-seagulls.co.uk/fo ... der#p14743

[one_riff_brian]

Rings and gaskets arrived this morning , which brightened my day until I took a really good look at the top of the barrel.

I honed the cylinder wall with a flap wheel revealing pitting in the cylinder wall I torqued the head bolts down to 18 ft lb, or 24 lb on the luggage scales on a 9 inch socket wrench, connected everything up, and gave it a spin, not really expecting much. And you know what? I wasn't disappointed. The compression is still suspect, and I'll have to start looking around for a barrel, which, AIUI, are like hen's teeth. Does anyone rework/recondition/remanufacture them?

Anyway, for now, a break to fix my head, then recheck everything.

To be continued.....

[Hugz]

I had a pair of riptide heads repaired with similar problems. An engine reconditioner would be able to buil it up and grind or just shave it down a tad and increase the compression.

[Charles uk]

Can you post a full size picture of that cylinder.

Flap wheels are a no no for cylinder honing, the intention is to break up the shiny surface layer so that the lubrication holds on to it slightly better, not remove material!

The only hope you've got now is to try new rings, PM me your landline number & I'll give you a ring you must be quite close to me. I might have the rings & a cylinder.