Saving Old Seagulls

Maybe swapping over the carburettor may help to pinpoint the problem?

Hello Charles,

I've already changed the carb, and checked the jets, and it has made no difference. What concerns me the most is that the engine seems to have got harder to turn over. When I first rebuilt the engine it turned over easily, but was slightly tight, which I put down to the new crankcases that had unworn bearings, plus the new rings. But now I'm not so sure, as it has not loosened up/run in. I'll have another look at it today. It's all very odd

Strip it down again and recheck every thing. You will find the problem. Glad I did on my engine, found a conrod bolt loose.

New rings...

Did you gap them, ie adjust between the ends?

I think I may have found the problem. Stripped the top end down, nothing nasty found, ring gaps ok, no signs of any abnormal rubs in the bore or crank case. I then noticed that one of the magneto magnets was rubbing against the flywheel. So off with the flywheel, and I discovered that the woodruff key had failed This has caused the flywheel to slip around the crank, which will have moved the timing, just enough to cause difficult starting?

I have another woodruff key, but I'm not sure if the flywheel bore is damaged. I've got to get the remains of the woodruff key out first.

The woodruff key is really only for accurate location of the flywheel on the shaft.The friction of the interference fit between the tapered surfaces is what locks the flywheel in place, if this fit is imperfect then the woodruff key is subjected to shear forces which results in the failure you've experienced.

You need to check the fit between the shaft and flywheel with engineers blue if available, something like an 80% contact between the mating surfaces is needed to be effective.

It may be possible to lap the flywheel to the shaft but if the fit is very poor and the mating surfaces are badly ridged then you just transfer the imperfections of one to the other.The usual method of correction is to separately lap the shaft with a tapered ring which accurately matches a tapered plug that is used in the flywheel.These are usually made of a softer material so that the abrasive becomes embedded in them.
Unless you have access to a lathe this may be difficult.

Hope this helps.

The woodruff key came out in 2 pieces, as you say it looks like the key has been subject to shear load. The keyway in the flywheel did not look too good, so I put on another flywheel of my spare SD magneto. So much for keeping that as a complete magneto.

The new key and flywheel went together well, and the engine started first pull, very smooth & felt "right" It felt like it was running the best I have had it so far

Another one for "experience"

Whilst surfing around I came across this video, which looks like an SD in use by the British army on a general workboat, during the Hamburg floods of 1962. The video can be viewed as a series of stills which give a good view.

http://www.britishpathe.com/record.php?id=62650

Well spotted, Oyster.

It's certainly a Seagull, unmistakeably so. But I can't make out the flywheel as being an SD 'coolie hat' one, the film is indistinct. As that's a preview maybe the proper version would be clearer..

Here is a better view of it, looks like another engine in the boat also awaiting use also. The outline of the magneto cover is visible I think. Shame the mount is not clear, that would be a bonus! If you zoom in the outline of the short water jacket is just about visible.

I've been going through the stills, and I'm convinced you're right, it's an SD. The coolie hat is there, and the filler cap is right too, although it would be right for a couple of post war motors as well. I agree that there's a tantalising hint of what may be another in the boat, I just don't know.

The bracket would be a huge bonus. Having just yesterday had one delivered by a tortuous route from Jan - thank you Jan! - I have been peering at the image to see what may lurk in t, but to no avail. I suspect you would have to get hold of the still and manipulate the contrast and light/dark to try to separate something out.

That's the first time I've ever seen film of an SD, or even a period photo, so what a good find. What a shame it's twenty years after the original production run, oh how I'd love to see a photo from Burma in 1942!.

Brilliant.

Yes I about fell off the chair when I saw it, I was only playing around whilst having a coffee! You have one of the Dutch SD mounts? Can you post a picture?

Can't find the camera at the moment, but this:

http://www.saving-old-seagulls.co.uk/im ... %20102.jpg

is from the main site. The bracket is identical.

We still don't know much about these brackets. A few have turned up in the UK, rather more over in Dutch hands. They seem to be made for the job, but they don't appear to be a British Seagull product. They're just not in the same style, if you see what I mean. The surviving British Seagull staff know nothing about them.

I've played around with one of the stills, with my very basic photo edit software, the mount and engine is now better defined:

Could it be one of these? If so it will be the SD with customised ministry mount system? Side or transom mounted for 100% flexibility Blimey what a find, shame it is not a wartime picture.

Nice bit of work Oyster.
Thanks