40 Plus - poor starting,what to do next?

[Clifford Pope]

I have been given 40 Plus, 1964. It appears to have been well care for, but unfortunately I cannot make it run.
So far I have:
checked compression - good
cleaned plug and set gap at 15 thou as per instructions
cleaned and set ignition gap at 20 thou
tested spark - good
checked carb bowl and jet - good, clean

It refuses to fire or even cough when I use the cord, but I can get it running by whirring at speed for some time with a socket in an electric drill. It will run at speed, but won't idle reliably. On stopping it refuses to restart unless I use the drill again. There is no cooling water coming out, although I have tried back-flushing.

What else should I try, or is it just scrap?

Thanks in advance

Cliff Pope

[charlesp]

I'm not certain when British Seagull changed their plug gap instructions to 20 thou - the twenty second edition states quite clearly that the gap is 18 to 20 thou but no less than 20 for a centre fire plug. But that wouldn't be the problem, you've got a good spark anyway.

The one important thing you haven't mentioned is the fuel. This has to be fresh. Are you attempting to start it with what was in the tank when you got it?

It's a very good idea to dump what's in there, including what's in the float chamber, swill the tank and filters etc out with freshly mixed 2 stroke at 10:1, and have another go.

If you have compression, and fuel, and a spark, then it should fire....

Try it out of the test tank first - it'll do no harm running for a few seconds. When we've cracked that we can return to the water flow problem. Bear in mind that if the prop is still attched you may not get much of a flow anyway - if you try it in the tank then take the prop off.

Good luck

[Clifford Pope]

I got the plug gap from what it says on the fuel tank - keep plug gap minimal, maximun 0.015".

Yes, I did use fresh fuel. The carburettor was spotlessly clean, with no deposits or gunge at all. I checked the float and needle valve, and blew through the jet.

I had a very similar experience with a Stuart Turner. It too appeared to be in perfect order, but was almost impossible to start, and then would only run at full speed or it cut out. In that case I was advised the problem was probably that the main crankshaft seals had failed, so that although the bore had good compression, the mixture was leaking out of the crankcase. Can the same thing happen with a Seagull? Perhaps if someone had been using 25:1 instead of 10:1, and wrecked the seals?

[Ian Malcolm]

Seagulls usually leak from the crankcase joint near the mounting stub for the tiller. Cause? dropping them on the tiller, Over tightening the clamp bolts round the driveshaft casing then yanking on the tiller or whatever. There is a bit about it on the site. You know you've got this problem if its blowing bubbles or weeping from the joint.

The reccomended cure is split the case and re-make the joint with Silicone RTV gasket compound though personally I prefer to cut a paper gasket and install with the thinnest of smears of Hylomar (which can be diluted with celulose thinners and brushed on).

I think its more likely your plug is *not* sparking at the gap under compression. Try a brand new plug.

If you have access to another small block seagull in running order, try swapping complete carbs and see if the trouble follows the carb.
Easiest way I know to tell if a carb is *way* out of adjustment on an obstinate engine.

[Mark]

Just a thought - the fact that you have to use the drill - is your magneto clean and working? Is this points gap correct?

[Vic]

Is this one old enough to have the Silver Flywheel magneto with a non sealed coil assembly and a separate condenser.

If so inspect the condition of the insulation on the coil. If the condenser is separate it is in the back of the box housing the points. It could be on its last legs ( Later models either just had a cover over the points or no cover all all)

[CatiGull]

I have to vote for poor compression (either rings or crankcase bearings) on this one..I dont see how a magneto would only operate at running speed then fail at low speed (possible, but unlikely in my experience)

Compression test is in order.

[Clifford Pope]

To answer the questions that have been raised:

The spark plug is a Champion 8COM. The legend on the fuel tank reads "Keep plug gap close - 0.015" maximun" so that is what I set it at. It has a side gap, rather than the conventional car-type electrodes. Apart from surface external rust it appears brand new.

There is no separate condensor - none is visible at all (Villiers coil)

There is no evidence of leakage at the crankcase joint

The crankshaft sideways play, as measured at the flywheel, is 0.003"

I do notice that the gaps between the magneto and the magnets on the flywheel are about 35 thou. From my experience with lawnmowers that is enormous. They are normally set to be no greater than the thickness of a piece of paper, perhaps about 2 thou. Are the gaps adustable on the Seagull - is that what the two nuts underneath do, other than hold the wire clip for the HT lead?

[charlesp]

No there's no adjustment of the magneto.

From what you say it appears you've vtried almost evrything!.

One more suggestion. however, and that is the timing. Seagulls of that era have fixed timing, but it's only fixed in the right place if it was assembled correctly. The long slotted screw that tightens into the magneto baseplate should engage when fully tightened into a 'dimple on the crankcase nose. If this has been tightened in the wrong place then ignition will be at the wrong time - and according to whether it's too ardvanced or retarded it could affect the starting and the slow running.

Worth a look I think...

[John@sos]

The plug gap, and that of the points has changed over the years with the changes in fuel.

Today we use 20 for both points and plug, and in some cases some have found 25 thou on the plug works even better!? no idea why on that!

Points setting is down to octane ratings of the fuel. Remember years ago you could buy very low octane fuel, and Seagulls loved it.

Try asking for one star petrol today!

With the villiers ignition the condensor is hidden under the points. a very expensive part, £38!!! Some have used car type condensors with sucess. Others have thrown the points away and fitted 'Atom' electronic ignition systems, if you can still find them....

If the spark is white, suspect the condensor.

If the spark is weak, try thr electric drill tip on the FAQ page, it could be the magnetism in the flywheel is low.

Fuel over 3 months old is no good and do make sure you have the correct amount of oil, that helps seal the crank.

Comp on a 40, 85 to 100 psi, on a Century 45 to 55 psi! Not exactly high!

John
SOS

[Clifford Pope]

Thanks for those responses. I'll try widening the plug gap to 20 thou.

So the consensus is that the crank bearings are probably OK? The measured degree of side play is adequate (with the correct proportion of oil) to seal the crankcase?

I don't understand the point about altering the timing. Surely that is fixed in manufacture by the position of the cam on the crankshaft? The big screw on the points plate just seems to release the plate so that it can be turned to alter the gap. I appreciate that having an incorrect gap will alter the timing to some extent, but how can it be significantly altered?

I'm surprised about the magneto/flywheel clearance, but have to accept what you say, that it is non-adjustable. I've always understood with magneto ignition that it is absolutely crucial, and should be the barest minimum air gap. As I say, that has been my experience with getting lawnmowers to run.

So it seems I have run out of further options beyond trying widening the plug gap to 20 thou. It's already had the electric drill treatment.

[charlesp]

The large screw isn't there to adjust the points gap - you do that at the points themselves.

It's there to register the timing position. Normally the conical end of the screw engages with a dimple on the crankshaft nose - which absolutely fixes the orientation of the baseplate relative to the crankshaft. Once tightened down with the screw and dimple engaged then it's left there.

I increasingly feelo that the timing may have been thrown out here. If you've slackened the screw and rotated the plate to alter the gap, then it may be way out.

Not a huge job to check once the flywheel is off - in fact you can gingerly 'feel around' or shine a torch down the screw hole to check it but it's fiddly.

Good luck

[Ian Malcolm]

First put in a NEW D16 or A6 plug. The old 8COM may well be breaking down internally. If that cures it, you have got off easy.

As I said earlier, check the carb by substitution if possible.

Dodgy main bearings can be eliminated for a short test by oiling them with heavy gear oil.

John has given the compression readings you should be getting and info on the fixed timing.

At this point I would then swap the flywheel and magneto base plate assembly complete from a known working Seagull, but if you can't do that, the following procedure will let you eliminate the magneto to see if its the problem.

If you can isolate the points from the rest of the magneto and you have a few car or motorbike bits and pieces you can rig up a conventional couil/battery/points system for testing. You will need to disconnect the wire from the points to the magneto coil and capacitor.

You will need either a 12V rated vehicle ignition coil or a coil and its matching ballast resistor, a suitable capacitor (dont trust the one in the Seagull) , a lead acid battery, a decent length HT lead with terminals to fit the coil and the sparkplug, a switch, a fuseholder and a 10A fuse, a table or other stand to place beside your testing tank a roll of electrical tape and enough hookup wire to connect it all up.

Start by attaching a wire to the tag on the points you disconnected the capacitor and the LT wire to the seagull magneto from. Figure out how to get the other end outside without it getting damaged by the flywheel. Connect another wire between any convenient bolt or screw on the baseplate or crankcase and the +ve battery terminal (YES POSITIVE EARTH - there *are* reasons). Wire the fuse, switch and ballast resistor if required in series and connect the whole lot between the -ve battery terminal and the -ve coil terminal., Connect the wire going to the points to the coil +ve terminal and to the capacitor. Connect the other side of the capacitor to battery +ve. Connect the HT lead from the coil to the plug. (whenever I say coil, I mean the vehicle coil). Reassemble the flywheel etc. Switch on and test for spark in the usual way (though you should get a deceent spark just turning the flywheel by hand) Verify that the spark occurred with the piston somewhere near TDC. (Chopstick down the plug hole or a torch shone up the intake work for me)

Now you should be good to go with a 1900's style ignition system. Try pull starting the seagull. If still no joy, go for the drill on the flywheel nut again. If all is happy, well you've got a bad magneto coil or capacitor, weak magnets in the flywheel or possibly a bad Seagull HT lead. You should be able to eliminate the lead and the capacitor pretty easily and if you ar familiar with lawnmower engines, you should have some idea of how healthy the magnets are if you feel how much they pull on a screwdriver.

If you get to thhis point, it would probably be best to talk to John about sending him the power head and have him quote to sort it out or look for a parts engine (seized or busted gearbox or cracked block)

GOOD LUCK!

[Clifford Pope]

I've done some more investigating, but I still don't understand the purpose of the large and small screws.
I've removed the circular plate covering the points. I assumed that the larger screw loosened the quadrant plate with the fixed contact point, and the smaller screw then allowed fine adjustment of the gap. I then locked the plate by re-tightening the larger screw again. The small screw won't turn unless I release the large one first. Is that wrong? How does that alter the timing?

However, I have checked the timing and it does appear to be way out from what I expected. I presume the spark is meant to occur when the points open, as per a car ignition? I have determined TDC by using a stick, and carefully measured angular distance betwen that and the moment when the points open, and the timing is 50 degrees BTDC. Can that really be correct? If not, how do I alter it?

I like the idea of bypasing the magneto and doing a test using an ordinary 12v setup. However I cannot see any way of getting a wire out past the flywheel. The flywheel sits very close to the engine casing, and there is a raised rim on the inside, so there is no straight through access from inside to out. Nor can I see any convenient holes in the plate under the flywheel. Could I drill one, and plug it afterwards?

[Vic]

and the timing is 50 degrees BTDC. Can that really be correct?

Certainly not correct. Not sure what it will be in degrees but it should be somewhere in the region of 1/8" to 5/32" before tdc measured on the travel of the piston.

Assuming the points gap is correct and not way too wide there are two posibilites. Either the magneto base plate is incorrectly posioned or the fly wheel is incorrectly fitted on the crankshaft. I thought that was keyed but maybe not on an engine that age or the key is missing.

I reckon you have found the problem.