Wristpin

Good, Sounds like progress of a sort! Cant remember the exact figure but Magnetron units need around 350 rpm to produce a spark - considerably more than the old points and condenser set up , so you may not have lost the spark, just not pulling hard enough. If you have not already done so, remove the cutter belt until you have every thing working. On an Osprey there is a fair amount of inertia to overcome in the belt and cutter disc . if the engine will only run on full or part choke you have a carburettor problem - not ignition ; time for a strip and clean. Loosing your post - remember that we are into page three of a long thread!!!

Lets try to "un-complicate" this. Your Magnetron coil will produce a spark and run the engine with No wires connected to it - The spade terminal on the coil is for a connection to a Stop Switch to earth the coil and stop the engine. To find the Stop Switch, follow the throttle cable from the handlebars down to where it joins the engine at the throttle plate. Somewhere on that plate you should see a wire : maybe attached with a small ring terminal to a threaded "post" with a nut or maybe pushed through a spring terminal. That is the Stop Switch. The wire wire can be traced back to under the flywheel and may safely be cut or removed together with the other wire . You now need to provide a means of connecting your new coil to the stop switch. You could use the existing stop wire but to connect it to the coil you will have to find a suitable "lucar" female connector so it may be easier to use the new harness that came with the coil. If your throttle plate has the threaded post, that is where you attach the ring terminal on your new wire . In that case connect the push on connector to the coil and route the wire with the ring connector to the stop switch. You can then cut off the spare wire from the coil connector . If the Stop Switch is of the spring terminal type you have a choice. Either proceed as above but snip off the ring connector, bare the wire and poke it under the spring or use the bare ended wire on your new harness to make the connection between coil and switch and trim off the wire with the looped terminal. What you are trying to achieve is one wire connecting the coil to the Stop Switch - all other wires may be safely removed.

Just get stuck in and remove the two head bolts and pull the tank and carb off together. Take the carb off and clean the screens on the pick up tubes, fit a new diaphragm and probably a new 0 ring where the carb slides onto the inlet manifold as they tend to harden and flatten. Check the tightness of the two 5/16af hex head screws holding the manifold to the block. If they are slack it's probably time for a new manifold gasket.

I'm a bit confused by the wiring harness illustrated in your last post as it appears to have a two pin socket with one wire possibly being an earth. The normal set up for a Magnetron coil is one wire from the blade connector on the coil running to the engine stop switch on the throttle plate. That said, the coil in your post is unlike any BS coil that I've seen, but as four years have passed since retirement, perhaps things have changed. None of the wires that disappear under the flywheel are needed with a Magnetron coil but it may be easier to either disconnect the stop wire from the old condenser and take it straight to the blade / spade connector on the new coil or cut it off close to the points enclosure and do the same.. That way you don't have to make any changes at the stop switch end.

Interesting, certainly, with the keyways appearing to be just over 90 degrees apart , there should be no doubt about which one to use. Bet it really sings when put into work. Seeing that the ignition cam is on the crank and not on the flywheel boss makes some of my instructions for setting the points irrelevant - and makes the job far easier than on the smaller JLOs that I have worked on. Not only is it a fairly unusual machine but it also looks not to have been over worked or badly treated.

I'm still inclined to say that it's an ignition problem with valves as a close second. If memory is correct that engine has a single choke carb, i.e. both cylinders draw their mixture from a single source , unlike other engines with twin choke carbs which are, in effect, two carburettors feeding individual cylinders. The original post says that the front plug is wet , so the mixture is getting there but not being ignited. The lack of ignition could be just that - not enough sparks or, a lack of the conditions required for ignition such as the correct air to fuel mix or low compression - an air leak in the induction passage, leaking valves or more seriously and hopefully not, piston and ring problems. Diagnosing the cause is a job for logical fault finding . The most simple being a check on the loss of power or rpm by the isolation of individual cylinders by removing HT leads. Inserting cheap in line spark testers into both leads and watching for regular firing will also tell a tale . After that a compression test , or preferably a leak down test on each cylinder. My money is still with an ignition issue but long distance diagnosis makes certai assumptions that may not be valid. EDIT Too hot out side so have dug out and scanned a section of an old manual https://www.dropbox.com/s/88iutp8r69ppkn7/BS flat twin ignition0001.pdf?dl=0 If it is concluded that the coil is the culprit and its an old points system , the way to go is a Magnetron coil part number 394891

You don't mention pulling the back cap? Ideally you check the rpm drop with each plug disconnected and if the front pot is in trouble (ignition or valves) I would expect to see a drop or stall when the back one is shorted out.

I really like your " logging arch" , a very neat solution , if I may say so.

Is it the old boxer flat twin or the later vee twin Vanguard? Are you sure that it's not just running one one cylinder. With either engine, off load, it's not always immediately apparent. I'm guessing it's the flat twin with one ignition coil with both HT leads coming from it and over the years I've replaced more of those coils than any other BS ones . If you have not already tried it, pull off each HT lead in turn and see if it will run on one cylinder in turn , or with it running short out each in turn . If it's the Vanguard vee it will have two coils connected by a" diode harness" which stops the coils interfering with each other. Diode failure can produce a variety of interesting symptoms but the " try running on one" test is still a good starting point.

That would be good, it would be interesting to see a pic of the two flywheel keyways; it seems so strange that as their presence is bound to raise a question, there is no mention of them in any of the JLO literature.

A bit of a rare beast the 2-stroke Osprey. I've got a parts book but have never worked on one so this is just a suggestion. Set the points to .35-.45mm using whichever keyway gives the best access through the flywheel to their widest setting - clean feeler gauge and pull a bit of clean card through them to remove any trace of grease or dirt. Top tip - pull the card through but not out , then use a instrument to hold the point off the card to release it. That way you don't end up with paper fibres trapped between the points , defeating your endeavours! Having set the points then use whichever keyway causes them to start to open when the piston is 2.3 - 2.6 mm before top dead centre - (here I'm assuming that at no time you have removed or moved the stator assembly and lost the factory setting or that if you have you marked the stator position and returned it to there on reassembly). To do this you will need to devise some way of determining and measuring piston movement via the spark plug hole. I've made a gauge using the body of an old spark plug with a sliding plunger in it that I've used on numerous two stroke engines with the plug hole immediately above the piston. In fact I made two, one using a 14mm plug and the other an 18mm one - useful for some Villiers . Once you get the hang of it the whole process is far less daunting than it sounds. Interestingly none of my JLO literature makes any mention of the two keyways - seems a bit odd. https://www.dropbox.com/s/75lq2yhxl18oxrf/JLO 197.051 Hayter Osprey0001.pdf?dl=0

The most common problem is incorrect positioning of one of the bushes with locating " nibs" not sitting in theit cut outs in the casings.

The new coil armature requires setting up as follows. Turn the flywheel so that the magnets are furthest away from the coil . Pull the coil as far from the flywheel as the slots allow and pinch up one coil fixing screw. Rotate the flywheel so that the magnets are equally aligned with the coil armature legs. Place your gauge ( plastic or card ) between the armature legs and the flywheel. Release the screw that you tightened and the magnets will pull the coil onto the flywheel pinching the gauge . Tighten both screws and turn the flywheel to assist pulling the gauge out. In the absence of the correct gauge, Briggs used to suggest two thicknesses of an outdated micro fiche.

It's a straight forward job. The Briggs Magnetron kit illustrated includes a new flywheel key and a blanking plug for the points breaker plunger hole. Obviously, to fit those the flywheel has to be removed . I have to own up to fitting many Magnetron coils without removing the flywheel and leaving the original key and points assembly in place with no apparent ill effects over a number of years. The choice is yours.

The joys of country living. In the 80s two neighbours and I shared a 30+ year old alkathene water main along side our quarter mile track . It would spring a leak every three months or so. Eventually we bit the bullet and laid a new one. Wont mention the shared septic tank.

The small spring shares its anchor points with the rod and has an anti-rattle / hunting function. Its absence will probably go unnoticed on an old 21. It just keeps the linkage in tension.

As well as the obvious items Trojan used to supply a lot of stuff for the early days of karting in the late 50s including Clinton engines and I think that they were the Clinton distributor for the UK together with Lambretta scooters under the Lambretta Concessionaires banner.

Some while ago on an episode of Wheeler Dealers or Car SOS they took wire wheels to a firm in Slough. Not cheap!! edit. Just found them http://www.mwsint.com/site/cms/contentChapterView.asp?chapter=1 another, a bit nearer home http://oldcarservices.co.uk/tyres-tubes-wheels/

The same question has just been asked elsewhere and having failed to find a decent digram in any BS book a friend has marked up an image.

Substantial bit of kit. Possibly spent its working life on construction sites etc. Very interesting that it has a built in Excitation socket to make it easy to restore the residual magnetism when lost. So much easier than having to take the end cover off the alternator to "flash" it. EDIT Some additional reading on the subject!! http://www.dieselduck.info/machine/03 electricity/flashing_generator.htm

The thin wire from the coil low tension windings goes under the flywheel to connect to the contact breaker points and condenser. (Under a tin cover) . Another thin wire comes from the points to the kill switch which is positioned adjacent to were the throttle cable is anchored. The action of closing the throttle past the idle causes that switch to connect the coil and points to earth , thereby killing the ignition.

The early Minis had a similar push button starter switch on the floor between the front seats. May still be obtainable from classic car suppliers.

This may assist https://www.boards.ie/b/thread/2057437399

By the look of the image your machine has points ignition, no trigger module between the left leg of the coil armature and the coil itself. Plug caps. Comments have been made about these being the likely cause of failure. This is only likely to be the case if the original BS connector has been removed and replaced with an aftermarket cap. Again, from your image you appear to have the original connector and there's not a lot that can go wrong with those. Sometimes they have a simple rubber boot. The only exterior things left to check is the kill switch on the throttle plate or the kill wire that goes to it. If all is OK there, you have a choice, either remove the flywheel and examine the points etc , or find a later BS Magnetron coil ( with suitable leg spacing) and fit that in place of yours - a ten minute job and a direct replacement using your existing flywheel without the need to remove it. Personally I would do the latter as they are 99.9% reliable and obviate the need to ever remove the flywheel again.

Hope that this may help, it covers both points and electronic systems and has a useful bit on trouble shooting electronic issues and testing the trigger unit etc. https://www.dropbox.com/s/22z2sei39yp70qy/Kohler ignition systems0001.pdf?dl=0