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Many thanks Andy. Am going to have a go at taking the flywheel off at the weekend and will take a picture of the roll pin. It looks like there is a sleeve or spacer behind the pulley and the roll pin would lock it in place. The first numbers on the crankcase are 2AH, which I think means it’s a 2A manufactured in 1951. But the H is higher than the 2A and missing the bottom right leg of the font. Will take a picture of that too. Could you please confirm that the aluminium pulley will be attached to the slotted steel bolt. So all I have to do is lock the engine and undo the bolt. Have a Warrington hammer that fits perfectly inside the slot, so just need to keep it in really tight and turn. Have an attachment to a slide hammer puller that has 4 slots in it, so bolts at both 120 degrees and 180 degrees can fit. It was in the back of my mind I had something buried in a toolbox that would work and just found it yesterday after a rummage. Think in the first instance am going to try to use it as it is similar to JAP’s specialist puller. Did not know it was a straight shaft and key, was under the impression it was a taper shaft. Great to get that info too.
It looks like the engine was supplied to Alcon painted in red oxide and Alcon then covered everything in lime green. The inside of the cowling still has the red oxide paint on it. It does not look like it’s done much work and been kept in the dry, so will be a little surprised if the coil is duff. But until I get the flywheel off and test at the pickup, I will not know. Am actually not bothered if it is as I have been waiting to put an external single wire energy transfer coil onto such an engine. Know the theory, but have not put it into practice and this little JAP is an ideal candidate. Mocked up the coil I have yesterday and it will fit at the end of the fuel tank. Will keep you posted how I get on, but I will not be doing the full overhaul in one hit. Summer is the growing season when I use my machines, winter is tinkering time.
Best wishes and thanks again,
Grahame
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Hi Baz. Got the flywheel off yesterday, had a right game with it. Think Facebook only allow one photo in a reply to a post, so will send what I have in a succession of replies to illustrate the matters better. Believe the year of manufacture to be 1951 with the H (missing the bottom left leg) after 2A. Do not think the engine has done much work because there is no wear in the bore and what little carbon there was on the piston and head mostly wiped off with a rag. Took the head off, there was no gasket. Do you know if this is correct. I do not think the cowl has ever come off because the bolt threads for the tank straps and carrying handle still had the lime green paint I think Alcon put on at their works. Believe Jap supplied the engine covered in red oxide as it is inside the cowl and some of the cylinder fins. Put a large socket in the bore and replaced the head so the engine was locked. Knocked of the three sections of the roll pin and the pulley undid by hand! Half undid the three set screws on the flywheel so I could get the legs of a side hammer puller underneath. No go, was worried about damaging the threads on the flywheel. Went to see a mate who had 2” long ¼” Whitworth bolts and put these in a four slots attachment I have for the puller. After a lot of effort, it came off and immediately saw the reason why it was on so tight. The surface of the shaft and the hole inside the flywheel seemed to show signs of a seizure, yet the shaft does not rotate inside the hole. I think either there was swarf or similar on/in it during assembly, or a machining flaw and if known, may explain the roll pin. Initial continuity HT test showed a variable reading, think the black probe was not on a good ground. Have tested again yesterday, both HT and LT resistance is OK. Tested the condenser with a Megger, it failed. I do not use tradition condensers anymore, use a modern polyester film 630v 220nF/0.22uF capacitor. Was actually hoping the coil was duff so I could try again making up a single wire energy transfer coil system. Am still going to do it, but will take off the existing coil, make a former for a new coil, put the old one back on and complete the engine overhaul. Will test the spark from the existing system, then fit the internal coil I will have made and the external one. Then test that system to see if there is an improvement. Best wishes, Grahame.
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Andy Yes reckon the roll pin come the bodge it it up brigade as never seen a flywheel nut come loose had alloy break a few times where the rope hooks onto so fitted a new one and found the alloy is just a tight push fit so skimmed a bit off the steel and welded a nut and pressed the alloy back on this makes it so much easier to fit and all that I have seen had head gaskets made from soft 0.055 thou sheet alloy, the only major failure had was a die-cast flywheel with internal metal corrosion causing expansion and came loose from the steel boss causing a slight knock at idle.
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Andy,
I would agree that a 2A is a very simple engine to work on. Where we will diverge hugely is that because the flywheel was all but welded onto the crankshaft, it was a devil of a job to get it off. Your method would have failed in the first instance. Persisting in it would have damaged or broken associated parts.
Attached are more images of the state of the shaft and the puller method I used, complicated you may say, but a necessity if the seized flywheel was to be pulled off the shaft. It consists of two pullers, one with the 4 hole attachment that I could fit the 3 whitworth bolts into. The bolts ideally needed to be longer, but this is all I could get hold off on a Saturday morning. Because the side hammer element would not fit as the crankshaft was too close to the centre hole. I got another puller to go on the attachment and placed 2 nuts in the middle hole to act as a centring spacer. It involved a 1/8 turn of the puller hex end, followed by several sharp blows on that end, for another 1/8 turn to be done and more blows. Repeating the process many times until it was free. You may describe it as complicated, I believe that I used care, skill, experience and a range of tools, applying them all in unison to do a difficult job.
Again you may say my ignition testing technique that I have shown in the imagery is complicated. I would contend that it is a simple and quick diagnostic method of establishing where a magneto ignition trouble lay. In this case it was a 74 year old condenser with a wax paper dielectric, the primary and secondary coil windings are fine. Sending the ignition parts away to be tested, or just using the substitution method would have resulted in additional time and unnecessary expense in fixing the problem. FYI, testing took 4 minutes, the cost of the polyester film capacitor and board to mount it on is 45p, estimated time, 15 minutes.
You may say too that my intended fitting of an external coil is complex too. To my mind it is not, however I do concede a rudimentary understanding of mutual induction is required. Am not doing it to fix a failed coil, but to do an experiment to see if firstly, it actually works and secondly, if it does, is it better than a known good original system. I want to find out if winding a primary in my own workshop on a homemade jig and fitting an external coil is worth doing as opposed to purchasing an expensive new one. I could then advise others with greater confidence, as I would have completed the conversion myself. I also get great enjoyment and satisfaction from doing such projects.
Grahame
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Andy In Grahame’s photo just visible I recon can see hole in the thread towards its end, I have seen all these sort of things bodges get up to, like a nut coming loose so they found one with a tighter thread being a different thread rate. Going back many years the one of the engines I had was a bit flat for some time but always started and checked the timing think 30 degrees BTDC if I remember right that didn’t improve things, then changed out the complete unit, only difference was the points, seems a bit odd as complete arm made of Tufnell used a flexi wire from coil and the stationary point was earth, whereas all the others have been opposite so stationary was insulated and fed from coil and point arm had just a fibre heal rest all steel earthed through the spring so less likely to fail, well it worked.
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If using Windows on a PC, the default program will have a slider in the bottom right hand corner of the monitor with a – on the left, a + on the right. Move the slider to the right to zoom in. Alternatively, with the mouse cursor over the image, roll the mouse wheel up, away from your hand.
The roll pin is actually 3off, 2 larger ones and a centre spacer that is in the middle of the crank. Was going to not use them, but now am having second thoughts. After reading what David wrote, they could prevent the pulley pressing tightly on the flywheel because of a machining error on one of the associated parts. Rather than throw the batch away, fitting a roll pin was a more economic (bodge) solution. The ‘corrosion’ could be a type of loctite to prevent the flywheel moving in and out on the shaft. Am not sure about this. Going to grind the valves as I think this is the cause of the lack of compression, the seats look terrible because of years of storage with the valves open. When I re-assemble, will try to work out why the roll pins were fitted.
Have a 2a on a Colwood that I have had and used for 30+ years. The info I got all that time ago was the points gap is 0.018 – 0.020”, timing 30o BTDC. Have taken a picture of my points set-up and it looks the same as David’s. Believe mine has not had the cowl off since the day it left the factory, so it’s original. Can alter the timing by moving the armature backplate on the slots as shown in the photo. As the cam for the points is separate from the flywheel, can set the timing with the flywheel off. But expect it to be spot on as there is so little wear on the engine. Do not think it has done more than a few 10’s of hours since 1951.
Really pleased to hear Andy was approving of the external energy transfer coil trial. If it works, it should cost £25 max for the first one and £10 for the next 6 as the 125g roll of enamelled copper wire and a roll of heat resistant polyester tape will do several primary coil windings. Can get an external coil for under £6 if it purchased via Temu. It could save some old engines because it is so cheap to do.
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