Ransomes MG2 Serial number 137

[expeatfarmer]

Starting the engine is proving to be a real challenge not to mention hard work, you have to crank it over on decompression to charge up the magneto< I have a tell tale on the plug that shows I have a good spark, engine fires once and then will not run on, It may be that is is all tight from the rebuild and I am not getting up enough inertia, initially when you released the decompressor lever the engine stopped dead but seems to have loosened up after two days of cranking.Yesterday I changed the jets in the carb, the originals were stamped 5 on the main jet and 4 on the slow running jet from another MG2 carb I have installed a 25 on the slow jet and 100 on the main jet, I think the numbers relate to fuel flow rates. The handbook says to have the throttle lever closed for starting as there is a small bypass hole in the carb body but the actual slide seems to close this off, if you lift the slide slightly on the cable so that the hole is clear it still won’t start, it fires once. I have a petrol drill which I can use as a starter motor on MG5 and MG6 but it wont even turn 137 on decompress!With a machine of this age that arrived as many boxes of bits it has to be very much trial and error as to which bits are original and which are bits collected up that look right. The magneto was professionally rebuilt and seems to be in perfect order, I have fitted a long reach plug which the tell tale shows is sparking well on decompress but you cant crank on compression and watch the plug so it may be that the plug is failing under pressure I am going to take the plug from the digger and fit that as I know it is working. I am also going to fit a different carb. slide which has a groove by pass in the lower face. Fingers crossed.

[ransomes256]

Jonathan,
Why not try a complete working MG2 carburettor first before you try swapping slides and other bits.
Seems you have to much compression which may also be a problem if the inertia from the flywheel does not keep the rotational speed up.
Neil

[expeatfarmer]

I think that may be the problem I have sat and turned the engine over with plug out and oil down the barrel to try and loosen it off and bed things in managed to get 5 bangs so some progress. Cant swap carb as manifold is different it is screwed into the barrel and then carb fits with clamp.If I could tow start it I am sure it would go.

[andyfrost]

I’d hate to tiddle on your bonfire , but from your description , it sounds to me as if you still have a magneto problem.

Andy.

[expeatfarmer]

37 is alive and well!!!! After three solid days of trying everything I could think of to get it running I was at the point of despair and so knackered from cranking that I thought it safer for me not to try again whist my wife was out in case I had a stroke or something daft. Whilst she was out walking the dog I put the decals on and just sat and looked at it trying to think of something else to try. Some time ago I came across a very rusty ancient mica insulated three point spark plug which was in one of the heads that came with 137, I sand blasted it and polished it up as a keepsake. 137 had fired a few times, once it fired a five bang run so it was not far away. I took the plug out put some oil down the bore and then sat for about half an hour just turning the engine over to try to loosen things up. Put the plug back and tried again fired once and stopped. I then took the plug out and fitted the three point ancient plug turned the crank and off it went running like a dream. I ran the engine for half an hour checking for oil flow in the dry sump and any leaks. Stopped the engine and had a celebratory coffee and then tried to start it again hey presto off it went again. Thank goodness for that . Now I can make up a bumper, fiot some floor boards and then crack on with some other machines for Malvern.

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[charlie]

That is great news. Might be worth getting a spare plug of same type.

[will-haggle]

Excellent work, this would make a good book! Reminds me I have to enter for Malvern by 1st February!

[expeatfarmer]

Thought it was too good to be true 137 would not start this morning, found a major air leak on the engine side of the carb through the slot which clamps the carb to the manifold, sealed that up ,still would not start, I have never had any dealings before with a Lucas magneto but looking at it I thought the cam ring in the clamp did not look right when you advanced the timing the whole ring moved outwards. The cam ring has a notch cut out of it to limit the advance retard which locates against a pin. When you move the running lever to 20 degrees advance the cam ring moved outwards and was obviously disengaged from the limit pin. I made some adjustments to the advance lever and refitted the ring which showed that the ignition timing was out, I have reset the timing to top dead centre starting, still would not run. Now I have discovered that the main throttle slide is not snapping shut against the bottom of the venturi when no throttle is applied. I have now dismantled the carb with a view to ensuring the slides are free and snapping shut for starting.
In the morning I am going to make the floorboards and front bumper before I go near starting it again.

[trusty220]

Sometimes you just can’t see the wood for the trees and I find it best to move on and do something else for a while. Come back to it once you’ve had a break and (in my experience) you’ll probably find the problem quite quickly.

Above all else do not get disheartened. See you at Malvern.

[expeatfarmer]

At least today was productive, managed to bend up a new bumper out of steel strip fortunately I was able to take a template off 225. So started the day as a blacksmith and then spend many hours trying to figure out how the floorboards were meant to be. I thought I had gained some time by buying some part built sets from Neil only to realise that 137 had a totally different arrangement using two boards suspended under the cross shaft by four U bolts which I now have to make. I have made one complete board which required a lot of trial fitting and messing about, the second board is simply a mirror image so it should not take long to make that in the morning. Fortunately I had a couple of lengths of pitch pine ex church pew which are wide enough and thick enough.

[expeatfarmer]

Floorboards, U bolts and front bumper ( force drying over the Aga )

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[expeatfarmer]

Another frustrating day, fitted the bumper which I am pleased with, discovered that the decompressor mechanism was effectively preventing the engine drawing fuel when the exhaust valve is forcibly held open by the decompressor all the suck and blow takes place within the exhaust. I adjusted the mechanism and tried to just use it to get rotation started and then turn the handle against full compression, I can do it and managed to produce a couple of double bangs. One of my big hairy sons came round and he had a go with the same effect although frustrating it was quite satisfying that it knackered him as much as it does me ! I keep looking at the magneto and thinking that because it is fitted with a Lucas MA 1 magneto instead of an N1 L that this may have some bearing but then it has run and ran well. I am at a point now where it will fire once every time I turn it over but just will not pick up and go. I have had the same symptoms with MG6 engines and simply swapped to a new plug and away it went. Tried the same tactic with 137 fitting brand new N9y plugs via an adaptor but no change. If anyone has any thoughts please share.

[ransomes256]

Jonathan,
Is the magneto too far in advance? It may be worth retarding it mechanically rather the using the mechanism to see if it improves the situation. Warming the spark plug can help and I assume there is sufficient fuel reaching the plug. Not a favourite product but try some Easy Start or similar Ether to try and pick up a few more bangs.
I know you had the magneto rebuilt but is coil resistance and condenser charge / discharge time all good? These could still show a spark at slow engine rotate.
Good Luck
Neil

[expeatfarmer]

Today I am going to give it a try with a dynostart unit and a vee belt. If that does not work then I shall reduce the points gap to 14 thou and then try retarding the ignition to see what that does. next plan is to borrow the magneto from 225 but that is a total unknown as I have never run that engine. I will bench test both magnetos before I fit.

[expeatfarmer]

Thanks to a lot of support I have finally tracked down the fault with 137, I removed the magneto and bench tested it with a drill and rubber hose drive, poor spark. Removed the points assembly from the Lucas mag. which is a total rotating assembly within a static cam ring. The points were clean and good but then I noticed that where the main point spring is anchored the rebuilder had added a small piece of spring that curved very close too if not touching the insulated points post. Took it out and refitted the points, the whole spring was touching the post hence why the extra bit was added refitted the extra bit turned over so the curvature was the other way and tested mag again, brilliant spark. Refitted the mag good spark but still not running continuously two bangs and then stop opened the throttle a fraction and it started, quickly connected a timing light strobe and found that on the advanced run setting on the manual lever the timing was 36 degrees advance when it should be 20 stopped the engine retarded the ignition and tried again 25 degrees advance stopped and re set again just by rotating the flywheel rather than looking what was going on with the points, started it again measured the timing in the run setting, 20 degrees RESULT. Engine runs sweet at 450 rpm any faster and it is lumpy any slower the same. Using a compressed air gun I squirted air down the inlet and the engine ran smooth and then died back, slowed the engine down and tried the same , same effect. Current diagnosis is that the jets in the carb are too big introducing a rich mixture. That is my fault because the original jets fitted to the carb were much smaller than the 100 main jet and 25 slow running jet that are normally fitted to an MG2. I thought that maybe the car originated from a 400 cc lawnmower engine so fitted standard TB engine MG2 jets. My task in the morning is to refit the original jets and see what happens. At least I am ( i think ) in a position now where there is one fuel related issue rather than a combination of fuel ignition and buggeration factor.! I have added a couple of photos showing the extra spring piece between the screw head at 6 o’clock and the spring anchor at 7 o’clock.

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