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expeatfarmer

Ransomes MG2 number 137

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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.  

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Some of the problem is that you can't see what's going on whilst you are cranking the engine . I have come up with a plan for a belt drive electric start which i will try tomorrow. I am sure that if it could be spun over under full compression it would go.

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I agree it sounds like you are losing spark after the first bang I know you have a mag but ian and I had the same symptoms on horsegut drove us mad for three weeks turned out we had one good spark then crap ones =we had wired the condenser up wrong.

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The condenser on this mag is buried within the main armature, if it fails it is a new armature!

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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Ime very pleased for you I know first hand what it feels like, it drives you mad I was waking up in the middle of the night trying to solve the problem on horsegut

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Pulled the plug out of 137 this morning. Looking at it wet and very black after it's run yesterday I think my diagnosis of rich mixture may be right. Fitting the floorboards and then going to change the jets,fingers crossed it starts again.

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Fitted smaller jets,engine was an absolute pig to start again, managed it by opening the throttle 1 degree on the lever each attempt until it started. Once running top end revs were perfect, ran it for about 20 minutes before I slowed it down enough to get it into gear. Ticked over at about 350 rpm, tried to slow it down a bit more and it stopped. Ran yesterday with 18 thou plug gap, ran today with 20. Once it cools down I will take the plug out and have a look at it.

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Nice new air filter arrived today courtesy of a chap called Chris Pamplin an expert on Vokes filters, he had two made for me. I have fitted one but not run engine yet, yesterday the mixture was good at speed but rich on tickover so may risk fitting a smaller slow running jet especially as the filter will richen things up slightly. Finally fitted the second floorboard. The fan belt was annoying me and very difficult to tension so fitted a new one a bit smaller, it meant completely unbolting the engine and sliding it forwards but gave me chance to clean up the flywheel etc which were covered in grease and oil from bedding in the starter mechanism. The canopy has suffered a bit with the efforts at getting the engine started so have pulled it off to clean and repair the damage.Hope to give the engine another test run later today and then start a new project. 

 

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