Hi Jarek. The engine does not need to be removed to remove the Magneto.
Attached is the how to. Excuse me but it is written for dummies. I suggest a mega volt test on the leads for leakage. Cheers. Nige. From: [email protected] <[email protected]> On Behalf Of Jarek Steliga Sent: Saturday, April 13, 2019 5:53 AM To: [email protected] Subject: Re: [DOG mailing list] Limbach 2000 - spark plug on cylinder 4 getting black and sooty Martyn, Your first suggestion about the possible air leak between 4th and 2nd cylinder sounds devilishly logical. It will for sure be the very first thing I am going to look at. There is another symptom that points to this. While attempting to synchronize the carbs with vacuum gauges, the vacuum on the right side (cylinder 4 and 2) was half of that on the left side. As for the magneto I would have looked inside it long time ago if it had not required the removal of the whole motor. The prospect of doing that rather scares me. Laurie, Motor probably 1600 hrs. I say probably, because the documentation inherited from the previous owner is highly confusing. The colour of the deposit on the common exhaust pipe is distinctly blackish, however no visible colour of the exhaust air/fumes itself. Compression on cylinder 4 is around 10 bar and the other cylinders show very similar value. Rob, The needle seems to be tracking without a hitch. Atomisation of fuel is certainly worth keeping in mind in case other suggestions fail to produce results. I thank you all very much. A problem shared is a problem halved :-) Regards Jarek On Fri, 12 Apr 2019 at 07:52, Rob Thompson <[email protected] <mailto:[email protected]> > wrote: In addition to Martyn's suggestions here's another one to add to his list of things to check... If your fuel is not being atomised efficiently it comes out of the carb as fine droplets rather that a mist. The heavier droplets lose momentum quicker and then get sucked into the first and closest cylinder. This can be caused by 1- The needle spring is worn and the needle is not tracking smoothly up and down the jet. 2- The float level is too high and the needle adjustment has been wound down to compensate. 3- Worn needle or worn jet regards Rob Rob Thompson 0429 493 828 (Please note that my new email address is [email protected] <mailto:[email protected]> ) On Fri, Apr 12, 2019 at 12:06 PM Martyn Cook <[email protected] <mailto:[email protected]> > wrote: Hello Jarek I'm not sure if this will help, but you did ask for suggestions :-) One way that one cylinder could be leaner than the other is from an air leak around the intake structure, after the carburettor. So your carb might be set a little too rich, but the No 2 cylinder would then be leaned out by an air leak local to that cylinder, which could dilute the fuel mixture. Another possibility is that the compressions in the two cylinders are different, so one sucks better than the other. The air leak could be via the exhaust valve. Do you have compression readings available? I had to spend quite a bit of time with my Dimona getting the mixture settings correct. When I first purchased it - straight after a top overhaul - the CHT readings in flight were wildly different, and one side did produce blackened plugs. I very gradually adjusted the carb needles using the special tool (1/4 turn at a time) and I finally got the plugs all nice and powdery grey and the CHT readings within a few degrees of each other. On one side the front and back plugs are still slightly different in appearance, so I tuned for one slightly blackened plug to ensure the other cylinder was not too lean. Another possibility is your spark plug HT lead might be damaged. An intermittently-firing plug might cause the vibrations you report, plus a fouled spark plug due to partly-burned fuel. On my aircraft the HT leads look like they came from Noah's Ark, so to speak, and I'm wondering when they will need replacing. Or a magneto fault? The contact leading to that spark plug could be weak. Hope this helps! I look forward to reading what others write. With warmest regards Martyn New Zealand On 12/04/19 8:36 AM, Jarek Steliga wrote: Hello, I am at the end of my tether. Please help. I screw in 4 brand new Limbach spark plugs. The engine runs smoothly. After a while I detect vibrations, then check all the plugs and consistently one on cylinder 4 is black (all the others look fine). When I screw the sooty plug in on a different cylinder and run the engine, the plug will clean itself up (e.i. burn all the soot and look like new). Conversely, a clean plug mounted on cylinder 4 will foul up again. Has anyone had a similar situation? While checking the fuel mixture with Gunson colourtune https://www.youtube.com/watch?v=xEZ0-uN0NA4 , the mixture on cylinder 4 is slightly richer (e.i. slightly too rich) than on cylinder 2. How can that be when both cylinders are supplied by the same carburettor? Looking forward to someone's suggestion Regards Jarek
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