matt_k Posted February 6, 2011 Share Posted February 6, 2011 After a recent flight of around 2 hours i checked the plug on my top80 and it looked a little black. My Pap manual says default setting 1.5 turns from closed and adjust accordingly till Cafe au lait. Whats the best time of running to test right adjustment and at what revs? Any tips? (walbro carb) Bit windy to fly eh! Quote Link to comment Share on other sites More sharing options...
pete_b Posted February 6, 2011 Share Posted February 6, 2011 Warm engine, run flat out for about 2-5 mins (longer the better) kill the engine WITHOUT letting the throttle off at all (keep it flat out until it stops) , take plug out (Warning it will be very hot) check colour. Quote Link to comment Share on other sites More sharing options...
aquatix Posted February 6, 2011 Share Posted February 6, 2011 Black & oily or black & sooty ? Ideally you should be checking the colour of the porcelain about 1/4" from the base, not the tip. Low speed screw is best adjusted at idle with a rev counter. Make a note of current screw positions first so you have a 'fail safe' to go back to. Turn it in or out in tiny increments and note the rpm until it drops off again. The highest rpm with smoothest idle is your best setting, but I usually open the screw slightly to make it a tiny bit richer for safety. Check there is no hesitation when you open the throttle quickly. Max rpm can be checked or adjusted in a similar way, observing safety precautions of course, with the motor either on your back or strapped securely to a solid object with no dirt, debris or loose objects nearby. Final checks are done in flight, after either a good 5 minutes level flight or 2 minute full power climb, kill the engine without letting it idle (even a few seconds idling can ruin the plug colour) then glide down and check plug colour. If cinnamon brown you are all good. An overly rich engine tends to idle jerky and sound 'chirpy' (if it has a rubber drive belt) with visible exhaust smoke and a tendency to 'four-cycle' during acceleration phase. Too lean and it will also idle erratically and either hesitate or die completely if you open the throttle quickly. Quote Link to comment Share on other sites More sharing options...
matt_k Posted February 6, 2011 Author Share Posted February 6, 2011 I recently changed piston and decoked cylinder, it runs sweet but there is a streak of coking on top of piston when i look when plug is out, the plug is blacky coky ive only done 3hrs since new piston. Max rev is good up to 10,000 Quote Link to comment Share on other sites More sharing options...
lukebanks1 Posted February 13, 2011 Share Posted February 13, 2011 I had this problem on my PAP until I was told by Michel Carnet I was using too much oil. Diego of Miniplane recommends 1.6% (160mls per 10L unleaded) for the Top 80. Ever since, plug is perfect and not so much blue tinged smoke coming out of the exhaust. Regards, Luke Quote Link to comment Share on other sites More sharing options...
fanman Posted February 15, 2011 Share Posted February 15, 2011 Rumour has it that Diego has run a Top80 at full throttle for 24 hours continuously on a fuel/oil ratio of 100:1 with no problem. I have always used 65:1 in my Top80 as Miniplane recommends and never had a problem. PAP suggest 50:1 in the Top80's they sell but that is when people start getting coking problems. I also know someone who has been running FB simoninis at 60:1 for years with no issues despite FB suggesting 50:1. In my experience too much oil causes problems BUT running leaner oil mixes requires disciplined mixing. Quote Link to comment Share on other sites More sharing options...
matt_k Posted February 15, 2011 Author Share Posted February 15, 2011 Cheers guys Quote Link to comment Share on other sites More sharing options...
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