---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Fri 06/09/06: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:33 AM - #1 cylinder plugs are black (Thom Riddle) 2. 09:53 AM - CHT J thermocouple replacement for Rotax 912ULS (Martin Pohl) 3. 10:05 AM - Re: #1 cylinder plugs are black () ________________________________ Message 1 _____________________________________ Time: 05:33:14 AM PST US From: Thom Riddle Subject: RotaxEngines-List: #1 cylinder plugs are black --> RotaxEngines-List message posted by: Thom Riddle During our annual inspection we removed all spark plugs, cleaned and gapped them before re-installing them. They had about 100 hours on them with virtually no wear and all the plugs except for both plugs in #1 cylinder were perfectly colored. Both plugs in #1 cylinder were black. We also balanced the carbs and have sense flown the airplane about 5 hours. A couple days ago we removed plugs from #1 and #3 cylinder to see if the black sooty condition had improved. #1 plugs (both) again are black and sooty while #3 plugs are fine. Engine seems to run fine and smooth at all power settings. Apparently, #1 cylinder is running rich but both it and #3, which is burning clean, are fed from the same caburetor. Any ideas as to what's going on? Thom in Buffalo ________________________________ Message 2 _____________________________________ Time: 09:53:51 AM PST US Subject: RotaxEngines-List: CHT J thermocouple replacement for Rotax 912ULS From: "Martin Pohl" --> RotaxEngines-List message posted by: "Martin Pohl" I am trying to find a replacement for the standard Rotax 912ULS CHT sensors. Does anybody know what kind of metric thread is used on the Rotax 912 CHT sensors? Someone (Tony, EuropeKiwi) is using Westach CHT J thermocouples. Does anybody know what P/N they have? Thx, Martin -------- Martin Pohl Zodiac XL QBK 8645 Jona, Switzerland www.pohltec.ch/ZodiacXL Read this topic online here: http://forums.matronics.com/viewtopic.php?p=39605#39605 ________________________________ Message 3 _____________________________________ Time: 10:05:42 AM PST US Subject: Re: RotaxEngines-List: #1 cylinder plugs are black From: --> RotaxEngines-List message posted by: Hello Thom "#1 plugs (both) again are black and sooty while #3 plugs are fine. Any ideas as to what's going on?" Not in order just rattling: ****First off change the plugs. Unless you have access to a pressure tester to make sure they are not snuffing out under pressure ****Make sure you have the proper heat range plugs! If the porcelain is shorter, it will run cooler and could run black. ****You sure it is black from running rich, or could it be black from oil fouling?? Perhaps run a compression test, that will not tell you if oil ring leaks or valve stem seal, but if low hint to look further. ****Are you using Whacker Silicone based thermal conductive compound on plug threads? ****You have a CHT and EGT to help diagnose problems? ****If you look up mixture check procedures for 914 at take off power, they have you measure each cylinder for O2 content. They want a minimum amount to be certain that things are not running too lean. Eastwood sells such a tool, could be used to check for proper mixture at various throttle settings as well. ****Make sure float bowl shows no signs of overflowing, check needle valve and float look OK, clean carb while you are at it ****I am not certain on this one, but a restriction on exhaust is not a good thing, make sure clear on that cylinder ****If it is only happening on 1 of the plugs in that cylinder, could be besides a bad plug, faulty ignition pick up, coil, module or wires ****You getting cooling problems on that cylinder, like too hot or too cool? ****MAKE SURE YOU HAVE PROPER HEAT RANGE OF PLUGS especial on black cylinder ****If you could somehow get hold of a EGT put it in suspect cylinder. If you turn off gas, you should not get a very severe rise, if you do then too rich. Try it with a good cylinder to see what normal is. Remember black could be caused at many a throttle position. Choke motor when hot a very low throttle opening which you know is rich, and see what rise is. Just be very careful on purpose running lean like this above 50% power, do it just to get peak then retard throttle and turn on fuel. Had enough yet? If not, what motor you have? How does it start? How does it start in cold? How many hours? MoGas or 100LL? What is compression on 4 cylinders? Did you install new length dipstick? What type of oil you running? You checking oil properly where you do not have things overfilled? Is there blue smoke coming out of exhaust, if 2 pipes, then the one with #1 upon cold start up? How bout black smoke on cold start up? Is your oil pressure excessive high, has it changed since you did not have black plugs? Let us know how you make out Ron Parigoris Ron Parigoris