--> RotaxEngines-List message posted by: "Roger Lee" FYI My 912S does not start, what’s going on? All of the Rotax 9 series engines are known to start quickly and readily. (Many people report their engines start within 1 revolution of the crank). The 912S/ULS is a high compression engine and that can cause the engine to move (shake) in the engine mounts if the engine mount is not strong enough. Many 912S installations are designed for the lower compression 912UL engine and are not “beefed up” when the 912S is installed. This is the root cause of many 912S starting/operating issues and must be cured before proceeding with any other actions. Here are the factors related to hard starting: 􀂙 Engine shaking during the start cycle. This causes the fuel in the carbs to froth and spill into the venture and/or the vent lines. With the fuel system disrupted the engine cannot start. 􀂙 Carb shaking; even with a proper engine mount you can still have carb shaking problems. The best solution is installing the Rotax 912S airbox as it rigidly fixes the carbs, preventing most shaking. A side benefit is that SB-912-030 (inspection of the carb flanges) is not applicable with the airbox installed. 􀂙 Loose gearbox; If the gearbox is allowed to lose its spring pressure (see Gearbox related FACs) the engine will not want to start as the prop will be fighting the compression strokes. Basically the engine gets into a cycle of kicking back and forth between the compression/ignition pulses and the prop forces hitting the dogs in the gearbox. Remove and send your gearbox for re-shimming of the springs. Tips for hard starting in cold weather: • Increase starting jet size to allow more fuel. (SI-03-98) It may be necessary to switch back to small jets in warmer weather. • Modify choke rotary disc (SI-03-98) • Reduce spark plug gap to minimum. • Make sure you have a good battery. Does jump starting help? If it does you may want to change batteries. • Battery wire size, connections and grounds. Check for voltage drop between battery and starter. • Preheat is always a good idea. Avoid rapid methods that can damage your aircraft. • Check to see if the choke is full on and both are equal. Proper set up of the cables is critical. -------- Roger Lee Tucson, Az. Light Sport Repairman - Maintenance Rated Rotax Repair Center Home 520-574-1080 TRY HOME FIRST Cell 520-349-7056 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=321939#321939 _-============================================================ _-= _-= -- Please Support Your Lists This Month -- _-= (And Get Some AWESOME FREE Gifts!) _-= _-= November is the Annual List Fund Raiser. Click on _-= the Contribution link below to find out more about _-= this year's Terrific Free Incentive Gifts provided _-= by: _-= _-= * AeroElectric www.aeroelectric.com _-= * The Builder's Bookstore www.buildersbooks.com _-= * HomebuiltHELP www.homebuilthelp.com _-= _-= List Contribution Web Site: _-= _-= --> http://www.matronics.com/contribution _-= _-= Thank you for your generous support! _-= _-= -Matt Dralle, List Admin. _-= _-============================================================ _-= - The RotaxEngines-List Email Forum - _-= Use the Matronics List Features Navigator to browse _-= the many List utilities such as List Un/Subscription, _-= Archive Search & Download, 7-Day Browse, Chat, FAQ, _-= Photoshare, and much much more: _-= _-= --> http://www.matronics.com/Navigator?RotaxEngines-List _-= _-============================================================ _-= - MATRONICS WEB FORUMS - _-= Same great content also available via the Web Forums! _-= _-= --> http://forums.matronics.com _-= _-============================================================