procharger Posted March 29, 2016 Report Share Posted March 29, 2016 After replacing modules last week plane has started first try ever since last friday, today it would not start pulled spark plugs and they were very wet, all the plugs are firing, to much fuel on start up, I have been using choke but today no go, pulled all plugs out and waited a couple hours rotated engine by hand to help dry inside out put plugs back in no choke cracked throttle started right up, not sure whats going on. Checked fuel in float bowl to see how high it was, checked it several times, its a little over half way full each time I check??? I would be better off with a Briggs and Stratton engine Link to comment Share on other sites More sharing options...
Anticept Posted March 29, 2016 Report Share Posted March 29, 2016 Wet how? Fuel wet? I find that often I only need half choke. I go full choke is if it's cold out and half choke isn't cutting it. The "choke" isn't really a choke, but actually fuel enrichment circuit, and dumps a TON of fuel into the airstream. This is done on purpose, as fuel likes to condense on things, including inside the cylinder (hence, things will be a little "wet"). It should only be used for a few seconds. If no-go, close it, you can easily make it too rich to fire in the cylinders and take some cranking dry to clear it out. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 30, 2016 Report Share Posted March 30, 2016 Hi Porcharger, Many starting issues have to do with carb setup. Idle speed, choke setup, too high an idle speed or too low. Use of the choke at the wrong time or with the wrong idle speed. First make sure the carbs are synced. That's very important. Then set the idle speed around 1700'ish. Use full choke only on the first start wit a cracked throttle. If you have too high an idle rpm it will cause hard starting with choke. If the idle is set too low then lack of choke, but more importantly no additional throttle makes for a hard start. Make sure you hold the key with the starter engaged long enough. The lower the idle rpm then crack the throttle. None of my clients have hard starting issues. Make sure the plugs are gapped between .023-.027. .025 is a reasonable spot. The Rotax is a good engine. yes any mechanical thing made by man can have an issue. The huge majority of time Rotax issues are owner, operator or mechanic caused. Link to comment Share on other sites More sharing options...
procharger Posted March 30, 2016 Author Report Share Posted March 30, 2016 The plugs were wet enough with gas I could shake the fuel off and see drops on concrete, I don't understand why for 4 days I use the choke with no problem and today it floods out? carbs, are syn. and idle is 1700. I did the exact same thing on start up today just like I did the last 4 days. Link to comment Share on other sites More sharing options...
FastEddieB Posted March 30, 2016 Report Share Posted March 30, 2016 Just curious as to why the "cracked throttle". On BMW motorcycles with the same setup, the drill has always been throttle closed with "choke". Starting problems could sometimes be traced to riders subconsciously rolling on a bit of throttle when starting, which is more the drill with conventional slides. I really thought the enrichening circuit was designed with a closed throttle in mind. In any case, I get my best cold starts with full choke and a closed throttle until it fires. Once warm, no choke is needed. I may have experimented with partial choke before, but no longer - it really seems like all or none is what my engine likes. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 30, 2016 Report Share Posted March 30, 2016 having a cracked throttle hopefully puts you immediately above 2000 rpm for smoother less gearbox abuse at low rpms, but throttle use soley depends on what your idle rpm is. If it's only 1600 then throttle should be used. If it's 1900+ rpm it usually isn't needed. Link to comment Share on other sites More sharing options...
Anticept Posted March 30, 2016 Report Share Posted March 30, 2016 To add: a cracked throttle bypasses some of the enrichment circuit by providing a lower path of resistance, but also brings in more air. It's just like starting a regular aircraft engine with a cracked throttle is all. There's a sweet spot that brings it all together for starting! Link to comment Share on other sites More sharing options...
FlyingMonkey Posted March 30, 2016 Report Share Posted March 30, 2016 I crack the throttle on a warm start. On a cold start full choke puts the RPM around 2100rpm so it's not needed. Full choke seems to work better than half choke for me in all conditions, so that's what I use. Link to comment Share on other sites More sharing options...
gbigs Posted March 30, 2016 Report Share Posted March 30, 2016 Want a real starting issue? Try starting a hot Continental TSIO550K engine. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted March 30, 2016 Report Share Posted March 30, 2016 Want a real starting issue? Try starting a hot Continental TSIO550K engine. Way too expensive to have starting issue! Link to comment Share on other sites More sharing options...
Anticept Posted March 30, 2016 Report Share Posted March 30, 2016 These guys are having problems starting too! Link to comment Share on other sites More sharing options...
FastEddieB Posted March 30, 2016 Report Share Posted March 30, 2016 That one is clearly flooded! Link to comment Share on other sites More sharing options...
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