Starting Anomaly

[todehnal]

I am now approaching 70 hours on my RV-12, and since I bought the firewall forward kit early in the build; fall of 2010, the battery is now 4 years old. I always pull a few blades though before starting, which is an old habit from my round engine Cessna 195 days. Hey, old habits are hard to break! Anyway, I am experiencing an engine rotation stall, as the first piston approaches TDC. I immediately release the starter, then hit it again. It always goes on the second try, but I was wondering if anyone else is experiencing this, or if I need to do a load test on the battery. I do have soft start installed, and use ignition "A" only until I get a start. When pulling the prop though by hand, I have detected an increase in compression as the engine breaks in, which is perhaps why I didn't experience this stall on start-up until recently. I even tried leaving a battery tender on it until I am ready to fly, which did not help. Everything else appears normal, and I continue to see 13.8 volts during flight. I hesitate to start a systematic troubleshooting routine, if others are experiencing a similar stall on start-ups. Any thought out there??

Tom

[Hotscam]

When the kit is of 2000 the battery is 14 years, but guess you mean 2010
I am pretty sure it is the battery.
It cannot deliver high currents any more due to degradation, which is typical for long time unused batteries.
Measure the voltage when the starter is running.

[todehnal]

Thanks Jack. Yeah, I corrected my post to state 2010. I will check the voltage during start up, and I may go ahead and get a load test done on the battery at annual time, which is in October. We have a local shop that does it free. I was just curious if anyone else experienced a similar stall on start-up. Also, we head for Florida in December for three months, and if I need to replace it, I will wait until spring to make the swap...........Tom

[akarmy]

So one thing to keep in mind. The 912S does not like to have a weak battery. It's high compression engine and I suspect you are experiencing what the Rotax guys call "kick back" which if you let happen too much you get the joy of replacing your Sprague Clutch. Which is a costly experience. I know because I had to do it on my 912S in my Kitfox. I had the soft start which was supposed to solve that problem, but over time it got worse and started kicking back more and more even though my battery was new. I finally got the clutch replaced, had a new battery, and replaced both A&B ignitions to the new ones that have the start retard timing built in so no more soft start needed.

With all that, it starts great now!

[DRigotti]

I thought it was standard procedure for Rotax to pull the prop through until it "gurgles" and then check the oil level before starting if the engine has been off for 30 minutes or more. Pulling a few blades might be asking for extra oil in the crankcase that could lead to more resistance to turning over and maybe hydraulic lock?

[Bill_H]

You don't need to burp after an idle time of thirty minutes. It is done only to accurately check the oil, not for lock. Easier to burp after the last flight of the day and check oil level. If no puddle underneath the next time you fly, should be good.

[RFSchaller]

Harbor Freight has a cheap 100 Amp load tester.

[DRigotti]

So you don't check the oil during your pre-flight inspection? Hmmm....

Originally Posted by Bill_H

You don't need to burp after an idle time of thirty minutes. It is done only to accurately check the oil, not for lock. Easier to burp after the last flight of the day and check oil level. If no puddle underneath the next time you fly, should be good.

[rv3flier]

I check mine post flight - seems to take less time.

[Geico266]

Originally Posted by DRigotti

So you don't check the oil during your pre-flight inspection? Hmmm....

No need if you checked it last flight. It is much easier and faster to get the oil back in the oil tank when it is hot rather than cold. Fairly common practice for Rotax owners.