no start

by Tj Sch in General Tech Discussion 8 years ago

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Re: no start

by Tj Sch » 8 years ago

Tj Sch

7 13 0

You guys are amazing. I tickle charged my battery overnight and wow. First crank it started!!!
This site has been so much help for me. I am thrilled with the Rotax 912 and I have so much respect for its design and performance, but this site is just icing on the cake. I have learned so much.
Many thanks.
Tim

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Re: no start

by Roger Lee » 8 years ago

Roger Lee

127 5.2k 4.78k

Hi Tim,

Glad it was simple. Now it's time to fly.

p.s.
Most issues with the Rotax are simple fixes. Many try to make them exotic problems.
Good diagnostics and starting with the simple common issue is usually best and then follow a logical progression until you have found the problem. Jumping around and not having a clue where to look first usually causes long delays in finding the problem and can even cost money where it wasn't needed.
If your not sure then never ever be afraid to ask.

The only dumb question is the one you failed to ask. We all start at ground zero and have ask a million questions. If you are only up to question 145 then ask away because you have 1,000,855 to go. :P :lol:

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: no start

by Ian Rees » 8 years ago

Ian Rees

6 42 0

Hi Roger,

You and Kevin were both right on the money about this one (battery). Well done. Tim was very happy with the outcome.
In your last post, you suggested Tim has 1,000,855 questions to go. Now its only 1,000,854 after this one below.

Could you please give us the reason why the ignition modules need 92 RPM at the propeller to be able to start the engine?
Obviously, this also relates back to engine cranking speed (RPM) via the reduction gearbox to a specific engine RPM.

Thanks
Ian

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Re: no start

by Roger Lee » 8 years ago

Roger Lee

127 5.2k 4.78k

We have a CDI ignition and the engine rpm must be to a minimum to produce enough electricity to cause the plugs to fire with enough juice to ignite the fuel. If you have a 912ULS it has a 2.43:1 gear ratio. You need approximately 225 engine rpm, which is 92 prop rpm to excite a spark. A good battery with no engine problems will run considerably more than that so most of the time we have no issues with producing enough juice to cause the plugs to fire. The 92 is the bottom end. More rpm is better. Once you are down at the lower rpm limits the human ear can't tell the difference unless it is really slow. before I ever jump to any conclusions I always jump the battery with a good charge to rule this out. Then and only then will I move on to the next most common cause. Good diagnostics is about ruling out possible causes.

We all have this many to go. I'm only 5 questions ahead of Tim. :silly: :lol:

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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