New Flywheel

[procharger]

What is part number and price of the new flywheel for soft start setup?

[Ed Cesnalis]

I got a new sprag clutch but kept the old harder starting flywheel.  With the new ignition modules my starts are much softer.  I also have a Tanis pre-heater that means soft cold starts without the choke.  The sprag clutch was expensive enough without adding a flywheel.

[Anticept]

Procharger: before you go and replace the sprag, make sure the battery is not the problem. Just looking out

[procharger]

thanks even with jumper cables hooked up it still not staying engaged like it should, turns

plenty fast like that, its just to far gone I think, going to do it all hoses too, what the hell its

only money. Battery was new last year, I keep a maintainer on it all the time to. I going to fix

it if it breaks me. My brother tried to start it back in winter when it was really cold, the light

bulb I had in it was burnt out not sure how long it was off,but he tried to start it anyway

for 45 min. so I know that did a lot of damage to sprag can't imagine how low the battery got

with all those starting attempts, of course it never started. Did new floats today new needles for

seats and new arms for floats was some damage on one needle and the float level was a little

high.

 

 Charlie how many hours before failure, I have close to 1300 hrs.

[Roger Lee]

Before you tear everything apart put a load tester on the starter. It should pull a minimum of 75 amps at start. If it doesn't then it's most likely the sprag. The usual way the sprag gets trashed is from either many long cranking sessions and or kickback on a regular basis. If the sprag is failing you should see the prop disengage from rotation, but still here the starter running. Unless you trash the sprag it should go well past TBO. The other thing that will kill a sprag in as little as 600-800 hours is running rich with 100LL and low engine temps. It causes excessive lead build up.

[procharger]

Roger the prop does stop turning but the starter if still turning or running, question ,replacing

flywheel and sprag with the new modules does all that get rid of the kickback problems?

[Roger Lee]

Kickback isn't from either one of these. It comes from things like poor carb setup, poor starting techniques, weak battery, long term leading from 100LL, having the gaps on plugs so far out the firing is messed up,  It could come from the trigger coil air gap in the flywheel area being out, bad ignition modules (usually the starting circuit starting to go) and last but not least a starter that is getting tired and weak. The three underlined are the most common.

[Ed Cesnalis]

Starting with rubber debris from the hose change is what killed my sprag.  violent kick back and violent start.

[Roger Lee]

"rubber debris"

 

Is basically carb setup. It was just induced to cause fuel interruption.

[procharger]

Here is what I say to all these starting issues, it appears that this engine was poorly

designed as far as starting system goes by Rotax, its obvious to me that this

setup is barely good enough to do the job. I've worked on 7 different brands of

motorcycles, many types of boat motors, all kinds of car engines, lawn mower engines,

never have I ever seen a engine that had to have all these things such as carbs, spark

plug gaps, battery, cables, certain starting procedures have to be perfect, or dam close

to even get the engine to start. Nothing else even comes close to this engine as far as

getting it to start, if you got gas, compression, and spark most all engines will at least start.

Its been a problem for years with no real improvement except spending lots of money to

fix their problem. It's a shame the engine does a good job, but starting is such a big deal.

Just my 2 cents. Or yea I forgot the ice bag to.

 

I am 61 years old so this ain't my first dance.

thanks for all the advice and feedback maybe I will get

it all fixed soon.

[Anticept]

I would think that starting problems consist of a tiny portion of people... Most seem to be trouble free.

It's really freaking hard to make an engine that can run at 4/5 rated capacity for most of its life, and be able to go from frigid cold, to blazing hot, from high pressures, and low, all without using o2 sensors and a precise mixture control... None of the other engines you stated can claim the same level of flexibility without also seeing some ignition issues too, with the same limitations on o2 or mixture control.

Also, this is pretty typical of other aircraft too. Ignition problems are not isolated to rotax, I do see it about as much with regular planes too.

If we could at least use throttle body injection, o2 sensors, and better designed modules on the ULS, I'm pretty damn sure it would be bulletproof.

[procharger]

All it needs is enough power to drive through compression stroke, then I don't

think it would such be a big deal, but it seems to me it's just enough to barely

get it done, yea timing has a lot to do with it also. I  can only compare to what

I have experience with. Never had ign. failure with any of my bikes which I

have had many, some for long periods of time. I am talking some 20, 30

years old all Jap. bikes, yea things break but not like these problems

on this engine. As I look at all sites about this, seems that there are a lot

of the same problems every where I look. I've worked on Honda CBX with

6 carbs, they were never perfect but always ran well, try to set those and

see what happens, they didn't have to be perfect just close to work well.

[FastEddieB]

I think another thing that sets the ROTAX apart is the "need for speed" on starting. I think that's so the coils that power the ignition modules can generate enough voltage, and why hand propping is unlikely to work.

 

Planes with regular magnetos traditionally have an "impulse coupler", that allows for a decent spark with the engine barely turning over. Nothing like that on the ROTAX.

 

But I agree with Anticept that most of them start with no issues most of the time. Which, of course, is no consolation for those like procharger who are having continuing and difficult to diagnose problems.

[Anticept]

I think another thing that sets the ROTAX apart is the "need for speed" on starting. I think that's so the coils that power the ignition modules can generate enough voltage, and why hand propping is unlikely to work.

 

Planes with regular magnetos traditionally have an "impulse coupler", that allows for a decent spark with the engine barely turning over. Nothing like that on the ROTAX.

 

This 1000x over. And, I feel this is the big reason why the injected engine is actually easier to start.

 

EDIT: Procharger, I forgot a big point in my previous post, and left an incomplete idea. I wanted to say "None of the other engines you stated can claim the same level of flexibility without also seeing some ignition issues too, with the same limitations on lack of O2 sensors for live tuning or precise mixture control."

 

The nice thing about cars, boats, motorcycles, etc, is they generally don't deal with rapid altitude changes. Those that do, and don't have computer control, usually need some tweaking if you're going from the tops of mountains to the coast.

[Roger Lee]

Hi Procharger,

 

Do you have an authorised and or trained Rotax tech looking at this issue?

 

 

This may not be an ignition problem at all and you need to start at "A" and then go to B&C&D&E, ect... to diagnose the issue. Jumping around without any knowledge of the systems may take you a while to find and or lead you down the wrong path.

[procharger]

Yes I have a trained Rotax tech working on the problem. He just finished

retraining a month ago, he has  many years with Rotax 912 engines.

[procharger]

All these engines I was talking about still start at sea level or 10,000 feet without

fail, they need no tweaking to operate in these conditions. There will be a loss

of some power but that is it. This is not about Ign. problems, only poor design for

me. I can deal with part failure not design failure.