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Catalina engine replacement


17 posts in this topic

Posted

Hey Guys...a sad week end just passed. You probably already know that I was struggling with my previous GSC/warp drive prop. Indeed when I applied full power for t/off I usually set the pitch at about 5300 (that's before the plane is moving) and this way I got 5700rpm at climb out, later to be set at about 5500. Unfortunately my prop was feeding back too much force into / through the linkage and bending a bracket doing so. The result was that just when taking off, the prop went into a finer pitch and made the engine go beyond 5800Rpm. At first I did not realize what was happening as at each take off I had to dial in a bit more/coarser pitch....Once I had a real bad overspeed going well beyond what Rotax accepts. Of course I reduced power as quick as i could and as I was already flying I kept going and landed safely at my home lake. When I read out my Rpm gauge History my heart sunk....7400Rpm

Now officially this means the engine is toast even if it only lasted a couple of seconds. As I fly over lakes all the time, mostly alone I took the decision at first to do the overspeed inspection (compression, filter, borescoped the cylinders etc) and see if the engine keeps me going. There was no sign of anything wrong for about 7 Hrs (besides a little voice in my head) but on my last two flights....not so good. The engine was much harder to start and was running a bit rough (these are some signs of overspeed damage)

To cut the story short, I have removed my engine (912 UL) and I will replace it wit a overhauled 912 ULS. Here the reasons....some obvious 

1.Engine experienced overspeed

2.Don't know if previous owner has had issues / overs speeds (probably yes)

3.Engine was fitted with the Xtra kit boosting compression ratio....Rotax issued a service bulletin totally against that mod (maybe too much pressure on the 2 piece crank?)

4.I fly in very remote areas and if I have an engine out it will be VERY costy to get the aircraft back home.

5.I might damage the Cat doing an engine out landing....costing in the end more than an overhauled engine

6.Overhauled engine will have all SB. and mods done (by rotax distributor ROTECH)

7. Last and not least ...get rid of that little voice in my mind....do it right

Here some pictures of my ordeal....actually the Cat looks real good without engine....

 

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Posted

Well that sucks.  Are you trading this engine in on the rebuild or what are your plans for it?

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Posted

As it stands now, I have two options...buy a new 912 ULS engine at the canadian dealer (very expensive and they would only give me peanuts for my engine) or go to http://badasspowersports.com and they would go over my engine, install new cylinders (100Hp bore) pistons, a high performance camshaft and a fuel injection, and gear the engine from 2.27 to 2.47. giving me better than 100 HP, lighter weight (-8Lbs) and a thoroughly checked through engine..

Problem with all the official rotax dealers, they refuse to install or warrant the high compression Xtra pistons. So if I have my engine gone through them it would come out as a 80Hp 912 and nothing else......

Cheeers

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Posted

Do the overhaul of your own engine.  I seriously doubt you have any extensive damage after a 7500 run.

Their big bore engines are better than stock.

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Posted (edited)

Yes it is very tempting to do the overhaul myself.....but at this time my garage/shop is a mess (no heating, no insulation no electric power except a 300ft extension)...not ready to tacle a clean job. Also I believe there are quite a few special tools and products needed for the 912 engine besides the parts I'll have to buy at a premium price.

The solution I found (Jason at http://badasspowersports.com ) I hope is good as he has been working on the 912 rotax as the distributor for edgeperformance (  http://webshop.edgeperformance.no/index.php  ) here in Canada for some years now. They actually take brand new 100Hp 912's and turn them into 170Hp turbo monsters.......

My big advantage is that he has a stock of reasonably priced new 912ULS cylinders, pistons and even reduction gears  he can fit to my 80 Hp block. Also he has lower prices for all other rotax parts. Last and not least he will set up and adjust fuel injection and a high performance cam he sells....

To start with, for the dismantling, overspeed inspection of the engine it's about 750 bucks....I find reasonable.

 

I will keep you guys updated....I am really eager to know if my engine has damage....

 

 

Edited by flywise
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Posted

You misunderstand.  I mean have your engine rebuilt/overhauled rather than buying a new one.  I don't believe there is much if any damage to yours.

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Posted (edited)

Yes got you now.....and that is the route I am taking :BC:

 

P.s to anyone searching for a good used rotax 912 uls at a reasonable price......be aware, I have looked at 3 engines for sale ..... but in the end, all 3 actually did not belong to the person trying to sell them, just crooks wanting to make easy money

Edited by flywise

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Posted

Just curious,With an over speed what is the break/damage point.Im guessing the lube system may cavitate? The valve train would take a beating.Anyone done a tear down after an "event"?

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Posted

Bet she's just fine. Time to send it in for a Zipper kit. 5K investment vs 20K.

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Posted

Hey Dusty.

....this is the million dollar question. Before I decided to tear things apart I spent numerous hours on the net trying to find SOMEONE.. who's had an overspeed. Well I found NOBODY talking about it!!!!  I can only guess that some have had it and don't care, others might have had it and don't know the rpm reached (some early gauges only go up to 6000Rpm) not mentioning the difficult task reading a gauge precisely when sh...t happens. Last the rotax dealer stands on the cautious side when you ask him. They won't say what damage they found at what Rpm...basically if it's over 6500Rpm they say it definitely needs teardown inspection...

The other thing to consider is that 2 engines are never the same. My engine only has 127Hrs...maybe a higher time engine would have different results.

I am writing about my experience to help others in the same situation.

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Posted (edited)

The stock valve train will float at about 6400.  They are not an interference fit engine.

Hal Stockman runs his continuous at 6000-6200.

 

Edited by Av8r3400

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Posted

When we're talking overspeed, I mean something serious like I did at 7400Rpm (~130%). Also a note regarding the interference fit engines, if you go high enough in Rpm, then even a non interference fit type engine will experience valves hitting the piston crowns...it has to do with the excessive velocity of the pistons and the valve springs not able to keep up. Basically the valves are not shut when they should be. This is why on racing engines, one of the first items being modified are the springs to get a faster "shut" speed.

Hope that makes sense

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Posted

Hey, I found a crack in my engine mount......engine shipped yesterday

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Posted

ohoh.  Looks like the tube is cracked out as well as the weld.  There are a few ways to fix that properly and its not that bad of a fix.  For sure something to keep an eye on in the future though on all the mount tubes.

:BC:

 

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Posted

Hey everybody, at last the engine has been unbuttoned and assessed for damage....please remember that I had the Xtra pistons in my engine...

first the GOOD:

no piston or valve damage

crankshaft and bearings good

pushrods straight.

THE BAD:

on one cylinder the piston oil scraper ring was broken and there were bits of the ring in the crankcase....

one inlet valve had a bit of blow by.

I was lucky to take the engine down before damage even though it was still going well. Listening to your gut feeling pays off ......

I found out that the Xtra pistons were problematic. it was reported that oil consumption was high. The piston boss retainer clip is also weak and liable to break. Have no idea if the oil scraper ring broke because of overspeed....it is confirmed it did not break during disassembly....

Now my engine (912 UL) is going to be fitted with ULS pistons and cylinders and my camshaft will be a high performance type. After that my 80HP will pump out a good 105 Hp but retain good reliability at a reasonable price (~4500 all included)

 

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Posted

is that a scratch or a crack in the tube?  I would be watching out for that undercut as well, your looking at another potential crack location there.

:BC:

 

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Posted

Damn....you're right there is still a crack.

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