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Has anyone replaced their old Jab with the new Gen 4? Did it just fit right in with the old cooling ducts or are new ones required, is it really a direct swap? Are you happy with the performance, is there a noticeable difference in the operation? Thanks...

 

 

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Excellent. I'm a long way off future project so will keep looking with interest at developments.    I have 3 aircraft now that will end up in farm hangar in Melbourne. An unexpected developm

I had to replace my gen 3 engine with a gen 4. Gen 3 was buggered at 730 hrs, couldn't even do a top end on it. Gen 4 is a real aeroplane engine. I think they finally got it right. I cant find anyone

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I had to replace my gen 3 engine with a gen 4. Gen 3 was buggered at 730 hrs, couldn't even do a top end on it. Gen 4 is a real aeroplane engine. I think they finally got it right. I cant find anyone having problems with these new G4s and I have been looking hard for quite a while. Run really cool, Don't use oil, when pulling prop through it has heaps of compression like a bloody aeroplane engine should have. (doesn't feel like a worn out lawn mower engine). Please let me know if anybody is having issues with theirs.

 

 

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there were problems with cylinder cracking

 

Well supported and all replaced  - THIS is a big improvement

 

Not yet convinced they are that much better than older solid lifter versions

 

 

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I am not saying anything specific ...but....your not looking in the right places maybe...they are definetly better but still problems

 

Kyle

 

I have a Gen 4 and would really like a heads up on problems that you are aware of.

 

Mike

 

 

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I am not saying anything specific ...but....your not looking in the right places maybe...they are definetly better but still problems

 

Ok Kyle, show us the problems I know about the cracked cylinders but that was right at the beginning and rectified straight away. Havent heard of anything since then. Actually while looking hard for issues over the last 12 months I come across a lot of rotax problems that nobody seems to want to admit are there.

 

 

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old rivals meet again - jab vs rotax

 

always makes and interesting thread

 

there will be no winners but its good to get the laundry out 

 

I'm sure all of us wish all owners good value, reliability and economy ................ and a clean fight 

 

 looking hard for issues over the last 12 months I come across a lot of rotax problems that nobody seems to want to admit are there.

 

 

 

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TasMag    They still havent fixed the cylinder problem completely and  I know this for a fact but I cant say too much about it

 

Rotax dont have too many problems when you consider the numbers out there. Mine had a oil pressure issue and I know of at least 4 cases just around here which Rotax doesnt like to acknowledge but mine was fixed by a smart aftermarket mod...which by the way they seem to have fixed in the IS version of engines. It only seems to be a hit and miss with the 4 lobe oil pump engines..the IS have 6 lobe pumps

 

The only other issues I ever hear about is cam lobe wear and case fretting but thats after long hours . You cant use the cases after 2000 hrs if you go to do a rebuild

 

Its like anything the shear numbers out there means you will see more but as a percentage of engines actually out there the failure rate of the rotax is a lot less than the jabs

 

 

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 It's also how much engines are active (being used). not just the numbers. One of the main advantages of the 80 Hp engines by Rotax is they aren't stressed and didn't get fiddled with in the field. Some did have starter drive issues then there was redrive clutch work done. The engine itself is fairly easy to live with and will stand being left unused much better. than most. They are Bl**dy expensive for bits and heavier than the Jab. and far more complex. Both have the same (very ordinary) Carburetters. IF the jab is sorted better it has a definite future. For the people who Knew how to run them they have always  (almost) been acceptable. Merlins only ran 400 to finally around 650 hours. I spoke to the flight engineer on a Tupolev turboprop (Russian Ballet) in the 60's at Essendon who proudly told me they were now getting 450 hours out of the engines . Nev

 

 

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TasMag    They still havent fixed the cylinder problem completely and  I know this for a fact but I cant say too much about it

 

Kyle

 

Thanks for that, is there anything too look out for?

 

Mike

 

 

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Expensive parts..surely you jest Nev...my engine a std 912 ULS being rebuilt now for the S21 is mind boggling on some of the parts...I need 3 main bearings for the crank..that is 6 half shells of just white metal..usually reasonably priced...well 6 bearing halves is $600 !!! thats 100 per bearing half.  Sprag clutch is $440...You can buy the exact part used in a motorbike that is from the same OEM for $100..Exhaust valve for one is $330

 

The parts are overly excessive...its not Floods either its the pricing from Rotax

 

 

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Rotax failure rates have always been lower than Jabiru failure rates but it was the twisted data that CASA used in the 2014 Engine restrictions based on raw data rather than real data that eventually led to a Senate enquiry and a couple of ex RAA now CASA employees being let go. At the height of it CASA lists 40 Jabiru engine failures but this was reduced to 12 after such things as running out of fuel and shutting the engine down after an oil leak etc were removed from the list. The whole debacle nearly sent Jabiru broke. There have been well over 10,000 engines produced and they are in aircraft flying all around the world. Rotax had produced 50,000 engines by 2015. I'm not sure how many there are to date but I'd guess at least 60,000.. Both are good aero engines but require appropriate maintenance to ensure they keep running well.

 

One thing to note is that Rotax failure rates increased in 2013 from 1.5 to 2.7 per 10,000 hours and at the same time Jabiru failure rates came down from 4 to 3.3 per 10,000 hours. This was publishe in the ATSB report at the time

 

 

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Tasmag the only thing I know of is the cylinder issue is still a issue...I was really hoping the Gen 4 would have been a big success as I was going to use the 6cyl in my S21...but I decided to use a big bore 912 to get a bit more hp..but 120hp would have been really nice and a cheaper engine. My decision to stay with the Rotax was the info that I have been privy to see and collect. The Gen 4 is definately better but still have a issue I am not willing to play with. I hope they get it sorted as a cheaper lighter more powerfull engine is what is needed to knock Rotax off... because they just screw everyone over on parts...if there was more valid competition in engines then those parts would come down a lot and maybe The obscene engine prices.   Oh and another fun fact...NONE of the rotax engines are balanced when they are made and sent

 

 

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Yes, Austin A 40s were rebored at average of 45K MILES. The Engine Reconditioners Association put out figures on all popular makes but the aircleaners were not very effective in those days. Not much more than a silencer.  Other makes made up to 65 000 (Valiants) none of those figures are very good but were reflected in what actually happened  "in the field"  at that time...Nev

 

 

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Rotax failure rates have always been lower than Jabiru failure rates but it was the twisted data that CASA used in the 2014 Engine restrictions  At the height of it CASA lists 40 Jabiru engine failures but this was reduced to 12 after such things as running out of fuel and shutting the engine down after an oil leak etc were removed from the list.

 

KG...and you dont know how many of the Jab failures were never reported.....I know first hand of at least 20 just around my area...this also goes for rotax too I suppose but to be honest I hear of very very few rotax failures around here...jab failures ?..well many more but they are not reported

 

 

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Kyle re the balancing do you base that on no holes being drilled? . Sometimes when parts are machined all over dimensional accuracy is enough to produce a consistent result without individual balancing. I must confess I hate the pressed up idea on that crank. Did they intend to make it roller bearings? Why would you do it otherwise? Except to make the crankcase smaller dimensionally (and make it less rigid). Nev

 

 

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Nev...actual engines pulled apart..we have had 4 cranks on the balancer and all are out by the same amount and by the same angular. The flywheels are not balanced at all as we have made up a spindle to balance the flywheel by itself to see and when the combination of that flywheel on that crank the out of balance is a lot..and a big lot. My new engine has had the crank welded and it basically did not change the out of balance at all so now my crank and flywheel have been balanced as a spinning combination as it should have been at the factory. I dont know if the jabs are balanced though

 

 

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 Kyle, Do the parts separately or combined ? . I prefer to do them separately, myself.  It's crazy not to get the balance right in any case especially for a company with a generally good name.. Most mass produced engines are quite well balanced during production. Four cylinder motors will always have periods of vibration though due piston inertia. and offsets. Any six is so much nicer.  The Jab 6 is a nice feeling and sounding engine to be behind. Nev

 

 

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We checked the balance of the crank and flywheel separately and also combined....total crap...not just on 1 engine either as there are 4 being done

 

Going to trial balancing a flywheel to match up with the pretty std cank balance which is very similar between each crank. Then will balance a flywheel to suit and put it on a working engine as it isnt a huge drama to change just the flywheel. Hopefully it smooths the engine out a lot

 

 

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