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Have you ever broken a barrel base stud?


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It has been reported elsewhere in the Clubroom section that there may be an issue with broken or stretched barrel attachment/base studs.


An incident has been reported by Grantisaac and below is a post from that thread.


Have any other J operators had a similar problem on which they can provide details?






Based on this thread (bit of a freudian there) we have 1 reported problem from this cause in Gawler, but no other J owners are rushing forward to report similar incidents .... or are there?




I still have trouble grasping 5 mm stretching of these bolts as I suspect that they would fail before that.




So it could be a faulty manufacture, or crook material, or over torqued at some time in its life, or 5 mm longer originally or some combination.




Grant. We need a photo of the area of the failure on the stud. Can you post a closeup of the failed stud please?




Grant, please also advise whether that engine had ever been apart or any studs or other items replaced.




Given that I have spoken with numerous J owners who have done many hours more than 450 on their engines without issue, it seems to me that more careful consideration is needed before labelling this anything more than an isolated incident.




Now, can anyone list any other specific examples of this problem where we can collectively ferret out more details?




I'll also post this in a new thread in the J owners area in case this Clubroom location is missing someone.




Regards Geoff







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Do not know of any myself, Mine I believe are all A OK and 470+ hrs now.


About to rip all heads and barrells off for some new rings (2 cyls suffering blow by) and give the heads a polish in the ports etc and hone bores new rings etc. So will see how the studs go, but 5mm is a bit of a strange thing. Do not see them stretching that far.





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Guest grantisaac

Hi Jeff, our problem with the bolts happened about 12 months ago. The result was a forced landing.The problem was reported to the RAA and at that time we thought it was an isolated incident.Since then we have heard of at least 3 others with the same problem.It depends on how many people report the problem to the RAA. At the time we had the failure we decided as precaution to replace the bolts in our second plane. Placing the new and the old bolt side by side we noticed about a 5mm diff in the length of the bolt.Maybe the new bolts were slightly shorter as it only means 2.5mm per side.Maybe the old bolt was stretched?.The motor was as is after being rebuilt from Jab. The bolts were not replaced during its top at jab ( about 3 to 4 years ago) Now on a similar thread someone has stated they are to be replaced at 1000 hours. Is this fact? and if it is, when was this brought in? Jeff as far as an isolated incident if more than one engine has the same problem it needs to be investigated.The stud from the plane at Grawler may hold the answer.Maybe you should be asking the RAA on how many of this type failure is reported as there is only a small amount of flyers that use this forum. We are all lucky that no one was hurt or killed from these failures and hope that a cause is found. I still fly the Jab and enjoy it very much.



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Guest brentc
Now on a similar thread someone has stated they are to be replaced at 1000 hours. Is this fact? and if it is, when was this brought in?

Sorry :;)3: that was my fault.


I was referring to the 'best practice' methods of Jab owners. Whilst it's not mandatory to replace them, most people do for obvious reasons as you are finding out.


For your info, the following is from the engine manual for Top-End overhaul requirements:


Top end overhauls are performed on engines after S/N 119 and dependant on condition. Parts replaced are:- Conrod bearings, pistons, gudgeon pins and circlips, rings, valves, all relevant orings and gaskets, head bolts, spark plugs, induction hose joiners, rotors, relevant capscrews and fuel line. Other parts for inspection, measure and clean or replace are oil pump, starter, alternator, fuel pump, coils, ignition leads, oil seals, induction and exhaust capscrews, carby, heads and barrels.














Here's my strip-down results from the weekend. I'm up for all new valves, 3 x intake valve seats, 3 x exhaust valve seats, a hone on all 6, new rings, new rocker bushes, new exhaust bolts, gaskets, orings and a few other bits and pieces including the new richer carby modification. For 430 hours it will be an expensive exercise.










Leakdown test results at 80 PSI:






#1 82%






#2 75%






#3 50%






#4 55%






#5 56%






#6 52%










Front cylinders running much hotter than the others and INLET valves (surprisingly) pulled in flush and require replacing along with valve seats.










All remaining cylinders had the rings frozen due to carbon and crab build-up. Blow-by wasn't so much an issue.










There is definitely an argument for possibly running on Premium unleaded if possible to stop the ring choking up with crap and freezing.










The front cylinders were seemingly in perfect order after the leakdown test, yet the valves were nearing stuffed. Makes you wonder how many people have tested and thought it was fine only to find later that the valves are actually stuffed and about to break off inside the engine 049_sad.gif.af5e5c0993af131d9c5bfe880fbbc2a0.gif









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Help I am struggling here! I though the high lead in avgas would help protect the exhaust valves and seats?


Also "valves about to break off sounds alarming". What is the mechanism or evidence of impending failure.


Are new engines from Jabiru fitted with the new richer jet/needle settings? My 230c engine (#33A 1089) plugs seems to offer evidence of a reasonable mixture, but due to poor weather up here AC has mainly done circuit work before being checked. Suppose I should ask Jabiru, but the collective knowledge here seems a better source of info.


Due to nasty turbulence over inland Northen Qld in the summer, I used to cruise at about 110 knots (well below 2850rpm) getting very low consumption figures of about 18l/hr. Also cooling of my Engine is poor with care required to control both oil and Ch temps - Not fitted Brentc'c mods yet, but will just have to find time. Looks like I may be killing my engine prematurely.


The collective experience on this formum is invaluable I feel.





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Guest brentc

Ian, I don't have hydraulic lifters in my engine and my tappets are adjusted religiously every 25 hours. I use Avgas.


Alan, you think you're struggling!! True about the Avgas being protective, however you can't seem to have one without the other. My hot cylinders were the ones that had the best condition rings, but the valves were pulled into the heads the most. The cooler cylinders are the rear ones and they appear to not burn quite as efficiently so it's a catch 22. Premium might stop a carbon buildup, but on the other hand might damage the seats. I spoke to Rod earlier and he claims that the rear cylinders are the hotter ones which is the opposite of what I found ? The inlet pipes are much longer on the front so you'd have to assume leaner I would have thought, plus the cleaner burning I found, particularly with the rings. As far as I know you will have the lean mixture and the new AD released is for the hydraulic engines.


If you're having trouble controlling your CHT and OIL temps I strongly URGE you to fit the cooling modification. The 2 hours it might take could save you a top-end overhaul at only a few hundred hours!


How do you know if valves are going to break? You don't. Trouble is with mine as I was saying is that the one(s) with the best compression and less leakage was the one with the worst valve 'meat' remaining. Pretty soon it would have run out of meat and pulled through into the head and caused an engine failure and a lot of damage no doubt.


I'm not sure on the whole Jab engine situation right now.


The school ones in my neck of the woods run all day every day and are pretty much on 1,000 hours with no drama's to date. I don't think mine would have made it that far.


I spoke to Rod earlier and he suggested that I should be tickling my engine more often, leakdown tests at 50 hours and the occasional valve lapping-in. Needless to say I am not entirely impressed.


Parts bill thus far close to $1,500.



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Brentc when you do your tappets do you keep a record of adjustment ie no 1 cly inlet tight exhaust loose No 2 Ok no adjust No 3 inlet tight exhaust O.K We did ours at 25 h for the fist 300 h now only at oil change 50 h. By keeping a record of the adjustments you will be ably to see what is happening. ie if you a valve that you have to re gap every 25 h because its to tight you can bet is pulling into the head. Our 2.2 has 650h so far( Fingers crossed);)



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Brent, as an outside looking in. Perhaps your problems there are a result of the engine running too lean. I sort of gather that from the fuel consumption figures that you quoted a week or so ago. I wonder whether there are a few more engines out there that aren't perhaps flown as much as yours that are about to spit the dummy too. For an engine with a TBO of 1000 hours, it should be standing up to the sort of use you put it too, a lot better than it has.





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Guest brentc

Geoff, my tappet movement at adjustment time was consistent with the 'pulling in' found at pull-down time. Which makes things scary with hydraulic engine as you don't know what's actually going on. The 160's here are going well and have hit 1,000 without issue. David, I don't think it's too lean. Some of them are exhibiting signs of rich running and some lean. Unfortunately a fact of life that they are different due to the intake design.



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Interesting point. Does anyone else have an opinion about choosing between the hydraulic lift version or the older?


I have just that choice now. I can get a new 2200 with hydraulic lifters in my new Cheetah, or use a zero hour rebuild without.


I was leaning toward the new engine.


Any advice?





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Ross I haven't heard of any of the hydraulic lifters valves pulling in, we have one 2.2 that had done 1100 hr before rebuild [school aircraft] with no probs with valves. I probably would go for the new fine finned donk as the cht does run cooler. But still like mine.



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There HAS to be something really interesting here.


Dear All




I find this REALLY interesting as we have some engines doing 1100 hours with no valve issues and others causing consternation & wallet lightening to their owners at a little over 400.




And I am pleased to see that good results have been achieved with both solid & hydraulic lifter models (as I have the latter with bugger all hours on it).




I find it interesting that many schools get good results when you might expect their use to be harsher on the engines.




There must be a root cause for the difference.




I wonder what it is?




Could it be light cruise loads or perhaps operation between 2000 & 2400? But you would expect school aircraft to cop a pounding in those areas too.




In all of my bike and car motorsport I have always associated abnormal valve & seat wear with mixture issues which should directly relate to, and be seen in, CHT &/or EGT readings.




Can any of you see any definite trend?




Then we have a couple of broken barrel studs that appear not to be normal and I guess may be related to the way the engine was used or maintained.




What am I missing?




Regards Geoff





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Guest grantisaac

Our club which also a flying school have been flying jabirus for nine years now and started with the 1600cc engine.We have never been able to get more than 600 hours out of a Engine. We went through the process of fitting larger cranks and flywheel bolts after a new pilot took his wife for a fly and the flywheel broke on late final.She thought it was normal for the prop to stop when you land( he never did tell her the truth).We have been through the cylinder head upgrade a few years ago due to valve failures not to mention coil packs.We have stuck with jabiru through all these changes as they are constant improvements even though it has cost us a lot of $$$$.Flying training i believe will bring out problems if there are any. The engines we hear of doing 1100 hours are usually in flying schools that are busy where the plane is going usually all day and never cools down which help in reducing carbon build up.( like Company reps cars or taxis)As far as bad maintenance on barrel bolts there is nothing to maintain as they are set to the correct tension on assembly and should not need to be touched.If they are over tensioned on assembly which would be hard to do due to their location the nut would strip or the bolt would break.Our engine had over 450 hours which is a lot of expansion and contraction of the bolt before it failed.When we first had our flywheel bolts shear it was put down to bad maintenance and guess what? A larger crank and flywheel bolts were released.When our leg bolt broke about 3 years ago we were told Bad Maintenance! now there are larger bolts .


We now have a hydraulic tappet motor in our plane which is approaching the 500 hour mark and guess what? It is running fine and has been the best motor we have had.:)



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Guest brentc

\I thought of an interesting point yesterday.


My engine has done 440 hours and was fitted with the lean burn economy kit at 150 hours. It used to burn 27 litres an hour and now it burns 20.


Therefore, I've saved: 440-150=290hours @ 7 lph = 2030 litres @ $1.50 = ~$3045.


Cost of repairs due to engine running too lean = $2,810


Saving of $235.


Am I better off?????


The obivous answer to that is no, but it was an interesting thought.



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Guest brentc

Indeed yes. I don't have an hourly rate for myself, but yes, that does certaintly influence the cost. It was really just an observation.



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G'day Brent


Have just checked in for the 1st time in a while, and worked my way thru the new Forum layout, then saw your new photo on the post.


Got a bit of a shock ... as your eyes followed me around the screen.


Is that your election poster photo?


While you are a fine looking lad, I would much prefer a shot of your darling in that place.


Is it all back together and what is your fuel burn with the 285 jet? About half way between the previous 2, I expect.


Best regards Geoff



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Just reading your lines previous...


"Could it be light cruise loads or perhaps operation between 2000 & 2400? But you would expect school aircraft to cop a pounding in those areas too.




In all of my bike and car motorsport I have always associated abnormal valve & seat wear with mixture issues which should directly relate to, and be seen in, CHT &/or EGT readings."


In my days of pumping avgas for the car ralllies that used to come thru town, The aeroclub instructors were allways bemused about these guys thinking their cars might go better whereas they were more likely to wreck their engines.


Because avgas has a slower burn rate than most other gasolines the ignition timing needs to be more advanced, otherwise the stuff is still burning as it exits the exhaust valve, so I'm told. Theres also something about 100LL that came in the late 70s, the 0-200 engine was AD'd requiring the mag. timing to be set back 4 deg. to 24, to "prevent cylinder assy detaching from crankcase". The AD still applies, except to new design cyls.


So in expanding on our interest in what's going on, I think the fuel could also affect valvegear - I suppose most are using "green" avgas 100/130 - and we need to know exactly what metal composition was used on the seats and valves, for serial no. of engines. My engine is #1680, and has "Welltite" or similar engraved on each head, I presume that relates to the seat alloy.


Did earlier engines use iron seats? when did it change? what is it now? the ones that have failed, were they old type or new? Are all valves the same?


Appreciate if anyone has this detail, it helps for deciding if a particular installation is at risk. I've done 145 hrs on the leanest of the carb tuning, and will be altering that shortly.





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Just done a similar exercise to Brent at 475hrs, all valves and seats were fine, very good indeed. Valve guids on Inlet were out to or exceeding max bore.


How is that? The Exhaust wre fine. Two sets of rings carboned up, hence poor leak down and we did the work.


Total cost approx $2000-$2200.


Now it goes like a rocket! Has been machined and refurbed by very precise and tight tolerences so may be better than new!




PS And I had a economy jet that was leaner than all yours! I had the first experimental one, which was 0.07 smaller .....now running the 285 jet which is the standard economy for the 6 cyl and I understand the 290 or 295 makes them idle rough!



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300 hour leakdown figures


Just finished a leakdown test yesterday @ 300 hours.


Cylinders 1-5 all around 80/73 (Same as when engine was brand spanking)


Cylinder 6 80/50 (leaky inlet valve)






Jabiru SPT-3300 (19-3587)



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Guest Roger

Well just to add to this we did a leak down & compression test today and bar one they all leaked to some degree - from memory it went from 80/62 to 80/75 - not tragic I am told but they need attention.


With just over 200 hours I am less then impressed.....



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I probably should have posted it earlier but we did a leak down a couple of weeks ago and found the head to barrel seal leaking on the two centre cylinders.


They were lapped in again and now runinng "smooth as" once again . The L3 that did the job said that all the rest were fine and valves were good.


450 hours on the engine


This week the fuel pump gasket blew and was leaking oil around the engine.


An easy fix once the gaskets arrived.



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While reading the current edition manual for my 2200 / solid lifters it seems theres an error in the inspection interval charts.


sect 6.3 says the head bolts and valve adjustment is each 50 hour


Sect 7.11 inspection chart calls for this every 100 hrs


Am I reading this wrong? that would be nice, but I dont think so.... I usually have to lossen the exh valves on a couple of cyls by 2 thou, every 50 hrs.





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