--> Europa-List message posted by: Pete <peterz@zutrasoft.com>
Great advice Bud!
I’d add two points:
1) sample size = 1, the copper gaskets are effective and durable, even with
badly pitted heads unable to be rectified by lapping.
2) again, sample size = 1, my ULS (read high compression) classic with the
factory approved heavy (measured 5300 rotational mass at the upper region of
the rotax spec limit) 3blade fixed pitch non tapered warp drive prop, combined
with low throttle & lower rpm cruising (underdamped lightly loaded blades),
will set up gearbox dog resonances (as measured in flight with the smart
avionics balancer isolating to the rotational axis and measuring in all three)
which will ultimately pocket the dogs (amplifying the issue), and damage many
engine attached components - and cracking exhausts ad nauseam. Blaming the
engine/timing/start etc might be incorrect.
Yes, i am also running the smoothly sweet ignitech’s (start at ATDC), and a
lithium battery with small starter - both installed prior to swapping in my
super light e-prop (read no cruise resonances).
Cheers,
PeteZ
.
> On Jan 6, 2024, at 10:44 AM, Bud Yerly <budyerly@msn.com> wrote:
>
> --> Europa-List message posted by: Bud Yerly <budyerly@msn.com>
>
> I found simply lapping the exhaust into the head cured the issues with the
> exhaust leaks at the cylinder head. Attention to detail is essential as I
> covered in my troubleshooting document.
>
> The exhaust leak issues were normally with the 912S. The development woes of
> the 912S and its shaking, kickback, harmonic problems and cracking of the
> block were well covered up (probably a poor choice of words, more like
> "development issues") and many individual owners suffered (and still do) as
> Rotax blamed propellors, fuel, carb balancing etc. rather than just fixing
> the engine. By 2005 Rotax silently (in my opinion again) fixed most of these
> issues and after reinforcing the block, changing timing, carb mixture and
> stronger starters, we now have a well reinforced and timed 912S being
> produced. Those soldiering on with the older 912S engines have had to
> rebuild or replace the short block, gearbox, sprag clutch and other issues.
> The newer 912S is still not perfect but is an acceptable engine in my opinion
> as Rotax did address nearly all the original issues. I'm still not a fan of
> the 912iS or the big bores so don't ask . Time will tell on that. The 912
> and 914 do n!
ot!
> have near head leak issues as the 912S (pre-2006) but are not full proof
> either. Early models of the 912 and 914 had their issues also.
>
> Lapping of the exhaust down pipe to the head has to be done at the angle and
> orientation the final fit will be, so alignment marking is essential as is
> patience holding pressure and slightly rotating the downpipe during the
> lapping process. It helps to have strong wrists or a helper to push while
> the other pushes and pulls on the downpipe. We used valve lapping compound
> at Custom Flight, and in about 20 minutes of work we had a good fit curing
> the leak around the offending conical exhaust fittings used on most of the
> 912S exhausts supplied for the Europa. I found the lapping method to be
> superior to trying copper or asbestos exhaust gaskets. Just make it fit
> properly! Aluminum is soft and easily "machined by hand" with the lapping
> compound.
>
> The large cone to cylinder mating surface is ideal for lapping. Some have
> issues with the studs coming off with the nut. Remove the corroded nut,
> clean the stud or get a new one, and Loctite the stud back in and allow to
> cure. (Yes, the Loctite will fail with heat, but it will allow fitting and
> proper torque during cold installation.) PUT ON NEW NUTS as they are worth
> it. Don't be cheap or too quick to try Band-Aids as Aera 51 commented.
>
> The muffler ball joints on the muffler originally did not have a proper seal
> either. I had to use exhaust sealing paste on the older CKT mufflers as a
> Band-Aid (pre 2010). Later Robin at CKT redesigned his downpipe to muffler
> joint and I find the new exhaust to be nearly full proof as the cup and ball
> seal works very well, especially with a little exhaust paste. CKT also found
> that the exhaust springs were best to be made from stainless spring material
> and they did extensive work on the cause of spring failure as well as
> securing the tooling needed for smooth, nick free spring manufacture which
> greatly improved the spring life. Hence you see nearly all the LSA aircraft
> using his exhaust or a copy. I know that motorcycle springs are cheaper, but
> they also do not have proper hooks in most cases. Again, don't be cheap,
> even motorcycles have issues and quality springs are not used due to cost.
> If they cost more, they don't sell but they last longer. Flying is not cheap!
u!
> nless you like a lot of downtime or excitement in flight. As my old friend
> Walter Hudson said: You know what keeps an airplane airborne, MONEY. It
> costs time and or money to fly a well maintained airplane.
>
> Personally, I don't like springs on exhaust joints, so I also run .041 safety
> wire through my springs to the hooks to assure a broken spring did not become
> a FOD hazard. Plus, the exhaust stays together if a spring corrodes or fails
> because you chose cheap steel springs. To prevent spring harmonic
> resonation on the 912S I also run a thick bead of high temp silicone down one
> side of the spring which dampens the vibration increasing spring life.
>
> Note: Any 912S maintainer should change all the springs at the 5-year point
> in my opinion. The springs will be heat cycled many times by then, and
> although looking OK, will eventually fail. Corroded springs should be
> replaced period.
>
> Finally, exhaust manifolds and mufflers are not forever pieces of equipment.
> They endure extreme heat, vibration and are often abused with poor mounting
> on any internal combustion engine. Inspect your exhaust often and repair
> properly as an ill-fitting exhaust not only leaks, but it also causes
> harmonics of its own that contribute to fatigue around the heads. It is
> money in the bank if you have an original troublesome exhaust to simply "drop
> a thou" and replace the exhaust. (Engines don't last forever either. If
> your engine is excessively shaky, consider a short or long block overhaul if
> it is one of the early 912S engines. Maybe even a new replacement as even
> engines at or near 1000 hours are due serious maintenance, just like those
> dinosaur Lycoming and Continentals.)
>
> My "Rotax Engine Troubleshooting and Maintenance from Experience" paper is
> still on the Europa Club website and my website
> (www.customflightcreations.com). It was updated last in November of 2021 and
> is still current. It has many of my maintenance techniques over the last 20
> plus years maintaining the Rotax, including the exhaust.
>
> Just my thoughts,
>
> Bud Yerly
> Custom Flight Creations
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> <owner-europa-list-server@matronics.com> On Behalf Of Area-51
> Sent: Friday, January 05, 2024 10:59 PM
> To: europa-list@matronics.com
> Subject: Europa-List: Re: Slight exhaust leak at cylinder head manifold joint
>
> --> Europa-List message posted by: "Area-51" <goldsteinindustrial@gmail.com>
>
> Several possibilities; all treated differently.
>
> The cylinder head sealing contact surface itself could require lapping. Best
> way to affect this is removal and bench lapping with 240g paper glued onto
> the exhaust header with contact cement; some kerosene as lubricant and rotate
> header back n forth about 50deg for a bit, then lift and rotate 30-70deg and
> repeat several times Not much pressure required. Easiest to clamp header
> pointing up and rotate head upon it; makes cleanup easier... can use valve
> grinding past as well... soot or bearing blue at the start and end can be
> used to check sealing surface for gaps. Sealing surface only requires 1mm
> cross section.
>
> The 914 has part of the header extending into exhaust port; it is a very firm
> fit when new; long term slop flogs out this area in the head casting and
> requires sleeving insert to prevent leakage.
>
> Copper compress rings can be used as mentioned and should be set centered and
> tensioned again when hot. This is a bandaid approach to rotax factory sealing
> method and may work totally fine. Have found copper rings on some engines.
>
> Heat expansion of the header pipe may be causing movement at the sealing
> point and returning to normal once cooled down. Stainless steel pipes grow a
> fair bit when heated up. Some stainless steel exhaust systems on cars can
> grow up to 30mm... Try loosening off header at cylinder head and collector;
> give the header a few light taps with hide hammer and retighten just under
> spec and again once cooled down. Observe for outcome.
>
> Check the clamping collar when tensioned; there needs to be a gap between the
> collar and the head; the collars bend quite easily when over tensioned.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=513027#513027
>
>
>
>
>
>
>
>
>
>
>
>
>
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