Today's Message Index:
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1. 02:49 AM - Exhaust No 4 downpipe split (graeme bird)
2. 08:00 AM - Re: Exhaust No 4 downpipe split (JonSmith)
3. 09:57 AM - Re: Exhaust No 4 downpipe split (graeme bird)
Message 1
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| Subject: | Exhaust No 4 downpipe split |
Spotted an exhaust spring on the floor; on investigation found 2 had broken, port
outside front and starboard inside front. Changed them and had a good inspect
but only just noticed a small line near the top of No 4 downpipe (rear port).
On closer inspection, and removal of the small carb bowl shield I had wired
onto the pipe, to my horror I saw the crack went 3/4 of the way round the back
of the pipe up near the bend (I have seen other reports of this). I had wondered
about the general discolouration of engine frame etc. around that side of
the engine. It was just so hard to spot. I thought the engine had been sounding
a little different and maybe it was a contributing factor to a couple of hicks
i'd had recently.
New item ordered from CKT and fitted (said 4 on the new flange but 1 on the old
one).
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Graeme Bird
G-UMPY - Mono Classic/XS FFW 912S, Woodcomp SR3000/3W CS, trutrak Gemini 2 axis
AP, PAW, PFLARM core, ads-b out, 8.33khz, mode S, FP-5, Aera500, SD on Nexus,
Smart A3
350 hours & 6 years on the Mono, 930 total
g(at)gdbmk.co.uk
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=482694#482694
Message 2
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| Subject: | Re: Exhaust No 4 downpipe split |
Graeme, I dont know if the following is of any relevance to you but I had a history
of identical cracking to yourself on my 912ULS. Both rear down pipes,
twice each side. The photo attached shows the first time one went. Also numerous
springs lost too.
My engine was second hand to me, I had the first down pipe crack within 5 hours.
Although the engine was generally very smooth running I had an ongoing problem
with vibration immediately after starting (NOT kickback) and also when throttling
back during descent after cruising flight (unloading the prop). This
high frequency vibration was teeth chatteringly severe but only lasted a few
seconds each time. I learned to live with it by modifying my starting technique
and my initial descent technique but looking back now I fully believe it
was this that was causing my exhaust to fail.
On my description, Kevin Dilks immediately diagnosed it to be worn prop shaft splines.
He said this was common on ex-weight shift microlight engines which mine
was, due to their foot-throttles and very slow idling RPM habits. Kevin
fitted a new prop shaft and the result was absolutely fantastic. All vibration
problems completely gone for good and the engine is now like a sewing machine.
Touch-wood my exhaust has stayed in one piece since and Im very much hoping
that issue has been cured too....!
The new prop shaft was seriously expensive and I put it off for a while but it
was actually the best single payment for maintenance that Ive ever made on the
machine.
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G-TERN
Classic Mono
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=482697#482697
Attachments:
http://forums.matronics.com//files/48447328_3c26_4c04_9c95_355b72a47f88_464.jpeg
Message 3
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| Subject: | Re: Exhaust No 4 downpipe split |
Interesting Jon, I think, from the discoloration, mine has been cracking over
a period starting at the weld. I am now at 400 hours and had the engine from
new. But I will keep my eye on it and watch for vibration. I cant say I have had
any particular vibration at start up although there has been the odd start
when the prop seems to stick and needs a reprime and re start.
--------
Graeme Bird
G-UMPY - Mono Classic/XS FFW 912S, Woodcomp SR3000/3W CS, trutrak Gemini 2 axis
AP, PAW, PFLARM core, ads-b out, 8.33khz, mode S, FP-5, Aera500, SD on Nexus,
Smart A3
350 hours & 6 years on the Mono, 930 total
g(at)gdbmk.co.uk
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=482701#482701
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