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> On Mar 6, 2019 at 00:48, <Bud Yerly (mailto:budyerly=40msn.com)> wrot
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> Remi and Jonathan,
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> Of course the early 912ULS were happier running backwards than forward.
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> If you have done all you say you have, the list gets pretty small and e
xpensive.
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> Things which helped the kickback was most importantly, the soft start m
odule and the new ignition modules (six wire). Careful assembly of the
pickups on the electrics was also essential to assure the correct pickup
went to the correct box. An early spark just as the valves close will
kick right back. See your Rotax Heavy Mx manual. I have only seen
this once on a very early Rotax 912ULS where the A&P found some broken wi
res (another problem we all discussed before) and repaired the wires with
new wires and didn=99t quite get everything wired back up right.
What a nightmare. We ended up going to two new ignition boxes paying
extreme attention to the pickup wiring and all was fine. I was chasti
sed by Kerry at Lockwood for not changing both boxes initially, as tinker
ing with one old box and putting only one newer one initially with the ol
d one, really made a mess. Note that the timing controls changed as di
d the flywheel pickups in the early 2000s then again around 2009. The
new boxes even with the original flywheel really helped this plane.
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> The high torque starter was also a help on some of these older engines
with soft start or with starting on one ignition technique. On a 912/9
14 low compression, the low torque spins at about 300 RPM with a supercha
rged battery or booster charger at 50 amps. The high torque starter sp
ins at nearly 500 RPM on the 914. On the 912ULS I found the RPM still
hit 400 plus which is more than enough for quick starts. The Skytec st
arter is OK but I went with the Rotax. I was impressed and you know wh
at a cynic I am=21
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> I would also check for a spun crank shaft or a valve timing problem.
I don=99t do that in my shop. I pull the engine and go to Lo
ckwood and have Kerry speck out the problem. A spun crank is nasty exp
ensive and is usually better to replace the entire short block. Really
expensive. =2414,000 min with labor.
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> I had a sticky valve problem on two cylinders causing a problem which w
as just that, sticky valves. We never could figure what actually cause
d it but the kickback was spectacular. We redid the heads and that cle
ared up the problem. Changed a slightly bent valve and a pushrod, lapp
ed the valves, replaced valve springs (Service bulletin) and checked the
crank and ignition modules which were OK. Heck of a thing. And only
about =244300 which was a bargain considering two guys for 3 days plus e
ngine runs at Lockwood. I suspect that the engine was over revved and
hit a valve as there were some tell tale signs on the piston carbon of th
e valves hitting.
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> I=99m in =46lorida so cold engine starts occur only one month of
the year for about 2 days. If the engine is really cold (below 0C) the
cold oil and tight oil pump can slow the engine crank some 50 RPM on eve
n a semisynthetic oil. Warm your engine with a blanket or something.
I=99m not a fan of bock engine heaters that use the crankcase bol
ts however, they make heat pads for the oil tank and crankcase that work
if the cowl is wrapped fairly tight outdoors or in a hangar. A 100 wat
t bulb in the intake works if you leave it for an hour and wrap the cowl
tight. Mobile 1 MX4T or Motorcycle racing full synthetic oil helps, bu
t warmth is always nice for quicker starts.
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> Good luck. Remember you will find the problem. It is always the l
ast place you check.
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> Bud Yerly
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> Sent from Mail (https://go.microsoft.com/fwlink/=3FLinkId=550986) f
or Windows 10
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> =46rom: owner-europa-list-server=40matronics.com <owner-europa-list-s
erver=40matronics.com> on behalf of Remi Guerner <air.guerner=40orange.
fr>
> Sent: Monday, March 4, 2019 12:27:46 PM
> To: europa-list=40matronics.com
> Subject: Europa-List: Re: I'm puzzled, again=21
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> --> Europa-List message posted by: =22Remi Guerner=22 <air.guerner=40
orange.fr>
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> As an addition to my previous post regarding the kick-back problem, I
believe it is useful to add the following regarding the sprag clutch repl
acement. After reviewing the different issues of the 912 IPC, from 2017 u
p to now, I discovered that Rotax has made several changes in that area o
ver the years. The sprag clutch itself has not been changed but the sprag
clutch housing was modified several times. Housing P/N 852405 was introd
uced in May 2008 with the following comment: =22new housing with expanded
space for sprag clutch=22. Then in January 2017, P/N 852406 was introduc
ed with the very same comment. I guess the changes were designed to impro
ve the behaviour of the sprag clutch.
> My conclusion: when replacing the sprag clutch, it is critical to repl
ace also the housing and make sure the P/N is the last version.
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> Remi
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> Read this topic online here:
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> http://forums.matronics.com/viewtopic.php=3Fp=487913=23487913
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