Today's Message Index:
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1. 06:03 AM - Re: 912 80 hp back-fire on shutdown (Roger Lee)
2. 06:36 AM - Re: 912 80 hp back-fire on shutdown (ejessee)
3. 07:48 AM - Re: Re: 912 80 hp back-fire on shutdown (Lanny Fetterman)
4. 07:25 PM - Re: 912 80 hp back-fire on shutdown (dashwood)
Message 1
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| Subject: | Re: 912 80 hp back-fire on shutdown |
Here are a few things to check and try. First the header wrap isn't causing the
problem. You are running a little rich and this could be caused by your shut
down procedures. Is the air mixture screw on the bottom turned out only 1.5 turns?
This needs to be double checked before the next test. Are you venting any
fuel out the vent tubes? Slow the engine down to 1650-1750 before shutdown and
turn one mag off for 2 seconds and then the last one. The 2100 rpm shut down
may be part of the problem. Open the gap a little on the plugs to .025 -.026.
(not my first consideration)
.023 -.027 is the normal gap, but sometimes having a small gap gives an incomplete
burn. You just may have more than one thing adding to your problem. If the
above suggestions don't help then you may need to pull the carbs back off. This
is what changed since the problem started and someone may have done something
wrong on the carb rebuild. It could be something as simple as the float arm
at the wrong height. My bet is it will end up being a carb issue.
Have you done a compression leak down test? (This would be my last thing to do,
but would remain in the back of my mind).
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
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| Subject: | Re: 912 80 hp back-fire on shutdown |
Thanks to everyone for replies.
As to the problem starting after the carb rebuild... it didn't start then. It
has been happening for some time. I will check all the things suggested. I
have been shutting down at about 2100. I will begin shutting down at 1700-1800
RPM. I already do the 2 second per mag thing at shutdown. I will be doing
a compression check as my conditional is coming up.
I just changed the plug gap about 2 months ago to ease in cold starting. the regap
helped in cold start, but again... the backfire/after fire was happening
before that change.
I have checked the exhaust stacks... they are tight. There is no rust on the exhaust,
so small leaks are unlikely... but possible. I'll check that as well.
Thanks again to everyone.
--------
Ernest Jessee
N4931M
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| Subject: | Re: 912 80 hp back-fire on shutdown |
I joined this thread late, so maybe you already discussed this, also
I have NO experience with the 912. However, aren`t backfires and
ignition timing related? I fly a Kolb Firestar II Rotax 503.
Lanny At 09:34 AM 1/31/2012, you wrote:
>
>Thanks to everyone for replies.
>
>As to the problem starting after the carb rebuild... it didn't start
>then. It has been happening for some time. I will check all the
>things suggested. I have been shutting down at about 2100. I will
>begin shutting down at 1700-1800 RPM. I already do the 2 second per
>mag thing at shutdown. I will be doing a compression check as my
>conditional is coming up.
>
>I just changed the plug gap about 2 months ago to ease in cold
>starting. the regap helped in cold start, but again... the
>backfire/after fire was happening before that change.
>
>I have checked the exhaust stacks... they are tight. There is no
>rust on the exhaust, so small leaks are unlikely... but
>possible. I'll check that as well.
>
>Thanks again to everyone.
>
>--------
>Ernest Jessee
>N4931M
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=365298#365298
>
>
Message 4
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| Subject: | Re: 912 80 hp back-fire on shutdown |
i would also put much weight into Mr Lee's comments, thanks for jumpin in as always...
its hard to sit by and see someone misdirected. :)
thanks
--------
Ross Aalexander: CH701 driver 912ul 589tt
It only takes two things to fly, airspeed and money
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