Today's Message Index:
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1. 06:25 PM - rough running at 3400 RPM and above (MacDonald Doug)
2. 08:48 PM - Re: rough running at 3400 RPM and above (Richard Girard)
Message 1
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| Subject: | rough running at 3400 RPM and above |
Finally, after just over four years of building I am to the point of test running
the engine on my CH-701. Not surprising me at all, I am having an issue or
two along the way.
The engine runs great from idle of about 1850RPM up to around 3400 RPM and then
starts running rough and bogging out. If I pull the carb heat on or pull on
the enrichener I can get it up to about 4000RPM before the roughness starts.
This would suggest to me I am running lean.
My engine is a 1999 vintage 912UL with the older style Rotax log carb heat plenum.
This was a used engine that I got from a scrapped CH-701. There are about
13 hours on the engine before the plane was damaged and not repaired. The engine
was run on a test stand three and a half years ago but has not run since.
So far I have pulled the float bowls off and cleaned out the main and idle jets,
removed the gunk from the float bowls, and cleaned the little orifice in the
corner of the float bowl. After doing this the engine starts and idles great.
I have done a mechanical syncronization and think I have a fairly good pnumatic
one too. At least the needles on the lockwood syncro gauges move at the same
time. Not quite the same amount though. If it makes any difference I am running
100LL for test purposes so octane shouldn't be an issue.
Any suggestions as to why I am getting bogging out at 3400 RPM?
Doug MacDonald
NW Ontario, Canada
Message 2
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| Subject: | Re: rough running at 3400 RPM and above |
Doug, Look for gunk around the needle jet, the needle itself and in the main
jet. Also make sure the vent tube to the float chamber is clear. Check the
carb connector boots to make sure there are no cracks (you can miss this if
you don't take them off and get them up to a strong light).
Have you checked the plugs after a run up to where it starts to run rough at
3400 RPM? What EGT and CHT readings are you getting at the stumble point?
If you don't feel comfortable doing a full carb rebuild, you might want to
consider having a shop do it.
Rick Girard
On Sun, Jul 4, 2010 at 8:18 PM, MacDonald Doug <dougsnash@yahoo.com> wrote:
> dougsnash@yahoo.com>
>
> Finally, after just over four years of building I am to the point of test
> running the engine on my CH-701. Not surprising me at all, I am having an
> issue or two along the way.
>
> The engine runs great from idle of about 1850RPM up to around 3400 RPM and
> then starts running rough and bogging out. If I pull the carb heat on or
> pull on the enrichener I can get it up to about 4000RPM before the roughness
> starts. This would suggest to me I am running lean.
>
> My engine is a 1999 vintage 912UL with the older style Rotax log carb heat
> plenum. This was a used engine that I got from a scrapped CH-701. There
> are about 13 hours on the engine before the plane was damaged and not
> repaired. The engine was run on a test stand three and a half years ago but
> has not run since.
>
> So far I have pulled the float bowls off and cleaned out the main and idle
> jets, removed the gunk from the float bowls, and cleaned the little orifice
> in the corner of the float bowl. After doing this the engine starts and
> idles great.
>
> I have done a mechanical syncronization and think I have a fairly good
> pnumatic one too. At least the needles on the lockwood syncro gauges move
> at the same time. Not quite the same amount though. If it makes any
> difference I am running 100LL for test purposes so octane shouldn't be an
> issue.
>
> Any suggestions as to why I am getting bogging out at 3400 RPM?
>
> Doug MacDonald
> NW Ontario, Canada
>
>
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