Today's Message Index:
----------------------
1. 10:59 AM - Re: rough running at 3400 RPM and above (rampil)
2. 02:03 PM - Re: 914 Fuel Pump (h&jeuropa)
3. 06:57 PM - Re: rough running at 3400 RPM and above (MacDonald Doug)
4. 08:03 PM - Re: Re: rough running at 3400 RPM and above (Richard Girard)
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| Subject: | Re: rough running at 3400 RPM and above |
Check to make sure there is not soot on the float bowls, a loose exhaust joint
could boil the gas on one side when the engine power is set high enough
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=303919#303919
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| Subject: | Re: 914 Fuel Pump |
Hugh,
I just called them and asked for a pump for a 914. I had the Rotax part number
from the parts catalog. They said sure, just send money!!
Jim
Do not archieve
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=303961#303961
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| Subject: | Re: rough running at 3400 RPM and above |
The saga continues...
Tonight I pulled the carbs right off of the plane. I pulled them apart and this
time got the float needles right out. There was a small chunk of silicone beside
the needle in one of the carbs but after removing it and running the engine,
there was little improvment if any. I was able to get it up to 4200 with
the enrichener on but only the same old 3400 with the enrichener off.
Other things I have tried is raising the needle one notch to full rich. This also
made little to no difference. I stopped the engine while it was misfiring
at 3400 RPM and pulled a couple of plugs. They were sooty white so I think we
can say that this issue is definately a lean misfire.
I read someplace in the parts manual that there are slightly larger main jets available
when you run an air box. Since I have the original cone filters, I removed
the airbox and ran it with them (also on the richest needle setting) and
again the engine stumbles at about 3400 RPM.
One thought I had tonight after all of this playing around is; is it possible that
the throttle shaft o-rings could leak enough to cause this issue? I don't
know that they are leaking but given that the carbs are over ten years old, it
is possible.
While I had the carbs apart I re-checked all of the other passages and found no
buildup in any of them. Getting frustrating but this wouldn't be any fun if
it was easy.
Doug MacDonald
CH-701 Scratch Builder
912 UL
NW Ontario, Canada
Message 4
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| Subject: | Re: rough running at 3400 RPM and above |
Have you checked all the pieces of the equalizer line between the two intake
manifolds? Try checking the vacuum readings at the equalizer and then at the
carb taps with the equalizer line connected to see if there's any gross
difference.
As long as you had the carbs off, did you pull the carb sockets and check
them? I know you said they are recently replaced, but they're easy to check
and it eliminates one more possible source of a leak. There was a bad batch
a few years back that rotted out within a year. I couldn't see the cracks in
mine until I got them off and used a strong light, then the cracks were
obvious.
What about the o-rings at the socket and those on the intake manifolds?
Have you checked the diaphragms in the carb domes? You've had them out to
raise the needle did you make sure the tab on the diaphragm is set in the
slot in the carburetor body?
Also, from the IPC, there are no o-ring seals on the throttle shafts? Have
you miked them to see if the carb body is corroded or rotted out the
throttle shaft bore?
Personally, I wouldn't start messing with jetting until you've exhausted
every possibility of a gross air leak.
Rick Girard
On Tue, Jul 6, 2010 at 8:57 PM, MacDonald Doug <dougsnash@yahoo.com> wrote:
> dougsnash@yahoo.com>
>
> The saga continues...
>
> Tonight I pulled the carbs right off of the plane. I pulled them apart and
> this time got the float needles right out. There was a small chunk of
> silicone beside the needle in one of the carbs but after removing it and
> running the engine, there was little improvment if any. I was able to get
> it up to 4200 with the enrichener on but only the same old 3400 with the
> enrichener off.
>
> Other things I have tried is raising the needle one notch to full rich.
> This also made little to no difference. I stopped the engine while it was
> misfiring at 3400 RPM and pulled a couple of plugs. They were sooty white
> so I think we can say that this issue is definately a lean misfire.
>
> I read someplace in the parts manual that there are slightly larger main
> jets available when you run an air box. Since I have the original cone
> filters, I removed the airbox and ran it with them (also on the richest
> needle setting) and again the engine stumbles at about 3400 RPM.
>
> One thought I had tonight after all of this playing around is; is it
> possible that the throttle shaft o-rings could leak enough to cause this
> issue? I don't know that they are leaking but given that the carbs are over
> ten years old, it is possible.
>
> While I had the carbs apart I re-checked all of the other passages and
> found no buildup in any of them. Getting frustrating but this wouldn't be
> any fun if it was easy.
>
> Doug MacDonald
> CH-701 Scratch Builder
> 912 UL
> NW Ontario, Canada
>
>
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