MC carb for Webra
Lee Davis
lee at piedmontmodels.com
Thu Jun 5 18:35:41 AKDT 2003
If you're having problems in the mid-range lengthen the pipe. Currently,
I'm running mine at 28 1/2" plug to baffle. If there's still a stumbling
point in the mid-range throttle the engine up to the point where it is
stumbling right before it clears out with any additional throttle. Lean the
high speed needle until the engine runs clean. Go to full throttle and
tweak the high speed needle as required. If the engine hesitates in flight
when throttling up from idle, richen the low speed needle. The high and low
speed needles are not fully independant. If you richen one you might need
to lean the other.
The Webras will not tolerate lean runs. If the engine has a weak point it's
the con rod bushing at the wrist pin. A few flights of lean run, and it's
shot (look for marks where play in the bushing/wrist pin allows the piston
skirt to touch the inside of the backplate) which will cause a difficult
needle setting. The other side of the coin is that with a good setup and
use of after run oil the Webra will just keep on going. The one I'm using
now is my primary engine for the last 12 months (flew it at the Nats last
year) with no maintenance and the orginal factory rear bearing.
Lee Davis
Piedmont Models
http://www.piedmontmodels.com/
-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Jerry Budd
Sent: Thursday, June 05, 2003 11:26 AM
To: discussion at nsrca.org
Subject: Re: MC carb for Webra
Brian,
According to the Piedmont website the baffle is 4" ahead of the aft
end of the pipe so that puts you at ~27.5" from plug to baffle. When
I tried the Greve pipe that Piedmont sells, I found that to be too
long (way down in power compared to my ES pipe at ~24" plug to
baffle).
Lee, Jim W., Matt - Are these needle settings close? I haven't run
the ProMixII carb in a while.
It sounds to me like the pipe may need to be shortened some, and the
low end richened up a bit. You also probably got the motor a bit hot
when the pump got FOD'd and that's why the internals are a bit dark.
Jerry
>That is from the center of the glow plug to the end of the large portion of
>the pipe, does not include the stinger. Not sure where the first baffle is
>located at.
>----- Original Message -----
>From: "Jerry Budd" <jbudd at QNET.COM>
>To: <discussion at nsrca.org>
>Sent: Thursday, June 05, 2003 10:09 AM
>Subject: Re: MC carb for Webra
>
>
>> Brian,
>>
>> The 31.5" pipe length you quote, what is that from? In other words
>> what is the distance from the plug to the first baffle in the pipe?
>>
>> Jerry
>>
>> > Jerry, my setup is as follows: Webra 145 red head, greve pipe at
>31.5",
>> >os typeF plug, cool power 15%, APC 17*12, 10lb. 2oz. Prophecy. Current
>> >settings on engine are 1 turn on high speed needle, 1 1/16 on low speed
>> >needle. I am guessing low 8k for top end rpm on the ground slightly
rich
>> >{have not tached the 17*12 but I was getting high 8600 or so with
17*10.
>> >Engine starts good and idles reliably but transition is not very
>linerier.
>> >In flight it sounds good with straight and level flight at a little
less
>> >than half throttle, when pulling to a 45 up line it sags momentarily
but
>> >recovers, on tall verticals or loops it will sag toward the top and
loose
>> >roughly 1\2 of it's rpm and that is with me adding throttle through the
>> >maneuver, engine with not regain good power unless you go to at least
3\4
>or
>> >better with throttle. I get no smoke trail out of engine until full
>throttle
>> >and oil out of the pipe is pretty dark but not black, top third of
piston
>> >and ring is black like cyl. temps have been high. Condition is better
>with
>> >low speed needle set richer but it's easy to flood on start ups and is
>hard
>> >to keep running when cold {must keep a very fast Idle speed until your
in
>> >the air}. I have found trash in the pump and pump screws came loose
>twice,
>> >last week I pulled pump apart again and no trash was found but screws
>where
>> >loose, I cleaned all parts in warm water and dish soap, removed tank
and
>> >cleaned, ran large fuel tubing from clunk to carb. All fuel is filtered
>from
>> >the jug and I have a filter between tank and pump. That is about all I
>can
>> >think of, any suggestions would be greatly appreciated.
>> >----- Original Message -----
>> >From: "Jerry Budd" <jbudd at QNET.COM>
>> >To: <discussion at nsrca.org>
>> >Sent: Thursday, June 05, 2003 12:32 AM
>> >Subject: Re: MC carb for Webra
>> >
>> >
>> >> Hi Brian,
>> >>
>> >> What's your setup? i.e. pipe & length, plug, prop, fuel, airplane
>> >> (including weight), rpm's, etc.
>> >>
>> >> The reason I'm asking is I've got quite a bit of experience with the
>> >> Webra's (including the MC carb) and I may be able to suggest some
>> >> work arounds until the MC is available again via Horizon (I'm
>> >> guessing but they probably underestimated the demand for the carb
and
>> >> got caught short on stock).
>> >>
>> >> Jerry
>> >>
>> >> >Sounds interesting Jim, let me know how it works out. Mine is
>> >> >driving me crazy, I have it running ok right now but it is kind of
>> >> >off and on type of power. I have been flying her but I know it is
>> >> >not right, still managed to get a gallon through it sunday with
easy
>> >> >starts good reliability but as far as uplines go it is either all
or
>> >> >nothing, no middle.
>> >> >
>> >> >----- Original Message -----
>> >> >From: <mailto:jivey61 at msn.com>jim ivey
>> >> >To: <mailto:discussion at nsrca.org>discussion
> > >> >Sent: Wednesday, June 04, 2003 10:30 PM
>> >> >Subject: Re: MC carb for Webra
>> >> >
>> >> >Brian
>> >> >I put a cline regulator, a regular back plate with a press. tap,
and
>> >> >pressurized the tank on my Webra. The ground runs have been more
>> >> >stable for throttle position The needles are a lot less sensitive
>> >> >and it doesn't seem to be fat in the middle.
>> >> >When I find some time to fly I think it will finally run good. I
>> >> >must have had a pump problem because too many people are running
>> >> >this engine. I did find a piece of foreign material in the pump.
>> >> >This was in the pump from day one. I used a YS filter and nuttin'
>> >> >gets through a YS filter.
>> >> >Will let you know when I fly it, how it does.
>> >> >
>> >> >Jim Ivey
>> >> >
>> >> >
>> >> >----- Original Message -----
>> >> >From: Brian Billings
>> >> >Sent: Wednesday, June 04, 2003 2:10 PM
>> >> >To: discussion at nsrca.org
>> >> >Subject: Re: MC carb for Webra
>> >> >
>> >> >Thanks Tony, that is what I thought.
>> >> >
>> >> >----- Original Message -----
>> >> >From: <mailto:tony at radiosouthrc.com>Tony Stillman
>> >> >To: <mailto:discussion at nsrca.org>discussion at nsrca.org
>> >> >Sent: Wednesday, June 04, 2003 9:45 AM
>> >> >Subject: Re: MC carb for Webra
>> > > >
>> >> >Brian:
>> >> >
>> >> >Horizon is the USA importer for Webra, so if they are out, you
>> >> >probably won't find one. The only other answer is to go direct to
>> >> >Webra in Europe.
>> >> >
>> >> >Tony Stillman
>> >> >Radio South
>> >> >3702 N. Pace Blvd.
>> >> >Pensacola, FL 32505
>> >> >1-800-962-7802
>> >> ><http://www.radiosouthrc.com/>www.radiosouthrc.com
>> >> >
>> >> >----- Original Message -----
>> >> >From: <mailto:auto7832 at bellsouth.net>Brian Billings
>> >> >To: <mailto:discussion at nsrca.org>discussion at nsrca.org
>> >> >Sent: Tuesday, June 03, 2003 8:29 PM
>> >> >Subject: MC carb for Webra
>> >> >
>> >> >Does anyone know where I can buy the Webra MC carb, Horizon shows
>> >> >them on their website but they don't have any in stock and where
>> >> >unable to tell me when they would. Thanks in advance
>> >> >
>> >> >Brian Billings
>> >>
>> >>
>> >> --
>> >> ___________
>> >> Jerry Budd
>> >> mailto:jbudd at qnet.com
>> >> =====================================
>> >> # To be removed from this list, send a message to
>> >> # discussion-request at nsrca.org
>> >> # and put leave discussion on the first line of the body.
>> >> #
>> >>
>> >
>> >
>> >=====================================
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>> ># discussion-request at nsrca.org
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>> >#
>>
>>
>> --
>> ___________
>> Jerry Budd
>> mailto:jbudd at qnet.com
>> =====================================
>> # To be removed from this list, send a message to
>> # discussion-request at nsrca.org
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>> #
>>
>>
>
>
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--
___________
Jerry Budd
mailto:jbudd at qnet.com
=====================================
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