Engine runs lean, old Webra 61. Who can help?

[Tony Stillman]

Sir:

I ran lots of those engines in pattern in the 70's and 80's.  Great motor.
The trick with the Dyna-Mix carb is to make sure it is set-up properly.

Open the carb to full, and you will be able to pivot the throttle arm past
full, and slide out the assembly from the main housing on the carb.  Look at
the brass tube mounted to the slide.  You will see a "cats eye" shaped cut,
and a hole going through the tube, near the edge of the "cats eye".  This
hole MUST, MUST be COMPLETELY visible when the carb is full open!!!  This is
the trick with this carb.

Take the carb out of the engine, and turn it upside down and look through
the mounting flange area.  With the carb at full open, you should be able to
see this hole in the brass slide bar, right at the very edge of the brass
outer sleeve.  You can adjust the clicker on the end to move this bar in and
out until it is visible.  With the hole just completely visible at the edge,
this is the full rich position of the mid-range adjustment.  Note that you
must not move this bar so far that the hole is completely covered!  If you
do, you will never be able to get the engine rich at full throttle (most
likely the cause of your current problem!).

I start this way, set the high speed needle and go from there.  Make sure
you are using a very cold plug like the Enya #5 or #6, or the Rossi #8.  I
ran 25% Cool Power in my Webra, and it loved it!  You can use 5%--30% nitro
w/o problems.

The other issue with the Webra is that the con rod was cast, and was very
weak.  We would replace them with an aftermarket machined rod by a company
called "RPM".

I hope this helps..

Tony Stillman
Radio South
3702 N. Pace Blvd.
Pensacola, FL 32505
1-800-962-7802
www.radiosouthrc.com
----- Original Message ----- 
From: "Urs Baertschiger" <ursbaertschiger at hotmail.com>
To: <discussion at nsrca.org>
Sent: Friday, November 28, 2003 2:29 PM
Subject: Engine runs lean, old Webra 61. Who can help?


> Hi all,
>
> I very much would appreciate any advice that could lead to the solution of
> the said problem. -
> Recently I got an old pattern bird out again after storing it for a couple
> of years. I didn't fly it no longer due to a persistently lean running
> engine, a Webra 61 ABC rear exhaust. Had some spare time and thought I
could
> find the reason for the lean running. However, all my efforts didn't show
> any noticeable improvement. The engine is equipped with a fiber glass pipe
> (Hatori copy), a pump and the Webra Dynamics slide carb with remote
mixture
> control.
> I made the following changes or adjustment, always one at the time. All
test
> runs on the ground, no flying:
> 1) Checked tank, all fuel lines including fuel pick-up. Checked also for
> kinks in the lines.
> 2) Disassembled, cleaned and checked carb.
> 3) Bypassed pump.
> 4) Changed plug from Enya #5 to OS - F.
> 5) Extended pipe length by 1".
> 6) Tried different props. Instead of 12x10.5 I tried 11x11 and 12x10.
> 7) Changed carb.
> 8) Changed pump setting.
>
> What else should I check? - Apart from the usual replacement of bearings
and
> occasionally a piston/liner set the engine was running perfectly for
several
> hundred flights before this problem appeared.
>
> Many thanks in advance for any advice.
>
> Kind Regards
>
> Urs
> NSRCA #3069
>
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