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

[Urs Baertschiger]

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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