Hi.

I know MDS engines are criticized often, but I have had good luck with mine. Until recently, the only problem I had with my MDS 40 was that there was hestitation during transition from low-end to high-end RPM.

Then one day it started to just lose power when throttling up and maintaining high RPM - it would either lose power or stall out. It seemed like an air leak. A couple other guys at the club took a quick look at it as well, and we didn't see any air bubbles in the fuel line or anything obvious. For the time being, I richened the high speed needle valve and that helped a little. Then I remembered a fellow club member talking about RC glow cars at one of our meetings and he mentioned an o-ring lubricant/sealant that's commonly used on cars that corrected carb air leaks. He did say it could be used on planes as well.

I went to the LHS and they had a brand called "Green Slime". It was located in the RC cars section, not in the planes section of the store.

MOD #1 - I pulled the C2 carb off the engine and there are 2 o-rings - one at the top of the venturi, and one in a groove toward the bottom of the venturi. I cleaned everything up with alcohol, replaced the top o-ring (original one look good, but I replaced it anyway), put the Green Slime on both o-rings, and installed the carb back on the engine.

MOD #2 - I remember reading a magazine article about glow plugs and one of the things mentioned was to use a glow plug with an idle bar to help prevent the glow plug from getting 'drowned out' after idling for a bit then throttling up. I installed a FOX glow plug with an idle bar.

Let me tell you, this engine transitions MUCH better than it ever has and seems to have more overall power and consistent performance!

I thought this may help some MDS owners out there.

WDWings