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Engine basics => Engine set up tips => Topic started by: Allen Eshleman on May 26, 2021, 03:09:17 PM
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Recently I installed a tongue muffler on an LA 40. When I went to start it, I had to open the needle two turns - Smith NVA - to achieve an approximate same run as before with the barrel muffler. Is this common for the changeover from barrel mufflers to tongue mufflers?
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Yes. two full turns sounds a bit much, though. Tongue mufflers are more restrictive. If the engine can't exhale, it can't inhale as much. You might want to drill some more holes in the tongue muffler. There have been several threads about this same subject lately.
Type at you later,
Dan McEntee
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Study Randy's pinned posts at the top of this forum. He 'splains how drilling out the muffler makes the engine suck more air through the venturi. They're pumps, after all, and less backpressure increases the pumping efficiency. Your tongue muffler increased the backpressure and reduced the pumping efficiency quite a lot...assuming that you didn't also fiddle with anything else, like remove the venturi and/or spraybar, install another head gasket, or loosen the backplate screws and create a leak. Probably could add a few other things that would act similarly, like clogged fuel filter, kinked fuel hose, etc. y1 Steve