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Old NS3.5A.....stalls when throttle is opened (only when cold)

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whitegreg56

Regular Contributor
The sailing club has a NS3.5A (2-stroke, single-cyl.) that has
given us trouble-free operation for many, many years. Just
recently - from a cold start - it stalls when the throttle is opened
even slightly after starting. After it warms up for ~30 seconds the problem
goes away. If this is a carburetor problem, why does the problem
go away when the engine warms up? Mixture too lean?
A new carb runs only about $100....not bad if it takes care of the problem.
This is a Winter project!
 
The colder the motor, the less well the fuel atomizes. So, it needs to be richer cold. A sudden rush of air during tip-in also leans the mix. Yes, the issue is in the carb, and a thorough cleaning may help it; otherwise, if dedicated to that motor, a new carb should help. Those motors have an o-ring at the carb mating area. They can harden over time, and leak air, leaning the mix, so that's an item to review before changing carbs.
 
I happened to have an old carburetor, for this engine, sitting on the workbench. It's a real easy swap, so
I decided to try that. Yep....nailed it! I can now take my time in taking the bad carburetor apart...looking
for worn parts and dirt, etc. So, the problem is known....even before Winter has started!
 
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