1971 Yamaha JT1

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Enduro Fanatic

Plug fouling constantly

I had an early 70’s yamaha 60 in the burnt red/orange color. I’m 62 now and don’t recall much about it but I clearly remember I had to carry a spare plug and a wrench at all times because it fouled plugs all the time. I was to young to know that it was something that I probably could have fixed. Can anybody tell me what caused it and how I

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Devin

01 sept

•

Welcome to the site! there are quite a few reasons why your bike could have been running rich. Here are a few:

Common Causes of a Rich 2-Stroke Engine

Clogged or Dirty Air Filter: A restricted air filter chokes off airflow into the engine, increasing vacuum pressure that pulls extra fuel through the carburetor jets.
Incorrect Carburetor Jetting: Main or pilot jets that are too large for your elevation or temperature deliver an excessive volume of fuel.
Engaged or Stuck Choke: Leaving the choke partially or fully closed restricts incoming air and enriches the fuel mixture continuously.
Clogged Exhaust (Spark Arrester/Silencer): Carbon buildup or a blocked exhaust pipe restricts scavenging, trapping unburned gases and oil inside the cylinder.

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