The 'loose' spring is the main govenor spring. With the engine stopped, and the throttle lever in 'FAST' position, this spring should (via the connection to the govenor link) pull the throttle butterfly wide open. If the engine was running, the air pressure from the rotating flywheel should move the link, opposing the spring tension, and progressively closing the throttle butterfly. When the 2 forces balance, the engine speed will stabilize. Therefore, more spring tension = more speed.
If the spring is definitely loose, even with the speed lever at FAST, then it's either severely stretched, or the wrong one is fitted. If it's stretched to the extent indicated, it will be obvious.
On these engines, the speed is adjusted by physically bending the moveable spring attechment that's connected to the speed control on the handlebars. Easy does it - increasing the spring length by 4MM will give an increase of about 500 RPM. Engine should top out at about 3600. Get an optical tachometer, unless you know what 3600RPM sounds like. The engine will self destruct at about 5500.
phil_saunders@bigfoot.com
Phil Saunders
September 2008
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