Tech Tips

Tillotson Carburetor Throttle Valve Return Spring

July 13, 2017

Tillotson Carburetor Throttle Valve Return Spring

 If you are using a Tillotson HL334 or HW27 carburetors for your 2-stroke engine application, you may want to install a secondary throttle valve return spring.  

If you do, here are a few tips we can pass along.

First, make sure your carburetor is in good condition, the parts are not worn, and the throttle valve is opening 100% without over rotating.  If the throttle valve is not adjusted properly, do this first.  Inspect your throttle cable and housing for proper operation and no signs of wear.  If the carburetor cable throttle is frayed, twisted, or damaged, this will keep the inner cable from sliding smoothly in the housing and will affect throttle operation.

You can order new cables and kits on our shopping cart - Swedetech Throttle Cable Kit 

When choosing a secondary return spring, chose a light compression spring that is ample enough to return the valve to the closed position.  You want to avoid a heavy spring that applies to much pressure to the throttle cable barrell.  Excessive tension will break this part off.

Before installing the spring, mock up the spring and the throttle cable lever.  You want to make sure the spring is not applying pressure to the barrell when the butterfly valve is closed.  You also want to make sure the spring does not coil bind when throttle is opening, keeping the valve from reaching 100 percent throttle.

When choosing a spring, make sure the spring loop is closed at both ends.  This will keep the spring from un-coiling around and off the throttle cable.