LO206 Clutch Weights: How to Pick Hilliard Springs
Hilliard weights are small cylinders that snap into the clutch shoes. They are legal in the Briggs LO206 rules. About half the field runs them. They are not a secret horsepower part.
They change when the clutch grabs. That is all.
What weights actually do
More mass on the shoe means the clutch throws out at a lower rpm. Springs pull the other way. Stiffer springs raise engagement.
A typical black-spring starting point looks like this, and it will move with wear and clutch model:
- Four black springs, no weights: around 3800 rpm
- One weight per shoe: around 3600
- Two weights per shoe: around 3400
White springs are softer. Yellow and orange sit in between. The Inferno BLAZE / FLAME / FIRE tuning kit is the pile of springs, heavy and light weights, and snap rings you actually use at the track. Extra heavy weights and white springs are the common add-ons.
The weights live in the shoe, not the drum. A snap ring on each side keeps them from walking out. Lose a snap ring and you will find the weight the hard way.
Most tracks never get on the clutch
Look at the RPM trace. If the engine never falls below engagement, there is no lap time in a different spring. The clutch stays locked. Lift on the straight and the axle keeps the engine spinning until the kart slows enough to drop under stall speed.
Whiteland’s hairpins and a lot of tight club tracks still stay above engagement because the gear is short, often around a 3.75 ratio. You are not slipping. You are engine-braking.
Where weights earn their keep:
- Standing starts
- A slow, cambered hairpin where you actually bog
- A long technical layout where you can see RPM dip under 3600
If the trace never gets there, leave the extras out. Fewer parts in the clutch is fewer things to shed.
How to pick a combo
- Log a representative lap with a MyChron 6.
- Note the lowest rpm in the slowest corner.
- Set engagement a little under that number if you actually bog. Set it above if you only care about a clean launch.
- Change one thing: springs or weights, not both.
- Feel for slip heat. Extra slip is slower and cooks shoes.
A full BLAZE with Bully conversion is the usual LO206 piece. Lock the hub to the crank shoulder. A floating clutch eats the keyway.
The short version
Weights lower engagement. Springs raise it. On most sprint 206 tracks the clutch never opens. Tune for the start and the one corner that actually dumps rpm. Read the trace before you fill the shoes with metal.