1967 Ski-Doo Olympique: Tillotson HR Tuning

Machine: 1967 Ski-Doo Olympique
Carburetor: Tillotson HR-7A
Engine: Rotax 299cc single

1. Initial Settings

Before starting the engine, set the adjustment needles to the factory baseline:

• Low Speed (L): 1 turn open
• High Speed (H): ¾ turn open
• Idle Speed: Screw in until it touches the throttle lever, then 1 turn more.

2. Pop-Off Pressure Test

WARNING: Incorrect pop-off pressure causes flooding or lean seizures.

1. Connect a pressure gauge to the fuel inlet.
2. Pump air into the inlet.
3. Needle should hold pressure up to 10-12 psi.
4. It should “pop” off (release) at roughly 10 psi.

If it holds less than 8 psi, replace the inlet needle and spring.
If it holds more than 15 psi, cut the spring (carefully) or replace it.

3. Tuning Procedure

1. Warm Up: Run the engine for 5-10 minutes.
2. Low Speed: Turn the L screw in (clockwise) until the engine starts to stumble (lean). Then turn it out (counter-clockwise) until it runs rich/bogs. Set it halfway between these points.
3. High Speed: Run at wide open throttle (WOT). Turn H screw in until max RPM is reached, then back out ⅛ turn to ensure safety/lubrication.
4. Plug Chop: Run at WOT, kill the engine. Check spark plug color. It should be chocolate brown.

“A lean engine runs fast for a short time. A rich engine runs slow forever.”

Parts List

• Diaphragm Kit: DG-5HL
• Inlet Needle: 233-605
• Flange Gasket: 290-890

grid-system swiss-style