Harddrive 40 MM CV Carb Slide Diaphram - Diaphragm

Harddrive 40 mm CV carb slide diaphragm for V-twin motorcycles. This is a replacement diaphragm that regulates vacuum-operated needle position in constant-velocity carburetors, maintaining proper fuel delivery across throttle ranges.

Features

• OEM-equivalent replacement for 40 mm CV carbs
• Direct-fit diaphragm assembly

Specifications

• Brand: Harddrive
• Manufacturer Part #: 40039
• UPC: 191361512254
• Dimensions: 3 in x 3 in x 3 in
• Weight: 0.5 lbs
• Country of Origin: China (Mainland)

Fitment

Fits V-twin motorcycles equipped with 40 mm constant-velocity (CV) carburetors.

Frequently Asked Questions

What does a CV carb diaphragm do?

The diaphragm responds to engine vacuum to adjust the needle position, keeping fuel mixture correct at all throttle positions and RPM ranges.

How do I know if my diaphragm needs replacement?

Signs include rough idle, hesitation on acceleration, or fuel leaking from carb overflow tubes — common when the diaphragm ruptures or loses flexibility.

Will this fit my Harley or Indian?

If your bike runs a 40 mm CV carburetor, yes. Confirm your carb size and model before ordering — some bikes use different carb types.

Is installation difficult?

Moderate DIY job — requires removing the carb slide cover and carefully installing the new diaphragm without tearing it. Carb removal may be necessary depending on your bike's layout.