Carburetor Diaphragm A015058 The Quiet Part That Fails

The diaphragm is the quietest part inside a carburetor. The engine only speaks up when it fails. The A015058 is a replacement diaphragm for two stroke carburetors: a black rubber sheet, a metal disc in the center with five large ports and five small ones, a sealing edge around the rim, and mounting holes at the corners. Inside the carburetor, the diaphragm separates the oil side and the air side, and the rhythm of the fuel mix follows its movement.

What does a failed diaphragm look like? Three things are common. A rough, wandering idle, when the rubber has hardened and the rebound slows, so the fuel and air ratio drifts. A dull response to the throttle, when the diaphragm has warped and the ports no longer line up. Oil weeping near the carburetor, when the sheet has cracked and fuel seeps through. If the area smells of oil and the machine gets worse day by day, suspect the diaphragm first.

How do you check it? Take the carburetor off, remove the diaphragm, and look against the light: fine cracks, hard white rubber, a warped metal disc, or ports worn through. Any one of these means replace it. The sheet is thin, so do not scratch it with sharp tools, and when fitting it, wipe a thin film of engine oil on the sealing surface so it seats well and does not curl.

The A015058 matches the carburetor's original part number, and matching the old part's number and hole pattern is the surest way to order. Similar machines with close numbers are not always interchangeable, so photograph the old diaphragm's number and holes before you buy.