🚗 Classic Fault — MG GHN/GHD (1962–1980)
MGB SU carburettor dashpot oil level low — flat spot
💰 Estimated Repair Cost
Up to $10 GBP
Parts and labour estimate
🔧 Tools Required
Nil special tools
📋 Overview
The SU carburettors require oil in the dashpot for correct damping. Low or empty dashpot causes a flat spot on acceleration.
🩺 Symptoms
- Flat spot on acceleration
- engine stumbles when throttle opened
- fine under steady throttle
🔍 Possible Causes
- Empty or low dashpot oil
- wrong viscosity oil
- worn needle
🛠️ Diagnosis Steps
Remove dashpot cap and check oil level — should be 12mm below top of hollow piston rod. Top up with engine oil.
✅ Most Confirmed Fix
Dashpot oil top-up to correct level
95% of users confirm this fix worked (47 reports)
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