Triple Carburettor Synchronisation (XU-1)
Symptoms
Rough idle, uneven running, flat spots, poor throttle response. The engine feels rough and unbalanced.
Cause
The GTR XU-1's triple Stromberg carburettors must be precisely synchronised, all three must deliver the same airflow at the same throttle opening. Over time, the individual carburettors wear at different rates, the linkage develops play, and the synchronisation drifts. Modern fuel with ethanol also attacks the original rubber components in the carburettors.
Fix
Rebuild all three carburettors with quality kits ($150-300 total), then synchronise using a vacuum gauge or Unisyn tool.
Each carburettor's idle mixture, idle speed, and throttle linkage must be adjusted individually, then balanced against the others.
This is a skilled job, if you're not experienced with multiple carburettor setups, find a specialist.
Budget $300-500 for a professional rebuild and synchronisation.
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