Barn-find inline-four: a bank of carbs brought back to life
A 1980s inline-four that hadn't run in years arrived with completely blocked pilot circuits. Ultrasonic cleaning of the full carb bank got it idling again.
The problem
A rider near Murcia was recommissioning a 1980s Japanese inline-four that had sat for the best part of a decade. It would fire on full choke but died the moment the choke came off — the classic sign of blocked pilot circuits across the bank.
What we found
Stripping the four carbs revealed exactly what we expected: pilot jets and passages fully varnished shut, float bowls with a layer of dried fuel residue, and two stuck float needles. Poking the jets would have ruined them.
The clean
Each carburettor was fully disassembled and ultrasonically cleaned until every passage — pilot, main and emulsion — was verified clear. We rebuilt the bank with the customer’s genuine seal kit and bench-set the float heights.
The result
- Every pilot circuit flowing freely again
- Clean, even fuelling across all four cylinders
- Reassembled bank ready to refit and vacuum-balance on the bike
The owner had it idling cleanly the same weekend. A full set of used carbs of unknown condition would have cost far more — with no guarantee they’d be any cleaner inside.
Reviving a project? Read about motorcycle carb cleaning or request a quote.