What causes Primary chaincase oil leaks on the Bsa A65 Thunderbolt?

Oil weeping around chaincase gasket and seal area Estimated fix cost: $50-$150

What causes Worn or seized magneto points on the Bsa A65 Thunderbolt?

Spark consistency, check for corroded or pitted points Estimated fix cost: $100-$300

Inspect sump for thick black sludge, check breather valve Estimated fix cost: $80-$200

Excessive blow-by, blue smoke, low compression reading Estimated fix cost: $300-$700

Known issues to inspect before buying a used Bsa A65 Thunderbolt. What to check and how much repairs cost.

MODERATE

Oil weeping around chaincase gasket and seal area

Fix cost: $50-$150

SERIOUS

Spark consistency, check for corroded or pitted points

Fix cost: $100-$300

MODERATE

Inspect sump for thick black sludge, check breather valve

Fix cost: $80-$200

SERIOUS

Excessive blow-by, blue smoke, low compression reading

Fix cost: $300-$700

☐Compression test both cylinders before buying

☐Check all gasket surfaces for active leaks

☐Verify frame numbers match title documents

☐Inspect wiring for butchered amateur repairs

Temperamental but rewarding if properly maintained