My Triumph gets breathless when hot
QI have a Triumph Stag that runs well for about 30 minutes, but then won’t rev properly. Where should I start?
Dave Brisland, York
AMany of the checks outlined on the first page of
Ask Our Experts apply – but here are our suspicions. Is the coil excessively hot? If so, the points gap may be wrong or it may be a ballast coil fitted without a ballast resistor. The resistor in many Triumphs is cunningly disguised as a length of wire. If it’s been replaced with plain wire, this would explain the problem.
The resistance measured between the coil and the ignition switch (detach the wire at both ends) should be 1-2 Ohms. If it’s zero and your manual indicates that a ballast resistor should be fitted, then either change the wire or change the coil for a non-ballast type. If that’s OK, change the condenser.
On the fuel side, there may be a supply restriction between the tank and pump. Look for a blocked tank vent, a perished, softened or kinked rubber hose, a kink in a metal pipe or a blocked filter. Remove the sender unit, if possible, and inspect the tank with a torch to see if it’s excessively rusty.
Fuel evaporation is another possibility. Check the routing of the fuel pipe and shift it well away from contact with the engine and any water hoses. Is the carburettor adjustment correct? If it’s hugely rich, this will suit the engine until it warms up – after which it will cause havoc. Also make sure the oil isn’t full of petrol and the air filter isn’t full of oily clag.