A big problem with Tridents is oil pressure....If it falls much below 75 psi at speed the result is usually a thrown rod or spun rod bearing..The former usually writes off the crankcase, the later usually ruins the crank if the rod isn't on the outside..Very few use oil pressure gauges...The early 5 speeds also had reliability issues and gears are very expensive....A Trident missing the engine side cover and other parts may be such a case, blowed up and stripped of parts ....In general the engines are very fussy to assemble ...But done right and with $$ they are nice period piece and arguably the fastest Brit Bike...
