340 engine problems

sounds like you have a vacuum leak. is the carb tight? wiggle the air filter, if it moves your carb bolts are loose. next thing to try is the rocker cover.. you can test this by pulling the tube off the rocker cover t-piece and holding your thumb over it. if this is the leak then expect revs to rise and steadify..

ta for the advice, ill give that a go. its funny howw it only happens once in a while, though. ill probably be back on later asking how to put the engine back together!

hi check that your carb is not iceing check the flap in the air filter control box make sure flap is positioned for warm air when engine is cold make sure that pre heat pipe is not missing hope this helps

Thanks. is the preheat pipe the wide, ribbed one like a vacuum cleaner hose? i seem to remember that falling off years ago. also, should the moveable nozzle for the air intake be pointing down or towards the fan in cold conditions? How can you tell if you need a new air filter? my fuel consumption is going up, and ive a hunch the air filter might need changing, but dont want ot buy one if i dont need to. cheers, g

yes thats the pipe, halfords will have one you can use look at the filter, if its black get a new one, if its white, dont :)