how can i fix my cb400/4?

vin a simple test is to start it up and gently touch each exhaust pipe 1234 and see if one of them doesnt get hot if you find one then thats your problem cyclinder, if for instance its number3 then number two would also run bad if it was spark related as they use the same coil and points/condenser.more likely to be a carb problem or a low compression issue.as crispy says they are noisy engines the primary chains rattle like hell at low revs if the carbs are out of balance

adam bike doctor
May 2010

Hi, it might just sound like it's only running on 3, i seem to remember that they don't tick over that smoothly anyway but once on the move it should run turbine smooth. To check if it is a defective pot, start it up on tickover and remove and replace each plug cap in turn(remember to do this with a dry cloth for this test to avoid elec.shock)the engine will falter each time you remove a good plug cap, but if the engine runs the same when you remove one plug cap, that is the defective pot. If there's no change throughout then check the ignition timing and especially check the carbs for synchronisation, you'll need a vacuum gauge for this though for best results. Remember to use fresh unleaded if it's been standing a while. Hope thats some help.

Chris P.Duck
May 2010