1975 cb125s starting

Gerrit125s · L Plate Warrior Joined: 12 May 2013 Karma :

my 1975 cb125s starts easily for the first 4 or 5 times then just putters out and dies and won't start after that until I wait a long time then the whole process starts over. Any ideas what going on here?

stickybackbob · Trackday Trickster Joined: 23 Mar 2013 Karma :

Would be better posted in the 'Workshop' section but hey-ho....

The bike is displaying symptoms of fuel starvation. It'll run on what's in the carb bowl for a while but the bowl isn't filling fast enough to replace the used fuel.

I'd be looking at the following:

Pull the fuel pipe off the carb then turn the tap on. Should get a good steady flow of fuel.

If the fuel flows well, then take the carb off and clean it, the float needle maybe stuck/stiff.

If the fuel doesn't flow well, check/replace any fuel filters.

If they're fine and dandy, try opening the tank filler as there may be a blocked vent hole.

If the above doesn't do it, next in line is to remove the petrol tap and check the mesh filters for rust and crud from the tank.