trouble cranking

finished overhauling the carbs. Now I'm ready to tune it, but can't get it cranked. It breifly ran and then died and backfired.

Fuel levels look good and the mixture screws are set 3 turns back from closed.

Should I mess with the mixture screws to get it to crank?

I've been turning the idle adjustment screw a little clockwise after each attempt to crank?

Should I start to assume this is another problem?

 

By crank do you mean engine turning over or fired up?

If it won't turn over it's possibly the battery or starter solenoid or both that have packed up.
If it's turning over but not firing it could still be a weak battery.
It should fire even if the mixture screws are set weak or rich though a low fuel level in the bowls won't help.
Are you getting fuel to the carbs?

 

Start by pulling the fuel line off the rack & check for flow, pull the plugs & check for strong blue spark, make sure the battery is fully charged.

 

Sounds like its turning over but not firing.

 

Fuel is in the carbs up to level. Battery is fully charged. Pickups may not be connecting to the spark plugs.

 

Safety circuit may be involved (although it should keep it from even spinning over.)

Battery, though fully charged, may not be strong enough to turn starter AND fire ignition. Have it load tested at the auto parts.

Starter may be drawing so much current there's nothing left for the ignition.

 

Fits, battery is new. What would cause the starter to draw more power?

 

It happens when the starter gets gummed up and the brushes are worn or get oily and it becomes reluctant to turn any more. The starter is not as simple as it appears to be; there is a gearbox inside the nose, and the "motor" part is rather primitive (brushes and commutator.)

Be careful when R&R'ing the brush plate; if it gets back in the wrong position the starter can spin backwards.

Len has any and all necessary parts.