Motorcycle Repair: cb 900 custom, honda cb900 custom, chevron techron

Question
Is the 82 honda cb900 custom hard to start when cold?

Answer
No, not when you use full choke.  These bikes were built to EPA and DOT specifications so have lean idle and transition calibrations for the carburetors... and that was when they were new! They should start up with full choke which also has a fast idle function. If the choke cable is not adjusted properly the chokes won't close all the way.

So, 27 years later, the passageways have become restricted with corrosion and gummy fuel deposits and the tiny idle jets are probably restricted or plugged up altogether.

Added to that you have a vacuum operated petcock system that has a diaphragm that fails over time =  HARD STARTING.

If the bike does eventually start and run/idle smoothly, then the idle jets are probably okay.  Most owners will remove the idle limiter caps and then add in an extra 1/2 turn to the mixture screws, which usually does wonders for the idling and starting symptoms.

You do need to ensure that the valve clearances are correct, so that you have good compression for all 4 cylinders. The camchains need adjusting, too.

Check the alternator brushes for wear and pray that the rotor hasn't gone into fail mode for the charging system.

You can try filling the carbs with Chevron Techron fuel additive and let it sit overnight. Drain and refill carbs with fresh fuel. This may help or probably you really need to have the carbs removed and rebuilt with new O-rings, float valves and other bits.

Bill Silver