Carb heater info please.

[stevew]

My CB250 Nighthawk (single carb) has a carb heater as standard but I'm not sure if it's working correctly or even what it does. My assumption is that it helps the cold start. If so should it be energised all the time the ignition is on? That seems to be the way it's wired on my bike, maybe it only runs for a pre-determined time, I don't know.
Anyone shed any light on it's working?

[Cerberus73]

hmmm not that ive any experience of them, but from a purely practical point of view, id be a bit worried if it was on all the time, wouldn't that cause to much evaporation in warmer climates, and during summer here? i do know if fuel lines get to warm in a car, say by being routed to close to manifold or other hot engine bits, it can cause fuel starvation. id think it be same on your carb if the heater was permanently on... or i could be a complete numpty.

[stevew]

... or i could be a complete numpty.

Yup, you and me, both!!
Once i understand what it does i think i will be able to sort it out. Seems that all the USA CB250s and Rebels don't have the carb heater????

[Diesel Dave]

Carby Innova's have them too.

The carbs do freeze readily on an Innova if you disconnect it, I guess it's something to do with the high air speed through the small carb as there is always water in the drains on the air filter too.

What size carby do you have on these Nighthawks?

Many moons ago I used to run around on a CM200 with flat bars for many years, these were only 4 speeders but had a lovely flat torque motor.

[davebike]

Carb heaters
Yes worked on a few
about 3/10 Ohms from contact to body
Mostly temperature switched You need a wiring diagram and trace the wires
Temperature switch is either a flat black plastic lump often just taped to the loom or a brass bodied unit in the air box

Bike will run very badly in UK except in the hottest /driest weather without them

Dave