Topic: CB 400 F super sport air screws

[leovich]

Hi, someone who own a CB 400 F super sport here can help me with air screw setting? How many turns do you unscrew the air screws? Manual say 2 turns out but when the bike run at low throttle, I mean when you run at 50-60 km/h the bike seems not to run so smooth.

The bike have new honda genuine points plate, ignition synced with strobe lamp, carbs have all new brass parts from honda, I also have new genuine carb boots and the bikes has only 20 k km.
It’s not running so badly but it’s different from my 750 k0 that is much smoother at low throttle openings

[HondaMan]

It may be due to the nature of today's gasolines: the old setting of 2.0 turns out may now be too rich, especially if you're running midgrade or premium gas.

Some things to try out:
1. Turn the air screws in a little bit, like to 1-7/8 turns instead.
2. Add about 2 ounces of oil to the gas in the tank. Any oil will do: I use 2-stroke synthetic oils because they won't smoke or build up on surfaces.

[leovich]

It may be due to the nature of today's gasolines: the old setting of 2.0 turns out may now be too rich, especially if you're running midgrade or premium gas.

Some things to try out:
1. Turn the air screws in a little bit, like to 1-7/8 turns instead.
2. Add about 2 ounces of oil to the gas in the tank. Any oil will do: I use 2-stroke synthetic oils because they won't smoke or build up on surfaces.

Thanks for reply I’ll surely try this method, but if someone here have the same bike it will be nice to know how they set their air screws.

Another thing, today I was changing the final drive chain because it is still the original one and I have a spare DID 50 HD left from the 750. So I was changing this chain and I found the front sprocket loose on the shaft but still fixed on the fixing plate with the two screws , it seems to be worn out where it fit on the output shaft. Is that common?

[jaytee-nz]

That's the way Honda designed the front sprocket - nothing to worry about.

[scottly]

when the bike run at low throttle, I mean when you run at 50-60 km/h the bike seems not to run so smooth.

What gear are you in when going that slow? Are you lugging the wee engine?

[leovich]

when the bike run at low throttle, I mean when you run at 50-60 km/h the bike seems not to run so smooth.

What gear are you in when going that slow? Are you lugging the wee engine?

I usually try to keep the engine over 4k rpm, but I have this behaviour even at 5-6 k rpm with very low throttle