Idle Screw in to start... please can I have some advice!

[DavyJones963]

Hi everyone!

I have recently bought a cb100n from 1983 and have spent the last 2 weeks getting it running ok (sorting out air leaks, cleaning carb, basic maintenance that had been missed by PO). I know very little about working on bikes. The bike is running a replacement carb which is the only modification.

I have got it happily idling at 1300rpm (as stated in the haynes manual) but I struggle to get it started without screwing in the idle screw and having the choke on so it starts at 7000rpm . From there I can readjust the idle and take it off choke after a bit and it runs happily.

I know that this use of the idle screw may mean I am effectively starting it with throttle which can be hard on the engine. Should I rejet? Adjust the mixture screw? Any advice you could give would be invaluable.

Thanks,
Dave

[Hetzer]

You probably need to clean the carb's insides so that it not only looks clean but actually is clean (teeny weeny holes and stuff). They're notorious for remaining blocked even after a thermo-nuclear device has gone off above them.
____________________
"There's the horizon! Ride hard, ride fast and cut down all who stand in your way!"

[Im-a-Ridah]

You could always try swapping out the idle jet. When you say replacement carb, do you mean you bought a new carb or that the previous owner did?

[bikenut]

as hetzer says........you have a manual....do you know of cmsnl and the exploded views....they may help..........

from memory the choke on these only strangles the carb intake and does not increase the throttle opening slightly when used.......

the choke butterfly or flap, will either be sprung loaded or will have a " sprung loaded flap" on it.......which will open and close automatically with each breath the engine inhales.........so it dont over choke.........does that work??

float height is all ok and the "bung" in the float chamber ( carb main body actually ) is all ok, if it has one at all?

is there a white plastic "shroud" on the bottom of the main jet on this one??

cant remember if these had points ign and centrifugal advance on flywheel.............and the main jet "needle clip " is on the middle notch??
____________________
nuts about bikes