Choke doesn't affect idle speed

[goodfornothing]

Hey guys,
So the choke on my 450 does not affect the idle speed when it's closed and when it's a cold start. Half choke does help my bike to get started, however when I use full choke, my bike dies. I checked the butterfly valves and they are in the proper position.

I understand that with the choke closed, the rpms should be high and slow down when the choke is being opened but that's not the case for my motorcycle. What does this mean?

 

[Big R]

I believe you might have it switched around. A closed choke stops just about all the air from getting through the carbs (a cold motor needs more gas than air to start?) and an open choke would let in the perfect amount through (ratio of 14.whatever to 1). If the motor is running and warms up and you close the choke it strangles the mix and kills the motor.

 

[goodfornothing]

That's what happens with my bike. It's just that the rpms don't increase with choke from a cold start. I have to play with the throttle a bit to keep the engine from dying because the rpms are low.

Edit: The butterfly choke valves could be on the wrong side. I'll check that once I get home.

 

[Hannibal Smith]

I wouldn't worry about it. My current CB550 starts with the choke "on" and as soon as she fires, I open the choke and manually blip the throttle until she warms.

I have "jetted" the bike, and rich only goes for a few seconds before the mill chokes out.

It also depends on the climate, I live in Santa Barbara, California- so a cold morning is not cold at all!

Without burning myself, I usually turn up my idle a tad at starting, and by the second light or so, I crank her back down to 1000-1200, and she runs perfect.

 

[goodfornothing]

Thanks for the heads up guys! Looks like I won't have to worry about it much then.

 

[Flugtechnik]

I had the same misconception when I first got my bike. On my old bike, when I pulled the choke plunger out, the RPMs went up. What we have on our 450s is a pure, straight up choke. It is just a butterfly valve that restricts air going into the carb. If it is all the way closed (lever horizontal) your bike will not run. The only time I ever used mine was when I first tried to start it when it was dead cold to help prime the carbs. I would close it, give it a kick, then open it half way and try to start it. Once it started I would adjust the choke, open it more, to get the idle steady. During normal riding, it should be all the way open, pointing down.

I think the newer chokes have some mechanism that also opens the throttle butterfly valves a bit to increase the RPMs.

 

[goodfornothing]

Thanks Mike.

I read that somewhere too. Chokes on newer bikes actually add some throttle as well so I guess it's the same for these bikes, we just have to do it manually.