Questions about chokes

[Sarek]

I have a few questions about using the choke. My first is how do you tell if it's on or off? I don't mean for it to sound as stupid as it sounds. I know in one position the engine revs up and on the oposite end it doesn't. My husband says when the engine is revved up from the choke the choke is on. My friend says that's the off position. Which is it? Revved up is off or on?
I ride 2 Yamaha Viragos, a 250 and 750. I also ride an '05 750 kawasaki vulcan. The 750 virago is a pain to start, especially when it's cold. My husband says use the choke in the revved up position to start it. He also tells me to do that for the vulcan, and it's not hard to start but I think it's getting harder than it was. He starts them all the time and lets them sit and run, he says he uses the choke to start them. I think it's bad for the spark plugs and who knows what else.
My question is which is better, to move the choke when starting or not? Mechanic wise I know next to nothing about these bikes. My husband doesn't either but he likes to pretend he does. I'll be the biker that's been mentioned in other posts.....$50 to change my spark plugs? Ok, here you go.

[TechTMW]

Your husband is right on this one. The choke is on when the bike revs higher, which is what you want when you start the bike. Some people even call this the "High Idle lever" because it causes what you are seeing - Higher revs at idle.

What the choke does is it throws extra fuel into the cylinders in order to get the bike started and warmed up properly. This is necessary on today's carbed bikes especially because they already run lean from the factory. (They are a little fuel-starved with the choke off due to emmissions reasons) Once the bike gets to running temps, the choke is no longer needed because all of your parts have expanded out and you are getting maximum compression. It is wiser to let the bikes sit until they are warmed up because it prevents blowby (compression gasses seeping past your pistons - this is bad because it increases engine wear in the long run if you do not change your oil regularly)

So ... Use the choke when starting. The choke is "on" when the bike is idling high, and it's better to let the bike warm up before taking it out for a spin. Last little bit - if the bike is idling excessively high, you can back off the choke a little until the revs go down a bit.

Where's my $50 !!??

[Telesque]

The concept of a 'choke' is to restrict incoming airflow (thus 'choke') so that you end up with a enriched fuel-air mixture, isn't it?

I wasn't aware it affected gas flow.

[TechTMW]

Back in the bad old days a choke was just that, a plate that choked off the flow of air. These may still exist today, but not on any mainstream bike I know of.

The next development after the choke was the "Tickler" (Old Triumphs -delorto carbs- among others, used these) This was a button or lever on the actual carb which filled the float bowl completely, causing the bike to run rich on all the circuits for starting purposes.

Finally, most modern carbs have a starter plunger - this is like a carb within a carb - when you pull your choke lever, it pulls open a plunger which opens up a completely separate fuel/air path for starting purposes.

With the first 2 systems, you should start the bike w/ the throttle open - with the last system, you should have the throttle closed when starting.

(end of Choke 101)

[Sarek]

Thanks Tech

I just have one more little question. About chokes anyway. Does using the throttle to keep it revved up have the same effect? I like to use the throttle because I don't have to worry about messing up the spark plugs.
The instructor of my msf class said it fouls out the spark plugs if you forget to put the choke back and run with it on for too long. I did that on the second day of the class and the bike started running really bad. oops!
That's what started my debate with my husband about chokes in the first place.

[TechTMW]

Well - To be honest with you each bike is a little different on the startup procedure. Even two bikes of the same model will have their own quirks.

I have a Suzuki vx800 (V-twin) which starts up without the choke ... probably because the previous owner did a jet kit and free flowing pipes on it - but anyway I digress.

The biggest reason for not using the throttle to start the bike is that the bike requires the throttle to be closed for maximum richness for the easiest starting. (All a throttle does on modern bikes is control the flow of air into the cylinder) When you start the bike it's better to leave it idling for a sec to allow oil to flow up into the cylinder head and get everything well lubricated before revving out the engine.

My recommendation is that you try starting the bike as recommended in the owner's manual - use the choke and don't use the throttle. This is a good habit to get into primarily because you don't want to be revving the engine on startup which could cause increased engine wear.

[BMWBikerchik4]

I always start my little bike with the choke up, its nearly impossible to get it to start if its open...course im also sitting at my desk looking at the carburetor i just took off of it as i type <--and i just had to use that smiley just because it has a fro

[honda599]

The reason for the choke is because gasoline has difficulty atomizing at cold temperatures so additional fuel is required. Fast idle usually occurs during start-up..normal, but don't run too long on full choke as spark plugs can tend to foul up. Slowly back off choke and ride engine gently until it is fully warmed up.

In really warm outside ambient temperatures very little choke may be required....that's normal and often why choke is not required on a fully warmed up engine.