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The Use Of Choke

Discussion in 'Bling and Appearance' started by rthrelfall, Sep 8, 2006.

  1. how ya goin?

    Everytime i start my 01 kawasaki zzr250 i need to use choke for about is 2mins till the engine warms up, im just wondering if this a normal thing to do, if i start the bike without choke it runs for about 20secs b4 turning itself off??

  2. It's normal to need some choke on older bikes to give it time to warm up. I'd suggest giving it full choke, start it up and let it run for 2-3 mins and then turn the choke off and she'll be right.
  3. Yeah mate, I think it is fairly normal. I normally start my Across on full choke let it run for a few minutes for it to warm up than drop the choke back off.

    Also probably a good thing about doing this is throttle is a little advanced, and from what I have read here a 250 should not be left to idle at warm up as oil is not pumped effectively until running above idle.
  4. Really? Having to use choke is certainly normal, but 2-3 minutes seems a bit excessive to me. I try to use it for no more than 30 seconds or so, then I turn the choke off and just rev the engine for a little bit longer before taking off. That's enough for my bike, but then every one is different.
  5. yeah, i use an egg timer :LOL:

    very normal, thats what the choke is for.
    vehicles with automatic chokes have them activated for longer than 30seconds....i leave mine on until i am satisfied that it is going well. you will know if you leave it on too long because your motor will stall (as well it might rev its tits off)
  6. When i use my bike regularly, i dont need the choke to start my bike - which is a 1989 Honda CBR 250R.

    I only need to use the choke if i havent used it for a few days (ie a week). When i do use it, i only leave it on for about 10 seconds (which is enough for the engine to keep running).

    As soon as i let the choke go, i make sure i rev my bike to about 4000rpm for another 15 seconds otherwise my bike just dies. After the 10 seconds of reving, i can leave the bike running whilst i gear up.

    Leaving it on for 2~3mins does sound a bit extreme. I dont know where i've read this, but leaving your bike running with choke isnt good. Something along the lines of having excess fuel (unburnt fuel). Maybe somebody can clarify this.
  7. How does one stop the sucker from retracting the minute you let it go?

    I pull it out, hit the starter and i need to hold it out otherwise it retracts and the bike stalls :evil:
  8. mines a twist-around-the-clipon-type. it just stays there until i move it back.
    certainly choking a 2-stroke too long is bad, will foul the plugs.
  9. My bike normally starts without the use of choke. I only use the choke when it is very very cold in the morning other wise no choke.
  10. to be honest, i other than hot starting....i have always wanged the choke on. i might give it a hit tomorrow chokeless and see what happens. if it plays the mr whippy song ill make muffins
  11. MIne started without choke.. but it will die if you don't control the throttle well.. so usually, I will leave the choke half way.. and then start the bike.. leave it for about 30 seconds and then turn the choke off.. and give it a few good revs.

    There was once I didn't warm up the bike enough and started riding it.. and stall the bike at the lights no far away.. embarassing.. :LOL:
  12. yeah i have exact same bike, well not exact unless yours is red/silver :LOL: and same deal, choke full to start, sounds like revving high then drop it back easy peasy,, :grin:
  13. I never use the choke on my jamjar 250; it just makes the engine splutter and cark out
    pretty much every other 250 i've ever had needed some choke though ... pull it out, start up, ride to the end of the street, choke in and theyre sitting pretty
  14. Unless ambient temps are at over 30 degrees or so, you'll benefit from choke. Bikes that don't need choke either have their idle mixtures set way too rich, or have fuel entering the intake system from somewhere (assuming stock, unmolested carbs).
    The choke enriches the air/fuel mixture, allowing a stable mixture required for cold running. The choke does this either by blocking off the carburettor venturi (creating high vacuum, drawing extra fuel through the carb orifices) or by injecting extra fuel.
    The mix for a cold engine can be as high as 7 parts air to 1 part fuel, as compared to what the ideal or stoichometric fuel ratio is of 14.7 to 1.
    The best way to choke ANY engine is full choke till the engine starts, then slowly reduce choke, in accordance to what the engine needs. Let choke off too early and it'll run rough. Leave to much choke on too long and the engine will start to labour. Too lean is usually very rough, too rich, just slows down in rpms and sounds dull, if that makes sense.
    So, i usually ease back on the choke over about 15 seconds, until I am at about half choke, then slowly roll on some throttle, and remove the remaining choke, leaving throttle at about 1500/20000rpm till engine clears itself and runs smoothly. Then the throttle can be released until it maintains a stable idle.
    An engine needs cold enrichment (choke) to overcome engine friction due to tight clearances when cold, and thicker oil. This is the reason your idle increases as the bike warms up.
    The choke also compensates for the low engine vacuum when the engine is cranking, which is often insufficient on a cold engine to start fuel flowing from the normal carburettor orifices. This is why you can often roll start a cranky cold engine that won't start on the starter, the engine rpms during a roll start are much higher than with the starter. The low vacuum when cold also makes it hard for fuel to vapourise (the air is also very cold, which also makes it hard for fuel to vapourise inside the intake manifold). This is why ether starting aids work so well, it has a very low vapour point.
    That's probably a bit long winded, but that's how it is with me!

    Regards, Andrew.
  15. but always good advice andrew, you must have been a poor young bloke like me that had to fix up every bike ever owned.
    its the best way to learn!
  16. Sort of! Substitute bikes with Valiants, and well, you get the picture!
    Plus, modifying engines a lot means you need to understand the fundamentals, or you can't get them to run, and then what's the fun of that!
    Although, my Z did cost me $600...........and the GTR cost me $2600, so yeah maybe that is true!

    Regards, Andrew.
  17. totally normal to need schoke to help a cold engine along for a few minutes
  18. That's a gem of a post, Typhoon. Anyway it can be saved as an article?
  19. Yeah, thats right, especially at this time of year.

    They guys that claim they don't need choke, or very little are running too rich on their idle mixture.
  20. Flick on, start, flick off as soon as it fires up. Works for me.