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How to Adjust Idle

Discussion in 'Engine & Transmission' started by smithy658, Mar 1, 2013.

  1. smithy658

    smithy658 Member

    Messages:
    182
    Location:
    port macquarie
    Just converted my 75 bay to single carb kit and now it idles really low and sometimes dies on me just wondering if anyone can provide a step by step guide on how to advance the idle
    Cheers Jacob
     
  2. oldman

    oldman Super Moderator Staff Member

    Messages:
    10,990
    Location:
    Avalon Beach NSW
    Will depend on type of carb. you've put on......I'm no help really, I'm a fan of keeping stuff stock.
    Cheers, Mark
     
  3. poGo

    poGo Member

    Messages:
    156
    Location:
    Townsville
    a single can work well with some love and care. just about anyone can whack on a set of duels and be done with it. Just spend some time on it. What sort of dizzy do you have? You should have the stock Vac advance dizzy. I back the idle speed screw right off and only screw it in a quarter to half a turn after it comes in contact with the idle stop. Then I start the motor and turn the dizzy as retarded (clockwise) as it will go without stalling the motor followed by tweaking the idle mixture screw (turn in till huff huff huff, turn back out until pop pop pop and then back in between), finally rotate the dizzy back anti-clockwise to get 900 rpm, take it for a drive and drive it hard making sure it doesn't ping under load. Don't cheat and adjust the idle with the idle speed screw.. all you're doing is exposing more progression holes interfering with the carb's progression.. this mistake, along with intake leaks is usually what will cause a motor to stall pulling up at the lights.. think about it.. if the throttle plate is open too far at idle position (when your foot is off the gas) it will allow too much air to get through and therefore when you're gear braking in 2nd before pulling up extra air is being sucked through your motor causing it to stumble when you stop until you pump the gas and push more fuel through the jets.

    I hope the above is somewhat comprehendible. Remember to always let your engine warm up before adjusting anything.
     
  4. poGo

    poGo Member

    Messages:
    156
    Location:
    Townsville
  5. 68BUS

    68BUS Well-Known Member

    Messages:
    4,635
    Location:
    Brisbane
    Pogo.
    Just trying to get my head around that.
    Would turning the dizzy to get adjustment not stuff the timing?
    I though the dizzy have one location that allowed correct firing of the engine. And the idle speed would not affect the timing??
     
  6. poGo

    poGo Member

    Messages:
    156
    Location:
    Townsville
    no mate, you can set and forget with factory carbs to some extent, and even then you'll need to fine tune by a few degrees since any motor will have slightly different/worn internals from factory spec. but definitely with an aftermarket carb, the fuel curve has changed dramatically and therefore the timing will need adjusting to suit. have a think.. if the carb you have runs leaner than the factory setup then all of your mixture will be ignited sooner advancing your timing regardless of where your dizzy is bolted. Pretty much so long as when you really gun it she won't ping then you're sweet. Welcome to weber carbs.. you'll be driving around stopping and starting shoving your head in the engine bay for a bit maybe more but once you find the sweet spot you'll be damned.
     

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