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Carb balancing whats more important.

in 2 Stroke Technical Questions 13 years ago
Hi all as the title says....Carb balancing whats more important...first off I use a DIY manometer connected to the primer ports on my 503 DCDI....I set the idle with the idle screw's to get an even reading with my manometer....then I see what the readings look like over the full RPM range,

If I adjust the cable adjusters to give an equal reading on first opening the throttle....I find that the reading at my cruise RPM will be miss matched,

So I am just wondering....should I just aim to get a matched reading at the moment the throttles start to open...or would it be better getting an equal reading at cruise RPM which is 5000rpm for my trike..

Nick.

  • Re: Carb balancing whats more important.

    by » 13 years ago

    Nick, I'd have thought that correct balance is important at small throttle openings when tiny differences result in a lumpy idle. Once the throttle is more than half open, the differences become insignificant.

    At large throttle openings balance is achieved by simply ensuring the slides are at equal heights using cable adjusters. When closed (but not on their respective stops) they should still be at identical openings (if not, why not?).

    Dave
      
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  • Re: Carb balancing whats more important.

    by » 13 years ago

    Balance at your cruise rpm. EGTs should be nearly equal.

    Initially balance at idle with the idle screws. Then adjust the idle JETs to achieve best idle speed, plus slightly richer. (Small adjustments make a big difference. The point here is to get a smooth transition from idle to around 3000+rpm.)

    MAKE SURE at WOT that there is some slack in the cables at the adjuster on the carbs, with both carb slides equal, with a little more vertical movement left on the slides.

    CHTs should be pretty equal, but remember cooling airflow might be a little different between cylinders.

    Dave
      
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  • Re: Carb balancing whats more important.

    by » 13 years ago

    Nick'

    Dave is right. carb balance is much more critical at idle than at cruise. Balance with the idle screws, then adjust the jets for best idle. If both slides are starting up simultaneously, your EGTs will be pretty close at cruise with no further adjustment. If you want to really tweak it, you can then adjust the balance at cruise by lowering which ever slide needs it with the cable adjuster. If you raise the slide rather than lower it, it won't be right at idle. The idle screws determine the opening at idle and the cable adjusters determine the opening at cruise. Adjusting at cruise is a little more difficult because there is much less manifold vacuum to measure. Almost always, if you balance at idle, lift the slides together, you will be OK at cruise.

    Bill
      
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  • Re: Carb balancing whats more important.

    by » 13 years ago

    Thanks guys...makes me think my DIY manometer is not worth bothering with....just set it by eye getting the slides to open as one which is what I did last night with my welding rod idea.

    Nick.
    IMG_3704.JPG (You do not have access to download this file.)
      
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  • Re: Carb balancing whats more important.

    by » 13 years ago

    Time to throw the manometer in the bin I think....took my trike for a flight today after setting the slide cables adjustment with the 2 welding rods idea....result... near as dam it perfectly matched EGT and CHT gauges,

    Thanks for your ideas guys.
      
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