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Adjusting vacuum

  • Thread starter Thread starter sv650
  • Start date Start date
S

sv650

Guest
Well, Ive read Earlfor's description of how to adjust CV carbs. I don't understand how to adjust the #3 carb to get 10 in Hg at 1200 rpm. Currently I get about 6 in Hg at 1200 rpm, and can't figure how to get a different vacuum reading. If I sdjust the idle speed, the vacuum changes, but I can't figure any other way.


Can someone explain this to me?

SV
 
Re: Adjusting vacuum

If you're showing 6 in of vacuum at 1200 rpm, then your throttle plates are open a little too wide. closing your throttle plates will reduce the carb throat opening. Intake volume will be the same, but velocity will increase.
An increase in velocity will draw more fuel for the same volume and rpm will decrease. (this is what happens when you turn out the idle adjustment screw) Turning out the idle adjustment screw will close the opening and increase vacuum level. RPM will decrease because idle mixture become too rich. Lean the idle mixture screws slightly as you turn out the idle adjustment screw. At idle rpm, you're working with throttle plate position and idle mixture screws. The slides are not raised.

Earl



sv650 said:
Well, Ive read Earlfor's description of how to adjust CV carbs. I don't understand how to adjust the #3 carb to get 10 in Hg at 1200 rpm. Currently I get about 6 in Hg at 1200 rpm, and can't figure how to get a different vacuum reading. If I sdjust the idle speed, the vacuum changes, but I can't figure any other way.


Can someone explain this to me?

SV
Click to expand...
 
Hate to slip into this thread, but I don't want to post another one.

Earl,
Is there a "Bench" method I can use to synch the carbs until I can get a set of gages?
I saw one where a guy made one with tubing and a yard stick using Tranny fluid.
I know it's not possible to get the vaccuum you mention, but would this get me close until I get the proper gages?
What about adjusting each mixture screw til the best rpm method, then reading the plugs?
I just seem to have an excessive amount of vibration lately and hate running that way too long. I ride just about everyday to work.
Thanks.

SV, sorry to thread hop here. :wink: :wink:
 
Jets

Jets

Thanks, Earlfor,

When I installed the Colourtune plug in each of the cylinders, I learned that I cannot get the bike to show a blue flame at idle; it runs rich with the idle screws closed. Since the previous owner "cleaned" the carbs, and the float bowls show the use of a scraper tool, I'm guessing that the jets have been enlarged. I've therefore ordered a new set of jets (except jet needle & needle jey -having trouble finding those). I'll post more once I've installed those!

BTW, the Colortune helped all the previous comments make sense. Seeing (the flame) IS believing!

SV
 
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