Normal turn amounts when tuning carbs

[physlift314]

Hi Everyone,

Been slowly getting the bike back up together. Today I went to try and tune the carbs. I started with the mixture screws 2 turns out on each one. When I turned the R screw in, it went about 1 full turn before the engine almost died. When I turned it out (from 2 turns out initially), however, I was basically able to continue unscrewing it without the engine dying (I stopped at about 9 turns out from 2). I was able to see the mixture screw coming out of the bottom of the carb. I was wondering if this was normal or if there was something I should be looking into? At about 3 - 4 turns out from 2, the engine began to rev a little more (mostly around 1k RPM) and stayed around that RPM range. 

Thanks in advance!

[Blaine]

Thats normal...The sweet spot should be between 2 & 4 turns out.....Adjust for fastest/smoothest idle.

[bikeman]

yeah you are going overboard with the screwdriver.  before you start screw in both screws. then back them out 2 turns. start bike and set the idle to 1200/1300 rpm.


slowly turn one of the screws IN 1/4 of a turn. wait a few seconds for the adjustment to take effect. continue to do this 1/4 turn at a time until the engine starts to flutter. when this happens back the screw OUT 1/4 of a turn. then another waiting each time for the engine to catch up with the new adjustment.


you will find a point where the engine runs smoother and the idle speed increases do just one more 1/4 turn if it makes no difference there is no point in screwing it further out.  you have found the sweet spot. return the screw to where it ran the best. 


the idle speed may well have increased by now so return it back to where you had it and do the other carb the same way. when both are set return the idle and run it around the 1100/1200 mark.  


if you find you cannot set the screws properly it is possible the carbs are out of balance. but you should have done this before setting the mixture screws.

[Blaine]

Turn the idle down...It helps to hear the difference in speed when adjusting...Turn idle back up when finished.

[bikeman]

Dec 9, 2019 6:30:32 GMT -6 Blaine said:

Turn the idle down...It helps to hear the difference in speed when adjusting...Turn idle back up when finished.

I won't disagree with you I think it is a personal preference. but unless the OP knows what level to set the idle to it's just a guess.

my own preference is to have it at normal idle because that is where the it is the smoothest normally. too low and the engine is lumpy [because of the 180degree crank] it fights to stay running. too high and it comes off the pilots you are trying to adjust.  

[physlift314]

Roger that, everybody. Thanks for the input.

Here is a really REALLY basic question. When referring to turning the idle up or down, I assume this means the knob on the carbs that controls the butterfly valve opening?

[bikeman]

yes that's the one.