Do you have to Rejet with a slip on exhaust?
If you just a put slip on pipe on it, you don’t have to rejet, but you will want to adjust your a/f screw, which requires getting to the carb. A previous post explained how easy it was to change the main jet.
Does exhaust affect jetting?
With aftermarket exhaust you get more AIR flowing through the carb, so you need richer jetting to keep the mixture from being too lean. No matter how much vacuum there is, only so much fuel is going to flow through the jet.
What causes an idle mixture screw to not work?
An air (vacuum leak) at the boot, a restriction (dirt) in any of the idle passages (air or fuel), a improperly set float, even a throttle plate that doesn’t return to the closed postion can affect the adjustment. A cylinder that is not firing or has low compression will obviously affect it too.
What does idle mixture screw do on Honda twins?
What I have discovered however is that the idle mixture screw on the RH carb has no effect on idle of the bike at all. All the way in, all the way out, no difference at all.
When to start the idle mixture screw on a motorcycle?
The idle mixture screw is only one facet of overall carburetor jetting, however it is one of the first places to start when diagnosing a poorly running bike (motorcycle) or ATV (quad).
Do you need to adjust mixture at idle speed?
Yes, and the one near the manifold is the one that adjusts the mixture at idle speed. So that is the one you need to adjust for that particular mixture setting. If you are having trouble adjusting the mixture at engine speeds above idle rpm then refer to my Carburetor Jetting page on this site.
Can a car idle with mixture screws out?
The engine will not idle with the mixture screws out 1.5 turns, without rich black smoke with all possible adjustments to the idle speed screw. The only way I could get it to idle, was with both mixture screws fully closed (seated).
Which is idle speed screw adjusts engine idle?
Now the idle speed screw adjusts engine idle fine with no black smoke, but still a tad rich. 65 jets, 2.5 power valve, 16 psi vacuum at idle out of gear.
Why do the mains not flow at idle?
You need a good amount of airflow to cause a negative pressure change, to get the mains to start flowing. At idle, mains will not flow, unless something seriously wrong with carb. Again, you would see fuel dripping from the main boosters. I’m having basically the exact same problem with a new Holley 4160, I just purchased on a 351 marine engine.
What’s the idle mixture setting on a boat?
Initial idle mixture screw setting started at 1 1/2 turns out (counter-clockwise) from lightly seated. 750 RPMs. No vacuum leaks (that I could determine). Transmission in gear, idling forward (on boat trailer, in the water).