Carburetor jetting is crucial

(For Fuel Injection-Go HERE)

Carb Tuning
carburetor
carburetors
carb tools
carburetor 2 bbl

Easy to check

You can check to see if your carburetor is jetted properly by doing a spark plug check.

spark plug

Stop engine with throttle open

A spark plug check involves shutting your engine off, under load at a predetermined throttle setting. Then one spark plug must be removed and observed to check fuel/air mixture.

The engine must be shut off, while running under load
with the throttle setting wide-open
to choose the proper main jets.

The engine must be shut off, while running under load
with the throttle setting half open
to choose the proper needle height.

and so on
1/4 throttle = throttle valve
3/4 throttle = jet needle
Etc.

spark plug drawing

Reading the spark plug

You can check to see if your carburetor is jetted properly by doing a spark plug check.

Hold the spark plug upside down and look down inside it.

spark plug reading

There will be 2 colors that should meet at the bottom (A)

The darker shade (C) should be on the inside surface/outer wall.

The lighter shade (B) should ride up the middle.

If
The darker shade (C) rides up the middle
the engine is running rich

If
The lighter shade (B) rides up the outside
the engine is running lean

Make adjustments
by changing the jetting -then do another plug check...


It might take a few spark plug checks until you get the 2 shades to meet right at the bottom where "B" meets "C", at "A"


The carburetor idle screw adjustment must not be done under load. Simply close the idle screw(s) slowly until the engine starts to gallop, then open slightly until the engine smoothen's out.


For full directions
see books available on the
Resources Page

Is your carburetor the proper size?

Carburetor Size Formula


Contact Us Now to Help You Get What You Need