Helpful tips

What does raising the carb needle do?

What does raising the carb needle do?

Raising the needle by lowering the chip position at the top of the needle will richen the mixture. Lowering the needle will lean the mixture. WIDE OPEN THROTTLE: Changing the MAIN JET affects this range. Select the size which offers the best wide open throttle.

How do you remove a SU carb needle?

(a) Lift off the piston spring. (b) Carefully lift out the piston and needle assembly, and empty the damper oil from the piston rod. (c) Remove the needle locking screw and withdraw the needle. If it cannot be removed easily, tap the needle inwards first and then pull outwards.

Does needle height affect idle?

The needle position has no affect on idle, it basically affects mixture around the 1/2 throttle range. If you need to change the WOT mixture you need to change the main jet, then change the needle to suit half throttle needs.

Does needle position affect idle?

Can you straighten an airbrush needle?

Try using your fingernail first to straighten the airbrush needle tip as best you can, or perhaps use some tweezers or a small pair of pliers being VERY careful not to be too rough and damage the tip further. Once you have it reasonably straight pull the needle out of the airbrush.

Does needle affect Main Jet?

Fuel comes through the main jet and into the needle jet. So the main jet does affect the needle, especially as the throttle opening increases. The needle is attached to the slide and slides up and down within the needle jet.

Where is the hex nut on a SU HS4 carburetor?

Note: Type HIF carbs (With integrated float bowl) no longer have the hex nut to adjust the mixture. Instead, there is a screw to twiddle, on front of the front carb, and behind the rear. The screw is connected to the needle seat through a temperature compensated gizmo, which is said to make the carbs more stable.

What are the needle codes for SU carbs?

Needle codes for SU carbs. Needle codes for SU carbs. Here are a selection of needles codes and the vehicle specs that they were used in… EB – 850cc and rebores, 920cc, 1.25SU, 9:1 CR. ADE – 998cc, HIF38, Metro inlet, std filter, free flow exhaust. ABY – 998cc, 12G295 head, HIF-38, Stub Stack, K&N, 3 into 1, RC 40, std cam.

How big is the needle on a HS4?

Single HS4 1.5″ Engine Size Needle Std. Needle Rich Needle Lean Spring Type 850 Std H6 – M – – Blue 850 1974 (Bias) ABS – – Red 850 1975-on ADH (wax stat jet tube) – – Red 850 Automatic to 1974 AN H6 EB Red

What’s the best way to tune a SU HS4 carburetor?

The Uni-Syn is much easier to use, and can result in better balance. Alternatly adjust the idle screw on each carb, attempt to set the idle as low as possible (~800-1000 RPM). Adjust until the airflow is *close* to the same at each carb. The engine may now be running rough, just keep the idle speed high enough to keep running.