When should you increase pilot jet size?

A general rule is to increase the main jet as long as each jet causes the engine to run as well as or better than the smaller jet in it before. When there is no longer any additional performance gain from the larger jets the jet size is too big – go back down one size.

What does a bigger pilot jet do?

A larger jet number means a bigger hole and more fuel. A smaller jet number has smaller holes and should be used if your engine needs to run more lean. Whether your machine is running too lean or too rich is a good starting point for choosing your jets, but using a jet calculator minimizes trial and error later.

How do I tune my main jet?

How-To tune a main jet

1. Step 1 – Warm up the bike to operating temperature.
2. Step 2 – Install a brand new spark plug(s).
3. Step 3 – Perform a wide open throttle (WOT) plug chop.
4. Step 4 – Read the plug.
5. Step 5 – Determine if you are lean or rich based off plug color.
6. Step 6 – Repeat all steps.

Do you screw Jets all the way in?

Restart it and slowly screw it in till you can just perceive a change. If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet. Now very slowly, open the fuel screw till the idle is smooth.

Does main jet affect needle?

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. The needle is tapered, like a needle, and has a smaller diameter at the bottom than at the top.

What does Rejetting a carb do?

Rejetting Explained Carburetors provide the right mixture via jets which are brass parts with small holes in them. The holes regulate the amount of fuel that goes through the carburetor. Bigger jets allow more fuel and smaller jets allow less. Too little fuel and the engine may starve or overheat at high RPMs.

How do I choose a jet size?

The suggested change in jet size is to go down one jet size for every 1,500 feet in density altitude you go up. Conversely, for every 1,500 feet you go down in density altitude, go up one jet size.

What size pilot jet do I need for a CV carb?

Replace the Pilot Jet with one size larger. This of course assumes that you are starting out with the stock jet size. Harley Davidson Pilot Jets for CV Carburetors are normally sold in sizes 40, 42, 45, 48, 50, and higher.

What kind of carburetors have multiple jets?

Motorcycle, snowmobile, dirt bike and ATV carburetors have multiple jets and fuel conduits. Why so many carb jets, needles, etc? What do they do?

When to replace the jet on a Harley Davidson carburetor?

Main jet replacement should be reserved until after the slow idle jet is replaced and mixture is tuned unless a lean condition is apparent during full throttle. Harley carburetor jetting can be accomplished with minimal mechanical knowledge. Tools to perform this task include just a simple set of screwdrivers.

What is the best jet for a Holley carburetor?

Jet 2 The “as delivered” jetting from Holley is very close to optimum for the majority of high performance applications. For the most part, the jets delivered with the carburetor should suffice as your tune-up “baseline”. In a Holley carb, the jets are located in the metering block (behind the fuel bowl).