Jet size with +4 degrees

[Edster11]

I was just curious how many of you that advanced your timing 4 degrees had to get bigger main jets.

[boonman]

I didn't re-jet with it. maybe one size, but i doubt you will have to..

[Edster11]

how can you tell if you need to or not? I heard plugs read differently when u advance the timing.

[boonman]

Not that I've ever experienced... Here, read this..

 

 

Jetting

TO READ PLUGS PROPERLY YOU WILL NEED A 10x ILLUMINATED MAGNIFYING GLASS

1,2,3. This is how it's done!

1. You set your heat range from the ground strap. (this is the piece closest to the piston)

 

2. You do all the plug readings for jetting from the base ring (thebase ring is what the ground

strap is welded to at the end of the threads)

 

3. You determine detonation and timing issues from the porcelain.

(The porcelain shows preignition/detonation, it will not accurately determine jetting / air/fuel

ratios)

 

DO NOT BASE JETTING DECISIONS ON THE PORCELAIN COLOR.

1. How to determining plug heat range:

The ground strap is your window to getting this right. If the "color" of the ground strap

"changes" too-close to the ground-strap's end, (the end opposite of the base ring), then the

heat-range is "too-cold", (heat transfer is to quick to the base ring) If the "color" of the

strap changes near where it is welded to the base-ring, then it means that the plug heat-range is

"too-hot", (heat transfer to the base ring is to slow causing the deposits to be burned off the

strap completely) The strap at this point could start working like a "glow-plug", probably

resulting in pre-ignition/and/or detonation. The properly set heat-range is when the "color" is at

the half-way point on the strap.

 

2. Reading the base ring to determine jetting:

The base ring "color" is very close to the color of the piston crown and is used to determine the

jetting. Your looking for the soot color to be a nice light to medium brown, (color is always

hard to describe) if the color doesn1t go all the way around the base ring (at least one full

thread turn on the plug) or the color is whitish it is way too lean. If the color goes all the

way around, but there is a spotting of heavy dry soot on the top of the color, you are too rich.

( TWO STROKEJETTING WILL BE A LITTLE WETTER LOOKING AND DARKER THEN A FOUR STROKE )

 

3. Read the porcelain to determine detonation / preignition:

The first signs of detonation / preignition will be seen on the porcelain down in the plug, It

shows up as tiny black or shinny specks of aluminum. Also Look very close around the center

electrode where the porcelain intersects, this will appear to be melting between the insulator

and the electrode. Detonation is caused by the air/fuel mixture exploding rather then burning.

This gives off a sound, (a knock) this sound is the result of a shock wave, this wave disrupts

the boundary layer of cooler gases that cover the internal parts of the combustion chamber. This

causes a very rapid rise in pressure and temperature. The results are holes in the top or sides

of the pistons, blown head gaskets, broken rods, (all bad stuff) This can also shock the rings

from there seal causing oil to form as little spots on the porcelain.

 

 

Print this off and use it for reference.

 

 

Here is also a link I got from Wheatchex, it explains carbs and their respective circuits so you

can understand what these things do..

 

http://204.71.0.3/motoprof/moto/mcycle/car...01/carb101.html

[WickedBanshee]

i wouldnt think so because you not changing the amount of air coming in.

[Nightrider]

Timing has absolutely no effect on jetting.Jetting changes are required when you alter the amount of incoming air or outgoing air.Pipes,porting,reeds,nitrous,turbo or air filter changes require jetting because a larger amount of air is being introduced or removed from the engine thus increasing the need for extra fuel.Extra timing means the fuel/aircharge will be ignited sooner.Advancing the timing does not change the airflow to the cylinder(like Wicked said),it simply ignites the mixture earlier.I hope this helps.