Suzuki Central Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
42 Posts
Discussion Starter · #1 ·
i put in a new main jet and i rode it then checked the plug. The plug was dry black. should i go down a size? i am at 170. or should i buy a new plug then run it and see waht that looks like. i can get a pic if that would help.
 
G

·
Jetting/Plug Chop how to do.. UPDATED.. more complete info

Many of you will get by with a MAIN JET change and not really need to do anything more. You won't need to touch the pilot jet or fool with the air screw or change the needle. When doing your jetting it is always best to start rich and work down! Best to do the plug chops and such as mentioned in the following paragraphs.

The way I learned is that you do jetting in two stages.


First, you need to get the -idle and low speed- jetting correct and then work on the -high speed or main jetting-. One could be right on and the other off. Treat as a 2 stage test and fix. As I said, Get the -idle and low speed- jetting correct and then work on the -high speed or main jetting-.


Before you start, have if possible, 3 preferably new, unused (new not a must ) spark plugs gapped and ready to use. You will need at least three plugs for this test.


-Idle and low speed- jetting:


After installing a new plug, you want to ride around at part throttle gently accelerating but keeping below ½ throttle. You want to do low speed as much as possible. After about one mile, pull in the clutch and kill the engine with your kill switch. Coast to the side of the trail. . Remove the spark plug. Look at the insulator from the tip down as far as you can see. Look at the base ring also ... which is the bottom circular end of the plug. Use a flashlight and magnifying glass if necessary. If your having a hard time reading the spark plug, after the jet pass you can put the plug in a vice and hacksaw around the plug at the washer. Break the threads off with vise-grips, and the porcelain will be easy to read. You are also concerned with the grounding tip or the base of the plug.

**(Note: Some people do jet mainly by reading the tip and the base ring/ bottom of plug and disregard the porcelain.) **


This pic shows how a rich plug's base ring looks.


Colors on base ring you might/will see:


White or no color - LEAN (Bad News) - increase jet size
Dark Black - real rich; drop jet size
Medium brown - rich, drop jet size
Medium brown with some light spots - rich, drop jet size
Kinda turning from dark to light tan - closer, drop jet size
Mostly light tan - drop one size, you're pretty close.. see to how it feels
95% light tan - the way you want it!


Anyway, as far as the porcelain, you are looking for an off white, eggshell to very, very light tan on the porcelain. If there was not sufficient time to thoroughly color the whole plug, the insulator may still be white, just be sure to read the base ring and be sure there is a visible dark ring or at best 95% light tan ring at the base of the so you know you are not running lean.


With Idle and low speed- jetting, if you are reading to rich, you may need to lean out the pilot jet or close the air screw slightly. If you are reading very white or no color at all (BAD NEWS) you will need to open the idle mixture more or go up one pilot jet size. If the plug reading is good, you are set to do the main jetting.


Now the MAIN jetting....


--To do the MAIN JET you need a place where you can accelerate at wide-open throttle through at least third gear, preferably fourth gear SAFELY. The procedure is simple. After riding to the location and with a warm engine, change to a fresh plug. Start the engine and immediately accelerate at wide-open throttle as described above. Do not idle or use part throttle. After accelerating, pull in the clutch; hit the kill switch and coast to a stop. Remove the plug and examine as before.


Colors on base ring you might/will see - You saw this color list above:


White or no color - LEAN (Bad News) - increase jet size
Dark Black - very, very rich; drop jet size
Medium brown - rich, drop jet size
Medium brown with some light spots - rich, drop jet size
Kinda turning from dark to light tan - closer, drop jet size
Mostly light tan - drop one size, you're pretty close.. see to how it feels
95% light tan - the way you want it! With your MAIN jetting correct, your bike should rev out and feel strong all the way up through the rev range. Remember over rev and the rev limiter kicks in and you will wrongly think that there is a jetting problem when there is not. Do your plug checks so you know!


If the plug is reading very white of no indication at all, you are lean (BAD NEWS) and need to go up one size on your main jet. If you are reading a tan or darker, you will need to go down at least one size depending on how dark the plug reads. You will need to repeat this procedure until the plug readings are correct.


Fine tuning: When you are getting close on the main jet you can fine tune with the needle if yours has a clip raising the clip lowers the needle and leans out the mixture. Lowering the clip richens the mixture. If your carburetor is not equipped with a clip, thin washers can be used to do fine tuning if needed. A Dyno jet needle has places where you can move the clip to. After getting your plugs reading right, your jetting is on and you will be producing the most power.. Anyway, that is pretty much it.


Once again, many of you will get by with a MAIN JET change and not really need to do anything more. You won't need to touch the pilot jet or fool with the air screw or change the needle. Best to do the plug chops as mentioned. Remember you would be probably be jetted abit differently in the cold weather then Summer riding. Some guys jet when each season comes around. Also, Another thing I learned is it is better to run a little rich at the sacrifice of a tad bit of power then to chance running lean and possibly causing engine damage!
When doing your jetting it is always best to start rich and work down!
 

·
Registered
Joined
·
1,739 Posts
I don't change the plugs when I jet unless it is trying to foul. A new plug will turn black immediately if the engine is rich. And a used dark plug will immediately turn snow white if the engine is lean.
 
G

·
QUOTE
I don't change the plugs when I jet unless it is trying to foul. A new plug will turn black immediately if the engine is rich. And a used dark plug will immediately turn snow white if the engine is lean.[/b]
I hear ya... and know most people don't use new plugs as I mentioned.
Was told along time ago though to teach by the book and let the students short cut on their own.
Something to remember is those new plugs you use for jetting testing are still good after the test UNLESS you saw them up with a hacksaw to take a close look.

Aside from the new plug use thing can you add something more or maybe something I missed..... :p
 

·
Registered
Joined
·
1,739 Posts
You did good Bill!!! Over the years, I have tuned a bunch of Atv's. I could not find a new plug helped in the tuning unless the old one was fouled.
 
G

·
QUOTE
You did good Bill!!! Over the years, I have tuned a bunch of Atv's. I could not find a new plug helped in the tuning unless the old one was fouled.[/b]
I agree with what you said BUT some guys have old plugs that should have been changed long ago that are a REAL MESS and you cannot get a good look at the porcelain as it is so discolored. (I know, not all read porcelain but read tip and base ring/end of plug) Also tip can be deteriorated.. Lots of crud keeps you from seeing that lil band of light tan, etc. on the porcelain as you look up into the inners at the bottom of the plug. Suprisingly enough many people do not realize it is the lil band of color way up there has importance also. Obviously you know this as I... anyway, just need a decent plug old or new that you can get a good visual on so you can read it pretty accurately.
HEY.. for great plug prices go here.... you have to buy 10 though. A bit over $2.00 and they pay the shipping. http://www.clubplug.net/
 
1 - 6 of 6 Posts
Top