The right way to Read a Plug?

[ghodder]

Hey everyone,

I've been all over the net reading about how to read a plug, and there seems to be a number of ways, some contradicting others etc .... and I would just like to have a very good understanding of how to properly read a plug to determine safe jetting.

I called a reliable mechanic about this, and he said that he would never read Plugs to determine safe jetting ... only piston wash.

This link http://www.maxracesoftware.com/spark_plugs.htm
provided a good description, but it also stated that the insulator color of a plug should never be used to determine safe jetting.

Can anyone help clear this up for me?

Thanks, Greg

[Master of Faster]

You cannot just go off the insulator color, the only good way to read the main circuit is to look at the smoke ring around the base of the insulator, to do this you either have to be able to look clearly inside the plug so in most cases its easiest to make a WOT pass then chop a portion of the thread off. Wide smoke ring = rich and narrow = lean. Ideal is around 2mm. The middle and tip of the insulator will tell you only about your low end and midrange and you have to just be cruising around in those areas to check them. A wide open pass will mess up your ability to check your low-speed and midrange.

Thats how I do it, seems to work well for me.

[Skinner]

Hey everyone,

I've been all over the net reading about how to read a plug, and there seems to be a number of ways, some contradicting others etc .... and I would just like to have a very good understanding of how to properly read a plug to determine safe jetting.

I called a reliable mechanic about this, and he said that he would never read Plugs to determine safe jetting ... only piston wash.

This link http://www.maxracesoftware.com/spark_plugs.htm
provided a good description, but it also stated that the insulator color of a plug should never be used to determine safe jetting.

Can anyone help clear this up for me?

Thanks, Greg

Seems someone said something to that same effect here awhile back and the guy was told he's full of shit. Sooooo, I agree with the reliable mechanic. MOF,,,,good stuff!!!

[quadzillaracer]

Go to www.snowtechmagazine.com/articles/2001/baseline/baseline.php (http://www.snowtechmagazine.com/articles/2001/baseline/baseline.php) they have a well put together article about piston wash and how to read plugs.

If thats not good enough for you go to www.bikemanperformance.com (http://www.bikemanperformance.com) and look at their tech articles, they show you real pictures of pistons with normal, lean, and rich piston wash.

Also go to Hooper Racing and see what they think about EGT's and temps of products like Avenger and Digitron.

Personally, get it close and leave it alone for trail applications. Watch the piston wash and on the plugs watch the electrode. The electrode should have of slightly visable "silver" crown on the edge. If the silver crown follows down over the electrode over 1/3 of the length then you are ready to start reforming pistons. Also watch your ground strap on the plug, it should be a nice tan "cardboard" color and continue to the bend of the ground strap and then get slightly darker (not carboned up). Everyone has their own idea for what is right, I just say keep it simple.

Example: If your sled is drowning the plugs while idling on the line than you have more of a problem than just pissing around with air screws, like look at the pilot jet size. Keep carburation on a trail sled simple. Get it to perform well at 25 degrees so it runs good at both 40 and 10 degrees. Find a happy medium. Only on my race sled do I worry about messing around with the air screws to "fine tune" throttle response for off line performance. When you get the trail V-4 setup, it should never be an issue. You will have a safe sled that will run good at 10, 25, and 40 degrees. Ride and enjoy...leave the tinkering for the track!

[racer7x]

Very good article from snowtech.!!!

Bikeman's keep it simple about explaining piston wash, dont they ???

WOW, Hooper !!!!!!

[IZZ]

Good stuff guys!

I too have been instructed to never let the insulator color be the determining factor in adjusting jetting (too many variables influence it) The right size silver crown is what i look for now, together with the right wash.

[ghodder]

Thanks everyone for your responses. Excellent info!!!

[AL P]

Here`s another one..
http://www.dragstuff.com/techarticles/how-to-read-plugs.html

[nate b]

I use the same method as MASTER. Its a little pricey. I use a new plug, run it wot and pull the plug, put in different plugs, ride back to shop, put plug in vise and cut around base of threads with hacksaw, hit with hammer or break threads off with pliers, look for the 2mm ring at base.

If I'm out riding away from home I will through in a black or brown used plug and do a wot run, you can usualy get a good reading just off the porcelin. This usually wont work on a new plug unless you want to hold it wide open for 10 minutes to get color.

[AL P]

woops, I just checked out ghodders link in the first post, and realized, its basicaly the same one I posted..sorry bout that, shoulda checked out the other links before posting mine..


AL

[Master of Faster]

Also remember that the ground strap is a good timing indicator. Maybe not important on a trail Vmax-4 because you probably aren't messing with timing but the location of the color change on the strap gives you a good idea of where your timing is. Typically the color change line should be in the middle of the curve to just below the curve. If the change is more towards the tip then your timing is retarded and if its down by the weld or if there is no change at all then it is probably too far advanced.

[VMAX535]

You cannot just go off the insulator color, the only good way to read the main circuit is to look at the smoke ring around the base of the insulator, to do this you either have to be able to look clearly inside the plug so in most cases its easiest to make a WOT pass then chop a portion of the thread off. Wide smoke ring = rich and narrow = lean. Ideal is around 2mm. The middle and tip of the insulator will tell you only about your low end and midrange and you have to just be cruising around in those areas to check them. A wide open pass will mess up your ability to check your low-speed and midrange.

Thats how I do it, seems to work well for me.
:agree:

Again I agree with MOF, BUT then again this is not an exact science. It is a rule of thumb.

There is no garantees with any of this. If any of you guys want more then this well???

Good Luck.

[fastmax]

Only thing guaranteed thing on a plug reading IMO is "silver spacle all over = meltdown"