Help Read my Spark Plugs!

[Erich Z]

Finished balancing the carbs, now after a long ride my plugs look like this. Too lean? What's the easiest way to fix?

[goodwood73]

lean. you need to do plug chops at different throttle openings to determine which part of your carb to richen. What are your mods?

[don_gibb6512]

You need a baseline setting to start with. What bike, model carbs, stock air box or pods, stock exhaust or 4-1, jetting sizes, needle position and fuel screw settings.

[Hoges]

Your pilot screw setting should be around 1 and 3/4 and 2 and1/4 turns out for a standard setting for the GS450. I got this from the original Suzuki workshop manual.

[Zook]

It's lean. Insulator should be tan.

[chef1366]

You only have a thread to a thread and a half of color on the threads of the plug. This measures the heat range and it is good. If it was too lean your threads would have color about half way up. The leaner you are the hotter the bike runs.
Those plugs are still new. Ride it for a while and then pull them.

[Erich Z]

I'm gonna go with the last response here - they're new plugs, and only have about 100 miles on them tops. They might be a tad lean but not too much.

It's a GS450L, stock in every darn way.

[rustybronco]

I'm gonna go with the last response here - they're new plugs, and only have about 100 miles on them tops. They might be a tad lean but not too much.

It's a GS450L, stock in every darn way.

There is color on the side electrode, gray if I see the color correctly. I can't see the tip color or down deep at the base of the insulator.
it looks looks like the heat is at a thread or so and that should be fine for the correct heat range.
it's an '82 they run lean. how does it run?

[Erich Z]

Seems to run well, though I'm a newbie at tuning bikes. Too bad you're not closer, or I'd get your personal opinion. I'm learning as I go.

[rustybronco]

when warm is there any hesitation/stumble through any ranges? easy roll on, 1/2-3/4 throttle acceleration, full throttle (if you choose to do full throttle)
pulls hard to redline in any gear? (or some what up there, if you choose) yes I know the higher gear ranges don't give the same "thrill" as the lower ranges. but it still should pull without stumbling.
idle smooth?

[seuadr]

if you like eric, i can take a look at'em later this week. i'm on the west side of lansing.. i've got no tools, but i got an idea of what they should look like.

[Joe Guilbeau]

Spark Plugs and color

Someone correct me if I am wrong here, but mileage on a plug don't matter a whit.

If the carbs run lean, they run lean with o miles or 100,000 miles on the plug.

Same with a rich running carb, mileage should not matter... after all it is the ratio of gas to air that matters. Mileage on the plug does not consider this variable into any equation.

So, if the idle is lean and the mid range is lean but the main jet is rich, then when you go out on a ride and blast up into the higher RPM's how are you gonna tell what the main jet is contributing?

Unless you shut the bike down at high RPS's so the mid and idle do not curtail the Main's contribution... because you slow down and ride back to your garage... that is when the lean conditions on the mid and low range RPM's mask the main jet response.


Same with the low range of RPM's, start the bike let it idle and then shut it down, pull the plugs and monitor. That will tell you the idle circuits condition, whether it is lean or rich.

With mid range, you need to shut it down when the throttle is 1/4 to 3/4 open. Kill the engine in that range, don't run the bike on the street and drive back to the garage to monitor the plugs.

Here is an old magazine article on Motorcycles that appeared in the late 70's... still good information not much has changed...

http://www.strappe.com/plugs.html

[rustybronco]

So, if the idle is lean and the mid range is lean but the main jet is rich, then when you go out on a ride and blast up into the higher RPM's how are you gonna tell what the main jet is contributing?

take an eye loop, spark plug inspection light, a good light and a magnifying lens or what have you. look at the base of the insulator where it meets the shell. the color should be a tan to brown color on nearly the complete base circle, that should be your high speed circuit a/f ratio. yes it can be masked by running the engine without doing plug chops, or after putting around low to mid throttle, but when you run the plugs for a while it will let you know "within reason" how the engine high speed circuit is doing.
how the engine runs through the various ranges gives you a little more of the puzzle, when you can't see or hear it.
kind of hard to tell by the blue tint of the plug picture, but when you know what to expect (tan- lt/gray) number of turns on the threads, how far the heat is up the side electrode, it helps.

also good reading material

http://www.dragstuff.com/techarticles/reading-spark-plugs.html

look at these

http://www.dragstuff.com/techarticles/images/sparkplugs/jetxx20115ps016deg3.jpg

Ryan's Plugs AKA 66 283. Almost perfect fuel and timing, after this pull added 1-2 degrees more timing to take the heat in the ground strap just a bit more towards the corner bend and picked up 40rwhp.

[Erich Z]

Idle is smooth, and pull is smooth at all rev ranges in my experience so far. Running much better than it was last year this time - it was stumbling off idle and pulsing when accelerating noticeably.

[Zook]

Joe is correct, mileage means NOTHING. Race engine tuners will do a dyno pull and check plugs, then adjust jetting.
From tuning race engines, I learned to read the INSULATORS.
And it's tough when you burn alky. That stuff burns pretty clean.
P116 is much easier.
NOT threads, or tips, the INSULATORS tell you the temp of the plug.
White is lean.
Tan is good.
Black is rich-if it's not oil.