Spark Plug Reading - What's your read?

[MelodicMetalGod]

Here's a pic of the plugs in question:

According to the following images,

http://www.gnttype.org/techarea/engine/plugs.html

I'm thinking that the read is that my plugs are in the early stages of carbon fouling.

Would you agree?

Thanks for your time!

 

[Dave8338]

I disagree...if anything, they are slightly lean (not much) but IMHO, along way from fouling out.

 

[NickNoo]

Yep - perhaps a tad lean, but nothing to worry about.
Have a look here for some good spark plug info : http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

 

[denydog]

They look kind of new. I don't see any fouling of the electrodes and insulators. They look a lot like mine. I'll vote for slightly towards the lean side also.

 

[DimitriT]

I agree with everyone else

If you pulled these from a normal shutdown (idling) bike they are normal. The idle is a bit lean on these bikes but that's ok so long as your choke can start the bike. You don't want lean when your bike is on the main jet (with the throttle way open) as you can damage your motor.

 

[MelodicMetalGod]

OK, so it looks like I was reading it wrong. Guess it's a "Lean" read then. Well, I've got very little experience reading plugs and that's why I posted.

Thanks everyone!

 

[MelodicMetalGod]

I agree with everyone else

If you pulled these from a normal shutdown (idling) bike they are normal. The idle is a bit lean on these bikes but that's ok so long as your choke can start the bike. You don't want lean when your bike is on the main jet (with the throttle way open) as you can damage your motor.

Yep, lot's of idling and then I pulled the plugs. Still have some carb tuning to do. Now I have a good read to work from. Thanks!

 

[rustybronco]

Some more reading...

http://faq.f650.com/FAQs/SparkPlugFAQ.htm#Plug Chop
http://www.nightrider.com/biketech/readplugs.htm
http://www.4secondsflat.com/Spark_plug_reading.html

MORE... http://www.dragstuff.com/techarticles/how-to-read-plugs.html

if this doesn't fill your head, nothing will.

 

[Steve]

The outer edges of the plug do have black stuff on them, but that's not where you read them. :shock:

You read the porcelain cone in the middle that holds the electrode.
They are mostly white, with beginning tinges of tan, indicating slightly lean, but not enough to worry about.


.

 

[rustybronco]

Did you read the section about dividing the the center insulator up into three parts yet? how about reading for timing?
there is a lot to know about what effects what, such as a rich condition leaving the insulator white from fuel washing it clean, and the tan on top 1/3 not going all around.
how about way down where the insulator is near the shell that tells w.o.t. mixture.
there is a LOT to know my friend, and if you can grasp it all you're better than me!!!!!!!!!

yes steve imho is correct. thats how i read it also.

 

[steve-lloyd]

I would say they are more than a little lean.
The really important test is to run the bike hard at full throttle, uphill if possible, then cut the engine on the kill switch. Now remove the plugs.
The part of the plug you need to inspect is the centre cone shaped part, which should be light to dark tan.
White is dangerously weak, grey is weak, dark tan/brown is rich, and black is very rich.
Many Suzukis are running around too lean, because owners fit pods on the carbs instead of the standard airbox and filter without rejetting and readjusting the carbs.
GS bikes hate being meddled with like this and are very difficult to get running really well with pods.:|

 

[MelodicMetalGod]

rustybronco,

Thanks for the light reading. I have now decided to go back to school full time to major in Spark Plug Reading. First Course: Shades of Tan and What They Mean.

Seriously, very informative. Thanks.

 

[MelodicMetalGod]

Steve, thanks for taking a peek. Reading the porcelain I noticed that plugs 1 & 2 are showing tan where 3 & 4 are very clean. Could that be from carbs that aren't synched (which mine aren't yet)?

 

[MelodicMetalGod]

I would say they are more than a little lean.
The really important test is to run the bike hard at full throttle, uphill if possible, then cut the engine on the kill switch. Now remove the plugs.
The part of the plug you need to inspect is the centre cone shaped part, which should be light to dark tan.
White is dangerously weak, grey is weak, dark tan/brown is rich, and black is very rich.
Many Suzukis are running around too lean, because owners fit pods on the carbs instead of the standard airbox and filter without rejetting and readjusting the carbs.
GS bikes hate being meddled with like this and are very difficult to get running really well with pods.:|

Haven't really done much at full throttle yet. Mostly suface street driving (mid-range) and idling. I've got a stock airbox, but I suspect that I've had an air leak at the intake boots. In addition, I've got two pilot screws that are stuck and stripped out and I was running the other two about 1.5 turns out.

I'm thinking that I need to do the following:

1) Get the two stuck pilot screws unstuck and set all screws to 3 turns out.

2) Ensure that I've got an air tight system from the air box to the cylinders.

3) Sync the carbs.

4) Tweak #1 as needed based on future reads.

Sound about right?

 

[twistedwankel]

Yep. Those are spark plugs. They work better in the head. "Reading" is that you will meet a short dark stranger on a moonlit road in August. He will tell you where to go.

 

[rustybronco]

Steve, thanks for taking a peek. Reading the porcelain I noticed that plugs 1 & 2 are showing tan where 3 & 4 are very clean. Could that be from carbs that aren't synched (which mine aren't yet)?

at least # 3 shows tan, can't see #4 clearly.

 

[Steve]

Haven't really done much at full throttle yet.

This is the base from which all other settings are derived. :shock: The main jet also feeds the needle jet. Together they control just about everything but idle mixture. If you start tweaking at the idle end, then work your way up, if you have to change the mains, you have to start over. Start with WOT tests to get the main jet right.

I've got a stock airbox, but I suspect that I've had an air leak at the intake boots. In addition, I've got two pilot screws that are stuck and stripped out and I was running the other two about 1.5 turns out.

Just out of curiosity (so I can compare with the picture), which ones are stuck and which ones are 1.5 out?

I'm thinking that I need to do the following:

1) Get the two stuck pilot screws unstuck and set all screws to 3 turns out.
2) Ensure that I've got an air tight system from the air box to the cylinders.
3) Sync the carbs.
4) Tweak #1 as needed based on future reads.

Not bad.
1) Get the two stuck pilot screws unstuck (replace them, if necessary) and set all screws to 2 turns out.
1a) Bench sync the carbs.
2) While you have the carbs off the bike, check the intake tubes and their o-rings.
....If you haven't changed them, chances are they haven't been done.
3) Install carbs and use gauges to sync them.
4) Shouldn't have to tweak much if you started at 2 turns.


.

 

[GS750]

Yep, lot's of idling and then I pulled the plugs. Still have some carb tuning to do. Now I have a good read to work from. Thanks!

I was taught that you need to use the kill switch at W.O.T (wide open throtttle) to be able to correctly diagnose the fuel mixture from the plugs.

For nearly all engines I have worked on, at idle will run either rich or lean.

Thats why "emission" controlled carbs had the mixture screw capped off...... You can still change jets, but you cant f*ck around with the mixture.

 

[MelodicMetalGod]

This is the base from which all other settings are derived. :shock: The main jet also feeds the needle jet. Together they control just about everything but idle mixture. If you start tweaking at the idle end, then work your way up, if you have to change the mains, you have to start over. Start with WOT tests to get the main jet right.

OK, so I need to do plug reads after shutting down from WOT. Had NO idea. Thanks all!

Just out of curiosity (so I can compare with the picture), which ones are stuck and which ones are 1.5 out?

Stuck pilot screws are # 2 and 4. # 1 & 3 were set to 1.5 turns out.

Not bad.
1) Get the two stuck pilot screws unstuck (replace them, if necessary) and set all screws to 2 turns out.
1a) Bench sync the carbs.
2) While you have the carbs off the bike, check the intake tubes and their o-rings.
....If you haven't changed them, chances are they haven't been done.
3) Install carbs and use gauges to sync them.
4) Shouldn't have to tweak much if you started at 2 turns.

RE:
1) I've got two sets of backup carbs waiting for me to pull replacement pilot screws! I've been recommended everything from 1.5 up to 3.74 turns out. Why do you recommend 2?
1a) Bench syncing is part of my standard carb install process.
2) Are you referring to the infamous intake boots (between carbs and engine) and their infamous o-rings? If so, I've just rec'd a new set of both. I've seen a recommendation of applying a coating of hi-temp bearing grease to the o-rings to ensure against any leaks...?
3) Gauges sync is on the list.

Thanks!

 

[MelodicMetalGod]

I was taught that you need to use the kill switch at W.O.T (wide open throtttle) to be able to correctly diagnose the fuel mixture from the plugs.

For nearly all engines I have worked on, at idle will run either rich or lean.

Thats why "emission" controlled carbs had the mixture screw capped off...... You can still change jets, but you cant f*ck around with the mixture.

My pilot screws were capped off, but the PO drilled 'em out, as many folks do. My understanding is that the factoring settings are generally a bit lean, especially for emissions purposes.

Thanks for your time!