Spark plug pics

[mschor]

I've been riding regularly, she runs smooth with more than about 1/4 throttle, but still a tad stumbly in that pilot circuit range. Plugs 1,2,&3 are dark gray, 4 is a little darker. Pics below show the plugs. I've tried leaning out #4 mixture screw but it runs best at this setting. What do you all think of the plugs? Do those black spots on the insulators mean anything?
Fuel levels in 3&4 are right on; 1&2 are a little over the washer.

https://www.dropbox.com/s/98h3l9nw0j...03900.jpg?dl=0

https://www.dropbox.com/s/xm9rz8uzvf...03619.jpg?dl=0

https://www.dropbox.com/s/x1vt83zfb4...03138.jpg?dl=0

https://www.dropbox.com/s/4zdwb9me6y...02908.jpg?dl=0

[skids]

I am thinking they all look pretty good. Maybe even a bit lean.

[Schming]

I agree with Skids pretty lean, I'd open up the mixture screws 1/2 turn counter clockwise, at a time, til you get some color (tannish) on the plugs.

Is the bikes exhaust popping on decell?

[mschor]

Interesting that they look lean to you guys, but good because it gives me some options. I've seen these plugs light tan and white before, so the dark gray color here made me think it was rich if anything.
I richened them up a bit after hearing your thoughts, runs about the same but I may need to play with it a little more. It does pop on deceleration, not a backfire, but some popping. That's a lean sign, right?

[motoman]

Interesting that they look lean to you guys, but good because it gives me some options. I've seen these plugs light tan and white before, so the dark gray color here made me think it was rich if anything.
I richened them up a bit after hearing your thoughts, runs about the same but I may need to play with it a little more. It does pop on deceleration, not a backfire, but some popping. That's a lean sign, right?

Possible.........also check exhaust system downstream for any leak where outside air drawn in can cause that pop also.

[bikerphil]

Mike, I know from working on your bike that the clamps for the front intake boots seemed stretched and not able to be tightened anymore, the PO must have cranked them down too much at one point. Might be sucking air thru there under load. Possible that could cause some inconsistant plug readings.

[mschor]

Yep, that's true they're all bottomed out now, just saw that when I pulled the carbs again today. I was sure it was running rich from the plug color. Oh well, she's still running good; I'll replace those clamps first and see how it responds

[bikerphil]

Don't know where you would find narrow hose clamps like those. If you decide to go OEM, the P/N is 90460-54137-00.

[mschor]

Hmm, I got some at advance auto today, they are a little wider than the oem, but they went on easily and seemed to seal well. Do you think it makes much difference if they fit in that groove in the rubber boot? It does feel like it added some mid range power. Lower is still same though. If I hold it at about quarter throttle or below, it just feels like it's starving....but mixture screws are all at least 4 turns out. Bought a couple cans of sea foam today, and thinking I'll sync and tune it again tomorrow now that those boots are sealed better. Still a blast to ride regardless

[mschor]

Think there's a very small exhaust leak further down the pipe on the right side

[bikerphil]

As long as the rubber isn't getting torn then you should be ok, I would check the rear clamps too. Any air leaks in the intake system will cause lean problems. Make sure those airbox boots are completely on the rear of the carbs, it's easy to mess one up, esp the center ones.
If your plugs were running rich, they would look like black charcoal.

[motoman]

Hmm, I got some at advance auto today, they are a little wider than the oem, but they went on easily and seemed to seal well. Do you think it makes much difference if they fit in that groove in the rubber boot? It does feel like it added some mid range power. Lower is still same though. If I hold it at about quarter throttle or below, it just feels like it's starving....but mixture screws are all at least 4 turns out. Bought a couple cans of sea foam today, and thinking I'll sync and tune it again tomorrow now that those boots are sealed better. Still a blast to ride regardless

4 turns out...... Actually, nothing more than 2 1/2 turns out. If more, then there is other fueling issues, pilot jets too small, etc. I suggest for an initial bench setting, 1 1/2-2 turns out. From there, your still gonna have to set those idle mixtures at an idle(back mix. screw out several turns.....gradually start in till exhaust sound changes or slightest idle drop that stays constant that way......now back mix. screw out 1/8th and no more than a 1/4 turn). Do other three same way, and you will be making idle adjustments lower as you go.........NOW you can sync the carbs, but not before setting idle mixture. Sync carbs at 1100 rpm or a bit lower.

[motoman]

Think there's a very small exhaust leak further down the pipe on the right side

That'll pull in the bit cooler outside air at exhaust leak and cause it to pop through exhaust on decell.

[Schming]

Hi Mike,

A thought I had while reading your post had me wondering that maybe your butterfly shaft seals could be worn and permitting extra air into the mixture.
Depending on how and what you or others cleaned or soaked the carbs in may have compromised the shaft seals ability to seal.

[donebysunday]

I've been riding regularly, she runs smooth with more than about 1/4 throttle, but still a tad stumbly in that pilot circuit range. Plugs 1,2,&3 are dark gray, 4 is a little darker. Pics below show the plugs. I've tried leaning out #4 mixture screw but it runs best at this setting. What do you all think of the plugs? Do those black spots on the insulators mean anything?
Fuel levels in 3&4 are right on; 1&2 are a little over the washer.

Now that you have addressed the possible and known leaks ,,,,,, how old or how many miles are on those plugs ?
At O'Reilly auto parts the BP6ES NGK plugs are less than $3 each, well worth it to start your tuning with fresh plugs, maybe ?
Put these plugs in the box the new came in for future use if ever needed ?
Silver specs on the insulators is burning up the aluminum of your piston tops, the brown that you have I think is just a tiny bit of oil (no concern), plugs in my LH engine look much the same. I tried to get more color on the plugs but one size bigger pilot jets did not run as well.
I just found my new digital heat gun in the mail so I'm going to try and get the idle mix screws turned down from 3.5 turns out. All and all it's running very nice so I'll be just experimenting. Oh the gun was about $14 with shipping from Amazon.