What causes a plug to burn this way?

[MtnEX]

What causes a plug to look almost lean to perfect on the porcelain... perfect on the ground strap... but rich looking around the base ring???

Looks like this after typical use.
I just did a short hard trail ride on this fresh plug.

[bherriman]

Ride it for a while... a new plug can take a bit to get colored correctly but if you didn't do an actual plug chop and where just riding around the trails then you could maybe be rich on the slow jet.

[MtnEX]

Unless somebody can explain it to me, that is what I am going to do.

If it starts well in the morning, I'll just leave it as-is and see what happens. I know the outside is going to get blacker... just not sure about the rest.


As for the slow jet, here is the story on that. Never could get it to start for bunk with the stock 38.

I jumped to a 42 since it is so popular. It started well but had a little stumble sometimes on a quick blip from idle.

Someone suggested the 42 was too rich without a lot of mods... so I went to a 40. Tried everything under the sun and then just finally surrendered to once a day start and run testing.

I think I finally got it today... lost count of the number of turns out... but like with the 42 it had the stumble, maybe even worse. Backed it in a quarter turn and it improved way more than expected.

So yeah, rich on the pilot is believable, I just don't know how else I'd get it to start without cranking it 19 times and having it fire and die the first 18... you know what I mean.... lol...

[Wheelie]

Just a thought, put less emphasis on the plug reading for awhile. Tune the machine by how it's actually running.


Putting everything into plug reading can/will cause someone to chase their tail.


I repeat, quit reading the plug and tune the machine by how it's actually running.

[krt400ex]

i agree. and also when tuning the pilot circuit, get the quad to a high idle (1800-2200rpm) and adjust the fuel screw till it runs smoothly. dont want the engine to surge or cough.

[MtnEX]

Originally posted by krt400ex
i agree. and also when tuning the pilot circuit, get the quad to a high idle (1800-2200rpm) and adjust the fuel screw till it runs smoothly. dont want the engine to surge or cough.

Mine never does seem to be all that effected by adjustment.

It doesn't start to slow down or anything until I have it near all the way in. And adjusting it where it is at is so slow...

Well, I just had to use a tach to see where the RPM increased, and where it started to decrease as I went further out. Set it like that, but it didn't crank for....


Maybe I have something wrong?
Might need to check my bag of tricks and see if there is a pilot screw in there?

[MtnEX]

Originally posted by Wheelie
Just a thought, put less emphasis on the plug reading for awhile. Tune the machine by how it's actually running.


Putting everything into plug reading can/will cause someone to chase their tail.


I repeat, quit reading the plug and tune the machine by how it's actually running.

I understand that, and that is the plan for now. I am going to run with what I have for now because it seems better...


But I am still stumped why a plug would burn that way.... and I do plan to keep carrying a spare plug, because I figure it might finish dry fouling the rest in time... but I don't know.

[ds268]

If it was a short ride, like stated it won't tell you much at all. When I finished rebuilding my bro's 450, he raced for a couple hours then went cruising the rest of the day. Got home, pulled plug and looked exactly like yours. Come to find out on the dyno the following week it was well on the rich side. It just wasn't riden long enough to color the plug. Stick it back in and go ride. If it cuts out, pops, hesitates or sputters then you know you need to adjust something... just my op.

[MtnEX]

Originally posted by ds268
If it was a short ride, like stated it won't tell you much at all. When I finished rebuilding my bro's 450, he raced for a couple hours then went cruising the rest of the day. Got home, pulled plug and looked exactly like yours. Come to find out on the dyno the following week it was well on the rich side. It just wasn't riden long enough to color the plug. Stick it back in and go ride. If it cuts out, pops, hesitates or sputters then you know you need to adjust something... just my op.

That is what I am figuring...
It's going to show well rich like the base ring in time...

I don't really understand how though...
At this point I am only up one size on both jets.
40/150...

That's with full exhaust, lid on, and K&N.
1200 ft....

[bherriman]

Your 150/40 probably isn't far off...I only have a slip on and k&n and I run a 155/40 and should prob bump up to a 158 but I ride from 500-700 ft. so you are twice as high as me and need less fuel with thinner air. I still think the base of the plug is black because you were just riding slow in the trails. I bet if you did an all out plug chop it would color better (you might actually be a tad lean). If you ask me you jetting is pretty close just adjust on the a/f screw some more if it keeps getting better everytime you adjust that screw. Also has the carb been cleaned recently?

[MtnEX]

Yeah, I cleaned the carb and installed new seals, etc... changed the jets....

I actually took the pilot screw all the way out today also. It looks OK to me as well, compared to new.

I put it back in and set it 2 1/4 turns out.
Let it warm up until idle increased all it was going to.

Took it for a short drive and heard a pop out of the exhaust while engine braking down the first hill, but that was it...

I will see how it starts tomorrow.


As it has been standing in this weather, won't start with choke and has to start and die several times over before it actually runs.

[bherriman]

OK you say you took the pilot jet out and set it to 2 1/4 turns? thats not good lol your pilot jet should be seated all the way in or it could vibrate loose and fall out. But if you were talking about the a/f screw being 2 1/4 turns out I would probably go to inbetween 2 1/2 and 2 3/4.

Has it been rebuilt or had piston rings put it lately? With a 40 pilot in there it should definately start with the choke. I don't even have to use the choke and it starts with in 1 to 2 seconds of hitting the starter. The reason i ask if its had rings lately is because its starting to seem to me like its down on compression. If your rings are getting wore out your compression would be low and it wont suck fuel correctly causing it to be hard starting. Before I built my 416 I had a hell of a time starting mine I had to use the choke and hold the throttle partway open until it warmed up. Now with a fresh rebuild and good compression i dont touch the choke like I said it starts as soon as you bumb the button and idles perfect.

The plugs on my motor in my car after 3,000 miles look like that lol With some carb cleaner or something I could proabbly return them as new.

[f4iracer]

he's talking about the pilot screw not the pilot jet.

Ok, so if you're running a 150 main jet that's probably why you heard the popping on decel. With a full system and a k&N i would fatten up the main jet for sure. At least a 152, that's what i'm running with slip on and air filter.

I had some issues with my ex flooding out when i tried to put a 42 pilot in. I put a 40 pilot in and then also turned my a/f screw 3 turns out. It runs great now, maybe a little rich on the idle, but not bad.

Just

[rt20ps]

It's caused by pump gas. Tuning by reading spark plugs is a thing of the past. Unless you have access to a dyno and sniffer, tune it to what starts and runs well and forget the plug.

[MtnEX]

Originally posted by rt20ps
It's caused by pump gas. Tuning by reading spark plugs is a thing of the past. Unless you have access to a dyno and sniffer, tune it to what starts and runs well and forget the plug.

That is what I was thinking... pump gas...

Looking at some of my other stuff, it's like this too.... and has not really fouled a plug as I was concerned with.

[MtnEX]

Originally posted by bherriman
OK you say you took the pilot jet out and set it to 2 1/4 turns? thats not good lol your pilot jet should be seated all the way in or it could vibrate loose and fall out. But if you were talking about the a/f screw being 2 1/4 turns out I would probably go to inbetween 2 1/2 and 2 3/4.

Has it been rebuilt or had piston rings put it lately? With a 40 pilot in there it should definately start with the choke. I don't even have to use the choke and it starts with in 1 to 2 seconds of hitting the starter. The reason i ask if its had rings lately is because its starting to seem to me like its down on compression. If your rings are getting wore out your compression would be low and it wont suck fuel correctly causing it to be hard starting. Before I built my 416 I had a hell of a time starting mine I had to use the choke and hold the throttle partway open until it warmed up. Now with a fresh rebuild and good compression i dont touch the choke like I said it starts as soon as you bumb the button and idles perfect.

I took the pilot SCREW out, to check it since I have a new one on hand in case I need it later.

Looked fine.

I had it set at 2 1/4 turns out.
Tested that the next day and it did not work. Kept turning out 1/4 at a time.

You may be right about compression.
I don't know... don't have the stuff to check that.

I did mess with the air box lid and air filter while at idle (no change really) and so when I had the filter off, I was curious of the idle air flow. It's not much... may be normal though... never did that before.


Originally posted by f4iracer
he's talking about the pilot screw not the pilot jet.

Ok, so if you're running a 150 main jet that's probably why you heard the popping on decel. With a full system and a k&N i would fatten up the main jet for sure. At least a 152, that's what i'm running with slip on and air filter.

I had some issues with my ex flooding out when i tried to put a 42 pilot in. I put a 40 pilot in and then also turned my a/f screw 3 turns out. It runs great now, maybe a little rich on the idle, but not bad.

Just

3 turns out is where I ended up. I think it's going to work, but I will find out tomorrow. If not, I'll go too the 42, as I think 3 turns out is the max you are supposed to go?

I'm going to pick up some main jets first chance I get. My 152 and 155 fit, but are the wrong style, and are RD Precision.

[tayyo789]

Ya I had a plug look like that but when I got on a dyno, and hooked up the sniffer, my air fuel ratio was at almost exactly 13:1 for the first half of the rpm's. According to the guy that was running it, 13:1 mixture is the "ideal" mix, so I was pretty pleased to be that close

[MtnEX]

Originally posted by MtnEX
I took the pilot SCREW out, to check it since I have a new one on hand in case I need it later.

Looked fine.

I had it set at 2 1/4 turns out.
Tested that the next day and it did not work. Kept turning out 1/4 at a time.

You may be right about compression.
I don't know... don't have the stuff to check that.

I did mess with the air box lid and air filter while at idle (no change really) and so when I had the filter off, I was curious of the idle air flow. It's not much... may be normal though... never did that before.



3 turns out is where I ended up. I think it's going to work, but I will find out tomorrow. If not, I'll go too the 42, as I think 3 turns out is the max you are supposed to go?

I'm going to pick up some main jets first chance I get. My 152 and 155 fit, but are the wrong style, and are RD Precision.

Well friggg.....

I didn't have a chance to mess with it at all until today.

I dropped by the Honda shop for proper style main jets for the 152 and 155 sizes.

The only one they were out of was the 152... which tells me that's pretty popular for a main size around here. I picked up the 155 anyways....

And they ripped me off... so I will be returning the dang wrong ones they sold me before at a fair price next time I am that way.... that's what I get for saying well, they are local and it's only a few...



Anyways, what really has me griping is that it sat a good while, so I figured it was a good test for my pilot and fuel screw adjustments.

I thought for sure I was going to be good at 3 turns out now.....

Well, not as bad for sure.... but same dang thing on the cold cranking...

Still cranks up, lets you think it is going to run... and bang it dies.... and you have to go through that several times.

Dang that's aggravating....

[MtnEX]

Now what do you guys suggest I do?....

Do I go up to a 42 at this point?....
And if so where to I start with the fuel screw?

Or do I try the proper style main in the larger style first?

I don't want to just assume there is absolutely no bleed-over between the pilot circuit and main circuit on this carb.




Or do you follow the other guys and say it is time to check compression???

If so, do any of the part stores out there have this sort of tool in their loaner tool program or whatever you want to call it? I don't have these tools to check it.

[bherriman]

If you have messed with the carb that much and its still not better I have a hard time believing that a 42 pilot its gonna help. 42 in my opinion is a little over kill for your bike. I could be way off here but I'm gonna go back on what I said before and go with compression. If your rings are shot and you have very low compression it wont suck fuel properly which would explain why it does it when cold because you need more fuel than when its warmed up. Does it smoke at all?