WOT test opinion

[scheckaet]

I finally did the WOT test on a fresh plug last week end.

stock needle, clip on top
pilot: 45
main 155
air screw 2.5

Warmed up the bike (3-4 miles on trail), replaced plug, went through all the gears (didn't keep it rev very long on 6th maybe 4-5 sec) then pulled clutch and kill switch.
Here are the pics of the plug.







(Oh and yes I know the pics are not great)

Does this look right? I think it might be a bit lean.

I also wonder if my pilot is right, cause I can't see ANY difference with the air screw more or less open (unless completly closed)
When in the power band it's great, but it's a little slugish in low RPM (still pull ok)

What do you all think

Wilf

[canyncarvr]

Why do you think it to be lean?

What guideline/telltale are you looking for that tells you that?

How did you arrive at the idea that 2.5 turns of the air screw is good?

[Jeb]

Go look at page 3 of skipro's gallery and look at the pics of his throttle chops with 150 MJ and 145 MJ.

I would encourage you to do another chop - you weren't WOT for long enough. My opinion: even if I suspected I could be lean, I'd be comfortable being at WOT for at least 10 seconds.**

I'd bet money your plug's gonna look closer to what skipro's 150 MJ looked like. Why would I state that? I did the same thing you did, too short of a WOT duration - 'didn't give myself enough riding room. I pulled the plug anyway (pure curiosity) and it looked quite like yours. WOT again, about 18 seconds this time, much darker band.

Darn, I wish would've taken pics for illustration, that'll teach me.

**EDIT - Unless I suspected I was very lean, in which case, though, my bike would run rather poorly.

[IdahoCharley]

I think CC and Jeb are telling you what I would - too short of a WOT to really show-up the band on the plug. Just from what you have you can see the burn band width appears to be headed towards 3 mm or more in width indicating still rich to me. Electrode edge does not show indications of be being on-the-edge but maybe thats because of the short run at WOT.

CC questioned what makes you think its lean - hesitation? Not a strong steady pull? Surging at steady throttle or on let off?

[canyncarvr]

Ski's 150 pic doesn't look significantly different from sheck's does it? Not where it matters..in the thickness category. How dark it is (or isn't) doesn't matter.

All the gears and 4 seconds of 6th is enough time..again, dark not being the point.

I may be missing the whole point..but how dark the ring is is of no consequence.

W-H-A-C-K!!. Whew! I think that horse what WAS dead is REALLY dead, now!

[Mr. Wibbens]

Looks plenty wide to me, only thing staying on the throttle longer is gonna do is make that band darker

[canyncarvr]

So, you think it's wide, Wibbens?

Rule of thumb is to get that band more narrow than that..about 1mm thick. THAT will be pretty teensy jet-wise, it will NOT give you much room for temp/el and environ change.

The pics in ski's gallery do give you a good idea of the change you get with a couple jet size drops.

These pics being a correctly done WOT plug chop, they show a too rich main jet.

[Mr. Wibbens]

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So, you think it's wide, Wibbens?

Looks about like my 148



Which was about 2mm

[Jeb]

My point on more WOT time was supposed to be a darker band - same band, but darker. Not that it tells a different story, but that it tells it more clearly . . . 'least to my untrained eye. That was the beauty of Skipro's pictures - easy to see = easy to understand

Next time, though, I'll know, so no more WHACKs will be necessary - at least on this point

RE: "These pics being a correctly done WOT plug chop, they show a too rich main jet."
. . . which pictures, what makes them "correctly done"? Are all of them too rich?

[scheckaet]

Why do you think it to be lean?

What guideline/telltale are you looking for that tells you that?

How did you arrive at the idea that 2.5 turns of the air screw is good?

I though it was lean cause the ring wasn't very dark, but I guess if I could hold in 6th longer, it would have been darker. (I would have but the end of the road was coming FAST)
After reading all of your post about ring size, it seems my jetting is a bit rich then (which is good since it will get colder, so it'll be closer to what it should be...)
I might try 1 size down again and see, I know what to look for now

2.5 turns works and like I said, can't feel any difference

I forgot to mention the temp was around 50 F.

[canyncarvr]

All of the pictures are of the same plug, I presumed. Sheck's pics.

'Correctly done' meaning I have no idea (other than what was written) if it was 'correct' or not. He didn't mention letting off the throttle. If you don't, the pattern changes. Probably, if you did it several times in a row you would get slightly different results. There is a lot of room for differences between shifting (at WOT) let alone hitting the kill switch, pulling in the clutch, and dropping the throttle all at the same time.

I've done only a few myself, so I'm not the expert. I know when it's close..and I can tweak from there without having to chop up a dozen plugs. Guaranteed I've not often run jetting that would give me that 1mm ring. Too close for comfort for me. When a riding day has temp changes of 30-40º..when riding in the sand means I will at some time be riding with a 20mph wind at my back..2mm 'or so' is fine with me.

Wibby's looks considerably thinner to me. If it was darker fer c'rin out loud, it would be easier to tell!!

Sorry Jeb...I take back at least a couple of those whacks.

A 45 pilot is probably one too high...same with the main.

Set the air screw using throttle response as a guage. Say: 2nd gear, walking speed, crack the throttle to 1/2 or so. Response should be 'N-O-W'. With each adjustment, ride it for a minute before you check it again.

Clip-1 you said? Unlikely that's the best choice.

[scheckaet]

Yes same plug, done only 1 WOT on it. Full throttle all the way like a raving maniac. Just eased up on the throttle when up shifting.
After a few sec on 6th, no throttle, pulled clutch and kill swith (jump on the breaks cause of end of road ) till it stops

[Jeb]

This was a great thread IMO - first, 2mm is safe, second, a "visible" band should be sufficient.

And I'll second the "one too high" on the PJ.

[IdahoCharley]

Great thread - concerning the raving manic approach to doing the WOT check going through the gears - I like that!!!

Similar to what I attempt to do on a uphill section of road - but nothing wrong with a fourth or fifth gear WOT pull on incline where the engine is wound out but still working to keep the rpms (or like some have suggested in the past dragging the brakes): Hope that makes since. Some load on the engine AND operating in the upper rpm range are deemed neccessary IMO.

I'm also one which runs a MJ normally one size larger than ideal from a performance standpoint and base carb changes on the rider's perceived response from the bike.

[canyncarvr]

'...perceived response..'??

You mean.....what I make up to suit my own self?

Huh?

[IdahoCharley]

'...perceived response..'??

You mean.....what I make up to suit my own self?

Exactly!!! You know those times when your riding with younger, better, faster, more conditioned riders and you have no trouble staying out of the dust.......- their finishing lunch/cig/break when you arrive?? Must be the jetting on this pig .... etc.

[canyncarvr]

Exactly, indeed...but I kinda had the other end of that situation in mind.

I repeated what IC said to make the point that a well running bike is apparent by a 'seat-of-the-pants' perspective and not so much what the base of the porcelain of the plug looks like.

There is a balance to most everything. While there is something to be learned from plug inspection, there is also valid input from the seated portion of your anatomy (figuratively speaking..you can get it from the soles of your boots if you wish). Spending a weekend destroying plugs and making notes of all the different swirls and burn patterns on those plugs is likely NOT as beneficial as learning from a performance aspect what works and what don't...and using that weekend to improve your riding by riding.

In some cases (not that I would know anything about it), regardless of what the jetting situation is, 'they' may still be finishing their potty breaks/lunch/nicostiks when you arrive. You can still use the 'pig jetting' excuse when that happens!