Plug Chop

[spayne83]

Am I doing this right? I went for a ride to warm up the bike and then pulled over and switched in the new plugs. Then I rode about 3-5 minutes at wide open throttle with the bike between 4000 and 6500 rpm, each time I reached 6500 I would cut the enjoying and pull in the clutch until I slowed down enough to get me back to 4000, then I would start the bike and go to full throttle. I did this about 4 times and then pulled over and changed out the plugs. This is what the new plus looked like gapped at .32





Only 1 and 4 had any color on them

Here were the original plugs





They were all tan ish at the top of the insulator with maybe a tinge of yellow. I ship out to basic training in a month so I really need to have this squared away by then.

[natemoen]

A true plug chop is WOT top gear maxed out cut engine and coast to a stop.

[Eveready1100]

[QUOTE]each time I reached 6500 I would cut the enjoying and pull in the clutch until I slowed down enough to get me back to 4000, then I would start the bike and go to full throttle. I did this about 4 times and then pulled over and changed out the plugs.


Mate, after doing that about 4 times, did you kill the motor at 6,500 rpms or did you let the motor wind back down when you pulled over?
If you let it run back down, you will have an indication of what your idle mixtures are.
To get an accurate reading at any given rpm, the motor has to be cut at that speed to show what it's doing at that time.

[IanDMacDonald]

Why only 6500 rpm? When I did mine, I did a five-minute idle, a mid-rpm, a WOT (upto redline), and then a 5th gear, under 2k rpm to mimic an idle (same results as idle).

[Tat2demon]

A true plug chop is WOT top gear maxed out cut engine and coast to a stop.

So, what Im reading here is I need to hit 134 mph to test it? No thanks.

[natemoen]

So, what Im reading here is I need to hit 134 mph to test it? No thanks.

For a true WOT plug chop, yes. Would I do it that way, absolutly not!

[Petersg_99]

I was pondering this last night and it occurred to me that it would be really nice if there was a way to get an O2 sensor into the exhaust stream for tuning your bike.

Unfortunately I haven't thought up a way to do it without adding a bung to each header...

[CaptonZap]

I was pondering this last night and it occurred to me that it would be really nice if there was a way to get an O2 sensor into the exhaust stream for tuning your bike.

Unfortunately I haven't thought up a way to do it without adding a bung to each header...

You need to find an old garage mechanics that took one of the exhaust gas analyzer's home when they started the computer emission control stuff.
You know, the ones that had a wand that stuck up the exhaust.
CZ

[natemoen]

You need to find an old garage mechanics that took one of the exhaust gas analyzer's home when they started the computer emission control stuff.
You know, the ones that had a wand that stuck up the exhaust.
CZ

But that won't let you tune each cylinder on its own. It will be a mix of at least 2 cylinder if not all 4.

[IanDMacDonald]

I have a bung installed on one of my headers, as the po used an rich/lean meter on it and tuned it with some success. The emissions analyzer would not work well, as outside air entering the muffler would sway the readings.

[WMarshy]

Your original plugs look good to me. Why are you messing with it to begin with? Poor mileage? Poor idle? Hard start? Poor throttle response?

The point of the throttle chop is to kill the engine at the rpm you want to check the burn ratio at. That typically means the bike should be running at the rpm for amount of time to allow the plugs to color up, color doesn't change instantly. I if you are interested in knowing you main jet is sized correctly for WOT then you need to run the engine at WOT then kill the engine. BTW, I doubt your bike will pull 135 unless your going down hill with the wind at your back.

[CaptonZap]

But that won't let you tune each cylinder on its own. It will be a mix of at least 2 cylinder if not all 4.

In that case, you need to get one of the original factory sets of pipes with the bungs at the bottom of the down sweep. Someone on here surmised that that was the way the factory tuned them for emissions, and that sounds reasonable.
Unfortunately, they are a bit small for a normal oxygen sensor. Always some problem, huh Nate?

CZ

[natemoen]

In that case, you need to get one of the original factory sets of pipes with the bungs at the bottom of the down sweep. Someone on here surmised that that was the way the factory tuned them for emissions, and that sounds reasonable.
Unfortunately, they are a bit small for a normal oxygen sensor. Always some problem, huh Nate?

CZ

Yup, there always is......

[spayne83]

The reason for only doing it at WOT between 4500 and 6000 is that that is where the bike is stumbling. After each run in that range I would kill the bike including the last time right before I stopped, so I coated with the engine dead and the clutch pulled in.

The original plugs do look okay to me, but I want to get rid of the WOT stumble. From what I read, it is the throttle position and not the rpm that needs to be maintained

[CaptonZap]

From what I read, it is the throttle position and not the rpm that needs to be maintained

You face a problem with the CV carbs while trying for main jet readings.
The main jet is controlled by the position of the needle. The needle is controlled by the slide. The slide is controlled by the diaphragm, and the diaphragm is controlled by the vacuum created by the air going by the hole on the bottom of the slide.
So while you may have the butter fly's all the way open, if the engine is not sucking enough air, (Read high rpm's under load), the slides do not get pulled up enough to get totally on the mains.
It is a problem with these high performance bikes, and unless you live someplace that has dry lake beds that will allow you to go as fast as you want, or are willing to risk a costly ticket, you have a problem getting good readings on the mains.

CZ