Plug Chop

[WMarshy]

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

I agree. Just doing a WOT run between said 4-6500 RPM might not be enough time to let the plugs color up. If you had an area where you could do a few 1/4 mile passes and WOT through gears 1-4, that would be about the best.

[Rasputin]

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

The more load you can put on the engine the better. If you can do a WOT on an uphill grade without being ticketed even better. Any plug chop must be done at the RPM and speed you wish to be at. I still want to check my 79SF with pods and Jardine Spaghetti 2 into ones to see if I should go up one size to 145's.
A buddy says well hell you do not give a damn about mileage, but I do. A properly running bike will out perform a wrong running bike every day and in every way.

[spayne83]

So uphill through all the gears at WOT and then kill it and pull over and do that for how long? Would 10 minutes be long enough?

[Rasputin]

No gear changes needed, I use high gear and full throttle around here because we have plenty of places to do it. Just that an uphill makes the bike work harder so everything on the high circuit is open all the way. It is surprising how quickly the plugs will change color unless they are carboned up really bad.
If you run it down the road after being fully warmed up and do a plug chop it will show you one color. Now if you reinstall those plugs and do the same run but instead of doing a chop you simply pull over and check the color after it has idled for a few minutes (as if you were getting off and opening your garage door) then kill it you will see a different color.
This is assuming the carb setup is close to correct. If you are way lean then all scenarios lead to white plugs and vice versa.
All the other carb tuning techniques, be it by ear, colortune, Fuel/air mixture, Vacuum or what have you are only primary settings. The final settings on any well running and fuel efficient bike should be done with plug readings.
It is the only way to know what the bike is doing at that rpm/speed with your particular load. The load can be anything from what your fat factor is to what all is using horsepower. These can be electrical load or tire pressures or Jammer or not, basically any variables. Each bike and rider will have their own specific settings. That is why I think the plug chop is the final answer to what so many seek but never quite find.
I use it religiously on all my rides. YMMV

[Yahman]

Given all of the costs associated with a big ticket, not to mention the risks of high speed runs on the road, it might be a better idea to do this testing on a dyno. Just saying, be safe!

Larry

[IanDMacDonald]

Given all of the costs associated with a big ticket, not to mention the risks of high speed runs on the road, it might be a better idea to do this testing on a dyno. Just saying, be safe!

Larry

Considering the fact that most dealers won't allow our bikes on a dyno, and if they do, it's not cheap, a nice open stretch of rural road will do the trick. I have a very long on-ramp by my house that gets the job done.

[Rasputin]

Not all plug chops are created equal...but they give you real time results. I posted how I do a high speed chop and why I am ok with it in my area. Yes you chance a big arsed ticket if you do it at top speed... You spin the wheel and you take your chances. I feel I am ok with what I do and where I do it, enough to take the chance. Others may not be so lucky.
While the dyno thing is cool it does not give your bike the effect of being loaded down with the fat factor, jammer resistance or any other differences. Plus the expense. Now add in the excitement, plus that eerie feeling you get when at 110 -130 mph you simply cut all power and pull the clutch in. Trust me the first time will be a bit disturbing to say the least.
Any way back to the plug chops being more equal..
You can do a chop at any speed where your carbs are working mostly on one circuit. It can be done at an idle (preferably after the bike was ridden fairly hard to clean up the plugs) as long as the engine has a fan on it to maintain cooling. After a ride and while idling it will color those plugs like a four year old learning about crayons.
It can also be done during a 70 mph cruise. If that is mostly where you run your bike, it is good to know what the engine is doing at that speed/rpm. If one is not into high speed runs but just wants to cruise down the slab then that is where you want to read the plugs to get your best fuel economy and power.
I forget right now the RPM range that one can use for setting them for the middle circuit to be effective but it is something like 4000 rpm in second gear or some such number. I had it saved before, I bought my new puter but I am not certain I still have it. I will have a look see if I can find it.
So I am getting a bit/lot longwinded here. Do some searching on the site and elsewhere and you may find the plug chop will be invaluable to you.