Plug Chop Pix

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#1
The links below show the same thing; both are photo-type webpages to display pictures since I can't post on forum, (probably need to copy and paste links into browser). I wanted to include both to make sure it works.
They are pictures of the results of 2 consecutive plug chops on each plug along with the air box mods I did. Threads have been cut away. Brand new gapped plugs; no 'regular riding' done on either plug (ie plug was removed as I rode back to starting point). First one shows a chop done at Wide Open Throttle picture and the second one is at Half Throttle. Third is obviously the airbox. The half throttle chop was tough to do, because the rocky riding area doesn't lend itself to 60 seconds of smooth riding.

Bike is 2000 KDX200; FMF KG35 Gnarly Pipe; Turbine Core II spark arrestor; 155 main jet. Everything else is stock.

I ride in the northeast (NJ, PA, NY, DE); rocks and sand; hare scrambles/woods riding; most of time spent in 4th gear or less.
Ran the Hare Scramble yesterday in south NJ (Sahara Sand Hare Scramble for all those who live in the area) and the bike felt pretty hooked up.

Test were done in about 80 degree weather, <3000' elevation, and I know the results will change as the weather gets colder, humidity, etc. I am slowing trying to master the jetting art so any opinions are always helpful. Thanks.

http://www.ofoto.com/PhotoView.jsp?collid=77037068605&photoid=57037068605&&;
refreshkey=1066605142127


http://community.webshots.com/user/cheapo38
 
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#2
Doesn't anyone have an idea how to do this? I myself would like to know the proper way to read plugs so I can fine tune the jet sizes depending on the weather conditions. I have yet to see an article or post on the proper procedure for this. Someone please help us out.
Thank
 
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#3
If you are asking about plug reading as related to carb tuning, refer to the link below or do a search of this forum for a wealth of info (as stated in the top post).

Any comments on the plugs I posted are always welcome.
Thanks.

http://justkdx.dirtrider.net/
 
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#5
as for half throttle, well, you can't determin half throttle jetting by looking at the plug...
Isn't that how you check the needle?
 
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#6
The WOT looks to be safe. I've never done that half throttle thing. I would say to go by the seat of your pants for that and look for a smooth even pull without any flat spots or hard hits. That is if you prefer it that way. Some folks like that light switch / after burner feel of a hard hitting mid or top end rpm range. I personally look for strong pull right off the bottom. From idle. Adjustments there are again by the seat of your pants and the AS setting. Too lean on the pilot circuit is observed with an AS adjustment of less than 1/2 turn out and too rich would be anything past two turns out.
And finally, it is my opinion that using a consistant fuel will aid in jetting. I use a race gas so that every tank at any time of the year has the same formula as the last without any contaminates or unknowns. It cost more than pump gas but my jetting, and therefore my performance, is easily tunable without an unknown variable thrown into the mix.

P.S. Loose the whole airbox lid and enjoy free extra power with your jetting.
 
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#7
The ring at the bottom of the insulator on a properly jetted bike after a properly run plug chop will be around 1mm wide.
 
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#8
Wibby, take a look at the threads I put up in my last post, Rich Rohrich explains it in one of them. Can't remember wich one so you'll have to read all three, but there really a good read and worth your time. :)

Eric
 
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#12
Wibby, Ok read the article, I guess we all have our methodes for jetting, i just use Rich Rohrich's method(or try to...), cause he seems to be the leading authority on pretty much every subject on this board. The guy knows what he's doing... But like I said, To each his method and if it works for you, great.

Eric

Ps, how do you do one of those thumbs up signs? The only thing I can do is the stupid happy face! If only computers worked like bikes, I might understand something...
 

wibby

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#13
I have not done it either way, I’m still learning about jetting myself.

I just responded because day in day out, (it seems) everytime someone asks a question around here the first thing anyone does is drill them about checking the “Every Kdx Rider Should Read This!” thread. (not that I have a problem with that)

So anyway, Cheapo comes along and hey, from what he says in his thread, it sounds like he has actually done some reading on the http://justkdx.dirtrider.net/ site.

But then he gets told he’s doing it wrong, when he was just doing what CD's instructions say to do.

So that’s the reason why I brought it up :thumb:
 

Rich Rohrich

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#14
It's not that the half throttle plug reading method is necessarily wrong it's more a case of understanding it's inherent shortcomings. The basic problem comes from the characteristics of the needle at half throttle.You are into the needle's taper at this point. When you are trying to do back to back comparison tests it's obviously important to control as many variables as possible. Even small variances in throttle position near half throttle will have a dramatic effect on the plug reading. The point is you need a positive method to determine the exact point of half throttle (like a TPS reading). Without that you will have a difficult time determining if a change in the plug reading has been caused by a change you made to the needle setting or if it's from a difference in the throttle position when the reading was taken. The same problems generally hold true when trying to read the 3/4 open position.

I mean absolutely no disrespect to Canadian Dave by any of this. He wrote a couple of outstanding tutorials on carb jetting and needle selection. I just know from my experience that a mark on the throttle housing is totally inadequate if your goal is to compare spark plug readings generated by the half-throttle (or any other position) fuel flow. Determining the correct mid-throttle jetting ultimately gets down finding a useable fuel curve as the throttle transitions from 1/4 to 3/4 .

On the other hand, marking the throttle at various positions for use with the ride and feel method is an excellent approach and will pay huge divedends in terms of speeding up the process and improving your accuracy if you compare throttle positions to a needle chart like Dave provided. Even better would be to purchase the JD jetting program and really do it right.

In the end as long as you get the performance you are looking for, how you get there isn't really important. ;)