need opinion on plug chop...

1

1998RM250

Member
Nov 5, 2008
426
0
Hey guys I've raised the clip on the needle jet one notch
and it seemed to lean it out quite a bit. I did a plug chop and the plug looked extremely clean, slighty brown in color.
I'm just worried its running a little too lean, and the exhaust smells different (no joke). What would the plug look like if it was running too lean? Here's a pic of it though, it actually
looks more brown in pic then it is (there was no oil or anything on it). Thanks for the input guys. :cool:

 
J

julien_d

Member
Oct 28, 2008
1,788
1
If you're gonna do a plug chop, you have to chop the plug. As in, cut away enough of the threads so you can see the base of the insulator. Reading the end of the plug ain't gonna tell you a darn thing.
 
1

1998RM250

Member
Nov 5, 2008
426
0
wow great information... every single one of my 2 strokes have always had "gunky" looking plugs after a few rides, and i expected there to be some buildup on almost every "proper" running bike. So the outside of the plug tells nothing, wow was I wrong!!! I was a little nervous when I pulled this plug and it was completely dry, but light tan in color. So a good running two stroke plug should be dry, is that correct?
I will have to hack away at this one after tomorrow's ride and post pics.
The bike has an FMF gold series, and their sight says a 158 main 2nd clip position,
I'm running a 162 or 163 (cant remember) 3rd clip position (middle) and am a bit nervous!
 
B

Brandon H.

Member
Mar 26, 2009
199
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Wow thats an amazing thread. I am going to have to go through that thread many more times to fully take in all the info. I do have a question, since I was just about to make a thread like this :nod:

I am in the process of jetting my 2000 CR125, I noticed the manual says stock main jet is 360, but the bike has a 340 in it. I warmed the bike up, took it for a quick 3 minute ride up to a big open flat area by my house, pinned it all the way through 4th and killed the engine. Pulled the plug, popped a new one in and went back home. Here is a picture of what I got. I am running pump 93 with Castor927 at 32:1 on a BR9ES plug.



I thought the color was suppose to be in the mid-lower part of the insulator, but how I am understanding it, the color should be at the very very bottom. I saw a lot of black on the low to mid part of the insulator, but looks like the very very bottom is white. Does this mean I am lean? Why such a big change in color? This plug had about a hour of normal riding total before I did the chop (on a different day).
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
Saw the threads off and read the main burn ring is all the real information you can get from that plug.. You can use other parts for reference, if you use the information correctly. It is possible to read the timing, plug temperature and a vague picture of jetting. There are a lot of variables that influence this aspect of looking at plugs though. It is Not science. The pilot and needle are more important to my riding though. I like the seat of pants and look at the plug. Associate what is going on with the color and wet/dry. When you get it right, it should be QUITE a noticeable difference in throttle response. A run up through the gears on a warm engine is enough for a plug chop, on them big cheap ES plugs. That long a little lean will not kill the engine, yet you can feel how bad it makes it run. When you get it jetted, put the proper plug in. EG and EV are fair priced plugs, the real expensive ones are better. Vintage Bob
 
1

1998RM250

Member
Nov 5, 2008
426
0
Yeah I ran a tank of 93 with yamalube 32:1 through it today on the trails (mixed on and off the throttle) and it was still loading up a bit when I wasnt on the throttle.
Just pulled the plug out and the carbon ring u speak of seems to go all the way to the top of the plug, and it was still wet. I'm guessing it's still running rich in that case, and I will raise the clip to the 2nd notch (which is supposed to be stock from what i read).
FMF's website susgested a 158 main jet, but mines 163 I believe. How does that work when you have reeds also though?
 
2

2strokerfun

Member
May 19, 2006
1,500
1
whenfoxforks-ruled said:
Saw the threads off and read the main burn ring ...
Click to expand...

To do this, I use a drill press and a good hacksaw blade. Be gentle and careful as it's easy to break the top of the plug off in the chuck.
 
M

mj4trax

Member
Dec 8, 2009
48
0
2strokerfun said:
To do this, I use a drill press and a good hacksaw blade. Be gentle and careful as it's easy to break the top of the plug off in the chuck.
Click to expand...

Perfect. I got reading this thread (and the referenced one) and I'm curious to have a look at my electrode. The drill press and hacksaw method seems ideal.

Thanks guys.
 
H

helio lucas

~SPONSOR~
Jun 20, 2007
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brandon, you might want to get the engine to full operating temp before the plug chop.
also, 3 or 4 seconds until you hit 4th may not be enough. you have to let the gas off too many times.

warm up the bike, go there, out rev the higher gear you can and change the plug to a new one. do that some three or four times and kill the engine. change the plug to previous.

carefull to kill the engine while riding at high speeds, you may loose control. change the kill switch to right side might be a good idea since pressing the clutch and hit the switch may be difficult.

and this procedure is only to know the correct main jet, you have to feel like vintage bob mention. and\or exhaust smell and noise. :nod:
 
B

Brandon H.

Member
Mar 26, 2009
199
0

Thansk for the pointers man, every little bit helps :nod:

I had warmed the bike up first, then rode it to my big flat open riding spot. I would say the bike was around its normal riding temp, I warmed it up nice and good before the ride, and rode it a little around the house first before I left.

Once I got to my "special place" I lined the bike up, pinned it all the way untill 4th, and right before needing to shift to 5th I pull the clutch and hit the kill switch. Only reason I stayed out of 5th is because it seems to get a little boggy, so i stayed in 4th.

I had all the gears floored, is that enough for a chop?? I don't see how I can stay in a gear any longer without letting off the gas or over-revving the motor.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
You do not have to hold it wfo for long. Its more important to shut it down and yank the plug. Thanks Rich for the macro updated version, much better. And blow the excess particles from thread removal off, I remember now! And the plug viewer, saves cutting plugs! Wonder if led lights have changed plug viewers? Still wishing I had one$ Vintage Bob
 

XRpredator

AssClown SuperPowers
Damn Yankees
Aug 2, 2000
13,504
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I don't really like pork chops, but I prefer them over plug chops.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
XRpredator said:
I don't really like pork chops, but I prefer them over plug chops.
Click to expand...
Like Pred has never had a skewer of EIX plugs smothered in apple sauce? Not the cheap ES plugs mind you, thats like soy meat! Vintage Bob
 
1

1998RM250

Member
Nov 5, 2008
426
0
I only use the b8es for now trying to get the jetting right, then I will switch to the BR8EV. How come some B8ES' have a silver base color, and some are bronze though?
Bought two at the same time and one is silver and one bronze!
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Silver, an old plug? Almost always gold is my thinking. I did not rip on you about the cheap plugs, but to get the resistor plugs at least. You can still get them for under a dollar? If its jetted right, the meteor plugs should last longer than the EG's. You will not get me to justify their price though, the EG's are cheap! Vintage Bob
 
2

250buttbouncer

Member
Jan 31, 2010
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hi, i', new to this forum,but have been mxn since 1977. right now i ride a 2002/2003 cr250 with stock 03 reeds and fmf fatty gold pipe. that said my Dad taught me that when reading plugs you look at the ceramic where the electrode comes out. tan is normal white is too lean dark brown or black is too ritch. this was on cars he used to drag race, he also raced 2stroke gocarts and was very good at tuning motors. i never saw him cut a plug to read it. this does not mean thats wrong he just didn't do it.to me the plug pictured looks a little lean jmo.its better to er on the ritch side as lean can burn a hole in the top of the piston. done this with my sons 1999 yz 85 i new it was a little lean and the temp dropped apx25 degrees he burnt a piston the second moto. had most power ever according to him. my 250 is a 2002 with a 2003 cylinder,piston,power valve,head and fmf pipe. it also has 2003 reeds. runs great and has never fouled a plug.thanks
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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250buttbouncer said:
i never saw him cut a plug to read it. this does not mean thats wrong he just didn't do it.
Click to expand...

I'm sure I've done a lot of things your dad has never done. ;)
 
B

Brandon H.

Member
Mar 26, 2009
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not when it comes to dirtbike :cool: :nod:

There are many "dirtbike gods" on this forum, Rich is definitely on the top of that list. I know you are new though, so its ok. Go through the forum and search, Rich has some very VERY good info on this forum.
 

XRpredator

AssClown SuperPowers
Damn Yankees
Aug 2, 2000
13,504
19
Rich Rohrich said:
I'm sure I've done a lot of things your dad has never done. ;)
Click to expand...
There was that time you went and had the entire Manchester United crying like a bunch of little girls because you told them that soccer was a chick sport and they weren't even men enough to be placekickers in real football.
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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XRpredator said:
There was that time you went and had the entire Manchester United crying like a bunch of little girls because you told them that soccer was a chick sport and they weren't even men enough to be placekickers in real football.
Click to expand...

You know how it goes Pred, sometimes the truth just hurts. Especially when you hear it wearing knee socks and dayglo shorts. :whoa:

250buttbouncer said:
AND I'm sure HE has done a lot if things you haven't. But thanks for the slam.
Click to expand...

It was harmless ribbing, not a slam at your dad.

If you're going to post on internet forums it might be worth investing in a thicker skin. ;)
 
Last edited:

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Or, do not post "dark ages" technology. Look into the technical archives. Its been proven wrong a very long time ago, and way too many times since. Everyone thinks they are the first, I have been there and done that also! Vintage Bob
 
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