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Author Topic: What does chopping the spark plug do  (Read 144 times)

Online evaneyeball

What does chopping the spark plug do
« on: March 25, 2020, 07:22:43 PM »
Just wondering what chopping the sparkplug is and what does it do or tell you. I've heard people talk about it on draft applications.
LED built 269

Offline The norm

Re: What does chopping the spark plug do
« Reply #1 on: March 25, 2020, 08:32:32 PM »
A plug chop will tell you if your jetting is too rich, too lean, or just right lol.
This is how I do it. Probably not the text book version....
What you do is warm your engine.... Swap to a new plug and take off and get rolling. Pin it to win it while banging gears through 4th. Then kill the engine while at wfo. Pull your plug and put in the old one you warmed it up with. Ride back to camp and have a tasty pbr. Take a flashlight and look down in to the plug. If it's white you are very lean.... If it's black you are very rich. If it's a golden brown its just right. Some people cut the threaded portion of the plug off to see the ceramic better, but I can't afford to waste a $3.00 plug because of all the pbr I like to enjoy.
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Offline Michael88R

Re: What does chopping the spark plug do
« Reply #2 on: March 25, 2020, 08:44:02 PM »
Evan, skip the Pbr step for another 8 years.  😂.
88 R Esr 330PV, Esr trx7 porting, Esr trx6 pipe
88 R Esr ported stock cylinder, waiting for rebuild when my son gets a little older

Offline The norm

Re: What does chopping the spark plug do
« Reply #3 on: March 25, 2020, 08:48:50 PM »
Oh yeah lol! Add Mountain Dew to that step lol
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Online evaneyeball

Re: What does chopping the spark plug do
« Reply #4 on: March 25, 2020, 08:50:30 PM »
thanks i was just wondering. what it was for. i had heard about people chopping plugs on drag bikes. and even if i did have to do this i couldent last time i rode it. i admidantly chickened out in 4th gear. sand was too choppy. thats my excuse for now. dang it no beer, ok mom. lol
LED built 269

Offline desertR

Re: What does chopping the spark plug do
« Reply #5 on: March 25, 2020, 10:12:49 PM »
A plug cut as it's called, involves "chopping" the throttle (closing it quickly) while also pulling in the clutch. This allows you to "read" the plug. This can only be done with race gas, as today's pump fuel has too many additives in it to allow for a proper plug read. Very few people can read a plug correctly, it (like many other things) is a skill that requires a lot of knowledge to read the plug correctly (I get help sometimes). It will tell most the basic fuel mixture/condition at WOT, but careful study can/will tell much more. Also altitude, air temp, and air density come into play here, so only do your plug cuts where you are riding.
Example + At the Bonneville speedway, there is a very specific SCTA run weather station at the course/ track, , and the conditions change daily, even hourly.
I use a light along with a magnifier, to examine the plug (insulator, tip, and ground electrode) very closely. Most race teams all carry the necessary things to make those decisions. Modern race cars are very different from those 10/15 years ago, it's now the software flashed for each track that makes the winner/loser. Many of today's street cars have the ability to reflash the ECU for different uses/modifications, my software comes out of New Hampshire, and is based on data logs sent thru Email, Makes a huge difference and helps keep the motor together.
desertR



Online evaneyeball

Re: What does chopping the spark plug do
« Reply #6 on: March 25, 2020, 10:19:21 PM »
Very helpful thanks
LED built 269

Offline havinnoj

Re: What does chopping the spark plug do
« Reply #7 on: March 26, 2020, 12:55:00 PM »
I will add that it's really only useful on the main jet circuit. 

Offline Jerry Hall

Re: What does chopping the spark plug do
« Reply #8 on: March 26, 2020, 01:49:23 PM »

Years ago I was also misguided by the myths and folklore that has been passed down over the generations.  I have also read may of these myths on this site.  Being an engineer has caused me to question and try to understand why these myths exist and why past generations have come to their conclusions from reading spark plugs.

I am sorry that I do not have the time to keep answering these same common questions.

I think than I have posted on this site more than once, what I have learned about reading spark plugs during my 45 + years of designing, modifying existing designs, and testing two stroke engines.  You guys would be amazed at the size of the mountain it would create if I could put all of the destroyed cylinders, heads, engine cases, exhaust systems etc. in one pile that it took to learn what I know about two strokes.

Someone please do a search on this site and or on other sites and read what  I have learned/published about reading spark plugs.  It does not agree with a lot of the folklore/myths that has been published in books and the internet over the last 50 years or so. 

I will by happy to defend my answers and answer specific questions about these myths and what specific observations are revealing to the person reading the spark plug. 


Offline 2ndmoto

Re: What does chopping the spark plug do
« Reply #9 on: March 26, 2020, 10:13:22 PM »
Seems like should be a sticky...if there isn't already one.

Online croat1

« Last Edit: March 27, 2020, 09:25:37 AM by croat1 »

Offline havinnoj


 

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