Spark plug question!

racerx59m

Member
I'm running a clone in medium and in light and was wondering what the ar3910x spark plug should look like after you make a straight full throttle pass!Mine was clean in the center of the plug and carboned up on the outside!Been tinkering with the little flat head standard screw on the back of the carburetor!Am I close?
 

flattop1

Dawg 89
Thats pretty good . Full throttlle then shut off .
Or did you ride to the pit lane then shut off .
Either way thats not bad .
 

Outrider

Member
I've always gone with the idea that a dirty plug means incomplete combustion. Too rich!
Depends on how dirty, and based on on experience with 2 stroke motorcycle motocross engines, better too rich than too lean, unless you enjoy replacing the piston every week (with attendant cylinder honing and new rings) until you get it right.
 

alvin l nunley

Premium User
Depends on how dirty, and based on on experience with 2 stroke motorcycle motocross engines, better too rich than too lean, unless you enjoy replacing the piston every week (with attendant cylinder honing and new rings) until you get it right.
All very true! Still, most of those kinds of things stopped after we learned to use the EGT.
 

alvin l nunley

Premium User
"Too lean" what does that mean? When you use an EGT, it's really apparent when you've gone too far, (too lean) the EGT temp goes down. Some people make the mistake of leaning the engine down when they see the EGT readings go down, thinking they're too rich. Problem is; if you get too lean, the engine starts detonating, and the EGT temps go down. It takes some getting used to. I've tried to explain to people; if, coming out of a particularly tight turn, if the EGT is reading lower than before in that turn, open the low-speed needle, same with the top end, only you use the high-speed needle.
Another good thing about the EGT; it reacts to changes in exhaust gas temperature much quicker than the CHT reacts to changes in head temps. It's not so much that the CHT is slow but that the temperature in the cylinder is slow to get to the top of the head.
 

Chipg56

Member
"Too lean" what does that mean? When you use ayES USE EGT IN CONJUCTION WITH YOURn EGT, it's really apparent when you've gone too far, (too lean) the EGT temp goes down. Some people make the mistake of leaning the engine down when they see the EGT readings go down, thinking they're too rich. Problem is; if you get too lean, the engine starts detonating, and the EGT temps go down. It takes some getting used to. I've tried to explain to people; if, coming out of a particularly tight turn, if the EGT is reading lower than before in that turn, open the low-speed needle, same with the top end, only you use the high-speed needle.
Another good thing about the EGT; it reacts to changes in exhaust gas temperature much quicker than the CHT reacts to changes in head temps. It's not so much that the CHT is slow but that the temperature in the cylinder is slow to get to the top of the head.
Use EGT in conjunction with your air density gauge and you will not make those mistakes. Right AL?
 
"Too lean" what does that mean? When you use an EGT, it's really apparent when you've gone too far, (too lean) the EGT temp goes down. Some people make the mistake of leaning the engine down when they see the EGT readings go down, thinking they're too rich. Problem is; if you get too lean, the engine starts detonating, and the EGT temps go down. It takes some getting used to. I've tried to explain to people; if, coming out of a particularly tight turn, if the EGT is reading lower than before in that turn, open the low-speed needle, same with the top end, only you use the high-speed needle.
Another good thing about the EGT; it reacts to changes in exhaust gas temperature much quicker than the CHT reacts to changes in head temps. It's not so much that the CHT is slow but that the temperature in the cylinder is slow to get to the top of the head.
Al, why do you keep bringing up EGT in clone threads when being told a 100 times its illegal to use EGT in clone classes? Yes it may be the correct way, but when you cant use it, it dont do anyone any good.
 

alvin l nunley

Premium User
Al, why do you keep bringing up EGT in clone threads when being told a 100 times its illegal to use EGT in clone classes? Yes it may be the correct way, but when you cant use it, it dont do anyone any good.
So you think I'm wasting my time do you? I'm thinking you're wasting your time telling me to stop wasting my time!
 

flattop1

Dawg 89
I'm running a clone in medium and in light and was wondering what the ar3910x spark plug should look like after you make a straight full throttle pass!Mine was clean in the center of the plug and carboned up on the outside!Been tinkering with the little flat head standard screw on the back of the carburetor!Am I close?
Two things . The idle adjustment is not what your tuning with at full throttle .
There is a lot of metal on the outside of that particular plug too pull heat .
Thus it will carbon up .
The center electrode/porcelain being clean is good .
Three- - - running medium and light you aren't going to be using methanol.
 

alvin l nunley

Premium User
Never said youre wasting your time, please read what i posted again. I asked why you keep bringing up EGT when talking about a class its illegal to use it in.
Did you notice that the statement "wasting my time" was not in quotations? There was an implication (my interpretation of course) in your post suggesting I was. I apologize if I wasn't clear.
 
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