Spark plug trouble!

[MOTOX888]

The spark plug on my rm125(r6918b-8) has a problem, even after i replaced it. The thing that hangs over the electrode, sorry that i dont know what its called, gets all chewed up looking on the end. The motor has no overheating issues either and the jetting is spot on. I cant fgure it out, do i need a topend or what?

 

[TimberPig]

If the ground electrode is breaking off or being worn off, there are normally only 2 causes. Mechanical damage due to physical contact (piston hitting the plug, normally due to the wrong plug), or by burning/melting/breaking it off through excessive combustion pressures and temperatures. The normal causes of this are lean jetting, detonation, or ignition troubles.

I would double check that the plug is correct, and recheck your jetting. One way or another you need to solve this as the ground electrode going through the motor will lead to engine damage. It may require a teardown to ensure that there are no pieces of the electrode left in the engine. Don't just keep throwing plugs at it hoping it will go away, it needs to be fixed before catastrophic damage occurs as a result.

 

[Chili]

My bet is detonation. What jetting are you running? We had detonation issues with our 03 that required Octane booster or some race gas to clear up.

 

[crazyrydermx]

My bet is detonation. What jetting are you running? We had detonation issues with our 03 that required Octane booster or some race gas to clear up.

Sounds like it could be a problem. Also, if it is dentonation, you should hear what's called knocking or pinging. You will know what it is.

If the ground electrode is breaking off or being worn off, there are normally only 2 causes. Mechanical damage due to physical contact (piston hitting the plug, normally due to the wrong plug)

If this is the problem, it should be leaving small marks every time it does it. If you have any reason that you would be taking the engine apart any time soon, check it out.
I am REALLY leaning towards the detonation. Make positive that your jetting is perfect, and don't run regular gas if you already are.

 

[MOTOX888]

I am running a 30:1 mixture of oil and premium gasoline (93 octane)
and the jetting is this....
Main-440
Pilot-37.5
clip-3rd position
and 1.5 turns out on the airscrew

 

[MOTOX888]

Ok, i am talking about the ground strap that bends up over the electrode, and the spark shoots up to it from the electrode. On the end of the ground strap it is chewed up. The electrode looks perfect. Never seen anything like it!

 

[Chili]

Have you pulled the top end and inspected for other signs of detonation? We saw wear on the ground strap as well as small pitting around the outer edges of the piston on our 03. Jetting is different for all sorts of other factors but we were getting detonation with a 460 main, 37.5 pilot and clip in the second position, 32:1 ratio. Bike ran strong as heck so we just bumped up the octane to deal with it rather than fatten the jetting. We ran those specs at 700 feet above sea level for most of the summer, in the cold weather we fattened the main up to a 480 for safety.

 

[MOTOX888]

I have never pulled the topend since it was new in 03( i feel like and idiot) but i am going to pull out the old topend this month and get it ready for this upcoming season. Also what oil did you run in that bike. I am currently using maxima Super M, is this a good or bad choice?
Thanks for all the replys

 

[TimberPig]

Ok, i am talking about the ground strap that bends up over the electrode, and the spark shoots up to it from the electrode. On the end of the ground strap it is chewed up. The electrode looks perfect. Never seen anything like it!

Just for clarification, what you are calling the ground strap, is normally called the ground electrode. What you are calling the electrode is the center electrode. They are both electrodes, because electricity runs through both of them.

 

[Chili]

Nothing wrong with the Maxima, we've used Yamalube 2-R for years in all our 2 strokes.

 

[MOTOX888]

Chili,
What did you use for the tranny oil in ur guys' 03 125 as i am using 10w40 motorcycle oil from valvoline. It is wet clutch safe
(kind of gettig off topic now) lol
you seem like you know about the rm's
Thanks for the input!

 

[Chili]

We ran ATF Type F the first season and Pennzoil 10-40 Motorcycle Oil the second season due to sponsorship. I run the ATF Type F in my 02 RM250 currently as well. More important than what you use is that you change it regularly, we change the oil every ride.

 

[klunk yed]

help

could anyone help went out on my rm 250 last sunday within 2hrs went through 4 spark plugs. plugs endedup black and wet through WHY is my mix wrong or what

 

[crazyrydermx]

could anyone help went out on my rm 250 last sunday within 2hrs went through 4 spark plugs. plugs endedup black and wet through WHY is my mix wrong or what

There are two possibilities: Oil fouling or running too rich...Way too rich.

 

[crazyrydermx]

Here is a good link...which does your's resemble most?
http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

 

[DLHamblin]

could anyone help went out on my rm 250 last sunday within 2hrs went through 4 spark plugs. plugs endedup black and wet through WHY is my mix wrong or what

Did it just start doing this (in other words had been running OK and now suddenly started fouling)?

How old (fresh) was the fuel in the tank? What spark plug are you running?

 

[klunk yed]

help

fuel was fresh / plugs are br9s

 

[klunk yed]

help

where abouts is mix screw on carb 4r rm250