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300 XCW Questions

Shawn

Shawn

Just Hanging Out
Location
Holly Day
I know there are several on this board that ride 300's so I thought I would ask. I just got back from the dunes and experienced a bit of popping when I got home. Took a look at the plug and the electrode was basically burned off. The plug was pretty black and wet. I run a 50:1 mortex and hi octane gas. I have a lexan carb, slavens low altitude head on it, FMF gnarly pipe.

How long do these spark plugs last? This is my first two stroke and I was surprised to see the plug. I'm also wondering about my 50:1 mix, to much, too little?

Any thoughts would be appreciated.
 
anderson750

anderson750

I'm working on it Rose
Location
Price, Utah
First question I have is.....how many hours does the plug have on it? For racing purposes, I change our plugs about every 20 hours on a 2 stroke, and 50 hours on a 4 stroke. If it is a trail machine, I just look at it around those intervals and replace as needed. Your fuel oil ratio is not going to have a huge impact on the electrode wearing down. 50:1 is fine for that bike and is the ratio I ran in my 300 when I was racing. The age of the plug in combination with the heat you were producing in the engine by stressing the motor in sand probably had more to do with the electrode melting down.

As a side not to this, you should never adjust oil to try and correct a rich or lean problem. Most people think that adding more oil makes the bike richer, where in fact the more oil you have, you are actually running leaner since it is a ratio of air/fuel. Always fix lean and rich conditions with jetting.
 
Shawn

Shawn

Just Hanging Out
Location
Holly Day
Thanks for the reply, the bike has 32 hours on it so it sounds like it was ready to be replaced. I'll keep the 20 hour mark in my head.
 
Gravy

Gravy

Ant Anstead of Dirtbikes
Supporting Member
Location
The Land Northward (Bountiful), Utah
If you cooked a plug like you describe, you're too lean. If you're wide open for a long time at the dunes that explains it.
You're just fine on ratio if you're running a good synthetic. Although I think though your new 300 recommends 60:1...
 
Gravy

Gravy

Ant Anstead of Dirtbikes
Supporting Member
Location
The Land Northward (Bountiful), Utah
Remember what Paul said: uping the oil fuel ratio- leans the air fuel ratio.
You're fighting two problems in my opinion: you need a higher oil ratio in the dunes to maintain lubrication at high load high rpm and you've got to increase the fuel air ratio to keep it from running lean in those same conditions.
I don't have a ton of experience tuning with a Lectron (besides looking at the pretty one I have on my shelf) but I don't care for the limited tunability of the smart carb in conditions like this.
 
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R

rholbrook

Well-Known Member
Location
Kaysville, Ut
The jetting in the KTM Manuel you get with your bike is actually pretty close to where you should be. Find out what jets you have in it and compare with the manual if you have one. If you don’t have one post up what jets are in there and we can help you out. Don’t mess with your mixture ratio. I run 45:1 in my bikes but i am jetted for it
 
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