New cr125, weird noises and fouled plugs!

[Tinbox1]

Within the last month or so I bought a new 2007 Cr125 from the dealer, they jetted it for me with a 420 main, 50 pilot and the needle on 2. Well within 20 minutes of riding it with a brg9 spark plug it fouled. So I put in a brg8 and it ran fine for what Id say is 5-7 hours, but it slowly got fouled. Im wondering why it is doing this if im running 32:1 and keeping it revved when ever im not giving it gas, if I use a 9 spark plug it also gets more splooge out the back while with an 8 there is barely any spray at all.

And the next thing, whenever my bike is starting cold theres always this popping type noise which seems to sound like its coming from the front part of the engine/expansion chamber area. I cant really pinpoint it though. After it gets warm it seems to go away.

Could this be because my carb isnt tuned right? If not, what could be causing these two problems?

 

[jdager]

the spark plug sounds pretty normal to me. if it runs good, I wouldnt be too worried about replacing a spark plug every 6 hours of riding, I just keep some with me, and replace it as soon as it starts getting a little hard to start. maybe take the plug and do a plug reading on it, or do a plug chop test, and see where you stand. someone else will chime in with a better idea though

 

[whenfoxforks-ruled]

Do you ride it like you stole it? Or do you putt-putt around? Did the bike come with a manual? Do a search for spankys jetting guide.

 

[_JOE_]

http://www.dirtrider.net/forums3/showthread.php?t=159938&highlight=spanky's+jetting+guide

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