Help with jetting

[soupnutz]

A friend of mine upgraded to a raptor so I got his 98 blaster. It's got a fmf header and pipe, k&n filter, no airbox lid, a 240 kit, and a stock carb. I've known him for years and ridden it before, he rejetted it after he got the exhaust and air filter and it rode good, but he never rejetted it after the 240 kit install. I need a good place to start for jet sizes. I plan on ordering this kit, JET KIT BLASTER OEM CARB....

It starts right up and idles good, and 1st and 2nd gear feel good, then in third it starts bogging and backfiring and running like crap, from then on it runs like crap in any gear or idleing, and I couldn't restart it once I killed it. Not knowing anything about carbs or what to do, I pull the carb off and empty the fuel bowl. Upon putting it back together it starts right up and runs good until I get to third again.

Like I said I don't know much about carbs and I would think it's ajetting issue. I plan on doing the whole plug chop thing to get it as good as I can but need a good starting point. Thanks

 

[soupnutz]

UPDATE......

Started taking it apart today to learn more about the carb and have some more info if it helps.

The big jet is a 360, the little one is a 32.5. The needle has 5 slots, it was in the middle, I moved it all the way to the bottom one. and the last thing I noticed was the idle screw as all the way in, I screwed it out 2 turns and cranked it up, it was idleing high so I screwed it in one turn. It idles and revs up great in nuetral, but I havent put it in gear and taken it down the street yet. Oh yeah, did a compression test also and it's at 130.

 

[yb200]

you may want to bump up to a 34mm carb to get the most out of that 240

whats the plug look like the way it was?

 

[blasterfreek30]

i would put the needle back in the 3rd groove and put the airscrew at 1 and half turns and go from there

 

[soupnutz]

Yeah, I'll upgrade the reeds and the carb one day but for now I just want to be able to go riding. The plug was pretty dark, black almost, not sure how long it's been in there, I'm sure it could stand to be changed. With that along with it bogging, doesn't that mean its running rich? So should I try a smaller jet and the 2nd groove of the needle.

Doesn't the small jet control idle -1/4 throttle, the big jet controls 1/4-wot and the needle adjusts for all positions or something like that?

 

[royalt67]

Sounds like you have a good basic understanding. You want to set the main jet first. At this point, yeah it sounds rich, but you really need a fresh plug to be able to tell. Buy yourself a couple smaller jets, 350, 340, 330, and go from there. Needle in 3rd groove to start.

If it idles fine you are prob ok on the pilot, adjust the idle, then move the needle if you need to. It controls the mid transition.