Jet confusion!

[THH]

My engine is .090 over, basically im at max stock 209cc. I put a new stock carb on it and did a plug chop. I was prepared to open my vitos jet kit and realized my plug was a perfect brown color. Is this right? I have open airbox, full dg oval2 exhaust, +2 mag key installed, and it runs freaking great! 240 stock main, Vitos starts at 290 main, Should i try it? Leave it be? Its not making much sense. I ran my blaster sunday for about 4 hours chasing around a rappy 700r. Consistantly checking the plug for changes, Its still a brown, almost a deep brown. Input?!

 

[PikledBeats]

240 sounds small, are you just pulling out plug and looking at it after riding or doing actual plug chops. If it is a dark brown after plug chop (WOT runs) you are good. You might want to bump up main so it runs slightly rich just to be on the safe side in hot weather it naturally will run richer. Also are you sure your new carb is stock, a slightly larger carb like a 28mm would run around a 240 with your set-up. You should be in the 270-290 range on your main I would think ... but plug chops are the best way to tell so if your plug is right you should be good.

 

[Blaner]

in theory you should need to be a little richer but do some proper plug chops and make sure. try out a 290 and see what it does, will most likely be too rich, id stick in a 250 just from off the cuff info!

 

[Little-J]

go one or two numbers bigger on the main jet and see what difference it makes to the bikes powerband.

If it becomes to peaky or pipey with no low end and then a WHAM when the revs get high enough your a bit too rich.. the main jet will change the way the engine feels, so try it.

see if you can get a 250/260/270..