42mm mikuni flatside carb.
 

Well I'm installing a 42mm mikuni flatside carb. on my Sport 400, does any one have one of these carbs on their bike? What should I jet it to, I have a DG pipe, V-force reeds, K&N filter comming stright of the carb. with no air box, and have bored the cylinder .040 over with a Weisco piston, and adding a Pro Design cool head with a 45cc dome. I belive this carb. come with a 410 jet, should I leave it or should I go up or down on the jet?[img]i/expressions/face-icon-small-wink.gif[/img][img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img][img]i/expressions/face-icon-small-sad.gif[/img][img]i/expressions/face-icon-small-wink.gif[/img]

42mm mikuni flatside carb.
 

That carb is going to be way too much for what you have. It sounds like you don't have any porting. I had a 38 at one time and my jetting was around 300. You are a little higher than i am and you are going to Hve to jet that carb way down to even run, and lower the needle. I would stick with the stock carb or get the 38 or the 39pwk.

42mm mikuni flatside carb.
 

Like 1fast stated, kinda a lot of carb. If you have the funds, I'd ditch the DG pipe (lot's of noise, but lacking hp) and get some porting done. You can get leaner needles and slides to decrease the bog til you get some additional mods done. The Hot Seat folks have a lot of knowledge working with the Mikunis. [img]i/expressions/face-icon-small-smile.gif[/img]

42mm mikuni flatside carb.
 

How does a 'leaner slide' work?

42mm mikuni flatside carb.
 

Just like the jet needles, there are numbered slides with varying angles which enable you to change the air. [img]i/expressions/face-icon-small-smile.gif[/img]

42mm mikuni flatside carb.
 

You can add an adaptor to the back of the 42 and hook up an air box. This might work ok with the stock cyl.Jetting is hard,because everyones setups are differant,clutching,pipes,gearing,airboxes,cyl.,po rting,altitude,temp.,and fuel all affect jetting.