I just put a athena big bore kit on my z400 and it's running to lean I change my main jet to a 170 but it run like crap so I put a 165 in and it runs good but to lean. I have a yoshi pipe,K&N filter 440 kit,and hot camsin it so what do you guys think? I did have a 160 in it with just the pipe and filter and it was ok till I put the hot cams and big bore kit in it.

 

I run a 52 pilot jet and a 170 main with the needle on the 4th clip
try moving the clip down 1 on the needle and use the 165
and your air screw might need to be adjusted

 

I set-up a Z400 (stock bore, stock piston) a few weeks ago with a trx450r 42mm carb and we are at 190mj. I find it hard to believe you guys are so lean with the stock carb.

 

what type of carb are you using?

 

I have the Mikuni BSR 36 (stock carb) with the 165 main jet.Before I put the big bore kit in I had the 160 main jet put in and the local suzuki dealer put it in he had to drill six holes in the lid to make it alittle richer but now it woun't run right with the lid on!

 

It would help to know what jets you used. Dyno jet or mikuni. I know from experience that a dj 190 frows the same as a 175 mikuni.

 

I guess they must be Mikuni? I bought them from my suzuki dealer.

 

Drilling holes, and removing the lid makes your mixture leaner, not richer. I would lose the lid, and go up three sizes from stock [increments of 5]. Your main jet only controls 3/4 throttle to wot. Take it for a ride, and see what it does [3/4 to wot]. If it runs good try the next size bigger. Keep testing, and increasing the mj until performance drops off. Then go back to the last jet size that ran good. If your trouble is in the 1/2 throttle range your needle needs adjested. Start on the richest position[ clip in the bottom position of the needle] and test it. If it doesn't run good at 1/2 throttle lean it out 1 position at a time till it runs good. No easy way to jet, just trial and error. If this doesn't work, you might need a bigger carb for the 440.

 

I just received my jet kit from alba. they said I needed a 160 main jet, 25 pilot jet and the needle set on the fouth clip with the lid off. So I went out and tested it I had to put the 170 main jet, 25 pilot and the needle at the third clip with the lid off. It runs fine now the spark plug has a ( brown tint) to it that should be ok shouldn't it? It took alot of time to get to that point a whole lot of adjusting but it runs good now!

 

My factory needle wasn't adjustable. thats the reason I ordered one from alba.