Would it fire on starter fluid? Just to rule out a spark issue. If it was running with it before(I know it was poorly) and will not now suggests you did not put something back correctly. Check the O rings and make sure everything is tight. I would double check everything from the spark plug wire to the Governor links and springs. Gas issues? Put in Fresh gas to rule that out.
As IL Engine has said the aftermarket carbs today are a crap shoot. You may get lucky and it runs great. Often enough they are jetted wrong and you will get surging or just not running correctly. I know OEM parts are expensive. That is why 90% of the time I rebuild carbs. The Aluminum is better and they will work as they should after being cleaned out and replacing any bad gaskets and seals.
I think the EX675 has a plastic carb. Right? The benefit is that the plastic will not rust. Did you snap the main jet assembly all the way in? Is the spacers in place correctly ? When cleaning these carbs you have to be gentle with the any compressed air. You can blow out the ball plugs and lose them. I actually like cleaning these carbs. They are easier to clean. I can have one out, cleaned and reinstalled in 30 minutes.
As IL Engine has said the aftermarket carbs today are a crap shoot. You may get lucky and it runs great. Often enough they are jetted wrong and you will get surging or just not running correctly. I know OEM parts are expensive. That is why 90% of the time I rebuild carbs. The Aluminum is better and they will work as they should after being cleaned out and replacing any bad gaskets and seals.
I think the EX675 has a plastic carb. Right? The benefit is that the plastic will not rust. Did you snap the main jet assembly all the way in? Is the spacers in place correctly ? When cleaning these carbs you have to be gentle with the any compressed air. You can blow out the ball plugs and lose them. I actually like cleaning these carbs. They are easier to clean. I can have one out, cleaned and reinstalled in 30 minutes.