taking out the spark arrestor

[440exnacsracer]

i have heard that if you take out the spark arrestor on a stock 400ex, it will blow your motor because it will suck for air. my motor is in the shop now and im getting it bored over to a 440 with a wiseco 10.5:1 and cometic gaskets. would it still blow the motor if its bored over? thanks
Ben

[440exnacsracer]

also, what main jet, pilot jet should i put in since it is getting bored over? later
Ben

[racin 400]

Just cut the spark arrester off the tip i did and it didn"t blow out.

[YLW400]

mine runs fine. I have had it like that for 6 months.