i was wonderin what i can do 2 get some more power out of my 400ex with out boreing it out i have an Hmf pipe and a K&N filer and its jettedmbut what else can i do 2 get more power and speed

 

Well speed and power are two totally different things.. if you want more top speed that your going to have to change your sprocket sizes.. but beware the more top speed you give your bike.. the less bottom end power you will have. To achieve a higher top speed you want more teeth on your front sprocket.. if your running stock size sprockets ( I think they are 15 front and 39 rear) than you will need to increase the amount of teeth. For power without getting in the motor and boring it you are pretty much limited to aftermarket air intake and exhaust systems. I am no expert but these things I do know.. some of the others here have much more knowledge and may be able to help you out further.. but I really dont think you can get any significant power increase without getting inside your stock motor.
CGriff

 

i dont mind getting in to the engine i just dont want 2 bore it out

 

If you want to get into the motor but not bore it out you're lookin at a cam and a higher compression piston. However, without an increase in displacement i dont see a point. why not bore it out?

 

the stock sprocket sizes are 15/38 or that is what my 99' is. i changed the back sprocket down 2 teeth and it gave me prolly 3-4mph on top end but it did take some low end away too.

 

what do u think a safe boar would be if i was gunna bore it what do u think about a 426 with stage 2 hotcams

 

I didn't bore my cylinder, and the bike pulls the higher gearing just as easily as the stock motor pulls the stock gearing. Check out my setup, it's probably the wisest choice if you want to gain some mph and keep the motor reliable.

 

you only dropped 2 teeth on the rear, it should be able to pull ok. i personally like to gear down, i dropped a tooth on my front sprocket. this makes lifting the front end alot easier. but ian, you can get sleeves and move all the way up to a 440 kit. its probably not a bad idea to get a kit. ive seen them go for under $500.

 

but all my friends say that with a 440 it will have a good chance of blowing up and ill have way more mantence 2 do is this true?

 

with a good bore job , no more maintaince the normal, maybe change the oil more often. it will run hotter so you cant sit there and idle for a half an hour!