Well i get my sparks X-6 pipe in a few days full system and i plan on putting in a 426 kit in a few months. but if i don't decide to do that kit would the full system make more power then my stock headder pipe with my Yoshimura slip on? i have heard from about 4 pipe that its not worth buying a full system unless you have a moded motor. they say you wont get any more HP with the full system then to my slip on with a stock motor. is that true? but i am probably still going to get my sparks full system but i was just woundering if this is true.

 

I can't say for sure cause I've never dynoed my bike. However, when it was stock I put the fmf power core IV tail pipe on with K&N and it gave me a noticable difference. Hills that I had to do in second I could now do in third. After that I added the fmf power bomb header and it didn't make any difference that I could feel. Later I did the 440 kit and cam and that made a huge difference, so I can't say for sure how much the header does now that the motor is built but I can tell you that stock I think it was a waist of money.

 

With a oversized headpipe on a fairly stock 400ex you will loose HP and Torque

You need a BIG cam, and porting before a aftermarket headpipe will show higher numbers than a stock one.

 

hey fast 440 where did you get you 440 kit from??? i was wondering like what i needed to do like say if i ordered it off of rockymountainatv.com? i want to buy it for my 400 once i get it in the spring and then i want to do the 440 big bore. but no one i know has done that to there bike. so i was just wondering like if the kits come with instruction or if it comes with everything i need. or if it just comes with all the things in a box and no instruction?

 

if you get a 440, you will have to have a machine shop resleeve your bike and bore the new sleeve to the correct clearences

 

Do you have to bore the case for the new sleeve?

 

if by case you mean cylinder, then yes, the new sleeve if much beefier than the stock one, and requires the the cylinder be bored slightly, having a 440 piston in a stock sleeve probably would be a recipe for disaster.

 

Well sadly I must admit that I am not at all mechanically inclined. I change the oil myself and clean the filter and thats about it. I got my 440 kit through a race shop in the San Diego area called Yakkie Racing. The owner is named Rich Yakkie and he does great work. He did the 440 kit including resleeving and the cam all installed for around 800 bucks. Earlier he had installed my head pipe and rejet for like 15 bucks.