SMAH, I run both TPI's and Dialajet on my Predator. They are both really simple technology, and don't receive the hype other mods do - but they work. When I had my quad in for service at my dealer, they put on my pipe, and rejetted. It never seemed 100% to me. So I opened up the airbox (TPIs), added the dial-a-jet and the quad runs very strong now up to the rev-limiter. Of all the quads I've had, none has been more tempermental with mods than my predator, but now it runs great. The real reason that I purchased the dial a jet was because I ride at a number of different elevations, but it actually helped me "fine tune" the jetting at my normal elevation. As far as TPI valves go, not sure if I'd purchase them again, only because I run with them constantly 100% open (so the "tuning" aspect is worthless to me). I would probably just upen up the airbox with univents or custom venting, or even remove the lid completely from the Z/KFX400. I haven't purchased a dial-a-jet for my Z400 yet, only because I wanted to test out the Predator first at my highest riding elevation of 8k, and haven't been there yet since the dial-a-jet was added.

 

 

first of all there is no simple answer...nor inexpensive answer either...
what are you racing...or chasing i guess i should say...
for everything your talking about adding you will lose reliability...are you willing to sacrifice this?
if you are youll need a high compression piston,a hotter cam and a port job...youll THEN realize why you need the new cdi box...
youll be impressed by the gains but there will always be plenty of faster quads at glamis...
looks like a thousand dollars plus to me with labor and shipping...
good luck

 

Sand,
You might be interested to know that Dirtwheels mag currently has an article on their website that generally compares pro vs. pro production quads. In this article, they also mention that "The old 250R and the Z400 motors take a substantial cubic dollar investment to make them competitive and race worthy." Just judging from the specs & output of the z/kfx400 motor, I would have to agree with DW. I you want yfz 450 performance out of your kfx400, you will need to spend some big bucks to get it there (including a big bore kit to get more cubes)... and as mentioned above, any significant mods may ultimately come at a heavy price with respect to reliability.

If it was me that demanded yfz 450 power/acceleration, I would just sell the kfx and buy the yfz 450 or honda 450R...heck, I suppose you can always add softer shocks to the yfz 450/450R to make trail riding more pleasurable!

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

Trust me I've thought of selling my quad or trading up and I still might go that route. Problem is Im afraid I will not like the ride of the bike I end up with. I would hate to sell my quad at a loss only to end up with another quad im not quite happy with. The KFX400 is not a bad bike if I could just get a little more power out of it. I plan to test drive the kfx700 this week, I see that they go as low as 3k on ebay "slightly used" 3k is about what I will end up spending on my bike when all is said and done so a used KFX700 might be the answer.

The guys I ride with all have faster quads than I do and thats just not acceptable. Im facing a modded out Banshee a new YFZ450 and a Raptor 660. The one thing I have going for me is that I am a far more aggressive rider than all of them (maybe im better off with a slower bike [img]i/expressions/face-icon-small-smile.gif[/img]

 

Sand,
Caveat Emptor (let the buyer beware!). $3K for a used V Force on E-bay sounds a little too good to be true. I (and others on this forum) have noticed a lot of scams on e-bay lately with respect to ads for the V Force 700 and P650/P700. Mostly it involves a seller located outside of the USA. Personally, I wouldn't buy a quad off e-bay unless I could see the quad in person before I paid for it.

One more thing to think about...it may be cheaper to modify the stiffer ride of a yfz 450 or 450R to suit your liking (for trail rides, etc.) than to significantly modify the engine on your kfx 400 (and risk potential reliability problems as a result). Just something to think about. Good luck to you and happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

It would seem things are getting a little cloudy. Lets put aside the "new quad" or "trade up idea" for a minute and stick to my original question. Is there a proven combo or successful package of goodies that someone on this board has personal experience with. Even now I am no closer to a reliable answer. I have heard 3 differing approaches and 1 that combines them all. 1st Mission Yamaha thinks Head Work and a Cam upgrade with my current mods will be enough to "blow me away!!!!" While Sparks Racing thinks those mods are wasted without a 39mm FCR carb and a Programmable Ignition but the ignition carb combo will stand by itself "only of course if I dump my shoddy FMF pipe and buy one of theirs instead." Then someone here on this board suggested Carb and Cam which makes as much sense as the other two suggestions.

Im beginning to think no one actually has experience with the KFX400 and I am in fact the first person to ever MOD one out.

As for trading up to the YFZ or the 450R then adapting those to ride like the KFX400, that would be admitting defeat besides I am already 1k into my bike and there is no way I will get that back on trade in.

Now onto reliability. I will not sacrifice reliability at any cost. I might as well be a smoker spending money for a cheap thrill only to get cancer later. However reliability isn't a black and white term. Some mods are thought to cause problems other mods are known to cause problems and others are known not to cause problems. I will avoid those that we know for a fact will decrease the life of my engine or dramatically increase maintenance costs.

 

if youre not willing to sacrifice reliability then your only answer is external bolt-on modifications
for example...carb and cdi box...any time you go into the motor youre no longer riding a kawasaki but whatever kit you purchased...porting the head and adding a hotter cam shouldnt dramatically affect the reliability either but it seems to me your trying to make a zebra change its stripes...
your quad is not going to run with the ones you mentioned with out losing some reliability...at least not on the top end...
1 other question...are you a big guy?do you need a 700 for that reason?

btw...quads are not an asset...they are a liability...your quad isnt going to gain any value by adding expensive modifications...and it becomes a maintence issue as well...

heres my opinion,take it for what its worth...get the yfz450 or the 450r...and run with your friends
add a pipe,k & n and cam mod and be done with it...add some different suspension or better yet take the shocks off and have them revalved to suit your riding style...youll thank me later

 

When it comes to motor work and things like that u cant always listen to people that say if u put so and so's motor in its gonna blow up because your 400 is a kawi now u go and put a sparks motor in your riding a so called sparks atv thats like saying dont buy a yamaha because they just put in a 450 motor if all the pistons,valves,ect. are new then whats the difference its like buying a new 4-wheeler .
The point im getting at is dont listen to these guys that think they know whats going on and they think they are the gods of quads haha like they ones that own just a 4x4 and tell everyone not to do this and that with there sport quads let it up to the professionals,sparks and dunlap,and they will get you where u need to go.
I know one thing though sparks and mickey dunlap are the ones to ask they have been building winning motors for years for all the pros.

 

Thanks thats the kind of feedback I need to help me with my decision. I almost pulled the trigger today on a new Raptor after trade in I would owe 3k but would you believe that the salesmen didn't think it was a good idea he actualy suggested I check into the 450kit made by Yoshimura he said its a complete kit that will elevate my quad way past a stock Raptor.

Now I have heard it all [img]i/expressions/face-icon-small-smile.gif[/img]

Anyway does anyone here think 3k is better spent on a Raptor Upgrade or perhaps Engine enhancements? I here Yoshi even goes so far as to warranty the motor?