I have a kfx-400 and have the hotcams racing intake and exhaust cams.Had both installed and lost power, after that i had them removed and got all my power back. Some one had told me that i lost powere because i had the exhuast cam in with out a porting job. And was told to just put in the intake cam. What do you guys think?[img]i/expressions/face-icon-small-sad.gif[/img]

 

better lift and duration should at LEAST give you a little better performance, even if you do NOTHING with the ports. No way you shoulda lost power.

 

did you try rejetting when you put in the cams. Maybe you needed stiffer valve springs.[img]i/expressions/face-icon-small-confused.gif[/img]

 

If you got stage 2, you do need stiffer springs. Maybe you put the exhaust in the intake, and vise versa! I would try putting them in one at a time, and see if you gain power with just one in.

 

even with valve float, that would only happen at mid to high rpm... it would run like crap at higher rpm, sputtering/farting... it would sound weird, like there were a governor or something. I don't think it would just be a "lack of power"

 

I tried rejetting the quad like ten times, it ran with out sputter, it just had no power. I didnt do the work i had a kowasaki dealership do it. Even if they switchet the intake and exhaust, i dought it would even run, I am so agitated by the whole thing.

 

I am not familiar with the characteristics of the motor in question or the cams you speak of so my comments will be general. I will presume that the cams you describe as 'racing' are made with greater lift and duration than stock in order to allow better breathing and more power in the upper RPM range. That's usually what's meant by racing cams.
If these cams are significantly 'hotter' than the stock and the only other modification you have made at the same time was jetting experiments then I am not surprized you saw less power than the stock configuration.
Cam profiling is just one part of the science of souping up a four stroke. The 'hot' cams will have a greater than stock lift at the intake valve to permit more fuel mixture to flow, and probably have a bit earlier open time in the cycle and certainly will remain open longer. The exhaust will open significantly earlier and have a higher overall lift as well. These changes cause the motor to be a more efficient 'pump' at high RPM's and the burning of the increased volume of fuel mix creates consequently more push and more power results. The increased overlap permits the impetus of the fresh charge to help push the exhaust gas out at the efficient RPM. For this greater efficiency (in the narrower and higher rpm range) to occur though there must be reduced restriction at both ends. This is why porting is important. The larger diameter and straightened out and improved intake tract permits more flow, and an air filtration system with less restriction than stock is needed. Similarly the exhaust must be opened up to accomodate the greater flow asked of it. A less restrictive muffler setup, preferably tuned to the rest of the motor. It all works together.
It is not that the maker is stupid and cannot make as strong a motor as anyone else, but that the motor as supplied is cammed and tuned to the compromises that the manufacturer has chosen to best meet the needs of the cross section of buyers that will be using the ATV and so that it will be in a mild enough state of tune to survive at least the warranty period without a failure that will cost the maker money to put right.
The intake and exhaust systems and tracts are made to best suit the flow of full throttle operation as the motor is supplied. Once you require it to flow more gasses than that, you have to make the passages bigger, perhaps a bigger carb even, and smooth out turbulence points in the ports. (The manufacturer doesn't have to worry about the expense of polishing a port either, if he wanted it to flow more, he'd just make it that much bigger. It's the right size for his needs as supplied)
For that matter a higher compression piston may be required depending on the degree of overlap in the hot cams due to the loss of compression that the long valve openings result in.
What you're doing when you hop up a motor is changing the compromises that the manufacturer established to ones that suit what you want. You're willing to sacrifice low end grunt for more power when you're wailing on it. Cams alone aren't bolt-on power though, and the more so when their specs are a good bit more radical than stock.