Back from glamis with lots of info. 1st despite my $800 in mods the yfz still kicks my a$$. My bike clearly has the advantage through 1st and the early stages of 2nd but once the yfz gets its rpms up it pulls away at an embarrassing rate. However, I still prefer my bike. After riding mine most of the weekend we traded for the ride back to camp and within 20 minutes I was begging for my bike back. The yfz is to stiff a ride for anything but a quick race and the throttle is so stiff my thumb could barely handle it. Also the low end is absolutely absent on the yfz making wheelies very difficult and most other low speed maneuvers difficult aswell. My bike may not have the race ready suspension that the yfz does but there was nothing he could do on the dunes that I couldn't in fact I felt better on my bike in those conditions. In the end I am happy with my KFX400 but the YFZ gets more attention, looks better, and has a substantially more powerful engine.

Now the mods. Wow! what a difference. Everyone loved the new sound from the FMF pipes and the power gains where obvious. The best part is that by following the DynoJet instructions I ended up with a perfect tune. The bike ran flawlessly with no adjustment what so ever. I went with the DJ160 main jet, the 3rd notch on the needle and 3.5 turns out on the mixture screw. Problem is it wasn't enough im now thinking I need to do some head work. My ultimate goal is to beet the YFZ450.

 

Excellent post. It is totally possible for you to beat the YFZ power wise without the use of Nitrous or such [img]i/expressions/face-icon-small-smile.gif[/img]

You need BIG BORE if you don't already have it and a few more goodies.

 

My local speed tech. A guy by the name of Ted at Mission Yamaha Kawasaki in Southern California is trying to convince me that for $500 worth of head work he can make my bike screem. He even went so far as to promise that I could out run a stock YFZ450 and a stock KFX700. Im sure part of this is normal sales talk but Ted is some what of an icon when it comes to racing and im thinking about giving it a try.

 

Well you have to sort out in your mind what you will get for spending all this money to try and outrun a stock YFZ or a V700. All they have to do is add a new pipe and some air cleaner mods and it puts you right back where you started. Losing to them after spending lots of money. Even the stock raptor guys are trying to catch up to the YFZ and the raptor is faster than a z400. You’ll need a z440 to keep up with a stock raptor and this means you are no way near the YFZ. In a short while most of the YFZ and V700 guys will be running pipes some will even have gone the way you went and add some goodies to their bikes. Again making things worse for you and meaning you’ll just be wasting your money to try and keep up with them. The only way to beet the YFZ is to get more capacity and the z400 will never get you there without NOS or something serious like that.

 

Oh come on. You make it sound like its not worth trying. Your missing the point, isn't the goal of everyone on this board to improve their quad and their ridding ability. That seems to be the theme of most discussions here. I am no different I am also completely aware that YFZ owners can do the same thing to their bike that I can to mine but what difference does that make? I dont like the YFZ for the reasons I have already stated in this thread. The only thing the YFZ does better than my KFX400 is top end power. If all I do is match that then I will be a happy camper.

 

It's true-- you'll beed a big bore kit- 440, for starters. Then think about the head work that was proposed to you. That YFZ is a ripper alright- but it domain is pretty much exclusively the track..

 

I am not saying you should not try. What I am saying is that you are going to pay allot of money and in the end you are going to end up with a quad that will match a stock YFZ's power and acceleration. How much is it to add a new cam, 440 kit, higher compression piston and gasflow the head. Then you might have to add new valves and cam springs. After this you have a similar size motor and hopefully the same sort of power. Then, you have to add a pipe and you might also have to upgrade the carb on the z400. The stock YFZ450 with a new exhaust pipe makes 49HP. Then the motor is stock. It is also quite a bit lighter than the z400. This means you have to get more power out of the z motor to get over the power to weight ration. In the end...sure you might beat the YFZ in a drag. The other person has a stock motor that is very reliable. You now have a quad that needs to run racing fuel, much less reliable and no one can tell you how long the motor will last. How much is it to rebuild a blown motor?

In the end. IS IT WIRTH THE MONEY? You have a very very nice bike. Do the mods like a pipe, maybe a cam and the 440 kit. Don't try the catch the YFZ, it’s not worth the money and riding a quad that might give you endless trouble.

 

I am not interested in messing with reliability so I will avoid mods that will reduce the life of my engine. I'm pretty sure the head work and new cams will make a substantial difference and shouldn't effect reliability much at all. I have already done exhaust/intake/rejet... if I add cam and head work to that list I dont expect I will be far behind the YFZ in wich case I could leave well enough alone. The 440 kit sounds like an option when my engine is coming close to the end of its life and the high compression piston sounds likely to be the source of many problems when installed in a stock engine. The only other thing is the ICD for wich I know nothing about and am not sure what it does or why its talked about so much on these boards.

 

Not sure which CDI's you are looking at, but the one I kind of like is the Vortex units made in Australia. They are programmable, plus they have a switch you can use to switch between different settings to help with trail, drags, top end.... and I don't know what else. Buying a CDI to up the rev limits is a complete waist of time. They all claim 10 000 RPM limits. It helps nothing if your quad makes its maximum HP at lower RPM. You need a very heavily tuned quad motor to make max HP at 10 000 RPM. Then the last thing. As much as I like the Vortex Unit, I have not heard of any CDI units that give you more than 1 or 2 HP increase. They might give a little more torque here or there, but some hardly add anything. Making them an expensive unit to gain very little power. None of the CDI guys seem to have any dyno charts showing torque and HP readings before or after the new CDI. If you find some please let me know.

 

OK lets jut look ahead a little to our 450 that is ging to handle like the kfx/z - comfort and great expandable power.(and when duncan and lRD get them what doyou think will happen at the track-oh yea same as this year 1st-2nd- 3rd -)thats only my opinion- maybe some of yours!!