10 days since the purchase of my new white LTZ400 and 100 miles. After the first 75 miles I received and installed the my online order from Rocky Mountain USA. I installed a Dynojet jet kit for stage 2 mod. This requires pulling the plastic and gas tank to access the carburetor slide in order to change out to the Dynojet adjustable slide needle and main jet from stock 130 to 160. Then removal of the bottom bowl to access the mixture screw and turning it out 3.5 vice the stock 2 turns. The airbox modification instructions which tells you to remove the lid is a big mistake as sound waves travel directly to your head and noise increases unnecessarily. Instead like on my Ozark I drilled fifteen 1 inch holes on the sides and back of the airbox just below the lid and left the snorkel in place to deflect dirt and keep the filter cleaner longer which also allows for an easy reversion back to OEM should I sell or state inspections become mandatory like in CA. While dissembled I also installed a Streamline twist throttle vice the stock thumb throttle. The Streamline twist throttle kit is good quality but the install instructions are poor and minimal, however easy to figure out using comparative logic. Also noticing some tendency to stall during slow technical riding which requires allot of clutch work I decided to installed a DriveLine 13 tooth counter shaft sprocket replacing the OEM 14 tooth (eliminating the stall). I also installed a Armadillo six pack rack and swingarm protector plate. The OEM plastic protector is very weak and bends easily allowing both the sprocket and brake disk to be struck hard and possibly get bent causing a wobble. Lastly to get it street registered so I don't have to load it in the truck to get to the ride area which is .5 miles away, I installed an electric horn, side view mirror, and license plate bracket.
The jet kit in with side hole airbox mod in combination with 1 tooth lowered gearing made a huge difference extending power and torque delivery at the low and top end with no noise increase. The gearing is closer together making it easier to keep the engine rpm optimal in the trail twisties without allot of hunting for a better gear but also more forgiving at the low end eliminating the dreaded lug stall. The twist throttle performed just like OEM on a dirt bike and there were moments I though I was riding my CRF450x as twist power delivery was much easier and controllable especially when using the front brake simultaneously, no more hand cramps and thumb slip. The Armadillo six pack rack makes carrying all the things you need like cold drinks, snacks, and equipment easy. The Armadillo swing arm protector is the thickest and strongest protector available so even large pumpkin size rock strikes didn't bend it protecting driveline components from strikes that occur with using the plastic OEM protector (big mistake). Now my Z400 is a fast sleeper, quiet but fast. I seriously doubt if I will be changing out the exhaust as dyno test have shown very little improvement from installing $700 racing header and muffler system. The Z400 engine was so closely matched to the OEM exhaust, only major motor changes can utilize one, and I don't plan on racing anymore.
Today I passed an 04 Z400 on the trail visiting from CA and after introductions and a chat we exchanged rides for a mile or so and the guy couldn't believe how quiet and powerful my 07 felt while his 04 was ear busting loud with the baffles and spark arrestor gutted. I think in the future being cool will be seeing who can make their dirt bike or quad the quietest sleeper on the block instead of the loudest.
Well thats it, if anyone needs advice installing this stuff just PM me.

 

Hello

I also just brought a 07 Z400 (Black) I have added a yoshimura full exhaust, and have a jet kit to add. Can you explain the jets to me. I know it get more feul into the cab, but what the difference between stage 1 and stage 2. I also think the 130 is stock, and you stated to replace that with a 160. I have like 6 different jets. Why 5. I have never jetted any of my bikes. i used to have a 04 Z. with about everything but never jetted. Can you really fill the difference after jetting. Thanks for the information.

 

"I seriously doubt if I will be changing out the exhaust as dyno test have shown very little improvement from installing $700 racing header and muffler system."

Good read CWO, but I have to dis-agree about the pipe. Sure you opened the air box up, to let the air in, but you have to let it out. I can fart harder than the Z's stock pipe let's air out [img]i/expressions/face-icon-small-smile.gif[/img]
Believe me dude, and there's probably hundreds of Z owners on here that will attest, to get the most out of this engine stock, you have to upgrade the exhaust.

 

I too disagree about the pipe thing. My pipe made a big difference before I removed my air box.

 

the best cost effective thing you can do on this bike is to remove the spark arrestor with the three bolts on back.....this lets just as much air out as my friends Yosh....then put on a straight K&N with outerwear.

On to the jetting: I live in northern utah and with the above mods I tossed in a 175 main jet. I started at a 135 and worked clear up until the 175 when the engine stopped bogging and the plug wasn't white.

 

<div class="FTQUOTE"><begin quote>Originally posted by: scottphillips88

the best cost effective thing you can do on this bike is to remove the spark arrestor with the three bolts on back.....this lets just as much air out as my friends Yosh....then put on a straight K&N with outerwear.



On to the jetting: I live in northern utah and with the above mods I tossed in a 175 main jet. I started at a 135 and worked clear up until the 175 when the engine stopped bogging and the plug wasn't white.</end quote></div>

agreed no S A will differently allow better flow ,the 175 worked great ,unfortunately in my state S A's are the law . as it is the 172.5 is now the jet of choice, still , i'm not using the S A that came with the pipe , the one i use is not nearly as restrictive. no S A also gave a greater torque out put on the bottem but ya have to give it more gas hence the 175 jet

 

The term stage 1 & 2 are used subjectively in both the off-road and on-road motorcycle industry when describing upgrades to the engine intake and exhaust systems and each kit maker has their own interpretation. With respect to the kit I used for my Z400 made by Dynojet their instructions refer to a stage 1 as changing the slide needle and jets only and NO air box modifications, and stage 2 as changing out the slide needle, jets, and making the air box mod also (removing the lid). The last of the two gets the best results but removing that air box lid sends allot of pressure wave noise strait up so I have always kept the lid on and opened up the sides and back yielding the same results but keeping the pressure wave noise down and at right angles to the rider and allot less trail blown dirt out from getting into the air box caking the filter early. As far as which main jet to use out of all the ones they provide, the instructions tell you based on sea level altitude which is the best to start with. For me being below 5000 feet that is a 160 main jet and although they provided a 165 and 155 main jet to tweak it spot on, the 160 seems to be burning (spark plug color) and working perfectly.
With respect to full exhaust change on this engine which was not designed to be high performance race engine, before you would get an appreciable increase in power for the investment, the engine would have to be ported, high profile cammed, increased compression and probably kit bored to be of any use as the stock engine is closely match to the stock exhaust, and yes even with the air box opened up. But everyone need to reach the same conclusion on their own path so by all means buy one if you feel you must have it. Personally for the extra $700-900 it cost for a full header and can system, I would have just bought a new TRX450x for $5600 OTD, race ready right out of the box, and able to blow the doors off any fully moded Z400, given the same rider competing against his own time. So you have to decide on the right platform to begin with rather then trying to turn a a great trail and open desert ATV like the Z400 into a high performance race ATV like the 450r or 450x. Just like you dont buy hiking shoes and try and make them track shoes.

 

http://www.ctracing.com/ltz400...0shootout%20mag%20.htm