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Discussion Starter · #1 ·
I been trying to figure out what upgrades I wanted to do and then I found this website and thought who better to ask. I have a bone stock 2006 TRX400EX. I like the quad but want a little more power. I have read bad things about the 440 kit so I was thinking about the 426 with a cam and intake and exhaust along with an upgraded CDI. Since this is my first quad that I am thinking about breaking down the engine I would like some input from others. Also thought about building the engine for strength and adding turbo. I grew up riding motocross bikes but now have a wife, 2 children, and have beat myself up enough I enjoy the comforts of the quad. The other solution is to sell and get a bigger quad but really like the Honda name and I got this for a screaming deal. Is the 450 that much better? Thanks for any input.
 

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OR you could be asking a question on something those 30 people don't know how to answer. I read it but have no experience or opinion to share with you based on that particular model, although I'd love to have a 400ex.
 

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I don't know what "bad things" you've heard about the 440 kit, but properly installed it runs awsome. The downside is the expense vs reliability. The cost of sleeving the cylinder combined with the rest of the work (recommend a stage 1 Hotcam, a free flowing exhaust and some carb rejetting) is about $1000. Then the engine runs hotter requiring more frequent oil changes (recommend full synthetic oil with a JASO rating of MA or MA2) - it doesn't rev as high due to the added reciprocating mass - it puts a higher load on the rod, crankshaft, clutch, transmission and the rest of the drive line, so maint. is more frequent and more important. Other than that I don't know of anything "bad" about the 440 kit.
 

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I have the exact same bike, and all i have on mine is a slip on HMF pipe and UNI filter and i can keep up with the 450s in the dunes, a good full exhaust is the best place to start.
 

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Discussion Starter · #5 ·
I know I am going to start with exhaust. Question is is it worth the money to purchase full exhaust or just replace muffler? So is it worth a header? Has anyone tested slip on exhaust verses full replacement? Also new CDI any sugestions? I am thinking programable but that is it. Thanks
 

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both of my 400s are bored out to 440 and i dust stock450 with pipes or even camed or bored. some of it isnt only in your motor its sprocket size to. i had a stock 400 with a pipe, jetted, air cleaner and sprockets that got stolen a year or 2 back and i would much rather have that to just ride around on than my 440. dont get me wrong these 440 will scoot but i like the reliabilty of the stock. its not that this thing keeps breaking down on me but i have to frequently adjust the valves and higher octane gas and just the usual. i have a big gun rev box and its made alot of difference to. i ride out my gears until i start hitting the rev box and it helps out alot.i also have a small eagle talon car turbo sittin on the shelf that i was gunna put on this bike but havent got around to it. just got to find time. but for you, go with a full exhaust probally fmf or hmf for trail but if you wanna race go with a full sparks race exhaust. change the sprockets the bigger in teeth the more tourqe the smaller the teeth the more speed. also jet, take airbox lid off, just do small stuff and it will make a big differencee
 
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