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Discussion Starter · #1 ·
Hey folks I just bought a 2000 400ex. Extended a arms, axle, 450r shocks, hmf pipe, k&n filter, freshly rebuilt to 408. Pretty excited to get out and ride this thing. But its got a white bros rev box on it. Is that safe to run? I know white bros isnt the top of the line for rev boxes. Its also got g-force hubs on the rears. Ive been told they have a tendency to snap? I'll be doing alot of jumping so they'll take some abuse. Last question- whats the oil capacity on these?
 

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I'm not sure about the snapping, but I've heard they might bend a little because they are aluminum. I have a set on my quad, but they haven't bent or broke yet.
 

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Discussion Starter · #7 ·
Alright well those are the least of my worries now. When i got it I test drove it around and got it nice and warm, made sure it ran fine (which it did). Got it on the open road today, drove about 8 miles to my buddies house, where I found out that it smokes like crazy. There must not be any piston rings left. Talk about a let down. Theres absolutely no way the guy didnt know about this when he sold it to me. It puts out a good cloud of blue smoke. Some people...
 

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Alright well those are the least of my worries now. When i got it I test drove it around and got it nice and warm, made sure it ran fine (which it did). Got it on the open road today, drove about 8 miles to my buddies house, where I found out that it smokes like crazy. There must not be any piston rings left. Talk about a let down. Theres absolutely no way the guy didnt know about this when he sold it to me. It puts out a good cloud of blue smoke. Some people...
a hone job..new rings..top end rebuild..and it will run like new again.
 

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Discussion Starter · #10 ·
Is this something any mechanically inclined guy can do? I've rebuilt snowmobile engines and a couple tractor engines before but I've never touched a quad motor before. This weekend I should be able to get a quote from a local mechanic what it'll cost, but I'd like to do it myself and save some money if possible since junior year of college starts in a month and I'm pinchin pennies.
 

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yes u can do it just get the manual for the spec i would a magen some one here has it for a 400ex
 

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Is this something any mechanically inclined guy can do? I've rebuilt snowmobile engines and a couple tractor engines before but I've never touched a quad motor before. This weekend I should be able to get a quote from a local mechanic what it'll cost, but I'd like to do it myself and save some money if possible since junior year of college starts in a month and I'm pinchin pennies.
if you can turn a wrench..then your almost done !..lol....don't even bother asking a dealer or mechanic..they will rip you a new one !..lol..if you purchase all your parts ( top end rebuild kit, ring's ( standard ring's ) ?..you won't know this until you mic the cylinder !..all your gaskets if you need them..you should be fine. it's not very hard at all to do..just take your time..pay attention on how you take every thing apart ( this is where a service manaul comes in handy )..take pic's as you disasemble the motor if you think it might come in handy, have a hone handy ( for honning your cylinder after your ready to install the piston. VERY IMPORTANT..do not run your motor very hard in the first couple of hours..very your throttle..do not go WOT ( wide open throttle )..give your new rings time to seat in the cylinder. you should be good to go then. if you get stumped..just ask one of us..im sure we'll lend you some info ..oh..we only take cash for the info !..j/k..lmfao..good luck !..one more thing..get your hands on a good metric socket set..all nuts and bolts on these are metric.
 

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If you don't already have a service manual, you can download one from the site below.

maxmekker.com
 

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my bad..i over looked where he stated it was bored over..he will need to mic the cylinder..or even take it to a dealer or who ever..and they can tell him what ring's he will need...p.s. i did state to mic the cylinder in my post before on finding out the ring size..lol.
 

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Discussion Starter · #16 ·
Yeah I have to make sure and check the bore. The guy claimed he rebuilt it and bored it out, but I'm pretty sure he was full of it ( I did ask for papers, but he was an old mechanic and said he did it himself). I started it up today and it just POURED out smoke, but once it warmed up it cleared up almost completely. Which is odd, because when I first went to look at it and test drive it, the motor was cold, didnt smoke at all, and didnt when it was warmed up either. Drove it for less than 30 minutes total when I got back, and now this happened. Either way, its gotta be fixed. Should I use stock oem replacement parts for gaskets and rings? Or are there aftermarket ones that are built stronger?
 

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Yeah I have to make sure and check the bore. The guy claimed he rebuilt it and bored it out, but I'm pretty sure he was full of it ( I did ask for papers, but he was an old mechanic and said he did it himself). I started it up today and it just POURED out smoke, but once it warmed up it cleared up almost completely. Which is odd, because when I first went to look at it and test drive it, the motor was cold, didnt smoke at all, and didnt when it was warmed up either. Drove it for less than 30 minutes total when I got back, and now this happened. Either way, its gotta be fixed. Should I use stock oem replacement parts for gaskets and rings? Or are there aftermarket ones that are built stronger?
me myself.i stick with stock rings for sure ( just make sure you get the right size ) !..as for the gaskets..after market gaskets work just fine..one thing you will learn when it comes to wrenching on your atv..some things you can cut corners on..and others... YOU DO NOT CUT CORNERS...all depends on what part it is.
 

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Discussion Starter · #18 ·
How hard would it be to throw in a hotcam while I had the motor apart? Never swapped a cam before, but if I've already got the motor apart might as well make the most of it. And a buddy of mine suggested that it might have been the oil ring on the piston that broke, and so when it warms up it expands and seals up better. But in the case of a ring breaking, does that usually scratch the cylinder walls?
 

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How hard would it be to throw in a hotcam while I had the motor apart? Never swapped a cam before, but if I've already got the motor apart might as well make the most of it. And a buddy of mine suggested that it might have been the oil ring on the piston that broke, and so when it warms up it expands and seals up better. But in the case of a ring breaking, does that usually scratch the cylinder walls?
It will be easy to change cams, because you will have to take the cam out anyway. Yeah, if a ring breaks, it will probably scratch up the cylinder walls. The problem could also be the valve stem seals. When the valve stem seals are bad, after you shut the engine off, oil can leak down through the valve stems onto the top of the piston and then when you start it up again, the oil will burn off the top of the piston. This will cause the ATV to smoke, when you first start it, until the oil is burned off the piston. A lot of people overlook the valve stem seals when they do a top end rebuild and that may be the case with yours. The guy may have just replaced the piston and rings and failed to replace the valve stem seals.
 

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Discussion Starter · #20 · (Edited)
That would make sense too. It ran just fine at first, but somethin went wrong on my first cruise. I was in 5th gear WOT and I could feel it bog down slightly, slowed about 10 mph. Maybe a seal went bad at that time? Ill have to do some looking in that repair manual and see how that all works. Would a bad valve stem seal still cause it to smoke slightly after being warmed up? It shoots out a very small amount when revvin it up
 
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