400ex Using Lots of Oil Help!

[childert79]

I have a 400ex I just bought and the kid took off the airbox lid and put on a slipon with out rejetting it. Now its using alot of oil but from what I can see it doesn't have any leaks anywhere and no blown gaskets. However when you hammer down on the throttle it puffs blue/black smoke. I'm assuming its blowing all the oil out the exhaust so my guess is that the piston rings are burnt up. This thing is using A-LOT of oil. Please help. Any feedback is appreciated.

[vaget22]

Most likely it's a worn cylinder and rings. You can try checking the compression if you have acess to a guage. Or if you have a friend that has one. Could also be the rings are stuck in the grooves and are not expanding all the way out to the cylinder walls. Also could be the ring gaps are all lined up instead of staggered. These last two ideas are less likely than a worn cylinder and rings. If you pull it appart, I would replace the piston and rings with a oversize piston. Measure the bore size before you buy a piston because the cylinder may have already been bored before. Ask around your area and find a shop that bores cylinders and have them check it. Also don't skimp on what brand piston you buy.

[tri5ron]

Agreed to what Vaget22 suggested.

I would also add that you do not want to buy the new piston and rings PRIOR to having it properly measured,

AND/BUT, AT THE SAME TIME....

You DO NOT want to have it honed/bored, before BUYING the new piston/rings.

In other words, do not get impatient, and do not try to get it done in one day.

FIRST - you need to find out how bad it is, (measured, inspected).
This will tell you what you will need to do to it, AND what size piston/rings to buy.

SECOND - ONLY AFTER it is determined what size it will NEED to go to, is when you should buy the piston/rings of your choice.

THIRD - Once you HAVE the piston/rings in your posession, THEN you give it, (the piston/rings), to the machine shop, for them to hone/bore the cylinder.

Due to maufacturing tolerances of ANY piston you choose, this will ensure that the cylinder is honed/bored to the correct size for YOUR PARTICULAR PISTON.

Take your time, do it RIGHT, and it will last you many many hours of riding enjoyment.

or...

Get in a rush, (like so many people do),and end up going through the same thing as this guy.....
(Read the entire thread)
http://www.exriders.com/vbb/showthread.php?s=&threadid=441793

(obviously the previous owner DID NOT do it RIGHT, and now the new owner is stuck with the cost of cleaning up the mess)....

hope this helps.

[slightlybent47]

Putting on a pipe and taking the air box lid off was all the mods that the kid did to it, so saying he didn’t do it right in the first place has nothing to do with it.
Regular maintenance and how well it was done, plus how it was ridden and where it was ridden make all the deference.
Running with the air lid off and using the wrong filter and not keeping it clean will destroy the rings in no time. The reason these 4 stroke motors run so good is the tolerances are much closer then they use to be so any contamination is bad, keep it clean and it will last for years.

Now to your problem, I would agree with re doing the top end, both piston and rings and valves and seals.

Blue smoke is oil and black smoke is un burned fuel.

[childert79]

Thanks a lot for the quick replies and great advice. I'll be sending it in to my mechanics now to get the work done. Thought it was probably the pistons and rings but was hoping I didn't have to get it bored but I may get lucky and just have to be honed. The kid was running a foam filter with no lid in the sandy river bottoms so I figured that was what killed it. Its all cool though because I just picked it up for $500 with a clean title and its an 07. So far the only other thing I could find wrong with it was brake pads and I had to replace the axle bearings. So far I'm looking at around $1000 for an 07 400ex!

[MidnightBlade]

Originally posted by slightlybent47
Putting on a pipe and taking the air box lid off was all the mods that the kid did to it, so saying he didn’t do it right in the first place has nothing to do with it.
Regular maintenance and how well it was done, plus how it was ridden and where it was ridden make all the deference.
Running with the air lid off and using the wrong filter and not keeping it clean will destroy the rings in no time. The reason these 4 stroke motors run so good is the tolerances are much closer then they use to be so any contamination is bad, keep it clean and it will last for years.

Now to your problem, I would agree with re doing the top end, both piston and rings and valves and seals.

Blue smoke is oil and black smoke is un burned fuel.

you CAN do it wrong which this kid did, he removed the airbox lid (+2 on jets) and added a slip on (+3-10 on jets). so it was running WAY to lean, and when they run lean they run hotter, when they run hotter they score cylinders, ruin rings/pistons, and ruin your day. also with out the lid it lets more dust in than just the snorkel tube, did he still have the stock yellow filter? if so get a new UNI and a airbox lid. total is like $50 or so (dont know how much your shop charges). my vote is rings and cylinder walls.
if it was mine id bore it to a 416 and be done with it.

[slightlybent47]

Hey thats a good deal, I’d like to find an 07 like that.
There is nothing wrong with the stock foam filter, I still prefer it to any other, but like all filters it needs to be cleaned often and use the right oil on them. I prefer Bell Ray foam filter oil in the liquid not the spray. It’s real thick and sticky and won’t break down when it gets wet.
Good luck with the rebuild.

[childert79]

I'm going to try to keep it close to stock. I'm already building a good all around 416. I have a uni filter I'm putting on it with an esr lid. Without parts its $75 for all the labor besides having the cylinder bored.

[vaget22]

That's super cheap on the labor. If the guy knows what he is doing, jump on it.

[slightlybent47]

Originally posted by MidnightBlade
you CAN do it wrong which this kid did, he removed the airbox lid (+2 on jets) and added a slip on (+3-10 on jets). so it was running WAY to lean, and when they run lean they run hotter, when they run hotter they score cylinders, ruin rings/pistons, and ruin your day. also with out the lid it lets more dust in than just the snorkel tube, did he still have the stock yellow filter? if so get a new UNI and a airbox lid. total is like $50 or so (dont know how much your shop charges). my vote is rings and cylinder walls.
if it was mine id bore it to a 416 and be done with it.

If that were so then there would be lots of blown ex on here. Just changing the pipe and removing the air lid would not make it run so lean as to hurt the motor. I still say it’s do to no maintenance and riding it in dust sandy conditions.

[MidnightBlade]

SlightlyBent47,
all my family works on motorcycles and quads, we have seen many motors blown because of lack of fuel. i dont lie my family doesnt lie, many people do put slip ons on and do work but then they bore it and the shop they took it to jets it corrctly before too much damage was done.

[sc400ex_rider]

Taking the lid off and putting on a slip without rejetting WILL ruin your engine. Without re jetting and running it lean makes the head runs hotter. This will in turn cook the valve seals. Left unchecked it could starve your motor for oil, scoring the piston/cyl or throwing a rod. This has been discussed on here many times.

thats a good score on that 07. I wish there were deals like that around here. Here ppl always take them apart and never fix them or leave them out in the rain for 5 years then try to sell them LOL.

[slightlybent47]

Originally posted by MidnightBlade
SlightlyBent47,
all my family works on motorcycles and quads, we have seen many motors blown because of lack of fuel. i dont lie my family doesnt lie, many people do put slip ons on and do work but then they bore it and the shop they took it to jets it corrctly before too much damage was done.


Sorry but I never called you a liar, I merely disagree with you. I’m only using common since and my own experience to make that statement.
You may have a deferent opinion and that’s fine, go by what you know, and I’ll do the same. I’ve been playing with my jetting for a long time now and have gone from lean to rich and back and forth with no problems.

We don’t know how long the mods were in place and how many hours were on it. I would suspect the jetting would have to be off quite a bit and have been run a long time in that condition for it to do that much damage.

I only base that statement on the limited information we have, witch is he bought it from a kid, and he road it down at the creek, and having known many kids and when there low on cash, witch most are will cut corners, like not changing the oil and keeping the filters clean. If it was on daddy’s dime then he probably just road the crap out of it and didn’t do anything else to it.
In the end it doesn’t mater either way, the man still needs a top end and the steps you suggested would be right on and I do agree.

Again this all just speculation on my part and I could be way off. JMO!

[MidnightBlade]

Slightlybent47
sorry if i riled you but i didnt mean to make it sound like that. i agrree if you run it lean for a short time it wont hurt, but if you run it for more than a few days it will toast valve seals and rings. and iassumed that the kid had it for about a year with the exhaust and no lid, so i guessed he didnt rejet it. seen it many times before and will see it many times again. careless people not maintaining nything because "oh dad will buy me another one". i used to have that attitude until i realized we were tight on funds and he wouldnt get me another one. so i manitain the one i have and dont beat the crap out of it.

[slightlybent47]

No problem, nothing wring with a healthy debate. Hey I just looked at you cig and it looks like you need some new rubbers on your bike. Lol
I have some very lightly used stock tires and wheels “all four” I’ll let go cheap. Or I have a set of “used” 20% used 80% still left hole shots as well, make me an offer and I’ll send them to you. I can post pics if you like.
I like fresh rubber and don’t use them much before I replace them.

Take care and happy 4th!

[MidnightBlade]

just bought a new set of CST Ambushes, didnt change my sig yet. thanks for the reminder.