Ok so me and my dad rebuilt the top end on my 400ex. We put in new rings and valve stem seals.Me and him and a bunch of other guys went riding about 4 weeks ago. We rode about 4-5 hours that day. Came home and put the bikes up. Last weekend we were going to go out riding again but my fuel was pouring out of the overflow and wouldn't stop. Put the carb in the shop to have them clean it out. It's fixed and doesn't **** out. So we got that back today and put it back onto the bike. Turned the fuel on (bike was off) to make sure it wasn't going to **** out and it didn't. Turned the bike on and gave it the gas and let it idle and kept doing that to make sure it was fixed for sure. I was standing next to the bike and started to smell something burning. Didn't see anything so we let it idle. Then I started to see some white smoke coming out by the engine. The bike runs great and idles fine and everything. Smoke is coming from the front of the pipe. It isn't coming out of the end of it. It's pretty bad and is burning a lot of oil. Like I said, we replaced the rings and seals on the valve steams and we already went riding and it ran great and still does. The only problem we now have is it's started to smoke again. What can cause this problem? Another thing, at first he said it was only running on choke then after a minute or so it would run without. I'm guessing he didn't let it warm up enough but I'm not sure if this is/can be tied with why it started smoking while it was just sitting there. What can cause it to do this? We want to know if we can fix it without putting it into the shop!

 

You didn't seat the rings properly after installing them. You cannot just put rings on the bike and immediately start riding for extended periods of time. You actually wasted your time and money the first time around for not properly breaking the rings in. A four to five hour ride on a brand new set of rings is harsh...

 

<div class="FTQUOTE"><begin quote>Originally posted by: DWill58

You didn't seat the rings properly after installing them. You cannot just put rings on the bike and immediately start riding for extended periods of time. You actually wasted your time and money the first time around for not properly breaking the rings in. A four to five hour ride on a brand new set of rings is harsh...</end quote></div>

You know what, we never even thought of that this time. We rebuilt a kx80 awhile back and it ran great and never had a problem with it. That is because I took it easy on it for the first few rides out. We are going to put the bike into the shop and just have them rebuilt the engine from top to bottom so we don't have to worry about anything for awhile (it's an 03).

 

<div class="FTQUOTE"><begin quote>Originally posted by: BigRed400ex

<div class="FTQUOTE"><begin quote>Originally posted by: DWill58



You didn't seat the rings properly after installing them. You cannot just put rings on the bike and immediately start riding for extended periods of time. You actually wasted your time and money the first time around for not properly breaking the rings in. A four to five hour ride on a brand new set of rings is harsh...</end quote></div>



You know what, we never even thought of that this time. We rebuilt a kx80 awhile back and it ran great and never had a problem with it. That is because I took it easy on it for the first few rides out. We are going to put the bike into the shop and just have them rebuilt the engine from top to bottom so we don't have to worry about anything for awhile (it's an 03).</end quote></div>

It doesn't matter how hard you run it, but the time period is what makes the difference. You need to let it warm up first, a full warm up without hitting the throttle to "hear the motor rev", then shut it off and let it cool for 15 minutes. After that, start it up and run it as hard as you'd, just make sure you let the motor slow itself down some too (nail it in 3rd till nearly hitting the rev limit and then let off and coast down to low speed, try it in 4th as well). I would ride it for about 20 minutes or so on the first true ride and then let it cool for a while. Then keep increasing the ride time on it and don't be scared to hit it, it can handle it, but extended riding periods (such as 45 minutes to an hour) on a new set of rings is really harsh. The rings are cutting into the piston and setting themselves when they are new, so you want them to be run as hard as you are actually going to ride it so that they cut and seat as well as possible. The problem is that you get excessive heat on the new rings since it is cutting into the cylinder slightly and heat tends to expand metal, so as you keep riding for 45 minutes or so you are expanding the cylinder walls more than they should be with a new set of rings. Try limiting your ride time when you get your bike back from the shop on the first 5 rides so that you can get the new rings to seat well and you should be in good shape. It is a lengthy process if you want it done correctly, but it is well worth it to acheive a good ring seat. Don't be afraid to change the oil frequently either since there will be small metal shavings from the rings and cylinder wearing with each other.