Hey, I just went riding tonight, My brother was behind me and stopped me and told me my 400EX was smokin like a freight train, I just baught it in april, I have changed the oil twice already and i dunno why its doing it, Can anyone explain anything about why its doing it soo soon.

 

the color of the smoke would help [img]i/expressions/face-icon-small-wink.gif[/img].....lol
if its white you may want to check the carborators.
if its black its a oil leak somewhere and you may need new piston rings.
whites is gas. black is oil ( it would also stink). you may also want to look at the spark plugs.

if this dosent help let me know.

 

It is white smoke, And it does have a bad smell to it, My brother said it stinks........lol, Ill tell ya what its doing, When i go down the road, When i smack into it it burns just as clean as can be but just as soon as you back off that throtle it pours it out. Surely it wouldnt need rings already, its only 2 months old.

 

I guess i told ya wrong, I just got it out to look at it and when i took it down the road and looked back, I wound it out a lil more than i usually do before i shift but it poured white smoke out at high RPM's. Could the carb be messed up?

 

Use a heavier grade, high quality oil.

Back in Aug of 99 when mine was new, it did the same thing. Needless to say I was a tad unhappy.

Knowing I had broken it in correctly, it hadn't been abused yet, and the XR400 is bullet proof - there had to be an explanation.

I did some experimenting (if you're really ambitious, you can probably dig up the threads on this board). What I found was that with the high oil temperatures the 400EX runs, especially in hot weather, it breaks down conventional, light weight oils very quickly (i.e. 10w40, 10w30, etc). Even Honda's oil doesn't hold up.

I tried a couple different oils and settled in on Mobil1 15w50 and since have had no troubles with smoking on decel.

If you change your oil now, you will likely notice the smoke will go away for a while, then come back. Run to Walmart, get a couple quarts of Mobil1 and see if that takes care of your problem - I know it did mine and many others that were having the same troubles on this board, EX Riders, and my e-mail list.

Also, some guys run a straight HD30 with good luck. HD30 works well because it contains no viscosity index improver like a 10w40 does. VI Improver allows the oil to break down to it's lightest component with time and heat exposure, which is likely what you're experiencing.

However, you can get the same advantages with Mobil1 15w50. It's a synthetic and contains no VI Improver to get it's spread. You then also get the advantages of a very low cold temperature pumpability number, very high film strength, and a very high flash point. With it's good properties, I run it year round, I just give it a little extra warm up time in the winter to be on the safe side....

Also, don't believe the clutch slippage stories some will tell you of synthetic oils. I've been running this oil exclusively now for nearly 3 years in my 400EX which develops nearly 40 HP at the rear tires and is raced in cross country and flat track events. I've replaced one clutch due to mild slippage when I went to a taller front sprocket, that was earlier this year after two seasons of abuse racing, many trips to the sand dunes, and loads of play riding - in other words, it was due for a clutch...

For potential clutch slippage you want to watch out for friction modifiers which are contained in lighter weight oils like 5w30, 10w30, 10w40, etc - either conventional or synthetic. These oils are usually labeled "Energy Conserving". Mobil1 15w50 contains no friction modifiers.

One other point I would like to make is the other guy had it backwards. White-ish blue smoke is oil smoke. Black smoke is from too rich a mixture.

 

White smoke = burning coolant/water. This is usually associated with a blown head gasket. Is your oil a milkshake color? It seemsa bit odd that a 2 month old bike has a blown head gasket. Are you sure it doesn't have a blue etint to it? Could you have overfilled the oil?

 

Although you're correct pure white smoke usually indicates a coolant leak into the combustion chamber, I don't believe that's what he's experiencing as the 400EX is AIR COOLED [img]i/expressions/face-icon-small-smile.gif[/img]

 

my nephew's 250 rincon does that a bit also ( not as bad as yours by the sounds of it ) , a heavier higher grade oil will help , he went to a DMO ( deisel motor oil ) oil , it seems to keep its viscosity better. Also may suggest a synthetic oil ,they are about double the price for a good one . His Rincon usually does it on deceleration , dealer said it is nothing to worry about , but like I said yours sounds more extreme than his .

 

Honestly, I'd go the oil route like they're saying. I'd also add an oil cooler if I were you. It will extend your oil life and your engine will run cooler. FST sells a kit for under $100.

 

Boys it aint that terribly bad, I kinda over reacted, I changed the oil monday, The oil that was in it was milky colored. It just started smokin last night. I will try some heavier weight oil, I just checked it about fine minutes ago and the oil was thin again and like i said it was just put in there monday, i did get the engine real hott last night, so maybe if i put some heavier weight oil in it, it may straighten up