I have had my bike in the shop 3 times for smoking in the first 6 months and shortly after each time i got it back i would notice a light smoke come out if i would rev it up and then let off the gas. i was getting to wonder if maybe a little bit of smoke was normal. it's nothing major like a cloud, just enough to barely see. I know it's not gas burning because it's not blackish. My friend just bought a 2001 and it also does it, his is more noticeable than mine. i think he didn't brake his in correctly. when i got mine back last time i was told to run it easy for 15 min let sit till cold, run 15 min a little bit harder sit til cold, run another 15 min sit till cold then run as hard as i want. any body else's 400 smoke a little. P.S. I don't know the entire history of the 4 stroke engine i just thought that it wasn't supposed to smoke at all ever! let me know what you think. thanks, Wicked

 

I have covered this many times.

Get some heavier weight (preferably synthetic) oil in that thing. It's trying to tell you that the oil you are using is breaking down under the extreme heat and high RPMs of your air cooled engine.

I run Mobil1 15w50 synthetic and have convinced many here to switch (maybe post some testimonials here guys ), give it a shot...

Later

 

15w-50=goooooood
10w-40=BAAAD (smoke)

 

I run Honda HP-4 20-50 for the heat here in the desert

 

GN-4 is soo pathetic...

Gabe showed me the light with 15w 50 tri sinthetic mobile 1.

my siggestion, but mobile 1, it rules, just let it warm up for awhile before taking off... give the synthetic oil a chance to get around the engine, as it dosen't bond to metal as good (Better pumpability)

 

so all you guy's had problems with light smokeing and the thicker oil made it quit? does it have to be synthetic? or just thicker? 15/50 you say? i've heard from two people that you shouldn't use synthetic in the 400ex. any more people use thicker oil to clear up the smoke? thanks guy's.

 

very odd, I have owned almost every XR ever made and they all shair the same engine family as the 400EX and not one smoked a bit even with 10W30 havoline in them. Something just seems weird to me that alot of EX's smoke.

 

Maybe it's because the engine works harder in the EX, with more traction and more weight. Also, maybe the factory lean jetting causes it to run hotter than the XR (where the XR might have optimal-power jetting, because they don't seem to care as much about emissions on bikes). It does seem odd, I'm just glad mine doesn't smoke. First oil change I put 20-50 Castrol in it, 2nd change I bought the Honda 20-50, but I think from now on I'm just gonna run Mobil1 15-50.

 

Motorhead, I see you own one of the last carburated 460's made. I had a 87' F-350 with the 460 and C6 trans, Have you had any trouble with the intake manifold gasket (if yours is still stock)? Mine sucked 2 vally pan gaskets in the one year of ownership. Ford said there was a defect that made them weak. I had a Carter AFB 750 on it that really tore up U joints Also, if you still have the air-injection junk that came stock, be careful because a check vavle can go bad and cause some serious off throttle backfireing.

 

yeah, the stock oil allows "blow-by" and it breaks down very easily. Gabe switched me to the Mobil. Ever since then, no more smoke and i lost the excessive engine noise when my quad would warm up. It runs cooler (less friction) and covers a pretty good range of temp. Switch to the Mobil. It is safe for your engine, and it is availble at Wal Mart. Great convienence. don't have to wait until the cycle shop opens up/ rush to get there before the close. Just stock up on the Honda stock oil filter. You can't buy a better filter in my opinion.