Hello everyone

I would like to know if anyone with a 400ex has a oil smoke problem ?

I read an artical in a ATV mag that said the 400 ex should use a heavy oil ( 20-50 ) for summer. Now Its been smoking.

P.S. changed filter when I changed oil.

thank you wicked-ex

 

Well 400ex's run higher rpms, there fore the motors tend to wear out faster. Now things like dirty or dry air fitler after awhile let in unfiltered air. These dirty wears out the rings and cylinder and take out the intake valves

Far as the 20w50 no they don't really need that heavy of oil, unless you have a modded motor and use the racing oil like Bel Ray or some type like that.

What year 400 and what year? What brand air filter is in it. Does the air box have holes cut in it or lid removed?

 

I purchased it used, it is a 2001 and has a pretty new foam air filter and I had to purchase a new air box cover ( it did not come with one )

 

What brand of 20W50 oil did you switch to????

It is most likely coincidence that you began to smoke at the very same time as you switched oils (unless it us just totally crappy oil!). You need to do a compression and leak down test, and if those are ok, consider that your valve seals may be leaking. I have run nothing but 15W50 Maxima Extra ester synthetic in all my quads and bikes during summer for years now....no big deal...nobody smoking....my 400EX has thousands of miles on it!

Being air cooled, the EX can sometimes run hot...thining out the oil. The cam area is subject to high levels of wear anyway, and it is even worse with thin oils. Running a thicker oil will give you a margin of error in this area. Making sure you are running an API SG motorcycle oil will help as well (it has higher levels of ZDDP, than SJ, SL, or SM "car" oils).

 

I have Castrol motor oil 20W 50 in it currently.

I've riden it 4 or 5 times since the change and now it's level is low. ( lower end of dip stick ). I'm trying to find a pressure gauge now.

I,m prepairing for a trip to Ocala Florida, the rides are long HOT and it's very dusty. I,m using a twinair air filter with bel ray oil.