Just bought a new 400ex and asbolutly love it. Apart from driving for the first 2 hours with the joke on and having no power at all it was a great start to my quad biking life (will I have damaged the engine at all by riding with choke on?)
Anyway was reading through the owners manual and it was talking about valve clearance. Firstly is this really a problem for the 400 engine, is it hard to adjust if needed and how often should it be checked and adjusted?
Any other tips to ensure I maintane the bike in good condition?

 

Riding with the choke on? All you did was waste gas..dont loose sleep over it.

Check out this article for tips on the valve adjustment.
valve adjust 400ex
Change the oil on a regular basis, clean the air filter after every 10 hours of run time, and keep an eye on things loosening up.
And enjoy.

 

Actually don't most quads stall if you try to ride with the choke on after it's warmed up? What I'm getting at is wouldn't his jetting be off if it'll run for 2 hours with the air/fuel mixture being jacked with.

 

Ya, runningwith the choke closed is gonna make it way rich. But the honda butterfly choke, has a spring loaded door on it, and when the motor wants more air the door opens and more air can come thru.
But youre right, it was way rich, but being rich only wastes gas, its not gonna harm anything except maybe foul a spark plug.
If he didnt do alot of idleing, and the clutch lever was out, and the wheels were turning...the motor wouldnt die.

 

Thanks for the replies guys, much appreciated. I am not to sure about jetting but I will explain what happened.
Ovsiously I didn't know about the choke as the guy fromt eh shop must have put it on without telling me (First bike I have had so pretty naive I guess). So all I did ws start it, warm it up and drive around for a could of hours. I had no power and I couldn't get it past probably 1/4 throttle without stalling it (and a whole lot of unburnt fuel coming out the exhaust). But keeping it in the low rev range didn't cause it any issues at all.
Once some other riders told me what the problem was (to my embarrasment) and turned off the choke it was a different machine. It shows not signs of power loss or irradic running.
P.S
Absolutly love the bike. Was a toss up between the Z and the ex and I am stoked with the bike thus far. Now having the problem of keeping my girlfriend off it as she loves it more than I do.