hey everyone,
I'm having some problems with my 400ex. I've only owned it since this summer. supposedly it has 12;1 wiseco piston 100 over, carb rejeted. anyways, i've rode it this summer and just have to try a few times before it starts. no big deal. however, i was riding last week in first gear, slowing down to cross a creek, and it cut out and jerked to a halt - just died. i couldn't go more than 5 feet before it did it again. - eventually i gave it a lot of gas, got out of first gear and took off. it ran fine the rest of the day.

i put it up and went to start it a few days later. it kept acting like it was trying to turn over as usual, but the third time i tried i got this loud knocking sound 2 times, real quick one after another. eventually it started and idled fine for 30 seconds. i shut it off and havent' got it started again. keeps making that loud clanking sound every few times i try to start it. a guy at work said his 400 wouldn't start easily when it got colder or could be the starter hitting the flywheel but not meshing in with the teeth when i'm trying to start it???

i've heard all possibilities- one way bearing , flywheel, or solenoid going bad. some say to adjust the pilot for cold weather starting (but not sure that would help my problem). haven't torn it apart yet to check any of these.

it isn't a grinding sound, but just like a metal hitting metal sound. hopefully someone will know what's going on. any ideas out there???? thanks a lot!!!

 

it soundw like you've gotten alot of diffeswnt opions, all are good and sll good be it. the best advice i can give ya man is go to your local shop by a Hayens ook foryour 400 ex and read it. if you fairly comfortablewith tearing in to it than read up o nthe engine noise section and narrow down to what your sounds like. i've got a 400 i bought a haynes book and it has been helpful. im in iraq i brought my haynes book with me, on my free time ill read up on some stuff and get back with ya to seeif is fixed.

 

I know this may sound strange but check your air filter. Back in 99 when my brand new ex wasn't even a month old yet I was riding it and it started making a clanging sound and died. I got it stated back once and it ran for a few seconds then did it again. So I loaded it up and carried it back to the dealer and they tried to get it started and changed the plug and it still wouldn't start. So when we pulled the air filter lid off there it was, the air filter had fallen off and the screw that held it on was sucked through the carb and has hung on a valve. They put new valves in it and it has been bullet proof ever since. Just do a quick check cause who knows.

 

put it on reserve