I recently picked up a 2003 Honda 400ex that wasn't in running condition when I bought it. Owner lied to me and said "the valves needed adjusting." I wasn't too worried about it because the price was right. So I get home and hook up the battery to a charger cause it was dead, got it all charged up and attempted to start it. There was a very loud slap, rhythmically as it turned over, which ended up being a broken spring in the cam tensioner. So I got that fixed and now it turns over smooth as it should, I have spark, fuel, and compression (120psi). I tore the thing down completely just to check it over. Piston was perfect, rings good, cylinder flawless, crank bearings and all the bottom end stuff was still tight, no broken valve springs or anything. There was build-up on the valves but nothing looked out of the ordinary. Went through the whole carb and got it cleaned out. I've also checked and reset the timing several times and its all good. When I turn it over now, it sounds perfect; but it is dead completely. The motor is all stock with the exception of a Hotcam. I don't know what stage it is but it was stamped HCD7 I believe. Anybody have any idea as to whats going on here?? Unfortunately I'm running out of options for the problems location so hopefully I just missed something obvious. Thanks

 

Did you pull the plug and check for spark?
Does the battery voltage stay above 10 volts when cranking?
(Is the kill switch in the run position?)

 

I haven't checked the cranking voltage, but yes, I did pull the plug and its emitting a nice solid spark. The kill switch button is on and I even turned the key on too (sometimes the little things get ya[img]i/expressions/face-icon-small-blush.gif[/img]). I had a 2002 400ex a couple years ago and that one ran great. This one sounds just like it now upon startup (nothing unusual) so everything 'technically' should work. Of course, its always the technical details that get ya. Thanks for the reply and lets see if we can't solve this mystery???

 

As you are cranking it, spray some starting fluid into the carb. See if it fires.

Is it possible that the timing is 180 degrees off?

 

Hey man hope u get it fixed....on a diffrent subject i have skids,nerfs,bars,grips,guards,k&n filter,and a few more things...im getting ready to get a set of holeshots front and rear(waiting on pay check)and exhaust for an 01 400ex..
what would u suggest for an exhaust, and after that what would be the next thing to get for it...thanx

 

Can you compression start the quad?

 

The quad still isn't running. I tried flipping the cam 180 degrees with no luck. I pull the plug and it still sparks solid, but I'm thinking of getting a new one just to be sure it sparks under pressure as the old one is fairly corroded. I haven't tried pop-starting it yet with the clutch but that will be in the mix in the near future. Has anyone else had similar problems or have any other suggestions? I have spark, compression, and fuel...and it won't run...go figure? Thanks

 

Does it have an aftermarket CDI box on it. If you don't know, what letters or numbers does the CDI have on it?

 

I have read that for some aftermarket cams the valves may not be fully closed at TDC on compression stroke. So when rolling motor over counter clockwise check that rocker arms are stationary at location where you are adjusting valves. If rocker arms are not fully stationary the valves may not be closed and you could be adjusting at wrong point of rotation for that particular cam profile.

 

Also forgot to mention that it doesn't fire when I sprayed starting fluid down the chute so that is why I'm planning on checking with a new plug.