03 400ex. recently bought the bike. great shape but had a hard ticking, knocking sound. benn running great though and went to take it for a ride today and about 5 mins later it just died down completly out of no where. is would still run but just wwouldnt take any gas and had no power. then it stalled for good. wont start now just turns over real smooth & easy. sounds like theres no compression. whats the easiest thing to find out for sure. and whats the easiest way to just get it running, im not worried about boreing and all that. can i just get a piston kit? if my cam chain broke what would be the sympthoms? if i need to rebuild can i get away with just pulling the head and redoing the top end? this ruined my weekend, had big plans for sunday!
thanks
andy

 

We see a lot of these grenaded engine, "it was ticking" but I went and put 100 more hours on it anyway....kind of posts!

Had you ever adjusted the valves???

 

yes i had just did the valves last week when i had the carb off to jet it. when it died last night the knocking sounded louder and it just didnt wanna take the throttle. i turned it off and it started back up but when i was heading back home it gave out completly, and now just sounds like its reving freely. anny thoughts?

cam chain, burnt piston, broken pin,etc?just wanna check everything before i rip the head off. and what will a droped valve look like? this will be my first top end rebuild but im pretty sure i can handle it. just take my time and label parts.

 

<div class="FTQUOTE"><begin quote>wont start now just turns over real smooth & easy. sounds like theres no compression. whats the easiest thing to find out for sure.</end quote></div>
I would say do a compression test. Or even Just take the plug out and stick your finger in the hole and crank it.
<div class="FTQUOTE"><begin quote>and whats the easiest way to just get it running, im not worried about boreing and all that. can i just get a piston kit?</end quote></div>
Take it apart, find all of the parts that are broken and replace them. No you just can't get a piston kit if you dropped a valve or broke a cam chain. That won't fix the problem.
<div class="FTQUOTE"><begin quote>if my cam chain broke what would be the sympthoms?</end quote></div> No compression.
<div class="FTQUOTE"><begin quote>if i need to rebuild can i get away with just pulling the head and redoing the top end?</end quote></div> Not if you dropped a valve and trashed the rod or lower end rod bearing. You have to figure out what broke first.
<div class="FTQUOTE"><begin quote>cam chain, burnt piston, broken pin,etc?just wanna check everything before i rip the head off.</end quote></div>
Why check everything? If it has no compression your done. There is not quick fix for no compression. The engine has to come down to the block at the very least. If you trashed the rod and or bearing the cases have to come apart.
<div class="FTQUOTE"><begin quote>and what will a droped valve look like?</end quote></div> When you take the head off, you will know; believe me, you will know even if you have never seen a dropped valve in your life!!!
<div class="FTQUOTE"><begin quote>this will be my first top end rebuild but im pretty sure i can handle it.</end quote></div> That is a good thing, because it will save you a ton of money!!!

 

thanks for the detailed post thats really kool of you. i put my hand over the intake and it still has good suction, when doing the spark plug hole am i just feeling for the same suction basically? noticed the plug was pretty black, but ive only got a 155 main,42 pilot, removed choke,slip on,K&N with drilled box. when turning it over it dosent make any nasty noises and a coulpe times it acted like it wanted to fire up. could a cdi box cause whats happening?

 

Basic rule of thumb. If the piston does not blow your finger out of the spark plug hole when turning over, you have a big problem.
You NEED to do a compression test before you do anything. If that comes up bad, THEN you can start tearing the engine apart.

 

ok when i put my thumb in tight i can feel it pulsating if i let just a little pressure off it blows out strong. pulled the valve adjustment covers and everything is turning over correctly when i manually turn the crank. it got the same rebound pressure on the crank bolt as it did a week ago when i did the valves. if i was on the wrong rotation when i last adjusted the valves could this be the problem? how does a cdi act when it goes? guess i can find a comp tester. what compression numbers should i be looking for?

 

did u make sure it is firing? if the plug is black that means its burning rich and it probably fouled the plug, try changing it

 

also when i did the valves and just tried readjusting them, when on the timing mark, valves going down but i get no play, not even if i loosen the set screw. if i turn it jus a hair past the timing mark i get some play then. but its ran great since last adjusting them besides the ticking, but it seemed to go away once the motor was hot. could my cam chain jumped and through the timing off? ive got spark but it dont seem super strong when grounding to the frame, maybe it wont be,not sure. what usually happens when a cdi goes south?

 

if you take out the spark plug, the wire on it and stick the plug to the frame, turn and then the engine over, what color is the fire? if its red then you need to change the plug. if its blue then you got a bigger problem