yesterday I decided to try to do a valve adjustment on my brothers 400ex, I looked at all the videos and write ups I could find on the internet so I was sure of what I was doing. I set the intake valves to 0.004 and the exhausts to 0.005 after I lined up the T mark on the flywheel. after I was done adjusting them I put it all back together and now it wont stay running, it'll fire and run with the help of alot of throttle for about 2 seconds and then die acting like its not getting fuel or something. The quad was a little hard to start before the valve adjustment but I could always get it started and after it warmed up it ran like a top. I'm really lost on what I did wrong, i've re-adjusted them 15 times now and no matter what I do it will not run. i'm not sure if I missed a step somewhere or just didn't adjust them properly.. if anyone has any idea what my issue could be please let me know. The quad is a 2000 400ex by the way.

Thank you.

 

Assuming you did use TDC on the compression stroke of the engine, you did everything right. However, from experience, if you remove the fuel tank on a Quad, you disturb dirt that has settled on the bottom of it, this gets dragged into the carb and blocks a jet or jams the float needle open. I can't count the number of times I have had to clean a carb out after having the tank off.

 

You are likely not on the compression stroke Pull spark plug, put finger over hole OR piece of kleenex, turn flywheel until air rushes past your finger (or blows out kleenex) this is compression stroke. Now bring flywheel around to TDC mark
You can visually look inside cylinder and watch piston come to tdc

If the tdc mark is off then you may have jumped time or stretched timing chain?

sounds to me like you adjusted them on the 180 side of TDC compression

 

Sounds like a carb issue...see if it fires up on starting fluid easily...if yes then definitely a fuel delivery issue if you are confident valves are adj'd correctly. The hard-start may have been a carb issue all along...


I'd also check the intensity of the spark...make sure it has a good strong spark when grounded to frame...


Do you have a compression tester...you didn't mention a good compression number...

 

Today I cleaned out the carb and that seemed to help a tiny bit but still dies after 2 seconds. I'm going to buy a new plug for it tomorrow and try the kleenex method of adjusting the valves. I do not have a way to test the compression but the quad ran fairly well before I adjusted the valves so I would think it would be alright but not sure. I'll report back tomorrow. Thank you guys so much for the responses!

 

Ah ha!
If it ran fairly well before valve adjust and now not, it is very likely you adjusted them 180 out
Just because pointer is at TDC does not mean you are on the right stroke
Also its good practice to verify timing marks (cam to crank) when at TDC

 

410 - if it was 180 out he'd have made a large adjustment...right???

 

adjusted the valves using 410customs method and put a new plug in it today and it fired right up! Thanks for all the help guys.

 

 

Bitchin!!!!!!!!!!!!

You were 180 out
Now you know!!