400ex motor helpp!!

[starcrossed010]

my 400 ran alright but the valves tapped very loud, they needed adjusted for quite sometimenow....well the other day i was riding and it just killed it self as if the motor blew. i came to a stop and it fired right back up and was fine.... well today it started doing that again, i thought the engine was going to lock up, but it started again and then i made it home... so i figured it was time for a tune up i was going to change the plug oil and then adjust the valves. well i did all that and now it will not start. it started for like 5 seconds if you had the choke on and held it floored and then it woulf kill itsief, even while holding it floored. i thought maybe the valves were too tight but they have play in them, and were adjusted correctly. my only other guess would be out of timing, unless i have other serious problems, but keep in mind it still fires up just kills itself right away... anyone ever have this happen before??? any suggestions would help

ps does anyone know if they shut themselves off after being too hot?? maybe that could be my problem.?...??..

[BSTURDIVANT]

Sometimes the spark plug causes the same problem!

[prepracing]

I doubt the timing would have jumped, the timing chain would have to be so stretched out you would hear it slapping around. What clearances did you set your valves on ? and as BSTURDIVANT said check your sparkplug....was the new spark plug gap correct and is the plug seated all the way down, I have seen a loose sparkplug cause that.

[starcrossed010]

well i decided to rip it apart to see what was happening inside the engine and i have discovered that the timing chain was so stretched it jumped timing, the piston had scared the walls causing it to burn oil. so today im ordering the cfr 450 timing chain and a 416 kit from c&d racing, taking mu sleeve to get bored out and hopefully slapping it back together by next week..
anyone know the torque specs on the sleeve bolts, head bolts etc? it would be a help.. thanks

[starcrossed010]

for anybody wondering about going to a 416 heres what it costs..
Je 416 piston kit 87mm/.080 over 120.00
2002 crf 450 cam chain 33.00
top end gasket kit 40.00
shipping 10.00

exact total if you get your stuff from c&d racingcomes to $203.50

now keep in mind thats just to get it running aftr the rebuild, most people would get a cam to really feel a difference, but it is not needed, also youll need some fine tuning with the main jet and stuff like that...

[F-16Guy]

...anyone know the torque specs on the sleeve bolts, head bolts etc? it would be a help.. thanks [/B]
http://www.atvriders.com/articles/torque400ex.html

[slamdak8782]

There are torque specs for the 400 on this site under articles

[400exrider707]

If your chain jumped time then its possible you have bent valves as well, you might want to check that out.

[mikeboone]

If your sleeve is scratched deply .080 (416) may not be enough to get the gouge out. Did you have machine shop look at cylinder before ordering?

[bigredfan]

Hey no offence but just reading your post are you sure you should be doing a rebuild without any help? Cause if you let your valves go on that long with out repair, and wore out a timing chain on a stock bike it doesn't sound like you should be doing this without any help, because if you put this motor back together wrong you will be spending that money again and again and again. So please get some help from somebody that knows a little about motors at least.

No hard feelings I hope. I just wouldn't want you waste your money.

[RIDER11X]

You would be wise to take the head to someone and pay a little to get it checked out before putting it back together.......There are quite a few common wear items in there that can cause you problems down the road if not taken care of. ;)

[starcrossed010]

Originally posted by bigredfan
Hey no offence but just reading your post are you sure you should be doing a rebuild without any help? Cause if you let your valves go on that long with out repair, and wore out a timing chain on a stock bike it doesn't sound like you should be doing this without any help, because if you put this motor back together wrong you will be spending that money again and again and again. So please get some help from somebody that knows a little about motors at least.

No hard feelings I hope. I just wouldn't want you waste your money.

none taken but i know what im doing... i got all new valves, valve guide seals, cam chain, piston kit, gasket set, clutch assembly... the works i am eliminating anything worn out.... i thought about all of this before i started the project...

[starcrossed010]

Originally posted by RIDER11X
You would be wise to take the head to someone and pay a little to get it checked out before putting it back together.......There are quite a few common wear items in there that can cause you problems down the road if not taken care of. ;)

theres not much to a head, valves which i replaced, the valve gude seals, which i replaced, and the springs... its all new, then you have the cam... which is fine and rocker arms which are fine other then that theres not much to it.... but thanks for caring!;)