Uh oh what happened?

[rd2005]

Hey exriders users got a question....What broke here? What caused it? Was on the mx track riding & no previous knocking or any warning to there being a problem. The quad is a 00 400EX. Last Year put in a new 450 heavy duty cam chain, guide, removed the decompresser thing from the cam & removed the little pin & spring that is on the head there that helps with the decompresser. All was running fine. I was jumping & while in the air, it just quit, when I landed it locked up, & I pulled the clutch in & rolled it to the side of the track to find the oil pooring out of it. So now my toy is broken :-( Have not had a chance to tear it down to see what exactly broke but thought maybe someone here can prepare me for the carnage inside :blah:

[CJM]

Looks like the crank decided it didnt want to be in the cases anymore. Only other idea is the cases broke due a motor mount problem, possibly due to a tweak in the frame

Its toast, you need a new engine.

[rd2005]

Thanks CJM....Can I just replace the crankcase & use parts from inside to fix it?

[CJM]

Originally posted by rd2005
Thanks CJM....Can I just replace the crankcase & use parts from inside to fix it?

Possible. But honestly by the time you go that route and all the work and possibly a bad crank or rod or whatever-a new motors is easier and less of a head ache. A used bottom end might be the ticket if the topend is good.

We dont know what else was damaged, could have a whole host of bottom end problems and the piston and or rod probably violently smacked the cylinder when it stopped.

good news is if its just the bottom end-throw the 05+ bottomend on and get reverse
:D

[ajw2685]

Just smear some JB Weld on there and keep riding!

[Thumpin440ex]

I have a COMPLETE low end, that just needs a rod. Let me know if your interested. Might save you some money.

John

[buck440]

it might not be as expensive as you think. judging by the crack being open like that and being by the motor mount it may be from the preeload before jumping that cracked it. i'm going to be a optimist here and say at most you need a new case for sure and maby crank bearings and or a crank.

it really doesn't look like the bottom end blew up. looks like your HARDCORE!!! riding tweaked the frame too much imo lol.

[rd2005]

Originally posted by buck440
it might not be as expensive as you think. judging by the crack being open like that and being by the motor mount it may be from the preeload before jumping that cracked it. i'm going to be a optimist here and say at most you need a new case for sure and maby crank bearings and or a crank.

it really doesn't look like the bottom end blew up. looks like your HARDCORE!!! riding tweaked the frame too much imo lol.
Like the idea of getting a new bottom end with the reverse!:)
But all our extra $ goes into my son's racing so I have to keep this fix cheap as possible but do it right. buck440 I really like your thoughts on this especially being HARDCORE...LOL! :D Going to tear into it on Monday & see what exactly happened. I will post what I find. If the bottom end blew up wouldn't you get sometime of knocking or smoking or warning? :confused: She was running great.
Thumpin440ex will msg you on that low end...how far are you from Budd Creek?

[hocman123]

well if u think this happened bc of a bent fram then it would proberly cost a bit bc u would want to get a new frame or this could hapen again after u fix the engine. costing u a ton of money to do this all again.

[buck440]

Originally posted by hocman123
well if u think this happened bc of a bent fram then it would proberly cost a bit bc u would want to get a new frame or this could hapen again after u fix the engine. costing u a ton of money to do this all again.

if it turns out the bottom end didn't blow up this would be recommend.

http://www.google.com/url?q=http://www.jciracing.com/honda-400ex-9908-bare-performance-frome-gus4009908.html&sa=U&ei=z2CdT9fyI5Gf6QH32sCVDw&ved=0CC8QFjAJ&usg=AFQjCNEec6TsBYOt2TkQRKh1IDa2zE7c0Q

get'em welded on, spray paint them and RIDE RED!

i would definitely measure your frame for symmetry, straightness and check for cracks and if all is good, weld the gussets in.

[Thumpin440ex]

Budds is 2 1/2 hours south of me. I would have no problem boxing it up..


John

[rd2005]

Hey wanted to get back on here & just update on what I’ve found so far. After taking the top end off I found the crank intact, piston is fine, but as you can see from the pic it looks like the counter balance for some reason not sure why moved or broke right under the rod there & stopped it in its tracks. I also notice the rod got very very hot but everything is oily & smooth. The sleeve is still in great shape as well. Not sure if the balance bearing broke or what but that's all I have found yet. Going to crack open the case soon but have never done that so I am doing my research on the proper way to get into it. Any further advice or tips shoot them my way & thanks