My engine is ****ed

[Axis400exRider]

i put this White Brothers rev box on my 400ex and my friend is like "i should test it out" so he hops on it and this thing is cold, it hasn't been ran for hours, and he just revs the crap out of it and it dies. And now i started it and when its running you hear this klank-klank noise coming from the engine. I don't dare start it again that would just make problems worse. Whats wrong with it??????????????

if i were you i would first beat the crap out of my friend then tear the engine apart to see whats up then get your friend to pay for whatever it needs then beat then beat the crap out of him again

[Axis400exRider]

do you think he blew it up? and if so can you fix a blown engine?

[250-R-250]

I have NO clue what I am talking about when it comes to four strokes, but Could it be the Rocker or Valves? Yea, a suggestion for you, when you get it fixed you should let it itle alittle before you gun it, and knocking sound isnt uncommon

[95300exrida]

it is possible that he blew it up and yes you can fix blown up engines.do a compression test and see what kind of compression it has and go from there.if its low then you prolly fried the rings or blew a hole in your piston but i dont think it would run if it was blown up.does it burn oil when you had it running?if everything is fine in the engine move on to your rocker arms, valves, cam, and cam chain and see if anything is wrong there.

[400Rider022]

beat the ****** **** out of him

[Axis400exRider]

Thanks for the advice, and i probly should beat the **** out of him, i'll probly miss a load of races but thats alright. peace.

[plkmonster2]

You "friend" (hmm) most likely revved it so high it floated the valves, and they hit the piston, or stretched the rod. I won't let anyone ride my things, unless I get the ride theirs. ;)

[Axis400exRider]

what happens when you float your valves?? do they get really tight?????

[plkmonster2]

The valves stay open a little bit because they are being thrown around so fast that the springs cannot return them the the closed position. If the engine is revved fast enough, the valves momentum can push them farther open than the cam usually does. When this happens, the piston hits the valves, and dents them, adn the piston. then they hit the seat, won't seat properly, and end up screwing up the seats, by denting them up.

[plkmonster2]

It doesn't sound like that though, since you said it still runs, and makes a clank. Sounds like a bad rod. The bearings are most likely shot.

[bigvforcer]

If you still have the stocks cams in the motor you WILL NOT BE ABLE TO DO A COMPRESSION TEST. If you do it will give you false readings. The decompression feature on the stock cam prevents you from getting ana accurate measurement.

[Axis400exRider]

Well him and his dad fixed it, they said they loosened the valves cause they were too tight, and it seems to idle good. I haven't ridden it yet though.

[DaveEX7]

Tear the engine down asap..... a piece of one of the rings might have snapped off and be rattling around the engine causing more damage

[freak400]

It's gonna cost money

[Got_Mort03]

well i had something similar happen to me my cam chain tensioner broke and threw the chain off the cam after breaking and caused my valves to stay open hit the piston and bent them costing me 400.00 to get replaced.....making a very bad noise on my way back to the house and after i shut it off it would not start again.....that was a very bad day.....i would check out my cam tensioner to see if the spring broke inside it, because your chain could be hitting the top of the cylinder head like mine was..good lucj to you.