2006 Arctic Cat DVX400 Blown engine?

[toomanytoys]

Went riding today and my 06 dvx400 shut off on me again. When I tried to restart it the motor spun over very easily, like there is little to no compression. The motor was very noisy today. It sounded like loose rocker arms.

So what do you guys think? Rebuild time?

[sillymaster]

i have a 2007 with very low hours on it that i just bought not to long ago. i hope that dont happen to mine

[superchief]

i would say pull the top end and see wat the piston looks like

[toomanytoys]

Can the head come off without removing the engine first?

[DirtDemon]

There are no rocker arms, the cams sit directly above the valves, there is a bucket tappet with a shim underneath for valve adjustment. Take off the valve cover first and the valve train, you could have some tight or stuck valves being held partially open, there could be a problem with your compression release system. Start there before removing the head. You should be able to get to the top of the motor by removing the gas tank.

[Ajmboy]

* Added year, make, and model, to thread title.

[toomanytoys]

There are no rocker arms, the cams sit directly above the valves, there is a bucket tappet with a shim underneath for valve adjustment. Take off the valve cover first and the valve train, you could have some tight or stuck valves being held partially open, there could be a problem with your compression release system. Start there before removing the head. You should be able to get to the top of the motor by removing the gas tank.

Thats good stuff. I know there arent any rocker arms, I was just trying to describe what the motor sounded like. Sorry for the confusion.

I am leaning toward a broken timing chain myself. I cranked the bike and put my hand over the muffler and instead of feeling compression pulses I got suction. That would mean the exhaust valve is open right? What about the compression release you mentioned? Could that do it?

[rideon56]

You said it was turning over real easy,check your compression,it sound like it could have jumped time,if you dont have a compession gage hold your thum tight over plug hole ,get someone to turn engine over .The compression should blow your thum off the hole if not your compression is to low.

[superchief]

i would put the bike at TDC and check the valve clearence

[toomanytoys]

Well I finally got around tolooking at it and this is what I found: The exhaust cam retainer came loose (hence the noisy valvetrain) and tore up the cam and cylinder head. So the top end is shot. Im done with this p.o.s.

It is now up for sale for parts. With the exception of the engine everything else is in pretty good shape and it has a aftermarket exhaust.

Im taking offers.......

[DirtDemon]

That's a crappy end to the situation, I'm sorry to hear that it turned out that way. I know it's frustrating.

[toomanytoys]

And the worst thing is I only got to ride it once before the problems started. I should have just shut it down and brought it home at the first hint of noise but like a dumbass I listened to my friends "oh its just a little noise, probably needs a chain adjustment".

[DirtDemon]

IMO, it's a good machine and worth fixing. If it were me, I would be looking for an '87 or newer LT-250R Quadracer motor to put in there. That's just me, the regular motor is a good motor too. Don't think that this is typical for these machines, they are regularly reliable.

[toomanytoys]

Well its fixed. I changed the head and the cams. After putting it all back together,it started right up. Although it is still noisy. I hope this doesnt happen again......

[DirtDemon]

Good choice, I hope it stays reliable for you.

[toomanytoys]

Well it went boom again. After riding for about an hour the motor started to sound like a sewing machine so I turned around and headed back. About a mile later I heard a loud ping sound and the motor locked up. After I got it home I took a look and this is what I found : the timing chain isnt broken and I can only turn the motor about 3/4 turn by hand before it locks up (forward or backward). The spark plug is crushed so I guess the piston hit it. The crank isnt broken either. Did I stretch the rod? The piston does move up and down when I turn the motor it just locks at tdc.

Ideas? Opinions?

[DirtDemon]

Wrong spark plug maybe, could be sticking out too far. Where did you get the head, it could have been shaved, if it was taken too far down, you would lose the necessary clearance needed for the piston to travel up without interference. It would also raise the compression, possibly to a level that would require race fuel or a mix of pump gas and race fuel. I would definately take the head off and take a look, if the piston hit the plug, it is likely that the piston is damaged. Sorry to hear about your bad luck. Let us know what you find.