toomanytoys

My 06 dvx 400 has a Suzuki engine in it. And for the second time it has dropped a valve (2 different cylinder heads) Each time it was the valve locks that let go. Is this a common problem with these engines?

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?

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......

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".

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.......

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?

Can the head come off without removing the engine first?

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?

Good stuff. More things I can check. Thank you

I took the bike out for a ride with some friends this weekend. It ran perfectly. Lots of power. I had a hard time keeping the front tires on the ground. It just wouldnt idle. I could pull the motor down in gear until it started bucking and it didnt stall. But if I put it in neutral it tried to stall. How about the valves? Could I need an adjustment? Can they be adjusted? The top end of my motor is a little noisy compared to my friends 06 kfx400.

I started thinking about the compression as well. I just dont get how it went from running fine to not running at all in less than 5 min. When I first started it that morning it fired right up and settled into a nice idle and after letting it warm up I started down the trail. About a quarter mile later it just shut off and the problems started

Heres an update : I got a rebuild kit for the carb and when I opened it up I found lots of dirt in the float bowl and some scale throughout. After a thorough cleaning and a rebuild there is no difference. Its still hard to start and once I get it started it wont idle. I have also changed the vacuum hose and the intake boot is in great shape with no leaks. Im starting to wonder if I have multiple problems here. Could there be a crack in the head maybe?

I used a vacuum pump to test the valve. It opened at about 2 inches of vacuum. I tested the hose and there were no leaks either. I will check the intake boot. It seems to be really lean right now. I have to put the choke on and hold the throttle wide open to get it to start. It will not stay running at idle. I dont seem to have any control with the idle screw either. Its either racing or stalling. Im getting alot of backfires now as well.

Okay I did a little testing. I applied vacuum to the petcock and the fuel flowed quite easily. So it looks like the valve is good, I guess it is a carb problem. Rebuild time?

I have a 06 dvx 400 that has a strange fuel problem. It seems that there isnt any flow coming from the tank when the valve is in the "res" or "on" position. The only time I get any fuel is when the valve is turned to the prime position. And its only a trickle at that. I tookthe valve off of the bottom of the tank and it is clean inside and out. Has anyone else had this problem? Im having a hard time keeping this thing running like this.