God-awful KDX220 Rattle

[Daaj65]

Here goes! Probably the one-millonth to ask. 2004 KDX220 has developed (suddenly) a horrible rattle from what I think is top-side. I'm not ready to believe in my mind it's the lower end main crank bearing (been through that before). Rattle is bothersome, but overwhelming issue is the engine bog with little-to-now idle which eventually leads to complete chock-down and engine kill, terminating with significant back-fire out of pipe. Can't even ride, much less put in gear and take-off. Engine dies after about 3 minutes of idle and throttle manipulation just to keep running.

Any thoughts? Willing to take top-end off again to look around more. Power valve assembly?? Can study BikeBandit schematic long enough to completely remove and replace.

Want an expert to lead me in the right direction. Days ago changed piston rings, BUT problem was occuring before that!

 

[Hoffies]

Just as an easy to do precaution, check whether your flywheel has not come loose, as if it has and perhaps sheared key you could have a KDX running erratically and have a rattle/backfire etc?

 

[Daaj65]

Thanks. Teach me. What exactly do you mean? I know what you're talking about (the flywheel), but come loose? I had previously checked for warn / fading lower bearing by applying pressure up/down and left/right of the flywheel to see if there was noticable play. But what do you mean come loose? What is my give away sign?

 

[SVandal]

pull the bolt from the center of the flywheel, then use a flywheel puller to pull the flywheel and check the woodruff key (Part #92038 in the generator diagram on bike bandit). If is in 2 pieces, order a new one and a new generator cover gasket and reassemble. If not, look at something else, such as the kips valve (check justkdx website for a good description and picture intensive breakdown of the process). The flywheel is also the timing for your spark and if the woodruff key shears then it allows the flywheel to move and throw off your timing. Not a bearing issue, simply a 3.00 part with a checkered history.

 

[danfree]

I have heard the stock piston on 220's are prone to early failure. Maybe a bit of the piston skirt has broken off and is tumbling around. If the flywheel is OK, then it may be worth a look-see.

 

[crhines]

I had this happen on my 99' KDX220 - I heard a loud rattle for 2-3 seconds and then it completely seized. Ground up the piston skirt into a million pieces.

 

[Hughes 097]

the only thing that rattles on my kdx is the kick starter haha

 

[Green Hornet]

The "back fire" made me think of TIMING....Do as the others have said & check the stator to see if it came loose....

 

[jason33]

probly a noisy wrist pin bearing-, or piston skirt slapping the cylinder wall - check the piston to cyl clearance-, and wrist pin bearing for ware
you can tell the 2 sounds apart from each other-
the pin bearing sounds bright and pingy- the piston / slap- is a duller sound

 

[Daaj65]

Thanks to all who have commented. As work allows(!!!!), I will proceed. I have it apart now.

 

[Daaj65]

No problems whatsoever with woodruff key or flywheel. No problem with power valve operation. Cyclinder looks beat to death from piston. Think I have big problem with cylinder surface (shiny vs. dull spots of different surface texture). Any comments? Can it be simply honed, or is it special material????????!!!!!!!!!!!!