Maintenance & Technical > KX500 Original

mystery noise

(1/3) > >>

matzilla:
Ok, I have this mystery noise at low idle. Sounds like a big vibration rattle. If I bump the throttle slightly it disappears. Sounds like it comes from the top end area, maybe the exhaust header or something. Really annoying and concerning. Has done it since we put it back together. My friend had originally said it could be due to wiseco's .004 recommendation for piston skirt clearance. Engine is 0.5mm over bore, stock stroke, all new bearings and seals, PC pipe, V force reeds, bored carb,  running 110 octane gas, 40:1 with dumonde tech oil. 60 pilot, 180 main, CEJ needle 3rd from the top. It runs a little rich, but not fouling plugs. - am constantly checking bolts and am wanting to figure this out. Any thoughts?

Larry Wiechman:

 Center KIPS valve flutter. The 4mm pins rattle in the spiral grooves on the barrel valves. You made the mistake of cleaning it up so nice and pretty when you rebuilt? :-D
 Thats my story, and I'm stick'n to it.
 
Larry

demographic:
Mine does the same and as all the bearings are new, the pistons fresh all I could think of was the centre KIPS valve, makes quite a clattering noise though doesn't it?

DoldGuy:
Could it be the Pipe Retaining Springs? These will cause some annoying rattle. I usually run a piece of fuel line over the length of the spring & leave just enough of the hook exposed to grab with a spring hook to install & this dampens just about all of their noise.

Just something to consider.

DoldGuy

BDI:
It's the kips valve. The blast of exhaust gasses pushes up on the center valve and lifts the whole valve up including the two vertical valves that ride on the cases. The are definitely louder when they are freshly cleaned but there are several things that help to make them louder.The noise comes from the vertical valves crashing back down on the cases after each cycle. You can dampen this sound based on the type of base gasket you use. The stock gasket has big holes under the valves so it's all metal to metal and allows there to be a lot of play in the valve but if you make or order gaskets with the small holes it will dampen the sound do to the gasket material separating the metal to metal contact.It will also tighten up the extra play in the valves by pushing up on the aluminum plugs that hold the valves in place. My bike has two metal base gaskets with an aluminum spacer and it is super loud. Hope this helps.

Navigation

[0] Message Index

[#] Next page