200 Knock/pop: Sounds like metal on metal
Posted: 12:25 am Oct 07 2017
Hello all:
New member here.
I have just started to hear a disturbing metallic knock in my 2000 KDX200. This does not seem similar to the other "knock" threads I have read here, hence this post.
The bike appeared almost completely stock when I picked it up last winter, my first KDX, but not my first 2-stroke. (I see NO reason to prefer my old '92 YZ250 over the sweet KDX!) The piston appeared to be the original, which I replaced with new Wiseco piston, rings, wrist pin & bearing. De-spooged the KIPS system.
After nine total hours of riding, I felt pretty familiar with the engine characteristics, sounds, and rattles.
A couple weeks ago, 45 Miles into the 60 mile Rampart Range Poker Run, I dumped it (mostly inverted) on a slow-speed rocky switchback downhill. Not to suggest that as a cause, but within a few miles, I began noticing what I would best call an occasional pop at the un-aggressive throttle I was applying through the trails. Occasional meaning once or twice every few seconds. It also seemed like a "miss" in that it seemed like the power dropped for a split second coincident with the pop. I babied it to the end of the run. Clutch action and shifting did not seem to be affected. After finishing I could listen more closely, and it would happen even at idle. There I was able to hear a metallic-sounding knock every several seconds that sounded quite bad to me. The engine stuttered as if it was going to quit in the instant after the knock, like some thing was actually impeding the movement or rotation of something in the engine. <Serious worry started here.>
I neglected to take a video for audio evidence. Instead, I tore the top end off expecting a mangled KIPS valve and a destroyed piston. Instead, everything looked like it did when I assembled it ten riding-hours earlier. Piston and rings look fine ( I did not completely disassemble the KIPS yet, but it looks and works fine from the outside.) I drained the oil, which appeared to be clean. Coolant level was good.
However: I did notice (looking more closely than when I installed the piston) a really rough edge to the right side flywheel per the photo below:
Yikes, is that normal? Maybe from the original casting of the flywheel blank? If normal, then maybe just a red herring.
And here is a photo looking down between the flywheels (seeing the little puddle of purple Yamalube 2R down there and no chunks of anything):
I measured the connecting rod big-end side clearance and it was nicely in spec (0.46mm)
Anything else I should do before buttoning it up and trying again? If it goes back together as-is, I will be sure to record the sound for y'all to hear.
Thanks for any suggestions!
Jay
New member here.
I have just started to hear a disturbing metallic knock in my 2000 KDX200. This does not seem similar to the other "knock" threads I have read here, hence this post.
The bike appeared almost completely stock when I picked it up last winter, my first KDX, but not my first 2-stroke. (I see NO reason to prefer my old '92 YZ250 over the sweet KDX!) The piston appeared to be the original, which I replaced with new Wiseco piston, rings, wrist pin & bearing. De-spooged the KIPS system.
After nine total hours of riding, I felt pretty familiar with the engine characteristics, sounds, and rattles.
A couple weeks ago, 45 Miles into the 60 mile Rampart Range Poker Run, I dumped it (mostly inverted) on a slow-speed rocky switchback downhill. Not to suggest that as a cause, but within a few miles, I began noticing what I would best call an occasional pop at the un-aggressive throttle I was applying through the trails. Occasional meaning once or twice every few seconds. It also seemed like a "miss" in that it seemed like the power dropped for a split second coincident with the pop. I babied it to the end of the run. Clutch action and shifting did not seem to be affected. After finishing I could listen more closely, and it would happen even at idle. There I was able to hear a metallic-sounding knock every several seconds that sounded quite bad to me. The engine stuttered as if it was going to quit in the instant after the knock, like some thing was actually impeding the movement or rotation of something in the engine. <Serious worry started here.>
I neglected to take a video for audio evidence. Instead, I tore the top end off expecting a mangled KIPS valve and a destroyed piston. Instead, everything looked like it did when I assembled it ten riding-hours earlier. Piston and rings look fine ( I did not completely disassemble the KIPS yet, but it looks and works fine from the outside.) I drained the oil, which appeared to be clean. Coolant level was good.
However: I did notice (looking more closely than when I installed the piston) a really rough edge to the right side flywheel per the photo below:
Yikes, is that normal? Maybe from the original casting of the flywheel blank? If normal, then maybe just a red herring.
And here is a photo looking down between the flywheels (seeing the little puddle of purple Yamalube 2R down there and no chunks of anything):
I measured the connecting rod big-end side clearance and it was nicely in spec (0.46mm)
Anything else I should do before buttoning it up and trying again? If it goes back together as-is, I will be sure to record the sound for y'all to hear.
Thanks for any suggestions!
Jay