200 Knock/pop: Sounds like metal on metal

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200 Knock/pop: Sounds like metal on metal

Postby TheWhatNow? » 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:
Image
Yikes, is that normal? Maybe from the original casting of the flywheel blank? If normal, then maybe just a red herring. :please:

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):
Image
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
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Vossman » 08:13 pm Oct 07 2017

If it was the motor would it not do it all the time?
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Re: 200 Knock/pop: Sounds like metal on metal

Postby John_S » 10:36 pm Oct 07 2017

Sorry to hear about the problem. I'm taking a stab at it but I would remove the flywheel, make sure the woodruff key is in place, and also that the timing didn't somehow get knocked out of whack. If timing is way off it can have a pretty deep sounding knock to the engine.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Jason » 10:47 pm Oct 07 2017

What octane are you using? Fresh?
Thank you, Julien D for all your hard work!
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Re: 200 Knock/pop: Sounds like metal on metal

Postby ohgood » 08:04 am Oct 08 2017

what you're describing sounds like detonation/pre ignition , which is very bad for engines. I would dump the fuel, start with a fresh tank of gas and try again. you'll usually hear it more under slight/heavy load when the engine is hot.

your timing should be checked, pull the flywheel and look at the stator marks for Advanced timing.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Jason » 11:04 am Oct 08 2017

Also, you are at hat elevation with what jetting?

Plug pic?
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Re: 200 Knock/pop: Sounds like metal on metal

Postby TheWhatNow? » 12:11 am Oct 09 2017

I am running at about 9000ft. I can get a plug pic shortly. It looks a little rich, dark brown/black but not badly fouled (?) Currently running 148 main, 40 pilot. Was thinking of going leaner. R1174K needle, second clip position from top. I was at the end of a long ride (5o miles into 60 mile Poker Run, so it had been running for a few hours with one 20 min break.) Was running fresh gas (well, less than a month old), mid grade (which up here in Denver is 87) In the future I will stick with high octane. Yamalube 2R, 32:1. I will look into pulling the flywheel and checking the timing (new territory for me).
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Julien D » 07:50 am Oct 09 2017

Sounds like pre-ignition to me. Don't run 87, and don't store in plastic containers more than a week or so.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Jason » 09:44 am Oct 09 2017

87 octane that was a month old. You're killing me, well, not me, but your engine.

The manual says fresh fuel daily. The manual says high octane.

Do try fresh fuel and high octane.
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200 Knock/pop: Sounds like metal on metal

Postby cornishwrecker220 » 10:18 am Oct 09 2017

If 87 is all that's available in your area then I would add some octane booster to bring your fuel up to a better burn quality ....
Definitely drain fuel from your tank after use as the ethanol not only absorbs moisture faster through plastic tanks/containers but destroys rubber fuel lines & seals too !
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200 Knock/pop: Sounds like metal on metal

Postby pumpguy » 11:50 am Oct 09 2017

Check the website <pure-gas.org> for ethanol free gas.

The pages are divided by states, then cities in alphabetical order. Each entry lists city, octane ratings available, address and phone number.

Nothing listed for Denver proper, but maybe one or more listed for Colorado is close enough.

My pilot buddy tells me ethanol free gas is FAA legal to use if it's less than 5 years old. I have a station near me, and got a couple gallons just for the KDX.

One caution, if it's dispensed from a single multi-octane blend hose, I would put the first gallon in the car's tank to avoid any left over ethanol blended fuel from the last sale.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby bufftester » 07:34 pm Oct 09 2017

That looks like normal casting marks on the crank, definitely not the source of your issues. It sounds a lot like detonation to me as well. IIWM I'd pull the flywheel to check the woodruff key and your baseline timing. Also check your exhaust tract for any obstructions, if you have an aftermarket silencer, repack it. Try retarding the timing a bit. A new plug is a given, as it can be the heat source for the detonation problem. At least it's not a 4T and you don't have to worry about valves lol.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Jason » 09:25 pm Oct 09 2017

I say DO NOT waste another second of time on anything until you have fresh fuel (mixed same day as riding) high octane fuel (preferably non-ethanol).

And ALL of you that leave it in the tank, consider draining it back out into a metal can. Thanks for reading. :prayer:
Thank you, Julien D for all your hard work!
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Re: 200 Knock/pop: Sounds like metal on metal

Postby TheWhatNow? » 10:37 pm Oct 09 2017

Ok!
I accept the criticism for the octane rating and storage failures on my part. Any gas more than a week old will go into my truck instead of the KDX. I did look for ethanol-free gas in Denver a while back too and was not finding any. I'll keep trying. It looks like I can do the timing check and woodruff key inspection after the top end is back together. But it also looks like I will need a flywheel puller and flywheel holder. Do any of you approve of the cheesy "stuff a bunch of nylon rope into the spark plug hole" technique in place of a flywheel holder? Also, the Kawi flywheeel puller part in the service manual looks much larger than the standard "flywheel puller". Is the generic M27x1 thread flywheel puller an OK tool for this?

For the actual timing adjustment, to retard a "little bit", how much stator rotation are we talking about? The service manual shows me the direction, not the amount.

Thanks for all the help!
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Jason » 11:11 pm Oct 09 2017

I would not worry about the other stuff, just the gas. If that doesn't not do it, then worry about other stuff.

I once used the rope trick, worked for me. BE CAREFUL!!! DO NOT let it go down into a port. Make sure you are about at TDC when you put the rope in.

A cheap puller will work, 27 mm x 1.0 mm, left hand thread. Dennis Stubblefield Sales used to have good ones that were not too expensive. They were on eBay as DSS labelled.

See if there is a drag racing car engine hop up place anywhere around. They will either sell high dollar fancy gasoline or know where the locals are buying their gas.
Thank you, Julien D for all your hard work!
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Vossman » 06:39 am Oct 10 2017

TWN, I have a puller and flywheel holder you can borrow, I'm just down 25 in COS.
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200 Knock/pop: Sounds like metal on metal

Postby pumpguy » 10:44 am Oct 10 2017

I have a Vice Grip #20R locking chain clamp that I use for holding pump impellers. Works perfectly for holding my KDX flywheel, or just about anything within it's capacity range. I added a few links of #428 chain to increase it's capacity.

A very useful tool to have in the toolbox.
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200 Knock/pop: Sounds like metal on metal

Postby John_S » 07:04 am Oct 11 2017

The Tusk lock up tool is nice to have in the toolbox. It fits in the spark plug hole and is great for flywheel and clutch work.
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Re: 200 Knock/pop: Sounds like metal on metal

Postby TheWhatNow? » 11:56 pm Oct 11 2017

Thanks all for the additional tips. I will order the Tusk lock-up tool and a stator cover gasket.

I also looked again at pure-gas.org: we do have a few places in the Denver area, just none with an actual Denver address.

Now to find an real steel gas can!
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Re: 200 Knock/pop: Sounds like metal on metal

Postby Julien D » 08:16 am Oct 12 2017

I have a couple of these and like them....

https://www.amazon.com/Eagle-UI-50-FS-G ... al+gas+can
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