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2008 KX 450 Weird engine noise

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Alright, I have been on a non stop chase to finding the cause of a weird enging noise. The noise sounds like it is coming from the top end. It sounds almost like a dry bearing, or metel rubbing together where it shouldn't be. I thought it was maybe the exhaust cam bearing (I took it off and noticed some play so I replaced it), didn't solve it. I have replaced the timing chain not to long ago. (Haven't replaced to cam chain tensioner yet). My bike has quite a bit of hours on it. I bought it new in 2008 and have rode it often since then, mainly tracks and sand dunes. The valves are in good shape, no carbon build up or anything. If anyone has any info or comments that would be great. It would save me a lot of time and stress. Thanks in advance.

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Metal rubbing together where it shouldn't be would result in metal frags in the oil. Are you seeing any? When is the last time you pulled the cylinder off? Could be a little piston slap. Only way to tell is to pull the cylinder off.

Edited by Justin Hambleton

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Metal rubbing together where it shouldn't be would result in metal frags in the oil. Are you seeing any? When is the last time you pulled the cylinder off? Could be a little piston slap. Only way to tell is to pull the cylinder off.

There has been a little metal frags that i have seen. Nothing major at all tho. I have the cylinder and everything off now. The cylinder wall is in great shape. The side of the piston has some pretty mean scratches in it. I had my bro measure my cylinder with a CMM machine. The cylinder measured 3.7801 inches. Which is only .0001 oversized. The piston on the other hand measured 3.7612" on the top, and 3.775" around the center of the piston. Which the standard piston should measure between 3.7783-3.7787. So it is quite a bit smaller then it should be. Could this be causing excessive noise?

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There has been a little metal frags that i have seen. Nothing major at all tho. I have the cylinder and everything off now. The cylinder wall is in great shape. The side of the piston has some pretty mean scratches in it. I had my bro measure my cylinder with a CMM machine. The cylinder measured 3.7801 inches. Which is only .0001 oversized. The piston on the other hand measured 3.7612" on the top, and 3.775" around the center of the piston. Which the standard piston should measure between 3.7783-3.7787. So it is quite a bit smaller then it should be. Could this be causing excessive noise?

I would replace that piston, especially if you have over 100 hours on that motor, which it sounds like you do.

Are those metal frags ferrous (magnetic) or not? If their non-ferrous, it's aluminum, which could be from the piston skirt or a few other parts in the motor (i.e. shift drum, although rare). If the metal frags are magnetic, it's likely from a bearing or the tranny. If you're losing a bearing, you'd see magnetic metal frags every time you change the oil.

Have you had to shim the valves? Carbon build up or lack thereof doesn't indicate much. What's important is if those valves are cupping.

Edited by Justin Hambleton

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Does it sound kind of like a really coarse whistle?

Ya you could almost say that. But its not so much a whistle. Is More like a loud piston noise or something. ha its really hard to explain. sorry

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I would replace that piston, especially if you have over 100 hours on that motor, which it sounds like you do.

Are those metal frags ferrous (magnetic) or not? If their non-ferrous, it's aluminum, which could be from the piston skirt or a few other parts in the motor (i.e. shift drum, although rare). If the metal frags are magnetic, it's likely from a bearing or the tranny. If you're losing a bearing, you'd see magnetic metal frags every time you change the oil.

Have you had to shim the valves? Carbon build up or lack thereof doesn't indicate much. What's important is if those valves are cupping.

I have already replaced the piston once. The new piston is not very old. Maybe 20 hrs on it (maybe). The valves are not cupped, I had to replace the intake valves a while back tho. Someone accidentally had to timming wrong and bent them. Ha ha. oops. I check my valves regularly and change accordingly. The sounds is for sure coming from the top of the motor. If you put your ear next to the bottom of the motor you can't really hear it, as you move up it slowly get louder and louder farther up you go. Ill check when i get home if the metal is magnetic or not.

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A low hour piston shouldn't have major scratches or scoring on the skirt. That suggests dirt and debree is getting by or the rings weren't installed properly. Little details like the ring gaps being staggered are important.

Post a pic of that piston if you can.

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Did you mic the piston and rings before installing them, to make sure they were what they said they were on the box?

You usually have to file the ring ends down to get the proper clearance, before installing them.

Did you do a leak-down test after replacing the valves? Usually a bent valve means a damage seat as well.

Check for:

- light non-ferrous glitter in oil: piston skirt, shift drum, manf debris

- light ferrous glitter: tranny wear, tranny bearing wear

- dark or gold non ferrous: big end bearing: open motor now

Have you ever cleaned the bypass screen behind the flywheel? It is usually clogged shut with silicone from the factory after one ride, and causes oil starvation.

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Did you mic the piston and rings before installing them, to make sure they were what they said they were on the box? You usually have to file the ring ends down to get the proper clearance, before installing them. Did you do a leak-down test after replacing the valves? Usually a bent valve means a damage seat as well. Check for: - light non-ferrous glitter in oil: piston skirt, shift drum, manf debris - light ferrous glitter: tranny wear, tranny bearing wear - dark or gold non ferrous: big end bearing: open motor now Have you ever cleaned the bypass screen behind the flywheel? It is usually clogged shut with silicone from the factory after one ride, and causes oil starvation.
A low hour piston shouldn't have major scratches or scoring on the skirt. That suggests dirt and debree is getting by or the rings weren't installed properly. Little details like the ring gaps being staggered are important. Post a pic of that piston if you can.

I did not check all of that stuff on the piston. ha. And i have never checked the screen behind the flywheel. I will for sure before it goes back together. Im gonna check oil for the shavings tomorrow. I installed the rings according to my service manual. Im positive that the rings were put in right. The only thing i didn't really do is check the ring gap. The sound I hear almost sounds like something is dry. So maybe is has something to do with the oil pump. I'm surprised that the cylinder is not damaged at all after looking at the scratches on the piston.

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For some perspective, here's what near catastrophic failure looks like in terms of metal shavings in the motor and other misc damage. This is what happens when you run a pre-production K&N air filter in your KTM while prerunning the Baja 500:

IMG_2259.jpg

IMG_2244.jpg

IMG_2348.jpg

IMG_2334.jpg

Unfortunately, Kawis don't have magnetic drain plugs, but all you need to do is run a magnetic probe in your oil catch can. Hopefully there's not a chia pet on the end of it like mine :bonk:

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A low hour piston shouldn't have major scratches or scoring on the skirt. That suggests dirt and debree is getting by or the rings weren't installed properly. Little details like the ring gaps being staggered are important.

Post a pic of that piston if you can.

Im trying to post a pic but its saying that i am using the wrong format! UGGGGH

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For some perspective, here's what near catastrophic failure looks like in terms of metal shavings in the motor and other misc damage. This is what happens when you run a pre-production K&N air filter in your KTM while prerunning the Baja 500: IMG_2259.jpgIMG_2244.jpgIMG_2348.jpgIMG_2334.jpg Unfortunately, Kawis don't have magnetic drain plugs, but all you need to do is run a magnetic probe in your oil catch can. Hopefully there's not a chia pet on the end of it like mine :bonk:

Holy cup cake batman!!!! thats insane dude, i missed something, how'd the air filter do that?

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I did not check all of that stuff on the piston. ha. And i have never checked the screen behind the flywheel. I will for sure before it goes back together. Im gonna check oil for the shavings tomorrow. I installed the rings according to my service manual. Im positive that the rings were put in right. The only thing i didn't really do is check the ring gap. The sound I hear almost sounds like something is dry. So maybe is has something to do with the oil pump. I'm surprised that the cylinder is not damaged at all after looking at the scratches on the piston.

So just curious... could that much clearance between the piston and cylinder cause a different noise on the top end? That was the main reason for pulling my bike apart. Then i found the piston was scratched, maybe the scratched piston is causing noise? Any thoughts.

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So just curious... could that much clearance between the piston and cylinder cause a different noise on the top end? That was the main reason for pulling my bike apart. Then i found the piston was scratched, maybe the scratched piston is causing noise? Any thoughts.

Yes it can.

Mic'ing the parts before install is a must.

You gotta check that oil screen as it is a major oil path issue....

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My parts should be here in about a week. I ordered the stock kawasaki piston/rings, a new cam chain tensioner, chain tensioner guild. I'll put all that in and then see what happens. Hopefully all goes well.

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My parts should be here in about a week. I ordered the stock kawasaki piston/rings, a new cam chain tensioner, chain tensioner guild. I'll put all that in and then see what happens. Hopefully all goes well.

You know how to check the ring gap?

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Mic the cylinder to verify spec, drop in each ring and check the end gap.

That seems pretty simple. I already have the cylinder measurment. So all I'll need to do is drop in the rings and measure the gap. Simple enough. So I cleaned the oil filter screen on the magneto side today. There was quite a bit of silicone stuck to it. Some small metal shavings, Nothing to crazy. I would kinda imagine there to be a lot in there. I would have to say that the screen was about a quarter of the way clogged. Surprising. I have not cleaned that screen since i bought the bike new in 08. Honestly i didnt even know there was an oil screen down there. Good to know. Is there another oil filter on the other side of the case. (behind the clutch)? I've got the right side engine cover and everything looks pretty good. No shavings, fragments of metal. Thanks in advance

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