Noise in pipe after rebuild

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Ed5786
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Noise in pipe after rebuild

Post by Ed5786 »

So I got done doing a top end rebuild this weekend, and noticed a noise in the expansion chamber I never noticed before. When I rev the bike with no load, it makes a sound like something bouncing around inside the pipe while the engine is decelerating. I didn't notice it while riding it during break in, just when free reving from idle. It's an fmf gnarly desert pipe. I do not have much 2 stroke experience, is this normal?
1998 KDX200
Fmf gnarly woods
Boyesen reeds
13/49 gearing
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Noise in pipe after rebuild

Post by Jaguar »

heck no it's not normal. pull the pipe off and let what ever is in it come out.
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Julien D
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Re: Noise in pipe after rebuild

Post by Julien D »

And check your KIPS valves.
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Ed5786
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Noise in pipe after rebuild

Post by Ed5786 »

The noise is from combustion, just to be clear. I'm just not sure if it's a "ping", or just a common sound from the tin can sounding fmf pipe. It sounds crisper in general, I just want to be sure this isn't what pinging sounds like. It's the typical deceleration sound with a couple noticibly louder " TING TING TING's"
1998 KDX200
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doctord23
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Noise in pipe after rebuild

Post by doctord23 »

Check to make sure that the pipe isn't touching the frame.
Sounds can get amplified if it is.
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Re: Noise in pipe after rebuild

Post by KDXGarage »

Also, check to be sure the kickstarter end is not touching.
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Re: Noise in pipe after rebuild

Post by Ed5786 »

Negative on both kickstarter and frame contact. I'll try to figure out how to post a vid later when I get time. Then you guys can hear it and see if I'm just being over cautious. But until then, here is how I am tuned.

45pj
Needle in middle position
158 main jet
Boyesen 607's.

Air temps have been low to mid 40's
1998 KDX200
Fmf gnarly woods
Boyesen reeds
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Re: Noise in pipe after rebuild

Post by Tedh98 »

Need to know your altitude, otherwise your jetting information is useless.
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Re: Noise in pipe after rebuild

Post by Ed5786 »

600-700 feet
1998 KDX200
Fmf gnarly woods
Boyesen reeds
13/49 gearing
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bufftester
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Re: Noise in pipe after rebuild

Post by bufftester »

You just did a top end, so your compression is likely much better than previously. You didn't mention what ratio you are running or what a plug chop looks like. Could be a bit lean.
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Re: Noise in pipe after rebuild

Post by Ed5786 »

I'm running 50:1 premix. I have not had a chance to do a plug chop yet. After break in I did run it hard a little bit and it did feel a bit lean. Bogged a bit on the bottom at times after running hard.
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Re: Noise in pipe after rebuild

Post by Julien D »

50:1 is pretty light on the oil for a KDX. Just IMO and all. 50:1 seems to be fine for some folks.
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Re: Noise in pipe after rebuild

Post by Ed5786 »

Julien D wrote:50:1 is pretty light on the oil for a KDX. Just IMO and all. 50:1 seems to be fine for some folks.
That was going to be another question. I ran 40:1 before. After much reading on the web I decided to go 50:1 because the general consensus was its fine for trail riding. And I figured once gas got old enough I don't want to put it in the bike, I can just run it through the chainsaw, weed eater and blower since they all burn 50:1. However I am probably going to go back to 40:1 in the KDX for peace of mind. Right now I run Klotz TCW3 premix. What premix gets the popular vote amongst you folks?
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Fmf gnarly woods
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Re: Noise in pipe after rebuild

Post by bufftester »

Ed5786 wrote:...What premix gets the popular vote amongst you folks?
Lol, that's one of those questions you don't ask without starting a pages long discussion... :roll:

As long as it's 2 stroke oil, and you stick with the same brand/same ratio you'll be fine. Change anything and you may have to rejet. IMO I agree with Julien that 50:1 seems light, but lots of guys on here run it with no issues. Same with 32:1 (OEM recommendation) lots of guys run it (including my dad in his 94 which has had exactly 0 issues in its lifetime), though it seems my 220 smokes way too much at that ratio. 40:1 is popular because the math is easy :grin: Just pick one, jet to it and then stick with it.
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Noise in pipe after rebuild

Post by patreilly »

Hate to tell you, I have religiously used AMSOIL Sabre 100 to 1 for 35 years in every application you can name without any problem. I always break in new engine as recommended by mfg. then go to Sabre AMSOIL.
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Re: Noise in pipe after rebuild

Post by Friedom »

Ed5786 wrote:
Julien D wrote:50:1 is pretty light on the oil for a KDX. Just IMO and all. 50:1 seems to be fine for some folks.
That was going to be another question. I ran 40:1 before. After much reading on the web I decided to go 50:1 because the general consensus was its fine for trail riding. And I figured once gas got old enough I don't want to put it in the bike, I can just run it through the chainsaw, weed eater and blower since they all burn 50:1. However I am probably going to go back to 40:1 in the KDX for peace of mind. Right now I run Klotz TCW3 premix. What premix gets the popular vote amongst you folks?
Did you rejet when you switched to 50:1? And is it the same compression piston as you had before?
My 91 was really loud and had a ringing coming off the pipe. 20 hrs later I had a hole in the piston.
...make sure you keep your rads full...

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Re: Noise in pipe after rebuild

Post by Ed5786 »

Friedom wrote:
Ed5786 wrote:
Julien D wrote:50:1 is pretty light on the oil for a KDX. Just IMO and all. 50:1 seems to be fine for some folks.
That was going to be another question. I ran 40:1 before. After much reading on the web I decided to go 50:1 because the general consensus was its fine for trail riding. And I figured once gas got old enough I don't want to put it in the bike, I can just run it through the chainsaw, weed eater and blower since they all burn 50:1. However I am probably going to go back to 40:1 in the KDX for peace of mind. Right now I run Klotz TCW3 premix. What premix gets the popular vote amongst you folks?
Did you rejet when you switched to 50:1? And is it the same compression piston as you had before?
My 91 was really loud and had a ringing coming off the pipe. 20 hrs later I had a hole in the piston.
...make sure you keep your rads full...

"Fun Wheel Drive"
I did not rejet, other than the pilot and needle. It had a 42 pilot, and I went to 45. And I raised the needle one clip. I just bought this bike a little over a month ago. The previous owner also mentioned it has a BEP needle, not sure if that's much different than the stock needle. I may just order a DEL since that seems to be a popular choice. Or, just order a JD jet kit since I don't really have much time to tinker and experiment getting the jetting correct for different conditions.
1998 KDX200
Fmf gnarly woods
Boyesen reeds
13/49 gearing
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Re: Noise in pipe after rebuild

Post by Friedom »

Ed5786 wrote:
Friedom wrote:
Ed5786 wrote:
That was going to be another question. I ran 40:1 before. After much reading on the web I decided to go 50:1 because the general consensus was its fine for trail riding. And I figured once gas got old enough I don't want to put it in the bike, I can just run it through the chainsaw, weed eater and blower since they all burn 50:1. However I am probably going to go back to 40:1 in the KDX for peace of mind. Right now I run Klotz TCW3 premix. What premix gets the popular vote amongst you folks?
Did you rejet when you switched to 50:1? And is it the same compression piston as you had before?
My 91 was really loud and had a ringing coming off the pipe. 20 hrs later I had a hole in the piston.
...make sure you keep your rads full...

"Fun Wheel Drive"
I did not rejet, other than the pilot and needle. It had a 42 pilot, and I went to 45. And I raised the needle one clip. I just bought this bike a little over a month ago. The previous owner also mentioned it has a BEP needle, not sure if that's much different than the stock needle. I may just order a DEL since that seems to be a popular choice. Or, just order a JD jet kit since I don't really have much time to tinker and experiment getting the jetting correct for different conditions.
So you made the mix richer with a larger PJ, and you made it richer by putting less oil in the fuel (50:1 instead of 40:1), and you made it richer in the midrange moving the needle up one clip. Was the bike at a different altitude/location before the rebuild?

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Ed5786
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Re: Noise in pipe after rebuild

Post by Ed5786 »

No I bought it local
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Fmf gnarly woods
Boyesen reeds
13/49 gearing
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Re: Noise in pipe after rebuild

Post by Friedom »

Then that seems like a lot of change to to fuel/air ratio. Plug chops?

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