Author Topic: any pipe bangs on 2stroke 300 se ?  (Read 564 times)

motif

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any pipe bangs on 2stroke 300 se ?
« on: February 14, 2020, 05:17:41 PM »
Today after few stalls during practice session strange metallic noises started to sound when coming off the throttle,
never had that before and bike has almost 30 hours.  When on the gas it's OK. Wonder what could happened to cause this?


papa_j

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #1 on: February 14, 2020, 09:45:20 PM »
Could it be your power valve?
Farmington, NM, USA

motif

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #2 on: February 15, 2020, 02:06:25 AM »
Could it be your power valve?

what about it?

hannesd

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #3 on: February 15, 2020, 09:03:51 AM »
after getting heavy on the throttle?  detonation?

alang

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #4 on: February 15, 2020, 10:28:28 AM »
Never happens on my 17 300
2017 Sherco 300 2T Factory
2016 Aprilia Tuono 1100 Factory
2019 Santa Cruz Tallboy Carbon R
Azle, Texas

motif

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #5 on: February 15, 2020, 01:01:18 PM »
after getting heavy on the throttle?  detonation?

not detonation, more like metallic ringing, at lower revs. Coming off the throttle and going up revs. At higher revs it's fine.
Happened all of the sudden one day after wheelies practice.

papa_j

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #6 on: February 15, 2020, 01:42:31 PM »
Could it be your power valve?

what about it?

At least on my gas gas,  if the power valve slack (I don't know if that is even a thing) was not set correctly you would get a rattle from the power valve that happened at low revs or coming off the throttle.   There was a youtube video that captured the sound pretty well but I couldn't find it.  The fix was adjusting the tension in the mechanical power valve device.   Since the power valve is operated by cable pulley and electric servo you may need to adjust the cable. 


https://youtu.be/910C8o3JFJ0
Farmington, NM, USA

cesllc

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #7 on: February 17, 2020, 03:46:19 AM »
My '17 300 SE has always done it, from the first ride when it was brand new. Right at very slight throttle opening and no load.  It buzzes like crazy.  Crack the throttle and it goes away. I have my bike plated and with stock gearing right around 50-55 mph on a level surface is when it really gets going bad.  I just did my first top end at 140 hours, I didn't notice any damage occurring from the noise, but I won't wait until 140 hours on the next rebuild.  The power valve bearings and seals were getting bad.  Haven't ridden since the rebuild. I also have spent considerable time perfecting the jetting.  I ended up going to a 42 pilot and and NED? (can't remember which one off hand) needle.  I found that the pilot needed to be a richer and then the needle learner.  The extra fuel from the richer needle seems to help the problem some.  I ride 0-800 ft, 50-80 degrees.
2017 300SE Six Days with racing plastic
2017 300SEF Six Days
Southwestern Michigan

motif

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #8 on: February 17, 2020, 07:14:02 AM »
My '17 300 SE has always done it, from the first ride when it was brand new. Right at very slight throttle opening and no load.  It buzzes like crazy.  Crack the throttle and it goes away. I have my bike plated and with stock gearing right around 50-55 mph on a level surface is when it really gets going bad.  I just did my first top end at 140 hours, I didn't notice any damage occurring from the noise, but I won't wait until 140 hours on the next rebuild.  The power valve bearings and seals were getting bad.  Haven't ridden since the rebuild. I also have spent considerable time perfecting the jetting.  I ended up going to a 42 pilot and and NED? (can't remember which one off hand) needle.  I found that the pilot needed to be a richer and then the needle learner.  The extra fuel from the richer needle seems to help the problem some.  I ride 0-800 ft, 50-80 degrees.

interesting because my stock pilot 42 and main 172 is rich as hell and causing lot of smooge...similar elevation and temperatures.  Planning to go with 38 pilot and 170 main.
Another thing os that banging  happened all of a sudden at 30 hours along with increased smooge.

cesllc

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #9 on: February 17, 2020, 08:38:13 AM »
Mine produces no spooge.  Lean up the needle (by diameter) until it cleans up, then set the clip position for fine tuning throttle response in the middle.  I'm also running a leaner main then you, but I don't remember what it is (maybe 168). I spent a lot of time making one jetting change, then riding for a day, then making one adjustment, and repeating until it was nearly perfect.  Was not happy with the JD needle.  I like the NEDX series so far. I think I'm running the NEDH on clip 3. The NEDX has a smaller tip diameter (then the stock N8RG) so it might need to be run with a leaner main jet (like the JD needles). But my bike is buttery smooth with excellent throttle response, no spooge, and doesn't foul plugs. I ride a lot at 1/8-1/2 throttle in the woods.
« Last Edit: February 17, 2020, 08:51:26 AM by cesllc »
2017 300SE Six Days with racing plastic
2017 300SEF Six Days
Southwestern Michigan

cesllc

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #10 on: February 17, 2020, 08:42:09 AM »
Sometimes I wonder if there is enough manufacturing variation from unit to unit that it affects jetting, so what works for one person doesn't for another in the same environment.  Definitely check your power valve cables.  I had one fail around 50 hours I think.  Oh, and I'm running the spark arrestor exhaust (Fresco) on mine.
2017 300SE Six Days with racing plastic
2017 300SEF Six Days
Southwestern Michigan

cesllc

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #11 on: February 17, 2020, 08:43:24 AM »
Also, there are two torsional return springs on the powervalve that can fail after a while.
2017 300SE Six Days with racing plastic
2017 300SEF Six Days
Southwestern Michigan

motif

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #12 on: February 17, 2020, 08:49:34 AM »
Also, there are two torsional return springs on the powervalve that can fail after a while.

is there any example about checking power valve?

cesllc

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #13 on: February 17, 2020, 08:57:52 AM »
There is a page in the maintenance manual that shows how to adjust the cables.  Last I knew that manual was available online.  One torsion spring is visible by removing the cover over the cables.  The other one I think is underneath the arm/pulley, so you have to remove the screw and the arm/pulley from the end of the powervalve shaft. The part that rides against the pins wear and weaken the springs, or cause them to break altogether.  Mine were very weak after 140 hours. It looks daunting at first, but if you are mechanical at all it's not hard to work on.
2017 300SE Six Days with racing plastic
2017 300SEF Six Days
Southwestern Michigan

motif

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Re: any pipe bangs on 2stroke 300 se ?
« Reply #14 on: February 17, 2020, 09:54:46 AM »
There is a page in the maintenance manual that shows how to adjust the cables.  Last I knew that manual was available online.  One torsion spring is visible by removing the cover over the cables.  The other one I think is underneath the arm/pulley, so you have to remove the screw and the arm/pulley from the end of the powervalve shaft. The part that rides against the pins wear and weaken the springs, or cause them to break altogether.  Mine were very weak after 140 hours. It looks daunting at first, but if you are mechanical at all it's not hard to work on.

thanks, I think though after only 30 hours mine should be fine still.