KX 125 Pre-ignition? Pinging?

Dac1915 · 07-21-2009

My 1999 KX 125 is making a noise that I think is pre-ignition. If I am running it hard; as soon as it reaches the peak in the powerband while under load in third gear and 4th gear is will make a clicking rapppppping sound but then it stops as soon as it passes the peak and hits the over rev. While it is pulling through the next gear its fine until right at the peak of the power, then it makes the noise.
I am running 94 octane gas and 32:1 oil ratio of amsoil synthetic, it seems to be jetted perfect according to plug readings and part throttle operation.

Is this pinging? What is the best way to solve it?

2stroke173 · 07-22-2009

I would take the exhaust off and use the kick starter to slowly move the piston up and down and take a look at the piston and cylinder wall. You may also want to take the reed cage out and look from the intake side...

How long has it been since the last top end? Checking the crank rod bearing? Governor assembly? Exhaust power valves?

Dac1915 · 07-22-2009

Piston + cylinder look to be in perfect shape. powervalve seems to work as it is supposed to. The Reeds are in perfect shape. There is no movemebt in the rod and no knocking sound at any other point in time.

I am pretty sure it is "pinging" i was just expecting a higher pitch sound than the one I hear, it is more like the sound a ratchet makes when its ratcheting backwards.

Should I try cooler plug? Octane booster? can I adjust the timing? or would raising/changing the needle or main jet be the best bet? Can i addjust it out with the air screw?

It only happens right at power peak while under serious load (going uphill with good traction in higher gears.

2stroke173 · 07-22-2009

What plug are you using? What is the color of the plug? You can check the ignition timing and adjust it to see if it makes a difference mine is set to the center mark. If your using the competition plug you might try the NGK B9ES it's a standard plug that i like...it's a cooler plug than the NGK B8 series

I would try a 40:1 mix ratio...i don't know if octane booster would help because i'm not convinced that lower octane fuel like regular unleaded causes a lot of detonation (pinging). But you could try it...I was using super unleaded and then switched to regular unleaded and haven't noticed any difference in bike performance or experienced any pinging. I have a 93 kx125

Dac1915 · 07-22-2009

I am using a BR9ES plug, it is a golden brown color on both the electrode and the center ceramic. The jetting performs flawlessly. There is no sign of any aluminum on the electrode. I tried 40:1 and it was less of the rattle, but it still did it just a little bit under the same conditions; pulling right at the power peak under a load in 3rd and 4th gear. It only happens for an instant, then its into the overrev or I grab another gear.

I weight 175#'s, so I know I am not too heavy for it.

2stroke173 · 07-23-2009

I'm about the same weight too and my 125 pulls me around without any problems so your weight isn't a factor...do you notice a actual power loss when you hear the sound? I'm wondering if your exhaust springs are making a rattling type of sound at higher revs. I had a kx100 and the exhaust springs would make a rattling type of sound at higher revs

Sounds like your jetting is spot on...if there's no power loss when you hear the sound and everything else checks out it's hard to say what it might be

07-21-2009	#1 (permalink)
Dac1915 Newbie Join Date: Jun 2009 Posts: 20	KX 125 Pre-ignition? Pinging? My 1999 KX 125 is making a noise that I think is pre-ignition. If I am running it hard; as soon as it reaches the peak in the powerband while under load in third gear and 4th gear is will make a clicking rapppppping sound but then it stops as soon as it passes the peak and hits the over rev. While it is pulling through the next gear its fine until right at the peak of the power, then it makes the noise. I am running 94 octane gas and 32:1 oil ratio of amsoil synthetic, it seems to be jetted perfect according to plug readings and part throttle operation. Is this pinging? What is the best way to solve it?

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07-22-2009	#2 (permalink)
2stroke173 Clutch Cadet BTK Expert Join Date: Mar 2007 Posts: 360	I would take the exhaust off and use the kick starter to slowly move the piston up and down and take a look at the piston and cylinder wall. You may also want to take the reed cage out and look from the intake side... How long has it been since the last top end? Checking the crank rod bearing? Governor assembly? Exhaust power valves?

07-22-2009	#3 (permalink)
Dac1915 Newbie Join Date: Jun 2009 Posts: 20	Piston + cylinder look to be in perfect shape. powervalve seems to work as it is supposed to. The Reeds are in perfect shape. There is no movemebt in the rod and no knocking sound at any other point in time. I am pretty sure it is "pinging" i was just expecting a higher pitch sound than the one I hear, it is more like the sound a ratchet makes when its ratcheting backwards. Should I try cooler plug? Octane booster? can I adjust the timing? or would raising/changing the needle or main jet be the best bet? Can i addjust it out with the air screw? It only happens right at power peak while under serious load (going uphill with good traction in higher gears.

07-22-2009	#4 (permalink)
2stroke173 Clutch Cadet BTK Expert Join Date: Mar 2007 Posts: 360	What plug are you using? What is the color of the plug? You can check the ignition timing and adjust it to see if it makes a difference mine is set to the center mark. If your using the competition plug you might try the NGK B9ES it's a standard plug that i like...it's a cooler plug than the NGK B8 series I would try a 40:1 mix ratio...i don't know if octane booster would help because i'm not convinced that lower octane fuel like regular unleaded causes a lot of detonation (pinging). But you could try it...I was using super unleaded and then switched to regular unleaded and haven't noticed any difference in bike performance or experienced any pinging. I have a 93 kx125

07-22-2009	#5 (permalink)
Dac1915 Newbie Join Date: Jun 2009 Posts: 20	I am using a BR9ES plug, it is a golden brown color on both the electrode and the center ceramic. The jetting performs flawlessly. There is no sign of any aluminum on the electrode. I tried 40:1 and it was less of the rattle, but it still did it just a little bit under the same conditions; pulling right at the power peak under a load in 3rd and 4th gear. It only happens for an instant, then its into the overrev or I grab another gear. I weight 175#'s, so I know I am not too heavy for it.

07-23-2009	#6 (permalink)
2stroke173 Clutch Cadet BTK Expert Join Date: Mar 2007 Posts: 360	I'm about the same weight too and my 125 pulls me around without any problems so your weight isn't a factor...do you notice a actual power loss when you hear the sound? I'm wondering if your exhaust springs are making a rattling type of sound at higher revs. I had a kx100 and the exhaust springs would make a rattling type of sound at higher revs Sounds like your jetting is spot on...if there's no power loss when you hear the sound and everything else checks out it's hard to say what it might be

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