05 KX 125 won’t pull 2nd gear start

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4/9/2018 5:04 PM

I have a kx 125 that will not pull a 2nd gear start and feels low on power. Long story short, I replaced the piston and cylinder with an Athena kit, and replaced the v force reed pedals. I’m geared 12/51. I’ve owned several kx 125’s and this one is making pull my hair out. I read about a similar issue about a kx 100 that turned out to be a bad cdi box, which wasn’t advancing the timing through the rpm. Anyone have any advice for me?

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4/9/2018 5:31 PM

Sounds like the power valve isn't working properly, have u checked to see that is working correctly?

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4/9/2018 5:52 PM

Don't most 125 riders start in first gear? It's been a while since I rode one, but I always started in first.

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Take it to the limit, one more time!

4/9/2018 6:04 PM

ktm-5 wrote:

Sounds like the power valve isn't working properly, have u checked to see that is working correctly?

I pulled the cover off and it is opening when I rev it. I forgot to mention that.

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4/9/2018 6:05 PM

mx317 wrote:

Don't most 125 riders start in first gear? It's been a while since I rode one, but I always started in first.

I have always used 2nd gear to start, even on mini bikes, but this one doesn’t seem to have the power to do it.

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4/9/2018 6:17 PM

It’s a 125!!! How much did you weigh when you rode minis compared to now?

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4/9/2018 6:27 PM

mwssquad827 wrote:

It’s a 125!!! How much did you weigh when you rode minis compared to now?

I’m 145, I was 145 when I raced 125’s in the pro class. I grew up racing motocross, and I’ve had a bunch of kx 125’s. They’ve all been able to pull 2nd gear starts. I realize it is a 125 but I know there is something wrong with this particular bike.

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4/9/2018 9:35 PM

Yeah something sounds wrong with it. 125 can do 2nd gear starts fine. Ive been a 125 guy since '96, but not on Kawi's.

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4/10/2018 1:11 AM

Is it jetted right?

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4/10/2018 3:28 AM

That sounds like crazy high gearing, no?

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RPM Performance
CT
783

4/10/2018 6:24 AM

Does it sputter or bog? If you are in loose dirt, the wheel should spin versus going no where. Maybe your tire isn’t hooking up, it’s geared too high, or you have to clutch the shit out of it.

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If you're not mixing gas, you're not haulin ass.

4/10/2018 9:38 AM

Has it been like this since you've had it or did it just start acting up or??

Have you checked timing at the stator/flywheel?

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4/10/2018 12:25 PM

TrailDigger wrote:

Does it sputter or bog? If you are in loose dirt, the wheel should spin versus going no where. Maybe your tire isn’t hooking up, it’s geared too high, or you have to clutch the shit out of it.

It's actually geared for low end with 12-51 and he shouldn't need to clutch it like that

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4/10/2018 12:48 PM

ridinbeast932 wrote:

Has it been like this since you've had it or did it just start acting up or??

Have you checked timing at the stator/flywheel?

I’ve moved the plate from one extreme to another and it didn’t seem to change. Someone suggested today that I pull the cover off and use a timing light to make sure the timing is advancing through the rpm. It’s always been a turd ever since I’ve owned it. I thought it was the top end because the exhaust side of the piston was slightly scuffed right in the exhaust port bridge, so I just changed the piston the first time and after I rode it a couple times I pulled the pipe and saw the same damage, so I thought maybe the cylinder was out of round, so I bought an Athena top end kit and it runs the same.

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4/10/2018 1:04 PM

ridinbeast932 wrote:

Has it been like this since you've had it or did it just start acting up or??

Have you checked timing at the stator/flywheel?

stevemartin wrote:

I’ve moved the plate from one extreme to another and it didn’t seem to change. Someone suggested today that I pull the cover off and use a timing light to make sure the timing is advancing through the rpm. It’s always been a turd ever since I’ve owned it. I thought it was the top end because the exhaust side of the piston was slightly scuffed right in the exhaust port bridge, so I just changed the piston the first time and after I rode it a couple times I pulled the pipe and saw the same damage, so I thought maybe the cylinder was out of round, so I bought an Athena top end kit and it runs the same.

I would check to make sure the plate is in the stock position to start, as well as all the obvious shit you probably already checked, clean carb, correct jets etc.

Also, came across this thread. I'm not too familiar with the kx powervalve but maybe this will pertain to you. Seems like he had a similar sluggish issue.

http://www.kawasakimotorcycle.org/forum/kawasaki-motocross-offroad/50668-kx125-timing-mark.html

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4/10/2018 1:28 PM

ridinbeast932 wrote:

Has it been like this since you've had it or did it just start acting up or??

Have you checked timing at the stator/flywheel?

stevemartin wrote:

I’ve moved the plate from one extreme to another and it didn’t seem to change. Someone suggested today that I pull the cover off and use a timing light to make sure the timing is advancing through the rpm. It’s always been a turd ever since I’ve owned it. I thought it was the top end because the exhaust side of the piston was slightly scuffed right in the exhaust port bridge, so I just changed the piston the first time and after I rode it a couple times I pulled the pipe and saw the same damage, so I thought maybe the cylinder was out of round, so I bought an Athena top end kit and it runs the same.

ridinbeast932 wrote:

I would check to make sure the plate is in the stock position to start, as well as all the obvious shit you probably already checked, clean carb, correct jets etc.

Also, came across this thread. I'm not too familiar with the kx powervalve but maybe this will pertain to you. Seems like he had a similar sluggish issue.

http://www.kawasakimotorcycle.org/forum/kawasaki-motocross-offroad/50668-kx125-timing-mark.html

Thank you! That’s where I will start! Thank you for the info!

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4/10/2018 2:11 PM

Just because the power valve is moving does not mean its timed correctly .Refer to the service manual for PV timing !

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2018 crf 250r

4/11/2018 7:31 AM

There is no way to adjust PV timing in 05 kx?

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4/11/2018 8:16 AM

TrailDigger wrote:

Does it sputter or bog? If you are in loose dirt, the wheel should spin versus going no where. Maybe your tire isn’t hooking up, it’s geared too high, or you have to clutch the shit out of it.

ktm-5 wrote:

It's actually geared for low end with 12-51 and he shouldn't need to clutch it like that

Isn't that almost equivalent to 13-48? Seems like tall gearing for a 125. Stock is 13-51 for a 2005

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @hammerfamily_4 & @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

4/11/2018 8:20 AM

It's equivalent to 13-55

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4/11/2018 9:41 AM

polar wrote:

It's equivalent to 13-55

I think you’re right. My bad. Ya that’s still really weird gearing though

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2017 RMZ450
2005 YZ250-sold :,(
1998 YZ250
2005 KX250F

80% of the time it works every time
IG @hammerfamily_4 & @2HRacing
Thanks to : Factory Effex, N2Dirt, Acerbis, DT1, Fasthouse, Matix, FMF, ASV, 100% & Mika Metals

4/11/2018 1:35 PM

Even a stock KX should be able to pull 2nd gear starts. Is it jetted correctly?

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#1
KX125

4/12/2018 7:15 AM

Should be able to pull a 2nd gear start with 12/51. Did you check compression after rebuild? Crank seals in good shape?

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Tomac and/or Anderson for 2020.....

4/13/2018 10:02 PM

I was 240 in gear when racing mine. I did OK starting in 2nd. SOMETHING sounds wrong.

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4/30/2018 11:21 AM

I checked cdi function with a timing light, it will advance as it is revved. I took the power valve cover off and it is operating. I’m going to put the jetting back to bone stock and try it. It seems crisp but I’m running out of things to check... I’m also going to pull the power valve out and make sure it is assembled correctly. I put it together using the service manual but I am stumped...

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