150sx Power-valve tuning

5/20/2022 10:53am
Now that I’m on my mid season break from racing I’m looking to do further fine tuning on my 150sx. Currently running 14/49 gearing which is too tall so purchased a 51 to try which should help with some out of corner issues I’ve been struggling with. I have no clue why I Went with that combo when I ordered it I may have mis ordered.

Jetting is dialed in at this point using AJ’s specs but larger 520 main. Bike has many other mods but want to work on the power valve options.

Currently using the stock spring about 1.25 turns In, started at 1.5 and ended up here.

I’ve now purchased a 4 spring kit from Slavens which includes the green, yellow, and red along with their progressive spring.

Planning to pop in the red spring tomorrow to give her a shot. What have others experience been in swapping springs?
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Rickyisms
Posts
3247
Joined
10/5/2017
Location
FL US
5/20/2022 3:34pm
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I did it didn’t have the top end pull the stock spring provided.
1
5/20/2022 4:01pm
Rickyisms wrote:
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I...
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I did it didn’t have the top end pull the stock spring provided.
Hmm interesting but not the first time ive heard the red dies out up top.
Makes me curious about how the “progressive” spring works. They claim it hits like red but then get stiffer similar to stock.
Rickyisms
Posts
3247
Joined
10/5/2017
Location
FL US
5/21/2022 8:12am
Rickyisms wrote:
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I...
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I did it didn’t have the top end pull the stock spring provided.
Hmm interesting but not the first time ive heard the red dies out up top. Makes me curious about how the “progressive” spring works. They claim...
Hmm interesting but not the first time ive heard the red dies out up top.
Makes me curious about how the “progressive” spring works. They claim it hits like red but then get stiffer similar to stock.
The green and the yellow took away a lot of the hit/snap that a 125/150 is known for. Pulled good on top, but lost what I was looking for out of a fun two stroke 😎. Be sure to post back when you test, I always like hearing everyone’s opinions.
5/21/2022 6:15pm
Rickyisms wrote:
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I...
I preferred the stock spring on my 125 and 150. The red spring was good in low-mid but felt like no matter how much adjusting I did it didn’t have the top end pull the stock spring provided.
Hmm interesting but not the first time ive heard the red dies out up top. Makes me curious about how the “progressive” spring works. They claim...
Hmm interesting but not the first time ive heard the red dies out up top.
Makes me curious about how the “progressive” spring works. They claim it hits like red but then get stiffer similar to stock.
Rickyisms wrote:
The green and the yellow took away a lot of the hit/snap that a 125/150 is known for. Pulled good on top, but lost what I...
The green and the yellow took away a lot of the hit/snap that a 125/150 is known for. Pulled good on top, but lost what I was looking for out of a fun two stroke 😎. Be sure to post back when you test, I always like hearing everyone’s opinions.
So new gearing is a lot better and added bark back to the bike and let me slip the clutch a lot less.
So the slavens “progressive” spring is pretty much identical to our current stock SX spring when laying side by side. My guess is these were more marketed towards the TPI bikes oh well doesn’t hurt to have another. I played around with the stock spring and like 1.5 but I felt like the bottom end bark was kind of lacking for me.

I threw in the red spring and went with 1.5 turns and really enjoyed it a lot more. I personally didn’t notice a loss in top end performance vs the stock spring. It definitely now has more bottom and mid range bark. I think as someone who doesn’t love slipping the clutch to get into the power it helped me. For now I think this will be my setting, I need to play with the preload some more but I really was so happy at 1.5 I left it for the day.

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