Jump to content
Sign in to follow this  

2010 yz125 120 psi?

Recommended Posts

Just finished my yz125 project and had the cylinder sleeved and bored at a local shop. Got a piston to match. I’ve run the bike a few times and gave it a little rip. Has 0.4 hours since rebuild and has 130 psi compression. I’m kinda worried because that’s exactly what it had before I Freshend it all up. Is that a decent psi? Or is something wrong?

Share this post


Link to post
Share on other sites

Huh that does seem a little low if the bike is all original. Ours ran about 150psi.

Did you use OEM base gasket? Slightly thicker or thinner base gasket will change compression

Has the head had any work done?

Reeds new or atleast in good order?

Share this post


Link to post
Share on other sites

Are you holding the throttle wide open while kicking / testing?

I also question why you chose to sleeve and not replate your cylinder?

 

Although gauges all have some variances, I've never gotten less than 180psi on a new freshly broken-in top end (stock bore 2010 YZ125)

Share this post


Link to post
Share on other sites
Huh that does seem a little low if the bike is all original. Ours ran about 150psi.
Did you use OEM base gasket? Slightly thicker or thinner base gasket will change compression
Has the head had any work done?
Reeds new or atleast in good order?

Fresh Vforces along with vortex gaskets. The head is stock. I’m wondering if I haven’t completely broken it in yet and the wrongs aren’t set yet. Not sure about the science on that but is it a possibility?

Share this post


Link to post
Share on other sites
Are you holding the throttle wide open while kicking / testing?
I also question why you chose to sleeve and not replate your cylinder?
 
Although gauges all have some variances, I've never gotten less than 180psi on a new freshly broken-in top end (stock bore 2010 YZ125)

Throttle was wide open and I went with sleeving because I’m friends with the boys down at the local shop and they give me great deals on services. Everything looked great before assembly and I have a stock bore wiseco prolite in her as of now. And I posed this up above aswell but is it possible I haven’t seated the wrongs and compression will be low until a complete break in?

Share this post


Link to post
Share on other sites

That’s strange and low. Maybe someone didn’t size the piston correctly. Did you/someone measure the new ring gap? My gauge is pretty a accurate and I get 160 psi cold on a run in new top end. My base gasket is .65mm thick. 2009 YZ125

When I rebuild I check in the garage and get 157 or so then after run in I get 162.  

Edited by riles

Share this post


Link to post
Share on other sites
That’s strange and low. Maybe someone didn’t size the piston correctly. Did you/someone measure the new ring gap? My gauge is pretty a accurate and I get 160 psi cold on a run in new top end. My base gasket is .65mm thick. 2009 YZ125
When I rebuild I check in the garage and get 157 or so then after run in I get 162.  

I did check ring end gap it’s .009 and I can barely barely fit a .010 in there. But I’m not sure if this matters. When I was checking compression my powervalves were stuck open because my pins had fallen out. Not sure if the valves being op e would let for compression out or something but anyways. I’m curios as to if it’s possible that I haven’t finished breaking it in yet or something and the ring hasn’t seating in the bore

Share this post


Link to post
Share on other sites

What's the problem you're having with the bike?

Sounds to me like a case of just ride it.

  • Like 2

Share this post


Link to post
Share on other sites
54 minutes ago, NZracer said:

What's the problem you're having with the bike?

Sounds to me like a case of just ride it.

Agreed, if it starts easy and feels good then just check ring end gap in 20 hours or so and use it as normal

Share this post


Link to post
Share on other sites
Agreed, if it starts easy and feels good then just check ring end gap in 20 hours or so and use it as normal

I’m being a b*tch about it because I’ve sunk a lot into building my little track queen and want it to be perfect. I’ll give her a rip at mesquite and hopefully everything goes smooth.
What's the problem you're having with the bike?

Sounds to me like a case of just ride it.

[emoji23] i suppose I’m not actually even having a problem I’m just making a big deal out of nothing. Sorry for acting like a 7 year old at Walmart that wants a toy
  • Haha 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...