crprestridge

Yamaha YFZ450 compression?

8 posts in this topic

does anyone know the proper compression for a yfz 450?

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.


11.9:1

I dont think he is asking about the compression ratio... Stock compression should be 120psi plus... Im pretty sure you have to disable the auto decompression on it to get a good reading or you could do a leak down test on it...

Edited by jigolbeep

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.

had my compression checked and was about 170 lbs. you think i should run higher than 91octane?

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.


I dont think he is asking about the compression ratio... Stock compression should be 120psi plus... Im pretty sure you have to disable the auto decompression on it to get a good reading or you could do a leak down test on it...

Yes, I believe stock is:

Compression Ratio 9.2x1

Compression 834 kPa (121 psi)

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.
had my compression checked and was about 170 lbs. you think i should run higher than 91octane?

170 is pretty high, what kind of mods do you have? If it is really 170, then you should probably atleast run a mix of race and pump gas.

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.

only mods i had when my local atv shop checked my compression what yosh pipe, moose racing jet kit, k and n filter. the guys that checked for me have been doing it a long time so i trust them. we just finished re-jetting and took air box lid off, exhast cam mod, removed spark arrester, and am waiting on rev box and 15 tooth front sprocket. we checked the compression because we couldn't get the jetting right and thought maybe a valve had messed up. have since gotten the jetting right though.

Share this post


Link to post
Share on other sites
  •  Like what you are reading? Please help us by sharing this content.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now

  •  Like what you are reading? Please help us by sharing this content.
  • Similar Content

    • Guest Fox300exchic
      By Guest Fox300exchic
      The Hop-Up: You may be saying to yourself, “that’s a chick bike,” and you’re right. But honestly, it’s so much more than that. It’s one badass bike. http://www.quadmagazine.com/quad/features/article/0,24942,1587044,00.html
    • Guest Fox300exchic
      By Guest Fox300exchic
      If we had a dollar for every time the question “Which is really faster, the 700 or the 450?” shows up in our inbox, mailbox, or voicemail, we’d be putting this magazine together from a bungalow on a barely inhabited tropical isle named Quadhama.
      http://www.quadmagazine.com/quad/features/article/0,24942,1603755,00.html
    • By dyyjrr9
      I just got a 1991 Yamaha Moto 4 for my son and I am looking for a service repair manual. I know that the timing chain needs replaced.
    • By alexcross324
      Hi all, I try to find this manual in the threads but you have a lot of stock here
      Cannot find this particular manual.
      I found it for YFM200 but not sure if they are the same.
      Thanks if you could help me with that.
      Im new here so if I did something wrong, please tell me.