YZ 125 Loss of High End Power - Yamaha Forums
Welcome to the unofficial Yamaha Forums community! Please Register to gain full access and remove the Ads! it's FREE!    
LinkBack Thread Tools Display Modes
post #1 of 3 Old 02-09-2012, 01:57 AM Thread Starter
Join Date: Feb 2012
Location: California
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
YZ 125 Loss of High End Power

Hello all,

Let's first start off by saying i have a 2006 YZ 125, stock bore, stock pipe, FMF shorty, excel rims, Posey Motor (some shop that the previous owners had it freshened up by, still kept stock bore), BR1 suspension, etc....

I started loosing compression about a month ago, so i decided to rebuild the topend with a standard OEM 'D' piston (it was a wiseco before). After the rebuild it seems to have much more compression and runs great - one kick wonder. However, since the rebuilt i have had poor high end power. It almost seems like it doesn't want to hit the powerband anymore without flaking out. If i put it in second gear and hold the throttle wide open, i can hear the piston pinging a bit as well.

So i ripped it apart again, cleaned the power valves, checked my V-Force 3 reeds (one was chipped, so i bought brand new pedals), inspected the piston (all looks good), put fresh gas and premix in as well.

I even took the cylinder and piston to a shop to have them looked at by a professional and he said there's nothing wrong.

At this point i'm at a loss of what could possibly be the problem... Any info would be MUCH appreciated!

Thanks in advance fellas
06yzrider is offline  
Sponsored Links
post #2 of 3 Old 02-12-2012, 11:45 PM Thread Starter
Join Date: Feb 2012
Location: California
Posts: 5
Thanks: 0
Thanked 0 Times in 0 Posts
Problem Solved.

After all that work. As well as cleaning the carb, and taking it to a shop for an inspection on the topend and powervavles... it was simply due to the exhaust silencer.

I took it off (temporarily - my neighbors hate me now) to see if it had been inhibiting my powerband from engaging, and sure enough... the bike was back to normal, as far as power goes (if not better due to all of the tuning I had done.
06yzrider is offline  
post #3 of 3 Old 02-14-2012, 05:24 PM
Join Date: Jun 2011
Posts: 69
Thanks: 0
Thanked 5 Times in 5 Posts
Sounds like you may be a tad rich on your main jet... I wouldn't run it too long without the Silencer... the length of that plays into the overall tuned length of the exhaust
Burke_78 is offline  
Sponsored Links


Quick Reply

Register Now

In order to be able to post messages on the Yamaha Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome