SR125 cylinder and piston. - 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 4 Old 10-25-2020, 04:26 PM Thread Starter
 
Join Date: Oct 2020
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
SR125 cylinder and piston.

Hi, anyone know where I can get a replacement cylinder and piston for my sr125.

This is my first engine rebuild I brought a bike where the timing chain had come off I've replaced the valves and rebuild the engine (no damage to the piston). When I done a compression test on the bench it was showing 75 and not the recomend 114+ I put a bit of oil in the chamber and done the compression test again and it shows 125 which means it's the barrel and rings, correct?

There wasnt any oil in the engine when I turned her over will that change the amount of compression ?
Luke Wardrop is offline  
Sponsored Links
Advertisement
 
post #2 of 4 Old 10-25-2020, 09:24 PM
 
Join Date: Aug 2019
Posts: 301
Thanks: 0
Thanked 18 Times in 18 Posts
Quote:
Originally Posted by Luke Wardrop View Post
Hi, anyone know where I can get a replacement cylinder and piston for my sr125.

This is my first engine rebuild I brought a bike where the timing chain had come off I've replaced the valves and rebuild the engine (no damage to the piston). When I done a compression test on the bench it was showing 75 and not the recomend 114+ I put a bit of oil in the chamber and done the compression test again and it shows 125 which means it's the barrel and rings, correct?

There wasnt any oil in the engine when I turned her over will that change the amount of compression ?
I think I would crank it quite a bit with oil in it, or start it if you can then check the compression again.

But yes, sounds like rings. Seems the piston for that bike is impossible to find in the USA but you can get the rings from the UK for about $50 shipped on Ebay.
Warrior_Scott is offline  
post #3 of 4 Old 10-26-2020, 06:18 AM Thread Starter
 
Join Date: Oct 2020
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
I think I would crank it quite a bit with oil in it, or start it if you can then check the compression again.

But yes, sounds like rings. Seems the piston for that bike is impossible to find in the USA but you can get the rings from the UK for about $50 shipped on Ebay.[/QUOTE]

I'm gonna give it a try today with the oil today and see if the compression changes.

I'm actually in the uk so that's not to bad. With the rings how do I know if I need +1 or more rings and how would I know if I need the barrel honing?
Luke Wardrop is offline  
 
post #4 of 4 Old 10-26-2020, 04:17 PM
 
Join Date: Aug 2019
Posts: 301
Thanks: 0
Thanked 18 Times in 18 Posts
Quote:
Originally Posted by Luke Wardrop View Post
I think I would crank it quite a bit with oil in it, or start it if you can then check the compression again.

But yes, sounds like rings. Seems the piston for that bike is impossible to find in the USA but you can get the rings from the UK for about $50 shipped on Ebay.
I'm gonna give it a try today with the oil today and see if the compression changes.

I'm actually in the uk so that's not to bad. With the rings how do I know if I need +1 or more rings and how would I know if I need the barrel honing?[/QUOTE]

You should hone the bore with new rings. You can buy a cheap one for a drill. Youtube on how to do it, it's easy.
You would buy rings as a set, so you will get them all.
As long as there aren't any big scratches ect in the bore you should be good to go, you said the piston looks good so I bet you are ok.
Warrior_Scott is offline  
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

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

Password:


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

Email Address:
OR

Log-in










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