1986 Yamaha yz125 restoration

Geordie
Posts
41
Joined
3/12/2017
Location
Newcastle on Tyne GB
7/22/2019 11:18pm
Hi Matt, standard bore size is 56mm and you can go up to 2.00mm oversize, taking it to 58mm.

Check the bore size with a bore gauge aprox 1 to 2 inches from the top of the cylinder as the top 10mm doesn't wear due to the ring not reaching the top, don't use a vernier gauge as you won't get an accurate reading,
If your current piston has 1.25 on the top it it 1.25 mm over size (57.25mm) any wear in cylinder and you'll need to rebore it to 1.5mm or 1.75mm depending on how bad it is.
1
8/29/2019 9:58pm
I was busy while you were gone. I turned my efforts to working on my 1986 CR125.

3
fullfloater
Posts
3204
Joined
7/22/2009
Location
CA US
Fantasy
14th
10/22/2023 2:25am

I raced a YZ125 in '86 so this has been a nice trip down memory lane.

1
kiwi_daz
Posts
1
Joined
11/6/2023
Location
hamilton3204 NZ
11/6/2023 7:08pm
Geordie wrote:
Hi Brian. Sure is, I've been busy with it but haven't had much time to update the thread, I bought a 93 cr500 and couldn't resist...
Hi Brian. Sure is, I've been busy with it but haven't had much time to update the thread,
I bought a 93 cr500 and couldn't resist having a play so that's held things up too.




hey, im doing one of these bikes up and having a drama trying to get the lower linkage bushes out for the shock.  anyone had this issue and give any tips????

The Shop

450exc115
Posts
656
Joined
11/6/2014
Location
Hebron, CT US
11/9/2023 8:16am
Geordie wrote:
Hi Brian. Sure is, I've been busy with it but haven't had much time to update the thread, I bought a 93 cr500 and couldn't resist...
Hi Brian. Sure is, I've been busy with it but haven't had much time to update the thread,
I bought a 93 cr500 and couldn't resist having a play so that's held things up too.




kiwi_daz wrote:
hey, im doing one of these bikes up and having a drama trying to get the lower linkage bushes out for the shock.  anyone had this...

hey, im doing one of these bikes up and having a drama trying to get the lower linkage bushes out for the shock.  anyone had this issue and give any tips????

There are snap rings that keep the bearing in place, remove those and press out.  I've used sockets and a vise in a pinch.  Heat helps too if they are really stubborn.  

Had a 86 YZ125 in High school and race a 86 YZ250 now in the local vintage series.  Great bikes and still really fun to ride

 

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