xs400 1mm oversized piston rings

[David Houston]

hi there
hopefully someone can help me out , i have a 1979 xs400 it has been rebored and i require 1mm oversized piston rings. i cant seem to find them anywhere. does anyone now where i can get 2 sets.
appreciate any help.
cheers dave

 

[Tyler Shiells]

https://www.ebay.ca/itm/Yamaha-XS40...272834?hash=item3ab3a89442:g:1U8AAOSwK~RZ5a-e

This is the seller I got my .25 rings from. The seller also has pistons. They're in Germany. It's your best option.

Did you double check those measurements? And what number is stamped on your pistons?

 

[Tyler Shiells]

The seller also has the 1.25 oversize kit if you need it.
https://www.ebay.ca/itm/Yamaha-XS40...273419?hash=item3ab3a8968b:g:OHsAAOSwr1taAsQK

 

[David Houston]

Hi tyler
I have checked it many times know, it is reading 70mm all over the cylinders . The piston ring gap when in the cylinders is over the max recommended. The pistons and cylinders are all in good condition. When i did a compression test i got 120psi on a dry test and 145psi on a wet test before i stripped the engine. Valves and gaskets all good absolutly no leaks .
There are no I/D marks on the pistons. Which i found strange but they are just under the 70mm.
Cheers dave

 

[Tyler Shiells]

Great. I hope that link to the +1mm rings works for you then.

 

[David Houston]

Cheers mate

 

[walleye]

https://www.ebay.ca/itm/Yamaha-XS40...272834?hash=item3ab3a89442:g:1U8AAOSwK~RZ5a-e

This is the seller I got my .25 rings from. The seller also has pistons. They're in Germany. It's your best option.

Did you double check those measurements? And what number is stamped on your pistons?

Hi Tyler. Sorry to jump in on this thread but did you rebore and go oversize pistons or did you put the .25 oversize rings on the standard pistons? I've tried standard rings on mine but they come out over spec on the gap. Was wondering if I need os pistons and a rebore?
All the best
Chris

 

[Tyler Shiells]

Hi Tyler. Sorry to jump in on this thread but did you rebore and go oversize pistons or did you put the .25 oversize rings on the standard pistons? I've tried standard rings on mine but they come out over spec on the gap. Was wondering if I need os pistons and a rebore?
All the best
Chris

Yes I rebored the cylinders to the next size up. Found new old stock pistons that were the next size up and ordered new rings from that seller in Germany.

 

[walleye]

Thanks Tyler, much appreciated