Athena (P400485100003) 54mm 125cc Standard Bore Cylinder Kit

Great kit was very easy to put together had to dubble up on seals to get the proper squish but they give you more than enuf to use and the power difference is very noticeable and very fast compared to my previous 55mm cylinder only thing that wasn't great were the directions pretty hard to understand

REPAIRED MY GRANDSONS YZ125 WITH THIS KIT AND IT RUNS GREAT NOW. YOU SHOULD SEE THE HUGE GRIN ON HIS FACE EVERY TIME IT STARTS, FIRST KICK!

2 years still strong

I installed an Athena factory cylinder kit onto my 2004 Yamaha yz 125. I followed the instructions and made sure everything was installed correctly along with breaking in the engine before going riding. I went on a trail riding trip in West Virginia and with only 6 hours on the rebuild the top end blew 20 miles into the woods due to a circlip coming out of the piston and locking up the engine. The circlip came out because the groove it sits in wasn’t machined wide enough for it to seat all the way into the piston where the horizontal oiling groves are for the wrist pin bearing. The other side of the piston that the circlip did not come out also shows the same defect at the circlip isnt seated all the way in the same area. I have pictures that explain and show this better. This failure was very disappointing and aggravating after spending $730 on this kit.And I’m not sure who to contact now about a refund or replacement.

Great kit easy fit

Performs flawlessly just know that this is not a ready to install kit. There are a few things to check before installation. The ring end gap was too small i had to open some and some of the ports had rough edges they just needed polishing. The instructions and parts breakdown are not clear and easy to interpret. The kit included 3 gaskets i ended up using only the black base gasket for installation and it worked great. 2000 yz125

Exhaust didn't fit back to the head right.

Did not come with wrist pin bearing and had dents in head dome