KX65 motor died

[Mike-Evans]

Hi guys looking for some info aand advise please. My lads KX65 give up today, I removed the top end at the track and the piston has severe marks on the top so does tha cylinder head, cylinder has a score and the conrod is loose. Crank has blue/red heat narks so does the bottom of the conrod.

Looks like the bottom end has gone..

Question is, why?? Age, running too lean, not enougb oil etc.....?

We always run 125ml to 5l of putoline. Bike always starts first kick, no unusual noises etc.. .

This piston and bottom end is approx 17 months old, probably has alot of hours aswell and the boy does ride it hard....

Ive never stripped the bottom end on a 2 stroke so also looking for advise and tips here?

Have a look over the pics and let me know your thoughts 👍

Plan is to strip it down, buy hew crank piston and get cylinder repalted but I think I need to know why it give up??



















There is aa peice of the piston missing just infront of where the clip goes, theres was alot of debris ontop of the piston when I removed the cylinder.....

Appreciate any help

[Foxx4Beaver]

big end throw a needle bearing?

[Mike-Evans]

How would I tell? The big end bearing is rough to turn, main bearings are smooth.....

As you can see in the pics, the bottom of the conrod and crank is red/blue in colour so it looks like that is the failure area

[Foxx4Beaver]

you'll know once you split the cases...I'm just guessing....but it looks/sounds like the big end bearing suffered some sort of failure.

[Mike-Evans]

Yes that is where my money is too. Ill be splitting the cases in the next few days..

I dont yet have a case splitter tool, do I need one? Can one be made?

[Foxx4Beaver]

it can be done without a splitter....but it's too risky...so don't try it.
things always go much smoother, and sometimes cheaper, when the correct tools are used.