Bottom end failure - 2018 EC300

[riton63]

Hello my 300 ec 2018 had the same problem at 27h. Ignition side bearing broken. Then at 6500km the 2 rusty crankshaft bearings and now at 12000km too. I had changed the cylinder head in the meantime so for me the cause is cylinder or hot porous casings. It must be very low because I have never added coolant. I've been riding motorcycles for 40 years and this is the first time it's happened to me. In fact, this only happens on the 300. I use NTN steel cage bearings. I will try to put a lower radiator cap 1.4bar. I'll keep you informed. French rider.

[5valve]

At 65 to 67 hrs I've done 5 hones, had whole engine apart 2 times, changed 2 pistons, 2 crank bearing sets, con rod replacement.

Issue was too high compression from factory, at 15.4:1. It took long to realize, since air pressure gauge showed ok compression.

Fluid measurement went off the charts.

I have now deepened the head significantly and use 1mm base gasket (2x 0.5).

Finally, kick starter or electric have no struggles. Power is in abundance still. Somewhere in high 12:1 to low 13:1 compression now.

I did purchase and measure another GP head, and it was again same abnormal compression.

[SS109]

Too high compression... hmm... interesting. Could this be the source of a lot of the Gas/Rieju issues?

[5valve]

Most certainly. I was struggling with vertical lines in nikasil. Most probably due to high compression forcing rings outwards too much.

Slovak tuner who bumps up compession for max performance on a 250, uses 14:1 and high octane fuel. And 250 can handle more than 300.

[Jay Dizzle]

My 2018 XC300 just had the ignition side/ left side main bearing fail. It scored up the bearing race pretty good and am now thinking i need to get a new left side case. Did you guys have any damage to the case after the bearing failed? Also looking for a used 2018 xc300 left side case now.