Posts
978
Joined
10/5/2017
Location
Lafayette, IN, USA
Edited Date/Time
5/28/2024 6:26pm
Had my 16 KTM 250SXF eat its lower connecting rod bearing, sending copper particulates all throughout the bottom end, however it seems odd to me that the rod seized up, but everything else in the engine is in pretty dang good condition. Piston, Valve train, Cams, and Cylinder are all in pretty great condition with little to no wear marks. All bottom end bearings still roll smooth and seem in good condition. All of these parts are going to be replaced since im fully tearing down the motor anyway, however is it common for bikes to eat the lower bearing and not tearing up anything else in the motor? especially a 4 stroke. Just seems odd to me.
Are you the original owner? Sounds like you caught the failure just in time and the whole damn thing didn't grenade.
Nope. Bought it with roughly 120 hours on it when the previous owner grenaded the tranny. Put a 350 tranny in it due to this years specific trans issues. Didnt swap the crank however. Now it has close to 200 hours. Bike did let go under WOT but just sounded like how a two stroke loses a crank bearing, running out of gas type of sound. Rod seized up but would still slightly move but took quite a bit of force with my hand when I pulled the cylinder. Funny thing is. I jumped started the bike and it still even ran.
Yea, the lower rod bearing is a high failure point for 4 stroke engines. That's usually the bearing that will go before the main crank bearings.
Not uncommon. Have had it happen on my last few bikes at around 100 hours. The bearing will go and you will find brass shavings in oil or the bike will bog down and lock up. I ride pro btw but I’ve seen it happen on any bike regardless of skill.
oil changes obviously help. I change mine every 3-4 hours
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
All fun and games till your lower rod bearing takes a dump.
There was once a recall for both pairs from factory
Post a reply to: Four stroke lower rod bearing failure.