Jump to content
Sign in to follow this  

Ktm SX-F 250 2014 rod bearing failure

Recommended Posts

Engine started to sound bad and I think the rod bearing is shot...:)

Original lasted less than 30h, shit happens...

Has anyone else had issues?

Share this post


Link to post
Share on other sites

This can happen if you don't fill the oil filter cavity on oil changes , it then sucks air for a while and the rod doesn't get the lube it needs

Share this post


Link to post
Share on other sites

yes , we had . only with our 2013 sxf 350 and within 4 hours . the reasen it happend whit our engine was a little crank bearing lockplate bolt came out and goes into the return pump (no screen for it ) and lockt it and also the feed oilpump ,so no oil pressure . the plain bearing rod is outstanding but it needs oil. a roller bearing can run without for a few seconds but a plain bearing cant.

Share this post


Link to post
Share on other sites

Just did my 2012 350 at 55 hrs started to sound noisey so pulled it down and found big end rod bearing on it's way out better to catch it before it does any serious damage but wasn't to happy considering the low hrs

Share this post


Link to post
Share on other sites

the 2012 has a roller bearing ,and i think 50 hours is normal . the plain bearing most go 100 hours , but the firts go out in 4 and the second was fine till abouth 30 hours and than the rod broke just under the small end , but the plain bearing was fine .

Share this post


Link to post
Share on other sites

The rod failure must have been a fluke as I've not read of another , a few big end bearings have gone due to the incorrect filling of oil

Edited by mog

Share this post


Link to post
Share on other sites

wel the best way is to fil the filter room with oil ,or start the engine with the kill switch in so it turn round but not start.

Share this post


Link to post
Share on other sites

The stock plain bearings are coated in DLC, they can run for quite sometime without high pressure lubrication as a consequence of the coating. I bet it had poor lubrication for the entire life of the motor, which is why it kept failing.

The problem with high pressure lubrication systems is that if the pressure drops, then you loose all lubrication. This is why the Japanese bikes have stuck with roller and needle bearings that require substantially less lubrication in order to function.

KTM uses high pressure lubrication and plain bearings as a way to run higher RPM's (more power) but have better wear characteristics.

In the OP's situation, I'd say the oil pump is simply not putting high enough pressure oil through the system. Its extremely easy to check oil pressure. Just take the tank off, pop the spark plug out (so the motor turns freer) and take off the valve cover. Then turn the motor over with the starter and if all 4 oil jets spray perfectly onto the rocker arms, you've got good oil pressure. If they don't then you've most likely got low oil pressure. I did lots of testing when my motor was apart and found this to be the case.

Oil pressure builds VERY fast in this machines, it only takes a few seconds to have full lubrication at the top of the head using the slow turning starter motor. I also have never pre-filled the oil filter area, I always wipe it clean. My crank bearings looked brand new at 110hrs. So something for sure is going on and I doubt its dirty oil, as the double filtration system is pretty good.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×