Camshaft Failure

jjuarez62

New Member
I purchased a new RC390 in may of this year, at 650 miles i went to do my initial service and found the cam shafts to have unusual wear. So i take it to the dealer and 5 weeks later they finally replace the cam shafts. Well now it will not go over 86 MPH so i am taking it to a different KTM dealer. I showed them the pictures of the camshafts and according to them the wear was normal for a 390. Can anyone confirm that this is usual?
 

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fostytou

New Member
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The marks should not be there. What appears to be pitting in your 3rd picture would be even more concerning.

Realistically cams should not have any wear or scoring. I've seen bikes with 50,000 miles that are as shiny as a mirror. My 2017's exhaust cams look great (which should probably wear harder than the intake), but my intake cams are scored and I can *juuuust* feel it running my fingernail across the flatter side of the ramp. They looked like this at ~600 miles during the first service and just before 1,000 miles when I decided to take a look again since I was most of the way in there for a PCV install. KTM dealers seem to be suspicious on thier "they never need adjustment at the first service" and "some wear on the cams is normal" comments - time and time again those comments are proven wrong.

One part of the FSM that nobody seems to mention is that it recommends spraying air back through those oil jets on the cam bridge (when you have it off). With the sandy gunk that was in the oil filter/screen (that seems to be on everyone's bike) part of me is worried that some of that is caught in each of the intake jets. Part of me wonders if this is the real reason for the quick first valve service - to check for cam lobe wear due to clogged jets.

After seeing that the cam retails for ~$55 I wasn't motivated enough to take the bridge back off again. I did try to look at it with a mirror and couldn't see anything and tried a quick blast of air but through some tubing - I don't think it had much effect and if something is clogging it then it would probably wind up back in the same place in short order. My thoughts are going to be to check again in a few thousand miles to see if it is worse and replace the cam (and possibly the bridge and jets) if necessary. My main concern is that if I take it on track I don't want something to fail in a corner and cause an injury.

At least one of these other posts seemed to have KTM attribute a clog to extra threadlocker (which could be what that sandy looking stuff is) - but it seems this was not uncommon on earlier bikes:

Anyway, while not confidence inspiring if you are under warranty I'd make a stink about it, if not (like me) I'm just going to follow my plan and check back in and spend the stupid time and $100 to replace stuff if need be and grumble grumble. The biggest pain being that you basically have to do a valve job twice to put in the new cam, then check the gaps, then probably adjust again.


The first picture is at the first service, and the 2nd and 3rd pictures are after another ~400 miles on mine.
 

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yogafly

New Member
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Next time the cam cover is off , check if the oil spray jets are working and are not clogged by just removing the spark plug and cranking the engine .
 

fostytou

New Member
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Next time the cam cover is off , check if the oil spray jets are working and are not clogged by just removing the spark plug and cranking the engine .

Thanks for the tip. I was thinking about doing that but didn't know how bad the bike would complain if I did so / didn't want fuel spraying everywhere if I tried to connect everything and balance the fuel tank somewhere. I did wind up removing one of the jets with the bridge in place and attempted to clean it - but honestly after doing so I almost wished I'd just taken the bridge back out (I didn't have a tensioner gasket though). Getting the jet back in was a huge pain since there's very little clearance from the cam and who knows how clean the threads were for the loctite to set. The threads seem only half cut but I did get it to thread without dropping it thanks to some tape on the end of a box wrench and a mountain of patience. After doing the right jet the clearance was even tighter on the left one - I've heard tons and tons of these bikes have this issue from a reliable source so my mind is at ease enough that it may just be a future cost.

For clarity - I do not believe it was clogged. It was fairly easy to blow through with my own lungs.... easy enough that it wasn't worth charging up an air compressor late at night.
 
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