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790/890 Failed Cams

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#61 ·
charlie264 said:
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That reminds me of the early XR600 engines - the oil feed up into the head was just a dribble at idle, needed some decent revs to get enough oil to start splashing around up there. So people that were in the habit of warming up their bikes and then letting it rip caused premature tappet wear vs those that got on and just rode gently as it warmed up.
I'm not saying that's the issue or fix for the 7/890, but it was the same sort of "oil flow dribble at idle".

Makes me suspect that KTM are replacing cams and even heads as that is at least easily possible. It's not so possible for them to redesign the entire head/oil system. So maybe cams are now just a wear item to make up for bad engine design...
 
#62 ·
bigkuri said:
Makes me suspect that KTM are replacing cams and even heads as that is at least easily possible. It's not so possible for them to redesign the entire head/oil system. So maybe cams are now just a wear item to make up for bad engine design...
Click to expand...
Might be onto something there, might be something as stupid as cylinder base gasket, replacing cams under warranty works out cheaper....
 
#64 ·
Gonna check my smt in a couple weeks and I'll start it with the cover off to see what oil pressure and flows like running, just finished a 350 freeride that had the same problem on one of the cams turning over on the starter but it was fine when it was running because it was the furthest away oil gallery from the other 4
 
#65 ·
bigkuri said:
That reminds me of the early XR600 engines - the oil feed up into the head was just a dribble at idle, needed some decent revs to get enough oil to start splashing around up there.
Click to expand...
It could be something like that, it seems they can produce a good flow even when just cranking, once running if it still wasn't then the oil pressure warning would appear as the oil pressure switch is in the head.
So low flow from the cam jets when running but good pressure at the head must mean a blockage in the head, just before the cam jets.

Or could mean that some bikes have weak oil pumps and so the damage that we're seeing now has all been caused during cranking.
 
#66 ·
TrouserSnake said:
It could be something like that, it seems they can produce a good flow even when just cranking, once running if it still wasn't then the oil pressure warning would appear as the oil pressure switch is in the head.
So low flow from the cam jets when running but good pressure at the head must mean a blockage in the head, just before the cam jets.

Or could mean that some bikes have weak oil pumps and so the damage that we're seeing now has all been caused during cranking.
Click to expand...
I doubt that, for the hardened surface of the cams to fail its going to take heat. Its not going to reach those kind of temps just on start up. As its certain lobes and not all, to me indicates lack of oil at engine running speeds.

Too high oil pressure would blow the jets out. Not sure of the design, need to look through engine drawings but I did see on the LC4 the oil pumps are driven by a gear on the back of the clutch basket, 4 small bolts and they seared on an engine so the drive to pumps was partial.

It all depends where they've put the oil pressure switch, on the old LC8 its right at the end of the oil chain which is correct, pointless putting it on a main oil way after the pump.
 
#67 ·
charlie264 said:
I doubt that, for the hardened surface of the cams to fail its going to take heat. Its not going to reach those kind of temps just on start up. As its certain lobes and not all, to me indicates lack of oil at engine running speeds.
Click to expand...
Yeh, I agree.
That's why owners are checking for cold oil flow at cranking. If there's isn't a strong oil jet when cranking then there likely won't be one when the engine is running either.
If the oil pressure is at the head but there isn't flow then it has to be a blockage after the pressure switch.
 
#71 · (Edited)
TrouserSnake said:
Yeh, I agree.
That's why owners are checking for cold oil flow at cranking. If there's isn't a strong oil jet when cranking then there likely won't be one when the engine is running either.
If the oil pressure is at the head but there isn't flow then it has to be a blockage after the pressure switch.
Click to expand...
So blocked jet, that would lead me to think WP, coolant ingress to oil filter so paper swells and blocks filter, oil filter bypass valve opens on the oil filter and shit is free to block the jets. So my magnetic oil cover, if ferrous particles.

I would strongly recommend anyone with this engine to do a coolant flush, KTM have a long history of failing WP seals and in my opinion, even though KTM have upgraded WP shafts and seals, the cause of premature WP seal failure was casting sand still left in the cases.

After flushing mine twice on the LC8, WP seal is still good.
 
#72 ·
charlie264 said:
So blocked jet, that would lead me to think WP, coolant ingress to oil filter so paper swells and blocks filter, oil filter bypass valve opens on the oil filter and shit is free to block the jets. So my magnetic oil cover, if ferrous particles.
Click to expand...
Well.. hold your horses..
That oil jet looks pretty big, I'm not sure any particle likely to get stuck in that jet would get past the screen/gauze to even get to oil filter.
 
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