[fast4d]

started getting false neutral at the track last week. I have a bazzaz QS and several times I upshifted, it hung in neutral and I banged the rev limiter several times when it shifted back into the previous gear.

this didn't happen at all last time at the track and I did not work on the bike at all in between.

so I started hearing a loud valve train tick and coasted back into the pits. I loaded the bike and headed home. took it apart today and found massive valve clearance in one front exhaust valve. I removed the cam and the shim is MISSING. it is not in the head so it must have went down the cam chain passage into the crankcase?

I've got a telescopic magnet. been in the oil drain holes and all over the head. where else should I look?

 

[OldTLSDoug]

Drain the oil, it has a magnetic drain plug maybe you will get lucky. Unless it is under warranty, then I would take it to the dealer. Worst case, you might have to pull the motor and split the cases.

 

[Jkasal]

What would cause something like this?


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[chris79]

Dealer/team told me about that, happens on track.
They told me to mod the stock cam chain tensioner or put a manual one to avoid this at high rpm.

Mine is a stock modded so that it can't go back to much ;-)

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[The Wolf]

wow.. sorry to hear that dude. sounds like a massive headache.

 

[OldTLSDoug]

Forgive my ignorance, but how does cam chain tenstion affect the shims? It would seem that it would have to flat out be left out, as I cannot see enough clearance to pop one out without damaging the machine a bit. YMMV

 

[chris79]

That's what they told me, and like you I can't really see the thing...

But it seems to work on track bikes they do and solve the problem.

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[Slowstad]

Valve float but I find it hard to believe it's happening on your bike.

Nothing wrong with manual tensioners tho

 

[Jpburgos]

Do u have pictures of this, for future reference, have u solved the problem?


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[Dirtyrc8r]

started getting false neutral at the track last week. I have a bazzaz QS and several times I upshifted, it hung in neutral and I banged the rev limiter several times when it shifted back into the previous gear.

this didn't happen at all last time at the track and I did not work on the bike at all in between.

so I started hearing a loud valve train tick and coasted back into the pits. I loaded the bike and headed home. took it apart today and found massive valve clearance in one front exhaust valve. I removed the cam and the shim is MISSING. it is not in the head so it must have went down the cam chain passage into the crankcase?

I've got a telescopic magnet. been in the oil drain holes and all over the head. where else should I look?

Does the loud ticking happen at idle? or at certain rpm's.
I have a tick after hitting the rev limiter by accident, but it's at certain rpm's and it seams to go away above 4000 rpm's

 

[grim]

I lost both intake valves mid-race yesterday. Both broke off at the stem. All 4 shims (intake & exhaust) were out of place. I found them way down by the springs but only got them out after I got the head off and turned it upside down, although a magnet would have got them (my magnet was too big (that's what she said)). Right now I'm guessing I lost cam chain tension and had a valve to piston incident causing both intake valves to break. Just a theory. The head and piston are both a total loss. Definitely going to be replacing the cam chain tensioner when I rebuild it. Anyone have the part number for the correct DJH tensioner?

 

[Jpburgos]

Wow, thanks for the pics, maybe that is the reason why Ktm says to check the valves and shims after every track day on the street version, and replace them all after 3k miles on the track version, can u please load more pictures and procedures for future reference please.


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[Hollowfikation]

I lost both intake valves mid-race yesterday. Both broke off at the stem. All 4 shims (intake & exhaust) were out of place. I found them way down by the springs but only got them out after I got the head off and turned it upside down, although a magnet would have got them (my magnet was too big (that's what she said)). Right now I'm guessing I lost cam chain tension and had a valve to piston incident causing both intake valves to break. Just a theory. The head and piston are both a total loss. Definitely going to be replacing the cam chain tensioner when I rebuild it. Anyone have the part number for the correct DJH tensioner?

That sucks, were the valve springs ok?
If the tensioner went bad, did it jump timing as well since you had interference? Possible mis-shift causing an over rev, breaking a spring or valve float causing the piston to valve contact?

I just don't see how the valve shims came out before the valves themselves broke. I would think either the valve spring broke, or floating a valve....and usually you break the spring during that process. These are my thoughts......I do build many an engine....so I'm just curious as to the cause of failure.

 

[grim]

That sucks, were the valve springs ok?
If the tensioner went bad, did it jump timing as well since you had interference? Possible mis-shift causing an over rev, breaking a spring or valve float causing the piston to valve contact?

I just don't see how the valve shims came out before the valves themselves broke. I would think either the valve spring broke, or floating a valve....and usually you break the spring during that process. These are my thoughts......I do build many an engine....so I'm just curious as to the cause of failure.

None of the springs appear to be broken. I can't explain the missing shims either. Especially on the exhaust valves where there appears to be little damage. The motor wouldn't roll over TDC so it was difficult to say for sure if the can had skipped a tooth, but it looked like it was still timed right. One of the valve seats is gone so that may have dropped and then caused the valves to break, but I would have expected to see problems on the exhaust side as well if that had been the cause.

 

[fast4d]

an update:

my ticking is constant and based on rpm.

I know my valve train is intact because I run a lap (at less than WOT) after I heard the ticking to determine what was wrong. the bike was running ok since only one valve was staying shut (more or less).

I haven't touched it in a few weeks. got to order a camera/probe and take a look inside. I've been all over the head and oil sump with a magnet and no luck.

Sorry to heard of the catastrophic failure. I only looked at the tensioner briefly they are pressured by oil or spring?

 

[fast4d]

I lost both intake valves mid-race yesterday. Both broke off at the stem. All 4 shims (intake & exhaust) were out of place. I found them way down by the springs but only got them out after I got the head off and turned it upside down, although a magnet would have got them (my magnet was too big (that's what she said)). Right now I'm guessing I lost cam chain tension and had a valve to piston incident causing both intake valves to break. Just a theory. The head and piston are both a total loss. Definitely going to be replacing the cam chain tensioner when I rebuild it. Anyone have the part number for the correct DJH tensioner?

looks like your front cylinder went. my missing shim is from the front cylinder exhaust valve.

 

[Badger]

looks like your front cylinder went. my missing shim is from the front cylinder exhaust valve.

How did you get on with this, did you find the shim in the head?

Interested as i think mine might have done the same on over rev due to race shift gearchange and me not being used to it, going down a gear instead of up at max revs:cursing:

 

[fast4d]

I have been out of town for work and havent worked on it yet. as far as I can tell nothing was damaged but I need to find the shim

 

[Badger]

cheers, be interested to hear how you get on with it when you get the time

 

[zippy]

What is the exhaust on these bikes and what model of RC8R, I see fast4d is a twinspark.

Back in August I posted a Thread about EVO1 Akrapovics causing failures with Twinspark RC8R.

Turns out KTM (in the UK at least) sent out a notice to dealers saying the EVO1's on Twinsparks 'could' cause damage. My local dealer told me the problem is lost shims caused by valve float.

Perhaps the US never got notice of this failure.