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Old 06-04-2014, 09:45 PM   #1
rburkat OP
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KTM 990R leakdown test fail

I'm doing a leakdown test on my 2010 990R because Im hunting around for my loss of power and also, as my friend put it, your bike runs and smells like a KLR (that last part is clearly a cause for concern)

I have the cylinder at TDC, and am pumping 80psi into the spark plug hole, but the leak down is large, 50% because the air is coming out the intake valves at least as I can see them.

Here is the video.


I was trying to test how well the piston rings were sealing but clearly this is messing up my plan. Is this a matter of just pulling the head off and lapping the valves to their seats?

Thanks for any input and info.
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Old 06-04-2014, 10:10 PM   #2
fast4d
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you sure it is at TDC?

you have the VC off? easy to see and rotate so cam lobes are off the valves
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Old 06-04-2014, 10:26 PM   #3
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I'm sure you've checked, but to state the obvious... Is it not shimmed too tight?
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Old 06-04-2014, 10:41 PM   #4
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Quote:
Originally Posted by fast4d View Post
you sure it is at TDC?

you have the VC off? easy to see and rotate so cam lobes are off the valves
Yeah valve cover is off, dots aligned to outside, and locking bold in place.

I checked the the valve clearance and it's fine. To make 100% I also undid the bolts on the bridge so there is zero chance of valves being pushed down.
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Old 06-05-2014, 05:20 AM   #5
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is it the front cylinder?( it is nearest the intake snorkel) You can pure some isopropanol into the intake track and see if it leaks down into the cylinder. I had same problem with 950 with only 14000 miles on it, Had to rebuild the front head. I found out dirt was getting by the filter. The PO thought maintenance was fantasy. Now I have Rottweiler foam filter and sleep much better. I just watched your video and that was what Mine looked like. time for new valves and seats. I tried lapping mine but you may have better luck as my leak down test was 80%. I asked about the front cylinder because my machine shop guy(Halls Performance) said most all dirt getting in to the intake valves happens closest to the point of entrance, the snorkel.

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Old 06-05-2014, 07:58 PM   #6
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Yeah, looks like you need to freshen up the intake valves. New valves and CUT the seats, NO LAPPING!!!!

Might just do the rear while you are at it.
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Old 06-06-2014, 05:18 AM   #7
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I'd spin the motor a few times and run the procedure again.....You can pour a little petrol or alcohol....see if it drains slowly or fast.

Options would be to try lapping new valves, have a good look at the seats....they are the tougher harder part of the pairing. Use fine paste.

As mentioned you need to find the cause, could be shit getting past your filter so the bores and rings could be shot. You could have a look for a used head rather than having new seats pressed, could be a quicker cheaper solution.

In the vid, the valves just don't look fully closed to me.... maybe bent...
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Old 06-06-2014, 05:33 AM   #8
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You probably already saw this but if not, here's a guy who had poor leak down results which turned out to be a bit of carbon or dirt on the valve seats. Easy fix:

http://www.ktm950.info/how/Orange%20...0teardown.html
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Old 06-07-2014, 08:12 AM   #9
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Thank for the info. So I decided to disassemble things further than I have ever done before.

Engine out


Took the rear piston out. Thats a lot of carbon build up on this thing. Is this normal? Notice the clean spots at the front and rear edges of the piston. I believe that is a sign of steam cleaning where the head gasket is compromised and coolant is getting in and cleaning the piston.


Looking at the head, that's a lot of carbon also. I could see how little pieces could get in between the valve and seat and keep it open slightly.


The cylinder seem to look ok.


There are a couple of marks going vertically but but are not deep. Is this cause for concern? Should i have this thing cleaned up?


I cleaned up the head with a bunch of brake clean and a lot of scrubbing. Is there some kind of chemical that would do the job a lot faster? I'm now scraping the crap off the valve but I dont know if there is some coating that i maybe removing.


Exhaust valve and seat.


On the valve it's not as clean. I'm not sure if i should sand the sealing edge here or what?


Rest of seats


Intake valve.


Some things I noticed during the disassembly.

1. there is a procedure to measure the chain tensioner slack when removing it and mine was way past the limit. I imagine that means the cam chain is stretched and should be replaced.

2. the ring gap is is around .5mm and the max limit in the manual states .4mm so either I need new rings or the cylinder is worn. I'm not sure how I decide which. I figure I'll just order new rings and see what the gap is with new ones.
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Old 06-07-2014, 11:31 AM   #10
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New valve and rings, cut the seats and NO lapping. You don't need to fit new seats unless they are very worn and they look ok on the photos.
Of course someone will be along who'll tell you that it's all too worn and you should buy another motor rather than bothering with the minor work in freshening the top end

Steve
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Old 06-07-2014, 11:43 AM   #11
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Radek, Get ahold of DJH on ktmtalk. He does good head work and lives in Wash. not too far from you I think.
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Old 06-07-2014, 01:04 PM   #12
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Quote:
Originally Posted by Bowber View Post
New valve and rings, cut the seats and NO lapping. You don't need to fit new seats unless they are very worn and they look ok on the photos.
Of course someone will be along who'll tell you that it's all too worn and you should buy another motor rather than bothering with the minor work in freshening the top end

Steve
Hi Steve, What's the reason not to lap the valves? Curiosity has the best of me here. Thanks!
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Old 06-07-2014, 02:14 PM   #13
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I bought a cheap Harbor Freight ultra-sonic jewelry cleaner, and use a mixture of Pine-Sol and water. I give them a couple of hours in the bath and it works very well. Won't damage the surfaces of the valves and may allow them to seal. Then you can reassemble the head and do a solvent test on the valves to see if they're still leaking before putting the engine back together. The ultra-sonic cleaner also works well on carburetors and other small items.









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Old 06-08-2014, 10:07 AM   #14
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The seats and valves wear together, personally whilst you're there I'd replace the guilty valves and all the valve seals, lap them in with fine paste....Just by lapping you'll be able to see what the contact surface of the seats are like....ie they shouldn't be dished. The surfaces should be a clean 30-45 deg chamfer depending on spec, you'll see three different chamfers, the one in the middle is the sealing surface, I don't know the KTM lc8 spec off hand. Depending on condition and surface, you might need to borrow a seat arbour and cutter, or get a shop to do it....remove the bear minimum. Then lap the valves in. Pour some petrol in the head bowl, no fluid should leak past if they are lapped in nicely.
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Old 06-08-2014, 04:08 PM   #15
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Ok poking the hornets nest a bit.. but..

Valves should be ground, seats should be cut, lapping is for lawnmowers.

There is not a single top engine builder that laps valves since about 1965.

Lapping produces a rounded valve seat surface that does not clean itself correctly. To get maximum sealing you need the seat to valve surface angle to produce a slight wiping action that keeps the carbon from sticking in there.

lapping will almost always increase wear on valve seats if the engine runs over about 3500 rpm..

Ok done whacking the hornets nest ! :)
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