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Help diagnosing leaky valves

Mario

Mario

Member
Joined
Dec 20, 2015
Location
San Jose, CA
Moto(s)
Track and dirty ones
Hey all, got a question for the mechanical experts before I pull the engine out.

KTM 450 4 stroke 2013, trail riding. It has been sitting for about 1.5yrs (did not winterize it). As part of the long procedure to bring it back to life, I did a leakdown test. Here is the history and the result today:

2019 110hrs top end redone, 5% leakdown
2021 140hrs valve clearance check OK, 5% leakdown
2022 180hrs last time I rode it
TODAY >> 180hrs, 85% leakdown, all through both intake valves

I sprayed some sea foam on both intake valves and got a video of it. Looks like some even leakage on both valves. What do you think it could have happened? I cannot imagine that in 40hrs both valves went to hell. Air filter is clean, no dust or dirt in carb/intake manifold. Could it be that the bike was sitting with the valves open for 1.5 yrs and some surface rust on the valve/seat is preventing them from sealing properly?

[YOUTUBE]pdO2XOv8FOU[/YOUTUBE]
 
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First off, don’t use Sea Foam. It’s junk and can damage your engine.

Second, make sure the valves are properly adjusted, then run it for a bit, then redo the leak down test.
 
I am no pro mechanic, but from my experience, wear isn't a linear upward line, but a hockey stick shaped curve on items like valves. Once significant wear starts, it accelerates.

That said, the 450/500 KTM engines I am aware of, the head (valves) have lasted MUCH longer than that. The 350's life is closer to that of a 250F, some needing fresh valves in as little as 150 hours or less. Others lasting 250-300 or more hours without issue. I'm at 250ish hrs on my 350, with only 10% leak down loss and assume borrowed time. Seems to be a wide spectrum, perhaps maintenance, rider, and where it is ridden. :dunno

One 350 in our group went from fine to failure in only a matter of a day or two.. would no longer start.

15% isn't failing, but getting there. If you are truly concerned about it, perhaps disassemble and clean both the valves and seats. Carbon or other things can build up and affect sealing. Carb cleaner and lightly scrub with brass brush? Might not hurt to call Engine Dynamics and ask them what they would use to clean a valve without removing valve material.

I've read and always believed you don't lap TI valves in dirtbikes as it will remove the hardened layer from manufacturing to extend life (which leads me to be leary, cautious with what I'd clean them with and how.)

If you do reach out to Engine Dynamics, and they suggest what to clean with, I'd be very interested. I've seen a lot of YouTube videos, but most of them are idiots.

Either way, update us what you ultimately find. :thumbup
 
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Thanks for the feedback!

@ST Guy
I am curious as to why you say sea foam is bad? I am using it as fogging agent. I would assume a light coat of oil in cylinder and valves is better than leaving it dry for long term storage?

@OaklandF4i
This engine was reworked by Engine Dynamics at 110hrs. It was leaking 5%, probably didn't have a need to rework the top end, but did it anyways. They did a cylinder hone, new piston and they did a valve job. These valves should have 70hrs on them. I hope they don't go this fast at my slow trail riding speed :)

I will try to start it and see what happens like ST suggested, then do a leakdown. If it remains the same, I will take apart and inspect, but I fear this will be promptly packed and shipped to EDco.

Last question for my information, what are the valves and seat made of? You said valve surface is hardened titanium. Are seats machined on the aluminum head or do they have any steel/titanium inserts for these orange machines?
 
Mario said:
Thanks for the feedback!

@ST Guy
I am curious as to why you say sea foam is bad? I am using it as fogging agent. I would assume a light coat of oil in cylinder and valves is better than leaving it dry for long term storage?

@OaklandF4i
This engine was reworked by Engine Dynamics at 110hrs. It was leaking 5%, probably didn't have a need to rework the top end, but did it anyways. They did a cylinder hone, new piston and they did a valve job. These valves should have 70hrs on them. I hope they don't go this fast at my slow trail riding speed :)

I will try to start it and see what happens like ST suggested, then do a leakdown. If it remains the same, I will take apart and inspect, but I fear this will be promptly packed and shipped to EDco.

Last question for my information, what are the valves and seat made of? You said valve surface is hardened titanium. Are seats machined on the aluminum head or do they have any steel/titanium inserts for these orange machines?
Click to expand...

No, that is a good idea, as ST Guy suggested. Run it and recheck. I always put a tiny bit of oil on my o-ring of the tester to ensure I get a good seal. I assume it's the same tester and procedure as previously used. Didn't realize your top end included a valve jog. 70hrs is very short for a 500 in my experience.

No idea what the seats on KTMs are made of. Assume steel, or more likely some alloy. If it were just the aluminum of the head, they wouldn't last very long.
 
AND THE WINNER IS.... ST GUY!!!!

Put it together, started right away, let it run for 2 min, and here is the result. Will write down in my book of unexplained shenanigans...

Only thing I can think of is surface rust on the seat by sitting for so long. Or another that comes to mind is a sticky valve guide. I remember having an engine that was running rough and the mechanic found loss of compression due to sticky valve. Or maybe it is because I should have got a Yamaha or Honda :D

Anyways, thanks all! If it wasn't for your help, I would have taken apart this engine and send it for repairs. You guys rock! :thumbup :ride

JUBGuTb.png
 
Yea! One of my suggestions worked out!

Can’t tell you why it did, but I’m happy that it did. Possibly because of one of the reasons you mentioned.
 
As for Sea Foam, I consider it to be snake oil. I’ve heard of problems after using that crap. From engines that run worse than before to engines that will not even run after a treatment.

However, just spraying a little on the valves to help them seal probably didn’t do any harm. But if it did work to increase the seal, that wouldn’t be indicative of a cure because the Sea Foam wouldn’t be there after you started the engine.
 
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Sea foam snake oil? That would be a lot of snakes to squeeze for oil... :laughing

Thanks again! back to the garage to get this machine ready for dirty season :ride
 
Mario said:
Thanks for the feedback!

@ST Guy
I am curious as to why you say sea foam is bad? I am using it as fogging agent. I would assume a light coat of oil in cylinder and valves is better than leaving it dry for long term storage?

@OaklandF4i
This engine was reworked by Engine Dynamics at 110hrs. It was leaking 5%, probably didn't have a need to rework the top end, but did it anyways. They did a cylinder hone, new piston and they did a valve job. These valves should have 70hrs on them. I hope they don't go this fast at my slow trail riding speed :)

I will try to start it and see what happens like ST suggested, then do a leakdown. If it remains the same, I will take apart and inspect, but I fear this will be promptly packed and shipped to EDco.

Last question for my information, what are the valves and seat made of? You said valve surface is hardened titanium. Are seats machined on the aluminum head or do they have any steel/titanium inserts for these orange machines?
Click to expand...

Seafoam is not a fogging agent. You can find a proper fogging agent in a marine store. My assumption is that you had light surface rust on your valves, that was removed by running it. A fogging agent is designed to stop this issue as you know. I'm glad it all worked out for you.
 
Good stuff. I will comment on the Ti valves. They have a surface coating and if you lap them or reface them, they'll work great, but their life will be hugely diminished. Ti is soft. They tulip quickly. It's a problem on any motor with Ti valves. They tulip quickly with the coating, but without their life is very short.

I know one builder who refaces them and assumes that race motors are one season builds.
 
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