Jump to content
xz225f

KX250F Intake Valve leak?

Recommended Posts

So I recently replaced the headgaskets on my ‘05 kx250f due to a small leak. While I had the head off I decided to do the valve seals and found my intake valve springs were broken. I replaced the springs and put it all back together. It would not start so I began diagnosing and came to find I was getting positive and negative pressure when I sealed my hand against the intake port when the lobes were not opening the valves. I checked my valve clearances and they are all in spec, any ideas?

Share this post


Link to post
Share on other sites

I removed the valves , they look straight. The bike would run though but I had to blip the throttle and when I slowed dow it would idle high then drop low and die. How would I do a leak test?

Share this post


Link to post
Share on other sites
Posted (edited)

Any chance you didn't re-installed the valves in their same seats?  (right side valve is now installed on the left and vice-versa)

(different wear patterns, now not sealing)

 

With the cylinder head assembled and held right side up,

spray carburetor cleaner in the intake and exhaust ports.

Observe if there is any sign of liquid leaking around a valve.

Edited by mlatour

Share this post


Link to post
Share on other sites
8 hours ago, xz225f said:

I removed the valves , they look straight. The bike would run though but I had to blip the throttle and when I slowed dow it would idle high then drop low and die. How would I do a leak test?

You know the way to check 'em easy is to roll them along the edge of a bench so the head hangs off the side and it rolls on the stem only, and watch the head for wobbles. You usually can't see it by just looking unless it's real bad.

Mlatour's way of checking for leaks probably works better than mine, I usually invert the head and put a bit of fuel in the chamber and look for it flowing out of the port.

Maybe the first thing to do is double check is your timing and make sure that's right before pulling it down again.

  • Like 1

Share this post


Link to post
Share on other sites

I have spent hours on making sure the timing is right, so i think that is fine. I guess i will remove the head and check everything yall mentioned

  • Like 1

Share this post


Link to post
Share on other sites

OK so i put the gas in the port and it appeared like the opposite of what carb cleaner looks like when it evaporates. It was slow but eventually a drop formed. Is this fine or should i just lap them?

Share this post


Link to post
Share on other sites

As explained in another one of your posts,

IF the intake valves are Titanium (as are the originals), lapping them wears away the thin hardened coating.

It may improve sealing for a very short time but they'll quickly wear and leak again.

 

Your on-going troubles are the proof that cutting corners and 'fixing' things on the cheap doesn't work, what was likely done by the previous owner as well.

I know to want to get it running and sell it off ASAP but don't polish a turd and pass off the same headaches to the next owner.

 

Or at the very least, disclose to the potential buyer what you've done to get it barely running and, set the price accordingly.

Edited by mlatour
  • Like 1

Share this post


Link to post
Share on other sites
36 minutes ago, mlatour said:

As explained in another one of your posts,

IF the intake valves are Titanium (as are the originals), lapping them wears away the thin hardened coating.

It may improve sealing for a very short time but they'll quickly wear and leak again.

 

Your on-going troubles are the proof that cutting corners and 'fixing' things on the cheap doesn't work, what was likely done by the previous owner as well.

I know to want to get it running and sell it off ASAP but don't polish a turd and pass off the same headaches to the next owner.

 

Or at the very least, disclose to the potential buyer what you've done to get it barely running and, set the price accordingly.

So is the leaking i described bad? Also there is a small ring around the valve where it contacts with the head, is it not worn down there already so lapping wouldn’t hurt it? The guy before me took good care of this bike, the cylinder still has the cross hatch and there is a decent condition vortex piston installed and i believe he did valve work at one point because he had 2 springs installed in each intake valve before i had to replace them with the factory single spring. (He had one smaller spring inside the other spring)

Share this post


Link to post
Share on other sites

How long did it take the drop to form?  If a few minutes, yes that is bad.  If near an hour or more, it would be nothing of concern.

If the valves are stock, whether new or original does not matter, the stock valves are light titanium alloy with a hardened coating around the rim at the sealing surface.  If you lap these type of valves, that hard coating gets damaged or even removed.  The comparatively soft titanium will wear very quickly, resulting in valve clearances tightening within hours and needing adjustment often.  The only valves that can be lapped are all stainless - which is a whole different ball game.

mlatour is coming off a little harsh and preachy above.  It must have been a tough morning.  May needs more honey in the coffee cup to get back to his usual sweet demeanour.

OK, so you checked and rechecked the valve leakage test.  A drop formed.  But how quickly?

You checked and rechecked the valve to cam clearances and set them in spec.  I will advise to set them at the largest gap end of the spec. Set the intake valves at 0.15 mm (0.006", 6 thou).   Set the exhaust valves at 0.22mm (0.009", 9 thou). ... Ever so slightly more is absolutely fine.

You checked and rechecked the valve timing.  Remove the cam chain tensioner.  On the flywheel there are three timing marks.  Two of those marks are close together.  When looking through the timing port, line up the crank shaft on the second of those two lines that are close together.  Line up on the one just a few degrees to the right.  Holding the crank in that position pull the cam chain up along the front (exhaust) side of the engine.  Pull it tight, no slack in the front.  Set the exhaust cam in with the timing dot on the sprocket level with the top of the cylinder head metal surface, not top of the rubber valve cover gasket.  Level with the metal.  Now count off EXACTLY 28 chain pins, starting with first pin above that exhaust valve timing dot.  Set the intake cam in with the farthest to the right timing dot immediately AFTER that 28th pin.   The far dot on the intake cam sprocket may not line up with the top of the head metal.  IGNORE that.  What is critical is the exhaust cam dot being set and having exactly 28 pins between them.

Once you have it all lined up, install the cam chain tensioner.  Then go around the other side of the bike and look at the directions the cam lobes are pointing.  They should be pointing symmetric, exactly opposite of each other at the 10 o'clock and 2 o'clock positions.  Give or take ever so slightly.  If they are not even and opposite, then you have a slipped cam that is causing your problems.  To fix a slipped cam, go here:.   Then come back and redo the timing procedure.

Hope that helps!

 

 

 

Screen Shot 2019-10-30 at 8.59.20 AM.png

Screen Shot 2019-10-30 at 9.07.38 AM.png

Edited by FaceDeAce
  • Like 3

Share this post


Link to post
Share on other sites
On 10/27/2019 at 10:34 AM, xz225f said:

So is the leaking i described bad? Also there is a small ring around the valve where it contacts with the head, is it not worn down there already so lapping wouldn’t hurt it? The guy before me took good care of this bike, the cylinder still has the cross hatch and there is a decent condition vortex piston installed and i believe he did valve work at one point because he had 2 springs installed in each intake valve before i had to replace them with the factory single spring. (He had one smaller spring inside the other spring)

 

PS:  two springs on the valves is a tell tale that the valves are not stock.  Stainless valves are heavier than the titanium.  The heavier valves need stiffer springs to pull them closed at high rpm.  My recommendation would be to first get in contact with the previous owner and get information of exactly what valves (kit) he has put in there.  Then you can best to decide whether to work with them or whether to change them out to the stock valves.  This information from the previous owner is critical to your decision making and next steps at this point in time, and at figuring out how best to resolve your problem.  

Please get back to us here with what you find out and we can help guide from there.

 

 

Edited by FaceDeAce

Share this post


Link to post
Share on other sites
On 10/30/2019 at 11:30 AM, FaceDeAce said:

 

PS:  two springs on the valves is a tell tale that the valves are not stock.  Stainless valves are heavier than the titanium.  The heavier valves need stiffer springs to pull them closed at high rpm.  My recommendation would be to first get in contact with the previous owner and get information of exactly what valves (kit) he has put in there.  Then you can best to decide whether to work with them or whether to change them out to the stock valves.  This information from the previous owner is critical to your decision making and next steps at this point in time, and at figuring out how best to resolve your problem.  

Please get back to us here with what you find out and we can help guide from there.

 

 

Ok, the previous owner did not even mess with the valves. He bought it as a practice bike so it was probably used when he got it. Maybe the extra springs helped the valves seal better. Should I just get the extra springs? If so where would I get them?

Share this post


Link to post
Share on other sites

Different valve materials have different weight of the valve which requires different spring to have the strength to close it. For stock valves, single stock spring per valve. For aftermarket valves, most require their own specific springs which can be two springs.

Clearance requirements for either are the same spec.

So if using stock valves use stock spring.

If using aftermarket valve use the matched after market spring(s). Do not put a stock spring over an aftermarket valve. If you see two springs, that means it is an aftermarket valve. Cannot use a stock spring on it.

I do not see where you say how fast,how bad, or how good, the valve leak test with liquid was.

If you want to replace the spring(s) you have to know what the brand of the valves are so you can get the right spring. If previous owner does not know then you are left with choice of

- leave as is, set clearance to spec, time it properly and try it.

- replace the valves and springs with new ones that are known by you. Stock valve and spring or a new aftermarket matched set kit.

 

Given the age of the bike, if I were replacing valves on it I would go with stock valve(s) and spring sets. It is not necessary to replace them all. Only the problem one(s). It is also usually not necessary to have the seats cut. The valves are harder than the seat and the seat will self wear to seal. (run-in period of a few hours). So very small leak liquid test can be considered a pass. Within reason! If the seats are badly worn or damaged, fast leak test, then the seat also needs to be replaced and cut.

 

Hope that helps!

 

 

 

 

 

 

 

 

  • Like 1

Share this post


Link to post
Share on other sites

Ok, i just want to see if i can get it running for now with cheap parts. I will put quality parts in when i sell it. I am just asking if it would be fine to use these or is there too much risk? https://www.ebay.com/itm/INTAKE-VALVE-Fits-KAWASAKI-12004-0002-12004-0023-12004-0033/273092619594?hash=item3f9596ad4a:g:1SsAAOSwme5amctE:sc:USPSFirstClass!78368!US!-1

Share this post


Link to post
Share on other sites

When it comes to valves, I much prefer oem Kawasaki. Think about it. A defective valve can take out the entire engine catastrophically. I also do not promote high priced stuff as better. The oem valve is reasonably priced from dealer. From where you the buy oem the valve and spring is up to you.

Share this post


Link to post
Share on other sites
8 hours ago, FaceDeAce said:

When it comes to valves, I much prefer oem Kawasaki. Think about it. A defective valve can take out the entire engine catastrophically. I also do not promote high priced stuff as better. The oem valve is reasonably priced from dealer. From where you the buy oem the valve and spring is up to you.
 

Is there anyway to get them cheaper than $160 a pair? I know i sound like a cheap skate and honestly i am but i just dont have the money, im a broke 14 yo. Could i trade it in this condition for a xr400 maybe? It needs fork seals, oem valves and cam chain. Could i squeeze over 1200$ out of it?

Edited by xz225f

Share this post


Link to post
Share on other sites

Unfortunately, that is the range of what a valve set costs.  No way around it.  You may find them 20$ less or 20$ more depending on where you shop.  As for trade value or sale price, that depends entirely on your local area and what there are for buyers around you.

Share this post


Link to post
Share on other sites

Where do you live xz?

Slight parts discount in Huntington Beach if you're near OC.

mlatour is just as fed up with Ti valves as everyone else but sponsored factory riders...

What I want to know is does a magnet stick to the valves that had 2 springs?

I've ridden the crap out of hissy valves for hours...not crispy. But a toy still playing...

Also, if he hates a new valve...sure you could put it in and it not leak...that's what I would try and hope for...but if I had the funds, 3 angle seat cut for that new valve. But if it held gas I'd go ride

 

 

Share this post


Link to post
Share on other sites
On 11/14/2019 at 4:28 PM, notoriousE-R-I-C said:

Where do you live xz?

Slight parts discount in Huntington Beach if you're near OC.

mlatour is just as fed up with Ti valves as everyone else but sponsored factory riders...

What I want to know is does a magnet stick to the valves that had 2 springs?

I've ridden the crap out of hissy valves for hours...not crispy. But a toy still playing...

Also, if he hates a new valve...sure you could put it in and it not leak...that's what I would try and hope for...but if I had the funds, 3 angle seat cut for that new valve. But if it held gas I'd go ride

 

 

The magnet thing is a good idea. I will do that as soon as possible and post what happens

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...