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Timing issue? Valve adjustment gone wrong HELP!

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Hi everyone, so last time I rode my 2015 kx250f it was hard to start when cold and wouldn't idle all day even with the idle turned all the way up. I got it home and today checked my valves. Exhaust seemed good one intake was just a bit tight and the other was far too tight. (.0015") I got the new shims, put it all back together, and it fired right up ran great. Changed the oil and again, it fired right up and ran fine. I started it again and it was running just swell until I held it at about half throttle for 3 or so seconds and BAM! A large back fire, it died and wouldn't restart. It still turns over but is a little hard to kick, and almost seems to back fire as I kick it. I tore it all back apart, timing was still good (unless I'm 180 out but it ran good), all the parts are in their spot (didn't drop a dowel or C clip anywhere) and in my opinion everything seemed fine. 

I have no idea what I did wrong, I've adjusted valves before and never had an issue. Does anyone have an idea? Thanks in advanced! I really don't want to have to take it in $$$

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Valve cover, chain tensioner, both C clips, and both cams came out. I didn't pull back off the buckets, didn't see any reason to.

34 minutes ago, FaceDeAce said:

For a start, when you say your tore it all back apart. What "all" did you take apart and look at?

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looks like your cam timing went (hard to kick)

check the timing mark (tdc) on flywheel, don't mistake the ignition mark for it, put cams in and make sure you put the tensioner in the right way, not upside down...

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3 hours ago, Bernie Nottelling said:

looks like your cam timing went (hard to kick)

check the timing mark (tdc) on flywheel, don't mistake the ignition mark for it, put cams in and make sure you put the tensioner in the right way, not upside down...

So it appears as though I can see the mark on the flywheel twice per cam revolution. Meaning when I put the mark on the flywheel at what should be TDC my alignment marks on the cam gears match the top of the jug like they should, but if I spin the flywheel until I see the TDC mark again, the timing is then way off. I pulled the plug and both TDC marks are true TDC in relation to the piston, but are simply on a different stroke so I'm guessing this won't play an issue to my problem?

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There are a couple of possibilities to consider checking over.

A.  That valve which was tightest.  May be cupped to the point that it is nearing sticking point.  It would be good to lift the head to have a look at your valves and how deep they are seating. A cupped sticking valve is a stem soon to be bent or soon to be dropped valve.  In the picture, valve on the left is a normal wear the valve on the right is a cupped valve about to fail.  Btw these are off kx250f which I just recently replaced that cupped valve.  It was the intake valve, left side, when standing over bike facing forward.  Once the cams are out for clearance checks it is a bit more time, but not much really, to lift the head and have a look.

B.  Cam chain is near impossible to jump if it is decent condition.  If it is a worn stretched chain and the tensioner not working properly, then a chain jump will put timing off.  Check that the tensioner with spring, ratchet, and pin all move freely and are working properly as well as installed properly.

C.  Camshaft sprocket slippage.  This happens, it is doubtful to have occurred from what you described.  Unless you messed up on the timing initially and resulted in having piston to valve contact.  (There may be another reason to lift the off head and have a look).  The second picture shows a slipped cam.  The hole in the sprocket is supposed to be aligned with the peak of the cam lobes.  In this case, while all timing marks on the bike are all aligned and look good, the cam itself is out of time and will not work.  Causes a lot of head scratching if overlooked.  Check that the cam lobes are at the 10 o'clock and 2 o'clock positions when you have all the timing marks lined up properly. Third picture.

D.  Flywheel timing marks.  There may be 3 on yours.  Two are fairly close together and then there is another one about 120 degrees away.  Find the two that are close together, line up your timing to the second one, the one to the right.

E.  Electrical, crank sensor, throttle position sensor.  Check that the reconnections after you were done with the head and cams are clean, proper, and made.  Based on what you describe, particular attention to the TPS.

Based on what you described ..... I am thinking E is most likely.  A few things for you to consider looking at.   Hope that helps!

 

IMG_5308.JPG

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IMG_3732.JPG

Edited by FaceDeAce
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46 minutes ago, mason_kawasaki said:
So it appears as though I can see the mark on the flywheel twice per cam revolution. Meaning when I put the mark on the flywheel at what should be TDC my alignment marks on the cam gears match the top of the jug like they should, but if I spin the flywheel until I see the TDC mark again, the timing is then way off. I pulled the plug and both TDC marks are true TDC in relation to the piston, but are simply on a different stroke so I'm guessing this won't play an issue to my problem?

 

One TDC will be the compression/combustion stroke. All valves closed. Cam lobes up. no buckets being pushed. The other TDC will be the exhaust stroke. When you say way off ... look at the cam lobes at that TDC position. You will see that the exhaust valves are open; meaning the exhaust cam lobes are pointed pushing the buckets down. And the intake cam lobes positioned to open a few degrees later to draw the next charge in.     Four stroke engine cycle is

  1. Intake stroke, piston moving down (BDC) intake valves open (pointy part of the camlobes),
  2. Compression stroke, piston moving up (TDC) all valves closed (lowest roundest part of the camlobes),
  3. Combustion/Power stroke down (BDC) all valves closed (lowest roundest part of the camlobes),
  4. Exhaust stroke up (TDC) exhaust valves open (pointy part of the camlobes), .... repeat.  

Two BDC and two TDC with cams positioned differently pending which of the four strokes the cycle is in.  When lining up the camshaft and crankshaft timing marks, it is all setup at the compression stroke TDC.       Hope that helps!

Edited by FaceDeAce
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42 minutes ago, FaceDeAce said:

 

C.  Camshaft sprocket slippage.  This happens, it is doubtful to have occurred from what you described.  Unless you messed up on the timing initially and resulted in having piston to valve contact.  (There may be another reason to lift the off head and have a look).  The second picture shows a slipped cam.  The hole in the sprocket is supposed to be aligned with the peak of the cam lobes.  In this case, while all timing marks on the bike are all aligned and look good, the cam itself is out of time and will not work.  Causes a lot of head scratching if overlooked.  Check that the cam lobes are at the 10 o'clock and 2 o'clock positions when you have all the timing marks lined up properly. Third picture.

 

 

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C. Was the correct answer! My exhaust sprocket has slipped, which is good news to find what went wrong but bad news in that you're saying I had piston to valve contact...

How screwed am I? Full top end rebuild? Im a little nervous to try and pull the head myself, it would be my first time going deeper than the valves and I sure don't want to mess something up even worse.

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Sorry to hear that :( ...  Perhaps triple check to be sure.

Will have to give you one of those "it depends" answer.  It all starts with pulling it apart to determine what is damaged and what is not.  It depends on how far out it was.  It may be all you need is to retime the cam.  It may be you will need to replace bent valves and cracked piston.  It depends ......

If a person is mech inclined, has a decent manual to follow, and knows what critical things to be looking for when doing the work; eg proper tools, torque specs, clearances/tolerances ... then this really is not at all hard to do.  At very least I suggest you take it apart yourself so you can see what is or isn't damaged so you can have informed conversations and questions with shops and buds.  Then you could take to a shop to put it back together if you are uncertain about yourself.

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It ran for well over a few minutes before whatever happened did happen... So hopefully it wasn't that far out, but I now am noticing as I turn it over with a 17mm socket on the flywheel really slowly I can hear a gurgling and sucking sound which I'm hoping isn't a cracked piston... 

I do find myself pretty mechanically inclined but I'm definitely not sure about my skills now that I messed this up so bad. 

I think I'll try to find a good mechanic in my area thank you so much for your help though! 

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Note that the exhaust cam does have an auto decompression pin on it.  When engine is turned over slowly, this does bleed pressure out the exhaust.  It sounds like a leak when you do it.

We learn a lot by second guessing ourselves and going right back at it to confirm our worries or validate our confidence.  You may have not messed up all that bad.  You will not know for sure what you have until the head is lifted.  It isn't all that bad, the basic steps are  (2015 may have a couple things less or more)

  1. loosen the carb clamps on the carb to head boot and the air box,.  2 clamps, 2 screws
  2. loosen exhaust header to muffler bolt.
  3. remove the seat subframe with muffler, fender, and plastics etc all still attached. Take it all off as one piece. 3 bolts.  leave carb in place on the head
  4. slip carb off of the head, leave to hang on the cables
  5. remove the head to frame bracket.  3 bolts
  6. drain the coolant. 1 plug.  Loosen the coolant hose clamp, pull hose off, bent and tie it up out of the way. 1 screw.
  7. Remove the exhaust header pipe and thin ring gasket from the head.  2 nuts.
  8. pull the cams out.  
  9. pull the cam buckets and shim buttons out, keep track of which came from which!
  10. remove the 4 head bolts
  11. lift the head off .................  roughly 30 minutes of work to get to this point.
  12. inspect valves for depth of seat, signs of contact, smooth movement, etc.  Repair/replace as required.
  13. inspect top of piston for signs of contact, dings, cracks.  Replace if required.
  14. inspect cylinder wall for signs of contact, dings, scratches, repair/replace if required.

Reinstalling and reassembling is the exact reverse of above.  New head gasket recommended, about 25$ a piece.  If you pull the cylinder, same .. a new gasket is recommended, about 20$ a piece.  Use correct torque sequence and torque spec on the 4 head bolts and on the camshaft caps.  All other fasteners are fine to go to snug plus 2 UgaDooGa's.  Oh and do not forget refill coolant before running it!

For a read up on how to fix a slipped cam, go have a look here at this thread:  

 

 

open 250f engine.jpg

decomp 250f.jpg

Edited by FaceDeAce
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3 hours ago, mason_kawasaki said:

Im a little nervous to try and pull the head myself, it would be my first time going deeper than the valves and I sure don't want to mess something up even worse.

If you're already this far the question becomes not of whether you're capable of doing the work, but of do you have the money to do it?

Once that head comes off costs can snowball quickly...

Edited by Trfsrfr

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Would it be worth a try to pull the cam realign the gear and put it back together? Perhaps the gear spun with out any valve to piston contact? Or should it all be pulled apart to be safe?

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I would pull it personally.

And as FaceDeAce already pointed out, pulling the head is another 40 bucks minimum, and not that much further labor wise from where you're currently at. But that 40 bucks is assuming that the head is in good shape and your gonna reassemble it as is.

Something tells me that wont be the case when you open it up though...

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1 hour ago, mason_kawasaki said:

Would it be worth a try to pull the cam realign the gear and put it back together? Perhaps the gear spun with out any valve to piston contact? Or should it all be pulled apart to be safe?

No, if you are confirming that you have a spun gear - I definitely would not fix only the cam and put it back together.  The advice is to pull it apart "to be safe" as you say, to "know what you got" as I say.  Pull it apart, figure out what you have and are or are not up against.  Then proceed from there.   We are here to help you along the way, you are not alone.

 

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2 hours ago, FaceDeAce said:

No, if you are confirming that you have a spun gear - I definitely would not fix only the cam and put it back together.  The advice is to pull it apart "to be safe" as you say, to "know what you got" as I say.  Pull it apart, figure out what you have and are or are not up against.  Then proceed from there.   We are here to help you along the way, you are not alone.

 

Ok, I think I'll look into my options for getting it fixed or for selling as is. I know you guys would help me along the way and I appreciate all your help already FaceDeAce, but i just dont feel confident taking on a job like this. Buy if you know anyone in colorado that could do it or would want to buy it let me know! And thanks again guys you've been a heap of help!

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ok, my advise, put it back together.. and start it... I doubt that there have been contact, if something bends, the valve clearance gets bigger, and less compression. one teeth wrong will still keep the engine running...

 

and to check the valves, if pulled into the seat.. you measure your shims.. at around 2.20 mm its time to change the valves

Edited by Bernie Nottelling
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Ok, I think I'll look into my options for getting it fixed or for selling as is. I know you guys would help me along the way and I appreciate all your help already FaceDeAce, but i just dont feel confident taking on a job like this. Buy if you know anyone in colorado that could do it or would want to buy it let me know! And thanks again guys you've been a heap of help!


Probabilities; upon lifting the head off ....
Most likely - there is no obvious landmarks or damage to valves or piston or anything. Marks are faint. Fix the cam, carry on
Possible - bent valve stem. Replace valve only, carry on
Low probability - carnage. Broken valve. Beat up seat. Battered piston. Open wallet OR Prepare for sale adv writeup.

Word; do not toss your bike without seeing first hand with your own eyes what the situation is. Else you will lose confidence and faith in yourself, and loss investment.
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