2020 KX250 piston slap after valve adjustment

shortty761
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Newport News, VA, USA

Well I have a big problem it seems.


I’ve never adjusted valves before, and my bike has been super hard to start lately, to where I had to give it throttle to start and kick 10 times.


Anyways I decided to attempt adjusting my valves. Took everything apart just fine. When checking clearance I had 0.00 clearance on the intake side, and I was a little off on one exhaust shim.


Got all my clearances right, put everything back together. 

Im kind of sure my timing is right but im not 100% to me it looked like the marks on the cams were in line with the head (exhaust at 9 o clock and intake at 3 o clock) I may of been a little off

So anyways i put everything back together, and i was having a weird issue when turning the engine over with my ratchet to where i felt like it was almost not wanting to turn all the way over while manually turning the crank. It was like I was hitting something.


So then i thought maybe the chain was bound up or something, so i took the cams out and put them back in, made sure everything was top notch before putting my cam chain tensioner in.


After doing all that everything seemed good to go.


I fired it up and for like 4 seconds “CLANK CLANK CLANK CLANK” I just cut it off because it did not sound good.

Pulled the valve cover, and went to manually turn it over, felt like something was getting stuck. Wanted to see what it would do when I tried to slowly kick it and even the kick starter got stuck and couldn’t go through the whole stroke.


Is my timing just off that bad? Is my piston making contact with the valves? What the hell have I managed to do.


 

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FGR01
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Fantasy
9/15/2024 7:04am

Yeah, sounds like you made some piston to valve contact.  Here's the good news.  If your intakes were zero'd out... that head needed to come off for a valve job anyway.  

1
Factor E
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So Cal, CA, USA
9/15/2024 3:30pm
It should have taken more than the next size shim to get to right clearance If the shims are thin than you need a vale job
shortty761
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Newport News, VA, USA
9/15/2024 5:02pm
FGR01 wrote:
Yeah, sounds like you made some piston to valve contact.  Here's the good news.  If your intakes were zero'd out... that head needed to come off...

Yeah, sounds like you made some piston to valve contact.  Here's the good news.  If your intakes were zero'd out... that head needed to come off for a valve job anyway.  

That’s what I’m thinking. And yeah the intakes were completely zeroed out lol. I had to drop .40 and .35 to get them in spec! What’s a good place on the East coast that could do this for me with good turn around time? I NEED my bike for October 12-13. And what do I tell them? I need a valve job? What’s the typical cost?

shortty761
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Newport News, VA, USA
9/15/2024 5:02pm
Factor E wrote:
It should have taken more than the next size shim to get to right clearance If the shims are thin than you need a vale job

Yeah the shims are thin thin. Had to go .40 and .35 less on the intake valve shims

The Shop

shortty761
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Newport News, VA, USA
9/16/2024 11:10am

Any other insight would be much appreciated 

40acres
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Houston, TX, USA
9/16/2024 12:44pm

You have piston/valve cleance issues. You also need a valve job (new valves & valve seats). I'd recomend you find a local machine shop that can do the work for you and perhaps start cleaning your air filters more frequently. 

1
shortty761
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Location
Newport News, VA, USA
9/17/2024 6:28pm

FIXED. My timing was WAY OFF. Runs like a top now

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