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I recently purchased a 2010 KX250F from a friend of mine that had been sitting in his garage for about 5 years. The bike seemed to be in decent shape and the price was right so i picked it up. I went through most of the bike before riding it (air filter, oil, greased all the bearings, adjusted suspension, changed all the fluids, etc) The valves sounded a bit loose so i decided to have a "Buddy of mine" adjust the valves. I get the bike back, go for a ride and the cam chain tensioner falls out while i was riding, luckily i caught it very soon after it happened and it never jumped timing. I put the tensioner back in and continue to ride the rest of the day. as the day goes on the valves sound much looser than they were originally before the adjustment was done, I decided to call it a day and tear the bike down myself. I shim the loose valves and button the bike back up, but now the thing sounds god awful. Straight up clacking coming from the right side of the top end. Since then ive probably had the bike apart and back together 4 or 5 times trying to figure out the problem. Its not the auto decompression valve, every valve is in spec, timing is solid, and the cam chain tensioner is working fine. I'm stumped. anyone have any thoughts?

 

 

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Is there oil in the engine? Lol

Seriously, sounds like top is dry. There could be an oil delivery problem. If bike was sitting for 5+ years and wasn't prepped for storage first ... could have sludges blocking screens, the pump, filter, or ports.

Suggest not running it much until you've got those cleared up. Or you may just cook your cams and head.

 

Other than the noise, does it seem to run well?

 

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It wasn't making the noise the first time i rode it, and it had a fresh oil filter and oil before i rode. I did about 3, 20 minute motos on it and it ran great, but that's before this sound came up so i doubt it has anything to do with the top end not getting oil. the buckets are usually soaked when i break it open.

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Surprising no one else has commented yet. Here are the few things that I can think of that could cause such a sound. For you to consider checking.

 

- Cam valve clearances. Too large a gap. Double and triple check. See spec in pict. Intake and exhaust. Shim to upper range top gap of spec. As the engine runs and wears the gap closes.

- Broken or weak valve spring. Check this by pushing on them when you have the cams and caps off for shimming clearances.

- Broken valve stem guide. Pull the head off, look in through intake port and exhaust port for guides condition

- Lack of lubrication. Run the correct oil. 40W for wet clutches. Clean/replace oil filter. Pull head and cylinder off, blow through oil galleries to ensure they flow clear. Check oil pump shaft and gear shear pins, that pump is operating properly. Check cylinder base gasket that it is not deforming and blocking the oil path groove on the top of the case under the gasket and that the gasket is not squished into blocking off the head bolt holes up to the head. The oil follows the bolt to get to the head. Check oil ports in journals under the cams, ensure they are clear.

- cam chain and tensioner. Tensioner and guides installed properly. including the inner spring and rod. You mentioned it fell out of the bike. Did you lose those two pieces. Cam chain damaged, kinked, stiff, or stretched.

 

........ as a start of a few things.

 

This is all assuming the sound is originating from the top. If it is coming from the side of the cylinder or lower you have other issues.

 

 

 

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Damn, that was a well thought out response, thanks for the help. I tried a few on the list before I replaced the cam chain and it completely resolved the noise. Bike purs like normal again. Thanks brotha ??

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