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Loud Squeal, Stall, Now Excessive Valve Noise

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I recently bought a '97 XR250R that had a fresh top end rebuild. When I bought it there was a clear valve tick but I was told that they just haven't been adjusted since the rebuild (now doubting this info). I took the bike in to get the valves done and the guy said one valve was at 0.010 and the other had zero clearance. He was able to adjust them to the specified clearances but said that, since they were so far out to begin with, if they loose adjustment again it was worn lobes.

The bike ran beautifully for 5-6hrs of riding but this weekend it wouldn't start. I was able to bump start it assuming it was just flooded. When the bike finally did start, there was a loud squeal as the bike stalled. This happened again after another bump start. After letting the bike sit for about an hour, it started 2nd kick but now there is a lot of valve noise again.

Can this be related or is the squeal/stall and the sudden valve noise separate?

I did a search on this forum and googled it extensively and I realise there's a lot already written up on valves and proper adjustment but nothing that sounds like what I have going on. Any input would be appreciated!

Zack

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Has the oil level been checked?

I think I've read posts of the gaskets on some rebuild kits blocking the oil passages to the head/valve train. Shouldn't need to tell you what occurs when that happens.

The squeal, to me, sounds like a spun bearing, or if the head is indeed void of oil, the cam seats are probably toast.

Even when the valve clearances are adjusted correctly, ticking is not unusual and considered normal.

I think I would pull the head to have a look-see.

More than just the lobe wear determines clearances. There's valve seat wear, the valves themselves and the faces of the tappet arms that ride on the lobes. Wear on all of those add up to determine clearances.

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Oil level was checked and is good. The valve noise for the 6(ish) hours after the valve adjustment was non-existent or at least it sounded like your typical 4 stroke.  After the squeal/stalls, the valve noise was as loud if not louder than it was before the adjustment.

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I read these kind of experiences a LOT on here about rebuilt engines.
We've bought and sold hundreds of XR Hondas, never had a good running engine after a "rebuild".
Please keep us posted on the progress - Thanks

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The 97 xr250r has an external oil feed line to the cylinder head so it wouldn't be a plugged oil feed caused by a gasket. The camshaft runs on ball bearings and maybe one of them failed. It is possible to put them in backwards or if a seal on the bearing is missing or damaged it wouldn't force oil over to the cam lobes. If the valves came out of adjustment instantly I don't think it would be worn valves or lobes. That is something that would happen over time.  XR's are easy to check the valve adjustment just take the fuel tank off and remove the 4 pluggs on the top of the engine and check the gaps. Only tricky part is the auto decompression mechanisms because that could cause you to adjust the valve  way too loose if it is pressing down on the exhaust valve while your trying to check the valves. 

I have had the cylinder head off of my 1996 xr250r 4 times over the last 10 years trying to fix smoking problems. It always seemed to get better for a while but kept coming back smoking like crazy. I almost think best way to fix a smoking xr250 is to replace the cylinder head. I think the main problem I had was the valve guides were loose in the cylinder head letting oil leak into the exhaust.  

I would bet whoever rebuilt the cylinder head did something wrong. 

Edited by Toadster25

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That makes complete sense given the squeal and, like you said, instant valve noise right after... Guess I need to find time to open up the top end.

Thanks again for all of the help - this is my first post on this forum and am pleasantly surprised with the quick, knowledgeable, and thorough support!

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I was told by a coworker that he had a crank bearing go and it sounded just like bad valve clearances; I've never heard this happen before, has anyone else had it happen to them?

I just want to make sure I know all of the possible issues before going into this...

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All 96/04  Xr250s have one weakness stock Honda OEM intake valves soft. If they have not been replaced with None OEM valves the most common problem. As they get tight constant Adjustment as they sink in head.

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The valve cover gasket must be a thirty dollar Oem Honda gasket.  It's steel and .010" thick. If it's any other thickness or material, it can cause damage to the head.  A cheap aftermarket paper gasket in this location is bad, bad, bad.  Too thin and and it clamps down too hard on the cam bearing races, too thick and the cam bearings can jump up and down in their journals.. That gasket is a precision shim between the head and rocker box/cover.

Edited by Baja Rambler

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