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XR650l cracked head

By davegreg,
in XR600R & XR650R/L

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davegreg

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I was investigating an oil consumption issue that was pointing towards worn valve stem seals and after cleaning up the head I noticed a hairline crack in between the spark plug hole and a valve seat.

My oil issue looks like a worn piston and rings so that is going to be replaced along with the timing chain. I have not dissasembled the cylinder yet but the bore feels smooth even though there is a lot of front to back play in the piston. I was shocked that I could rock the piston in the bore by a lot.

 

Anyway back to my question about the head. I called a local machine shop and the guy said that I am just better off replacing the head because a repair will not last. An ebay search found a couple of used heads in the $500 price range. At that price I am leaning towards not doing anything with the head because I have no idea how long it had been that way and keeping a very close eye on oil temperatures. A little history on the bike, its a 2001 model with 33k on the odometer and the previous owner told me that the original owner had already replaced the piston. I replaced the clutch a few weeks ago and the little guide pin in the oil pump to clutch cover was missing. 

 

Any one have any opinions / experience with this scenario?

 

Thanks

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Onederer

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^^^

I just checked three sites for a new cylinder head and it ranges from $436-$640 here in the U.S.. Obviously got for the lower cost one because they are identical OEM parts.

 

A new head is bare, just the head and valve guide. The guides will likely have to be sized when new valves are used, so that is an extra cost, that and new valves. There's no reason to put old valves on new seats.

 

It's a completely bad idea to run a cracked head, you're flirting with more problems and ultimately risk turning the engine into a paper weight.

 

I don't know what decent used XR650Ls are selling for there, but here I could be patient and find a good runner for less than $2,000, sell what parts I could off of the damaged one and probably break even or come out ahead and with no down time or my own repair labor.

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davegreg

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As an update, I stopped into the engine shop on my way home and the guy took a look at it and said he sees hairline cracks all the time on alloy heads off cars. He said I should not worry about it because it may have been there for a long time and that the likelyhood of the seat dropping out is small unless the crack progressed significately. Apparently it takes around 500 deg of heat to remove the seats.

500 bucks for a used head is crazy but its supply and demand I guess.

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condershire

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As an update, I stopped into the engine shop on my way home and the guy took a look at it and said he sees hairline cracks all the time on alloy heads off cars. He said I should not worry about it because it may have been there for a long time and that the likelyhood of the seat dropping out is small unless the crack progressed significately. Apparently it takes around 500 deg of heat to remove the seats.

500 bucks for a used head is crazy but its supply and demand I guess.

It is not supply and demand, Fleabay (and yes, I shop there for CERTAIN items) is not quite the place to find deals it once was.  In your situation, probably the best plan would be to purchase a NEW head (save up for a couple of months) and when it is time to do the top end, send the new one off with the old and have whatever useful parts "transplanted".

 

Unless you are lapping valves, it is typically CHEAPER to just send it off to a REPUTABLE shop for overhaul.  I just had mine done and XR's Only replaced ALL valves, repaired a dropped valve seat, and did a few other services for around $250, other shops, such as Engine Dynamics, probably charge similar.

 

The problem with buying a used head off E-Bay and just "dumping it on" is that you do not know the HISTORY of the part.  Putting your engine back together only to find it is burning oil (through the guides/seals/both), has a loose valve seat, or the center journal is unusable does NOT make for an afternoon of fun.

 

I had have the valve seat repaired at just over 18,000 miles.  The AVERAGE top end life I have seen and read from various sources is somewhere around 25,000 - 30,000  (yes, I know there are exceptions, on both ends of the spectrum).  The GOAL is to perform an overhaul which can meet this...  Just my humble opinion...

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garthr

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i would get a second opinion at least. i personally would have it repaired and not knowingly run any kind of cracked head. id rather be riding than tearing down again because it failed and trashed more parts. aluminum heads on cars are repaired all the time. i had one cracked in the same place but a crack between the plug hole and each valve on one cylinder. got it fixed, i think 16 years ago. still runs great.

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davegreg

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An L will occasionally drop a valve seat, they may be a little more prone to it.

How about a big-fin head with custom chamber shaping?

This is what I am finding out about the seats and this tiny crack in mine is probably the start. This bike may not be for me expecially with the tight and slow trails around these parts that I have seen up to yet.

Anything to lower the temperature is a bonus.

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davegreg

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^^^

I just checked three sites for a new cylinder head and it ranges from $436-$640 here in the U.S.. Obviously got for the lower cost one because they are identical OEM parts.

 

A new head is bare, just the head and valve guide. The guides will likely have to be sized when new valves are used, so that is an extra cost, that and new valves. There's no reason to put old valves on new seats.

 

It's a completely bad idea to run a cracked head, you're flirting with more problems and ultimately risk turning the engine into a paper weight.

 

I don't know what decent used XR650Ls are selling for there, but here I could be patient and find a good runner for less than $2,000, sell what parts I could off of the damaged one and probably break even or come out ahead and with no down time or my own repair labor.

Used bikes up here are bringing insane prices. I picked mine up for that and was pretty rough, looked like it had lived outside for most of its life. Im sure it will turn into a nice ride once ive got it sorted.

I had the cylinder and piston checked and its at its service limit so its getting a 25 over bore and probably look for a head down the road.

What other heads will bolt on and work?

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Alex DeFreitas

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I have an extra cylinder head.. has some of the valve cover bolts sheared off and stuck in the holes. also has 2 of the exhaust studs sheared. I tried using a screw extractor to get them out but couldn't. I now have new screw extractors and if I can get them out maybe we can make a deal.

 

Valves and seals were fine. Center journal fine as well. I bought one off ebay for $225 .. guess I got lucky on the price. So my original one is sitting in the shed. I'll post some pics. Where are you located?

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ThumpNRed

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Go with the deal that Brian offered up. His contact in Cali is a quality guy... you'll get a good head that you dont have to worry about.

btw... an XR600R head (newer singe-carb) will work. It will not have the smog ports in the front, but otherwise, it's the same.

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davegreg

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thanks for the info Im going to go that route.

Go with the deal that Brian offered up. His contact in Cali is a quality guy... you'll get a good head that you dont have to worry about.

btw... an XR600R head (newer singe-carb) will work. It will not have the smog ports in the front, but otherwise, it's the same.

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