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XR250 sand in head again?

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My 2001 XR250 had trouble starting last year. I ended up putting in a new piston and bored the cylinder. See here for history:

I was starting it the other day after a carb rebuild and could not get TDC. It just went away? Adjusted valves and manual decompressor to no avail. Did a leak down test and problem appears to be in piston/cylinder. Here is what I saw. See pic #1.

So I looked at the source of the crud/sand and see arrow pointing to the scuffed area on the gasket. Pic #2

The pattern of the scuffing matches the orifice directly above that location on the head. Picture #3 and #4. The odd shaped port doesn't go into the head above. There is a small hole inside the port that I could not see where it led to by use of a feeler wire and a flashlight. It's almost like that area got super hot or something . 

In pic#4 it also seems like the hole below left it's shadow on the gasket as well, as it is white there. That leads to one of the 4 bolts that secure the cylinder head, and there was nothing unusual about that bolt or the hole it is in.

For the love of God can anyone help me get this bike diagnosed? I am anal about air cleaner maintenance, and there is no evidence of sand in the intake past the air filter. How is this crap getting in?

I just had a thought - if sand is getting in somehow to the cylinder, it means I have a leak or a hole or a lack of a tight seal, aka lack of compression. Find source of crud= solve compression issue?

 

IMG_3490.JPG.1d73be6b20d566ce2f12428ebc3b2180.JPG

IMG_3492.JPG

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Edited by dogeddie

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4 hours ago, dogeddie said:

There is a small hole inside the port that I could not see where it led to by use of a feeler wire and a flashlight. It's almost like that area got super hot or something . 

You need to determine where that hole leads. If it leads to outside atmosphere, any water that makes it into that port, between the upper and lower cylinder gaskets, will boil off, leaving behind any impurities that were in the water. And boiling off of the water would leave those bleached marks in the gaskets.

Just thinking out loud here. I might try to seal up the valve seats side of the cylinder, like with a piece of plywood and a sheet of rubber or gasket material, bolting it on using the stock holes or even holding the plywood and seal in place with a bunch of clamps. Then fill that port with water and see if and where it drains out from.

I would look between the cooling fins of the cylinder real good for holes or breaches of any kind.

Head scratcher for sure. Never seen this.

And you haven't said it's a part of your routine, but you know to ALWAYS scrape the bottom of the spark plug well with a screwdriver to break up caked grit and blow the well out really good before ever removing the plug, right?

Edited by Trailryder42

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Yes - the placement of the spark plug blows. I do clean it before removing the plug.

So weird cuz it was literally a pile of sand before I bumped it and it fell into the cylinder. I tried shining light into the little hole in that triangular port and could not see where it went - seemed like it just stopped.

Maybe I will try to use a liquid like you said to track down where the hole goes. Weird fo sho.

What purpose does the triangularish shaped port serve?

 

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That is weird !! looks like it fell out of the head somehow when you lifted it up. It's quite a bit too.

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2 hours ago, DPete said:

That is weird !! looks like it fell out of the head somehow when you lifted it up. It's quite a bit too.

You need to blow / wash the bike down b4 you disassemble it  :facepalm:

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21 minutes ago, S.O.A.N.Z said:

You need to blow / wash the bike down b4 you disassemble it  :facepalm:

No Kidding!! The sand was already in the head. :lame: Read the whole post and the link to the prior post. Thanks

Edited by dogeddie

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On occasion have you by chance pressure washed the engine at point blank range. (pushing dirt in past a damaged seal)

Edited by mlatour

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1 minute ago, mlatour said:

Do you by chance pressure wash the engine at point blank range. (pushing dirt in past a damaged seal)

No I use a garden hose. We did have to use a pressure washer a few weeks back on an out of town ride as we were completely covered in doody, but I stay clear of the motor and try to use indirect pressure in that case.

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Perhaps one of the carburetor's "overflow" or vent lines is actually routed to a vacuum port ?

 

Damaged / leaky head to exhaust pipe seal ? (sucking in dirty external air due to 'reversion' / scavenging)

Edited by mlatour

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2 minutes ago, mlatour said:

Perhaps one of the carburetor's "overflow" or vent lines is actually routed to a vacuum port ?

 

Damaged / leaky exhaust seal (sucking in dirt due to 'reversion' ?

I just rebuilt the carb and the vent line runs up under the seat.

Not sure what reversion is, but if you mean the gaskets at the point where the exhaust meets the head -  a possibility.

So odd in a little nice pile like that, and so concentrated to one area.

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I'm not familiar with XR's but your last pic shows a 'KK1' casting number,

a quick search shows that suffix is more common with earlier '84 to '96 XR's 

 

Any chance you have a mis-match of engine parts ?

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I bought it used a couple years ago. Anything is possible. Geez where would you start trying to get to the bottom of that.... I have replaced the piston and rings, and had it bored over as reported in my previous post noted above due to wear.

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18 minutes ago, mlatour said:

I'm not familiar with XR's but your last pic shows a 'KK1' casting number,

a quick search shows that suffix is more common with earlier '84 to '96 XR's                                                                                                                                                                                                                

 

Any chance you have a mis-match of engine parts ?

I would look closely at this thought, almost has to be an open hole to get that much sand in

Edited by DPete

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13 minutes ago, S.O.A.N.Z said:

So 12 months later you still havent sorted it out   :lame:

Thanks for your help. But the bike ran fine all summer after reassembly.

26 minutes ago, mlatour said:

I'm not familiar with XR's but your last pic shows a 'KK1' casting number,

a quick search shows that suffix is more common with earlier '84 to '96 XR's 

 

Any chance you have a mis-match of engine parts ?

Where did you find that info? I should look into that. Thanks again.

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Pretty un-scientific as I just typed "Honda KK1" in a Google search bar, 

all the parts that came up were for '84 to '96 XR250's, nothing newer.

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1 minute ago, Greenwrench said:

Am I seeing things or does that gasket look like it's not right to anyone else ? Looks like the holes don't even line up ?

Sent from my Moto G (4) using ThumperTalk mobile app
 

It got moved when I pulled the head off and was working around the cam chain

Edited by dogeddie

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And if you look up the 2001 XR250R parts microfiche,

the suffixes for the following parts are :

 

cylinder : KC2

cylinder head cover : KCE

cylinder head : KCZ

crankcases : KCE

 

with only some smaller parts having a KK1 suffix.  (example: decompression cable)

Edited by mlatour

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Thanks for the help. A good place to start. I will look, but I don't think they changed much from '96- 2002 though if I recall

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