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What did you do to your dirty bike today?

wow. taking this to PM...
 
Put a new shock on the EXR today and am trying out those little mirrors that attach to the handguards.

p.jpeg
 
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schweet!
Edit: that is some big bad ass motor in the picture.
 
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Last week - rebuilt carb and installed.. Today Changed the oil and oiled chain...
Good to go for a bit.. Valves after next few rides.
 
They worked great. I had an inch and a half of unused travel up front though, going to try backing the compression damping off a touch for our next ride considering how much washboard these trails have. I've never seen blue groove washboard like that, it was something else.
 
Fresh air filter and fresh front brake filter in preparation for Moab.

Edit: front brake fluid, doh
 
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Tore the top-end apart on the '01 CR250. 40 hours on a brand new cylinder/head, piston, rings, etc. Hondaline HP-2 at between 32:1 and 40:1. Jetted lean with a Keihin carb, but still spooging a bit out of the pipe. Oversized radiators w/ water wetter. The temp gauge sticker on the cylinder never read more than 170-180 degF. It always ran nice and crisp without any weird noises (rattling, piston slap, etc).

This is what I found.
 

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I've never found lean or rich made that much difference in sponge out of pipes, always seemed to relate more to rpm and oil ratio. Do you lug/trail ride your CR?
 
SpeedKills said:
I've never found lean or rich made that much difference in sponge out of pipes, always seemed to relate more to rpm and oil ratio. Do you lug/trail ride your CR?
Click to expand...

Jetting made a huge difference for me. I had an embarrassing, spoogy mess with the stock recommended jetting. The leaner I went, the less spooge I had. I think I have a 170 main, 42 pilot, JD Jetting needle in the middle position, air screw between 1 1/2 and 1 3/4 out. And, I'm trail riding, but I’m all over the place in the RPM range. I lug the bike as much as I rev it out. I'm just not sure I should be seeing this kind of wear on a 40 hour engine that's been ridden "medium duty."

My main concern is in that first picture. It looks like the plating is gone from the bottom portion of the sleeve. The plating seems to be intact in the rest of the cylinder.
My second concern is there's a bunch of really, really small pits throughout the cylinder. I'm not sure what that's about. The pictures above aren't big enough to show it....maybe I'll post a larger picture when I get home tonight.

After I posted the pics last night, I went back to the garage and started measuring. Ring end gap: good. Piston pin OD: good. Piston diameter: good. Blah blah blah: good. There wasn't a lot of carbon buildup on the piston crown, nor the exhaust valve parts. There was good ring seal, evidenced by zero blow-by on the piston skirt.

It think I'm just going to send the cylinder to Millennium Tech and have it replated. But I don't want the same thing to happen if I can avoid it.
 
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A cylinder shouldn't need re-plating after 40 hours. Hell, you shouldn't even have to replace the piston. The pics look good except the first one. That's the intake side, correct? Got a pic of the corresponding side of the piston?

Are you sure the piston-cylinder clearance is good?
 
OEM plating?

Here's some info regarding porosity, from Millenium FAQ's -

Q.What is porosity, and will it affect my engine?


Porosity is gas trapped in the base metal aluminum during casting. These “holes” are exposed when the cylinder is machined or subjected to various chemicals in the plating process. The pits are usually small in size, and in good castings few and far between. When kept under acceptable levels, porosity will not adversely affect the performance or longevity of the engine. In fact, it will improve lubrication. The pits will not cause the coating to peel, nor will a ring hook on them. As far as our specifications on porosity our cylinders carry a lifetime warranty against defects in materials and workmanship. Therefore, through extensive testing we have found that porosity is a cosmetic problem only. In our pursuit to have both cosmetic and functional perfection we do everything possible to remove these pits. In some cases, this is not possible, so we release the cylinder only in cases where it will not affect performance.
 
The rings only extend into that weird spot at the intake side about 1/4", most of the rub I see is well below that point. Only thing passing there is the skirt so it may be anti friction stuff off the skirt sticking to the cylinder; like 2sys said, what does the piston look like?

The other thing odd about that spot is it has a defined perimeter, almost like you had a piston port rubbing against the cylinder and creating it. Cross hatching is still visible so it doesn't look to have hurt the plating; at 40 hrs it should just be breaking in. Typical timing for 250 piston is 150 hrs; cylinder should be good for 2-3 times that easy; depending on how you ride of course...
 
The cylinder measured 66.34mm (at multiple spots per the service manual).
The piston measured 66.24mm (per the service manual).

This is a 0.10mm clearance, vs. the 0.16mm max clearance that the service manual spec'd. So, all should be good there.

Oh yea, ring end gap was good, too:
Top Ring = 0.58mm
Bottom Ring = 0.43mm
Spec = 0.65mm max

Piston Pics:
 

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In the past week:
Oil changed, new air filter, exhaust modified, rejetted, new stiffer fork springs and heavier oil, bar risers, new fork boots, spark plug, hour meter installed, new chain and sprockets and rear drum brake cleaned/sanded.
 
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