Project: 2001 XC300 bare frame rebuild

[blanc]

Looks great dude, well done.

[motogroove]

Piston and bore look OK to me. Maybe a little backspooge on top of the piston, but just a thin deposit that wiped off.

My next guess is that the excessive backpressure from the damned paper towel, followed by the lean rev, could have damaged a ten year old reed.

Something broke or changed durring that lean rev.

Spark plug is black. Note blackish oil deposit on top of piston.
110 octane Sunoco leaded race fuel with motorex 40:1

Edit: the silver color around the water passages on the head is excess antisieze. what a slob.

[PEB]

I wonder if your race number has anything to do with forgetting to remove the paper? Your bike looks awesome by the way! If your reeds are ten years old it is time to replace them anyways.

[motogroove]

Originally Posted by PEB

I wonder if your race number has anything to do with forgetting to remove the paper? Your bike looks awesome by the way! If your reeds are ten years old it is time to replace them anyways.

I can neither confirm nor deny.
It is a classic mistake, except usually on the intake side.
I'm sure I'm not the first one to do it. And I won't be the last.

Maybe I'll get some reeds just so I get a nice firm baseline.

Thanks for liking the looks of the project. I love my Gas Gas.

[motogroove]

Prompted by the paper towel incident and a hint from the
"Internally cleaning exhaust " thread where AZRickD wrote:
"As far as cleaning the silencer, the one thing I look for is old disintegrated packing in the very back of the tube. That packing can pack up back there and restrict the exhaust flow reducing low end torque as well as upper revs. I use a metal hook to clean it out. "...

I went one step further and drilled the four rivets on the powercore2 and did a full soak and inspection. In the picture I'll call the parts the body, the main tube, the turbine, the tip and the cap.
As Rick predicted the turbine's exterior was packed with old spoogy disintegrated packing. This might not be surprising around the perforated area that fits and works with the main tube. But I was surprised to find a large amount of superfine spoogepack on the closed end. I guess I shouldn't have been surprised because that area is part of (or open to) the flow path.

Roughly a decade's worth of spoogepack in there was taking up ~1/4 of the volume in that little cavity. If nothing else, it's weight.

If you are on an older bike, you might want to drill down on your silencer.

BTW, my carb was a complete mess at the race. Somehow the carb cleaning was checked off on my list. But when projects drag out for months, things get stupid fast. <:-)