Ok so heres the story, I took my mc21 for a ride and the engine seized, probably from a bad oil injector... took heads and cylynders of and found lower piston looked fine but the upper had some issues. First there was a ring around the top of piston where the metal was torn away, fragments everywhere, (ring was about 1/4 inch all the way around outside edge of piston.) Second a large piece of metal that I assume is a bearing, but not sure due to its condition was laying in the exaust port of the case.


So does anyone know where I can get parts for the lower case, and for that matter the upper as Tyga only has one piston head available. Also, the cylinder walls look smooth, but someone has told me that with that kind of metal flying around they will definitely need to be bored out, oppinions on that? Thanks in advance and I will post pics, as soon as I can in case they will help!
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Mike

if the cylinder walls look fine (no gouges, scratches, cuts in the ports, etc) then they are fine. No need to bore them out (you really don't want to bore that much as the port walls can be thin in some places).

I would check the cases (bearing journals, etc) and the heads to make sure there is no damage there. If there was metal above the pistons, check the heads to make sure they didn't get nicked up. To properly inspect the cases at this point, you need to split them and take the crank out.
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Charles Gallant

If you want new parts try www.redline-ci.com. He can get anything that is still available, and the heads probably are. Fixing the cylinders is more complicated than boring them out. I'm not sure they can even be bored out since I don't think oversize pistons are available. The cylinders are Nikasil plated and that needs to be restored to OEM spec to fit new pistons. But like Charles said, lets check your stuff out before jumping the gun. I would be more worried about the crank.
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james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Upper Piston
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Mike

From the side
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Mike

From the front
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Mike

Lower piston
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Mike

Lower piston
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Mike

Large piece of metal found laying next to upper piston appears a copper color
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Mike

The piston doesn't look too bad. How does the cylinder look? Here is what I see: The inside on the motor is extremely dirty. It looks like you have rust on the crankshaft. I think you may have some "real" problems.
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james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm

Like has been said the inside of the cases look in really bad shape as does the crank. About the copper-ish thing in the bottom end is the big end thrust washers so I would be checking the crank very well before putting a new top end on it.
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If I have to take the carbs off once more...

By the looks of that crank it probably wasnt an oil injector

I would recommend pulling the engine out of the frame. Then remove the gear box and split the cases. Take the crank out and turn it into a paper weight.

Inspect, and clean the cases as well as you can (inside and out). Clean as much of the water transfere ports as you can as well. Replace the studs that hold the cylinders on, get a new crank and put it back together. Depending on the cylinders, you may be able to re-use them (at least the lower piston looks good, so the cylinder may be fine). Check the heads as well. My guess is the upper head has damage, but possible not. Cooper is can be pretty soft so maybe it didn't destroy your upper head/cylinder.

But, it looks like you had water getting down into the crank cases. Probably due to the base gasket being so old.

Good luck, it's only a lot of work and money but you can make it run again I am sure.
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Charles Gallant

Looks like my crank that blew off while i was at the track

mhunter1175 wrote:
Large piece of metal found laying next to upper piston appears a copper color

I reckon that's part of a main bearing cage.

Whatever it is, the crank's GOT to come out of that one. (You can get the crank out without removing the motor if you want.)
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Andy.
NSR-WORLD.COM

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