Top End kit CR250

TX_187
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TX_187
Edited Date/Time 7/28/2019 4:02pm
Picked up a clean 02 CR250 off CL about a month ago and wanted to throw a new top end in it before I really started riding. Couple questions: I know Wiseco is forged, but won't I have to drill holes in the piston because of the bridge? What about Vertex or Pro X? Are they pretty solid, or should I just go OEM?

Also, what about the A,B,C,D sizes? When looking on motosport, I didn't see anywhere to specify that.
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DTHA70
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DTHA70 6/2/2014 9:14am
6/2/2014 9:14am
TX_187 wrote:
Picked up a clean 02 CR250 off CL about a month ago and wanted to throw a new top end in it before I really started...
Picked up a clean 02 CR250 off CL about a month ago and wanted to throw a new top end in it before I really started riding. Couple questions: I know Wiseco is forged, but won't I have to drill holes in the piston because of the bridge? What about Vertex or Pro X? Are they pretty solid, or should I just go OEM?

Also, what about the A,B,C,D sizes? When looking on motosport, I didn't see anywhere to specify that.
just stick with OEM, everything is superceding to the B size now i think so you'll want to stay on top of your cylinder wear. i dont remember if the oem come drilled or not but if not then you NEED to do it. best bet is to have multiple cylinders, and theyre not too pricey for the CR's
Socket946
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Socket946 6/2/2014 9:15am
6/2/2014 9:15am
Prepare for the shit storm of opinions.

Bottom line, if you go forged, you have to drill. It took me 10 minutes longer to drill said holes. Some people drill stock pistons. I wouldn't recommend that.

Vertex, Wiseco, OEM, pro-X (oem copy) all will work and work well.

Look for my build thread of my 04, ton of information there. The 02 airbox liked to suck dirt, so seal that badboy up tight.
Socket946
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Socket946 6/2/2014 9:17am
6/2/2014 9:17am
TX_187 wrote:
Picked up a clean 02 CR250 off CL about a month ago and wanted to throw a new top end in it before I really started...
Picked up a clean 02 CR250 off CL about a month ago and wanted to throw a new top end in it before I really started riding. Couple questions: I know Wiseco is forged, but won't I have to drill holes in the piston because of the bridge? What about Vertex or Pro X? Are they pretty solid, or should I just go OEM?

Also, what about the A,B,C,D sizes? When looking on motosport, I didn't see anywhere to specify that.
DTHA70 wrote:
just stick with OEM, everything is superceding to the B size now i think so you'll want to stay on top of your cylinder wear. i...
just stick with OEM, everything is superceding to the B size now i think so you'll want to stay on top of your cylinder wear. i dont remember if the oem come drilled or not but if not then you NEED to do it. best bet is to have multiple cylinders, and theyre not too pricey for the CR's
David, stock doesn't come drilled, and not sure you'd want to drill it. I'm not an engineer, but drilling cast doesn't sound like a good idea.
Rmartin508
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Rmartin508 6/2/2014 9:30am
6/2/2014 9:30am Edited Date/Time 6/2/2014 9:37am
Stock piston, 05 base gasket, Air stiker carband seal your air box. TX 187 you live in the same area as I do I would imagine ride the same tracks. I have a tmx carb with a JD jet kit that works pretty good for our climate, if you decide to re jet your bike. also 50/50 with c 12 for our climate makes a world of difference once your bikeis dialed. Wiseco are great pistons as well. I have just had good luck and solid running with my sock piston and do not drill a stock or cast piston stock piston. I have some extras like plastics and stuff that are in decent shape, couple sets of stock foot pegs stuff like that give me a shout if you need anything. 281-236-O51O

At Socket did you find the guards?

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newmann
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newmann 6/2/2014 9:44am
6/2/2014 9:44am
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes?

Not sure how big of a problem that is with plated cylinders but a huge issue with boring out cast iron sleeves for oversize pistons. Hard to find local machine shops and even motorcycle shops who complete this simple operation.

2) Drilling holes will allow for a loss in the bottom end compression charge won't it?



Socket946
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Socket946 6/2/2014 12:11pm
6/2/2014 12:11pm Edited Date/Time 6/2/2014 12:12pm
newmann wrote:
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes? Not sure how big of a problem that is with...
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes?

Not sure how big of a problem that is with plated cylinders but a huge issue with boring out cast iron sleeves for oversize pistons. Hard to find local machine shops and even motorcycle shops who complete this simple operation.

2) Drilling holes will allow for a loss in the bottom end compression charge won't it?



I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust bridge is supposedly the hottest part of the cylinder because it's so small. Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool.

I went wiseco. It works, not sure I'll buy wiseco again, just for principal that they didn't drill them for me, which I think is bullshit.
JW381
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JW381 6/2/2014 1:15pm
6/2/2014 1:15pm
newmann wrote:
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes? Not sure how big of a problem that is with...
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes?

Not sure how big of a problem that is with plated cylinders but a huge issue with boring out cast iron sleeves for oversize pistons. Hard to find local machine shops and even motorcycle shops who complete this simple operation.

2) Drilling holes will allow for a loss in the bottom end compression charge won't it?



Socket946 wrote:
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust...
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust bridge is supposedly the hottest part of the cylinder because it's so small. Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool.

I went wiseco. It works, not sure I'll buy wiseco again, just for principal that they didn't drill them for me, which I think is bullshit.
Is there another forged piston maker that would drill them for you? I'm thinking about going forged next time for a few reasons mentioned here and on TT, but it would be nice to find one pre-drilled. I'd just hate to fuck up an $80+ piece of metal before it even goes in my jug.
Socket946
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Socket946 6/2/2014 1:19pm
6/2/2014 1:19pm
JW381 wrote:
Is there another forged piston maker that would drill them for you? I'm thinking about going forged next time for a few reasons mentioned here and...
Is there another forged piston maker that would drill them for you? I'm thinking about going forged next time for a few reasons mentioned here and on TT, but it would be nice to find one pre-drilled. I'd just hate to fuck up an $80+ piece of metal before it even goes in my jug.
Vertex is saying you don't have to drill theirs.

But people do anyways.

I guess this is where my experience specifically stops - I don't know of a company that does drill them for you.

I've wondered if you could special order from wiseco a pre-drilled piston?

Or you mark the holes, and have the machine shop drill them for you? It really wasn't hard to do.
CR250Rider
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CR250Rider 6/2/2014 1:39pm
6/2/2014 1:39pm
I've never used a drilled one and never had a problem.
TX_187
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TX_187 6/2/2014 1:46pm
6/2/2014 1:46pm
Rmartin508 wrote:
Stock piston, 05 base gasket, Air stiker carband seal your air box. TX 187 you live in the same area as I do I would imagine...
Stock piston, 05 base gasket, Air stiker carband seal your air box. TX 187 you live in the same area as I do I would imagine ride the same tracks. I have a tmx carb with a JD jet kit that works pretty good for our climate, if you decide to re jet your bike. also 50/50 with c 12 for our climate makes a world of difference once your bikeis dialed. Wiseco are great pistons as well. I have just had good luck and solid running with my sock piston and do not drill a stock or cast piston stock piston. I have some extras like plastics and stuff that are in decent shape, couple sets of stock foot pegs stuff like that give me a shout if you need anything. 281-236-O51O

At Socket did you find the guards?
Motosport has 25% OEM, so I went that route for the piston. I'll give you a shout about that carb. Appreciate it.

-Dustin
Socket946
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Socket946 6/2/2014 2:15pm
6/2/2014 2:15pm
TX_187 wrote:
Motosport has 25% OEM, so I went that route for the piston. I'll give you a shout about that carb. Appreciate it.

-Dustin
Partzilla and Rocky Mountain are cheaper.
TX_187
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TX_187 6/2/2014 2:50pm
6/2/2014 2:50pm
I didn't check partzilla, but Motosport was cheaper than rocky mountain with the 25% off.
Ebs
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Ebs 6/2/2014 3:05pm
6/2/2014 3:05pm
newmann wrote:
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes? Not sure how big of a problem that is with...
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes?

Not sure how big of a problem that is with plated cylinders but a huge issue with boring out cast iron sleeves for oversize pistons. Hard to find local machine shops and even motorcycle shops who complete this simple operation.

2) Drilling holes will allow for a loss in the bottom end compression charge won't it?



Socket946 wrote:
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust...
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust bridge is supposedly the hottest part of the cylinder because it's so small. Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool.

I went wiseco. It works, not sure I'll buy wiseco again, just for principal that they didn't drill them for me, which I think is bullshit.
"Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool."

Other way around, forged is going to have some more expansion, cast is more stable (dimensionally).
newmann
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newmann 6/2/2014 3:23pm
6/2/2014 3:23pm
newmann wrote:
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes? Not sure how big of a problem that is with...
1) If the exhaust bridge is properly relieved, what is the benefit of drilling the holes?

Not sure how big of a problem that is with plated cylinders but a huge issue with boring out cast iron sleeves for oversize pistons. Hard to find local machine shops and even motorcycle shops who complete this simple operation.

2) Drilling holes will allow for a loss in the bottom end compression charge won't it?



Socket946 wrote:
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust...
I don't think it does. That said, from what I understand, you drill the holes so that oil/fuel can keep the exhaust bridge cool. The exhaust bridge is supposedly the hottest part of the cylinder because it's so small. Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool.

I went wiseco. It works, not sure I'll buy wiseco again, just for principal that they didn't drill them for me, which I think is bullshit.
Ebs wrote:
"Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool." Other way around, forged is going to have...
"Because forged pistons don't expand/contract as much as cast, this part doesn't get enough oil to stay cool."

Other way around, forged is going to have some more expansion, cast is more stable (dimensionally).
Yep , forged expands and generally has to be set up with a looser tolerance. Gotta warm them up too before you ride it like you stole it. Got to the point that I rarely run a forged in my old 125 Elsinores. Tried every clearance known to man, drilled holes , relieved exhaust bridges..... but when you stick a big Mikuni and a pipe on them it's hard to keep a Wiseco alive in one of those little revvers. Stock cast Honda pistons or private labeled ART castings (oem Honda) have been my go to pistons. No drill with a good relief on the bridge and they last and last. Oddest thing I've had happen on a cast Honda OEM piston was the ring locater pin blew out of the piston and trashed a bore. If you look, Honda pistons don't have a hole going all the way through behind the pin. If there is an air pocket behind the pin, pressure builds as the piston gets hot and out it comes. I noticed on a Wossner piston (damn nice forged pistons and priced well) they drill the pin holes all the way through.

Had a forged Wiseco in my 74 CR250 fire breather for three hard years, spring and fall race seasons before swapping it out for a fresh one. Good stuff obviously, but the Wossner is a thing of beauty.
Big Lenny
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Big Lenny 6/2/2014 4:41pm
6/2/2014 4:41pm Edited Date/Time 6/2/2014 4:43pm
newmann wrote:
Wossner pics and link. Notice the dry film coating that comes stock?

http://www.vitalmx.com/forums/Non-Moto,21/Wossner-forged-pistons,1231051
Those are the one's from Zee-Germans..I bought some from ProX awhile back they say they're good...Funny when I opened the box the first thing I said was, "Damn that's nice looking"...
Socket946
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Socket946 6/2/2014 5:49pm
6/2/2014 5:49pm
Fix to that 2nd to last line...Use a stock '07 crank.
CR250Rider
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CR250Rider 6/2/2014 7:21pm
6/2/2014 7:21pm
$124 delivered to my door


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