WANTED: 2003 CR 125 Cylinder

Spagina767
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Spagina767
Edited Date/Time 8/14/2014 6:19pm
Building a 134cc 6-speed screamer. I bought the bike and it has a stock bore cylinder, with a steel sleeve. For building a race motor id rather have a punched out stock cylinder so it can be nikisealed.

Looking for a junk stock bore cylinder

I'd even work out a trade - your trashed stock one for my good sleeved one.
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Mr Bean
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Mr Bean 8/11/2014 3:41pm
8/11/2014 3:41pm
FWIW, if you can't find another cylinder, the steel sleeve can have a nikasil coating applied over it. They'd bore it to the desired/required size and then coat it and hone to proper clearances.

You'd have a harder base metal with the steel sleeve than with the aluminum casting.

My only question is how big the sleeve can be bored.

Might want to check with some of the nikasil coating companies.

Daniel Mata
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Daniel Mata 8/11/2014 4:18pm
8/11/2014 4:18pm
more suggesstions ?
Daniel Mata
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Daniel Mata 8/11/2014 4:19pm
8/11/2014 4:19pm
do you have more suggesstions ?
Spagina767
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Spagina767 8/12/2014 4:25am
8/12/2014 4:25am
Well, disregard my question. I found a very, very good shape 2003 on craigslist yesterday and picked it up for $1,100. I'm going to combine both bikes, one with an original cylinder punched out to 134cc and nikisealed, and the other with a stock bore sleeved cylinder. I'll end up with one flawless bike, and one in good condition.

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rmartin517
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rmartin517 8/13/2014 3:14am
8/13/2014 3:14am Edited Date/Time 8/13/2014 3:19am
If you can get your hands on an 02 motor you can put a 92-99 HPP cylinder on it and punch it out to a 144. I have a few mod CR125s I was gonna go the 6 speed route but was told on the dyno the actual weight of the 6 speed tranny robbed HP on the dyno. Change your air boot to a 05-07 with (4) 1" uni filters in the air box, switch over to a 38mm Kehin airstiker carb with your big bore kit and and change your intake manifold either to a boyesen rad valve wich is 12mm bigger in diameter of go with a 98 intake boot which is 10mm bigger with a V force and she will rip. Higher compression will also be your bestfriend as long as you get your air intake and jetting to spec. Also one of the best mods to the bike was switch over to SHOWA suspension off a cr 250.
rmartin517
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rmartin517 8/13/2014 3:41am
8/13/2014 3:41am
Dis regulars the 98 air intake boot I forgot it changed bolt pattern in 03.
Spagina767
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Spagina767 8/13/2014 11:50am
8/13/2014 11:50am
rmartin517 wrote:
If you can get your hands on an 02 motor you can put a 92-99 HPP cylinder on it and punch it out to a 144...
If you can get your hands on an 02 motor you can put a 92-99 HPP cylinder on it and punch it out to a 144. I have a few mod CR125s I was gonna go the 6 speed route but was told on the dyno the actual weight of the 6 speed tranny robbed HP on the dyno. Change your air boot to a 05-07 with (4) 1" uni filters in the air box, switch over to a 38mm Kehin airstiker carb with your big bore kit and and change your intake manifold either to a boyesen rad valve wich is 12mm bigger in diameter of go with a 98 intake boot which is 10mm bigger with a V force and she will rip. Higher compression will also be your bestfriend as long as you get your air intake and jetting to spec. Also one of the best mods to the bike was switch over to SHOWA suspension off a cr 250.
Awesome info, thanks man.

So the 6-speed isn't the way to go? I feel like the dyno may not show what you feel on the bike.. but what do I know.

Right now what I have is 2 2003 CR 125's. One has a perfect condition stock bore cylinder, and one has a perfect condition sleeved cylinder. I want to make one a 134cc and leave one a 125 (for cost reason) but from what everyone says, sleeved cylinders suck. so i'm still looking for a junk 03 cylinder to bore. I cant get myself to bore the perfect condition one I already have. I have new cranks, and the 6-speed internals ready to go in... so I'm not sure what ill do now. I'm not trying to invest TOO much money into the bike, so the 2002 motor and other cylinder is out of my price range.

I have a boysen rad valve, and showa twin chambers from a 2004 CR 250 that are going on it.
Spagina767
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Spagina767 8/13/2014 12:24pm
8/13/2014 12:24pm
well I just found an 03 cylinder on ebay, complete with power valve, for 70. so ill send that out with my head hopefully this week, so I can get this 134 project going
rmartin517
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rmartin517 8/13/2014 2:47pm
8/13/2014 2:47pm
Well the problem with sleeved cylinder is getting the porting to match up and the steel sleeve eats pistons. Who is doing your big bore? I belive you can take that 03 up to a 139cc with eric gorr and he will give you any porting as well. Yeah the RAD valve is good becasue you get a bigger intake boot. The V force is great as well but runs the stock intake boot which will restrict the air. You need to get as much air as you can. Going to be a fun project. I like running a 88-89 dome top piston but you have to have the head cut. I use them in mime to gain compression. As far as the 6 speed you dont have a whole lot to gain. I would be interested in your 5 speeds if you decide to take them out. good luck on you builds. CR 125s are very slow stock but you can make them fast and they just handle so well.
Spagina767
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Spagina767 8/13/2014 3:22pm
8/13/2014 3:22pm
rmartin517 wrote:
Well the problem with sleeved cylinder is getting the porting to match up and the steel sleeve eats pistons. Who is doing your big bore? I...
Well the problem with sleeved cylinder is getting the porting to match up and the steel sleeve eats pistons. Who is doing your big bore? I belive you can take that 03 up to a 139cc with eric gorr and he will give you any porting as well. Yeah the RAD valve is good becasue you get a bigger intake boot. The V force is great as well but runs the stock intake boot which will restrict the air. You need to get as much air as you can. Going to be a fun project. I like running a 88-89 dome top piston but you have to have the head cut. I use them in mime to gain compression. As far as the 6 speed you dont have a whole lot to gain. I would be interested in your 5 speeds if you decide to take them out. good luck on you builds. CR 125s are very slow stock but you can make them fast and they just handle so well.
That's why I bought the cylinder off eBay today. It's trashed, so I'll send it out to have it bored. Eric Gorr is doing the work for me, but I have someone else to port it.

The cylinder I have now that is sleeved I'll just sell on eBay and try to get 75+ out of it.

I'm going to end up doing the 6 speed, just because it will be unique and I'm tearing the bottom end apart anyway. So, I will have the 5 speed internals to sell. They are in good shape.
rmartin517
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rmartin517 8/14/2014 11:37am
8/14/2014 11:37am
6 speed will be cool to play with. I know some years had better materials than others on the parts. Pretty easy to research. Good luck with your build out some pics up. Cr 125 02-07 are always cool. I personally think they came before their time they still represent a modem bike look.
rmartin517
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rmartin517 8/14/2014 1:15pm
8/14/2014 1:15pm
Spagina767 wrote:
well I just found an 03 cylinder on ebay, complete with power valve, for 70. so ill send that out with my head hopefully this week...
well I just found an 03 cylinder on ebay, complete with power valve, for 70. so ill send that out with my head hopefully this week, so I can get this 134 project going
That's the sweet thing about having the cr 125 parts are dirt cheap on eBay.

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