suggestions on my kids 02 CR 125 motor

Jerkolantern
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Jerkolantern
It's way down on power, which co. Do you guys suggest? I'd like to get it done locally, I live in New Richland Minnesota. We have about 500 to play with. Thank you in advance for your suggestions
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pete24
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pete24 10/31/2016 11:34am
10/31/2016 11:34am Edited Date/Time 10/31/2016 11:35am
sell it, there is no way to make it fast, a god dam kx85 is faster
mx621
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mx621 10/31/2016 11:42am
10/31/2016 11:42am
I own one. I'm 225lb and hurt a lot of feelings with it. I've had people
Come up to me on several occasions and say how the hell in I even moving on that thing, let alone passing them on there brand new 450, slowest 125 ever etc... If your boy is still learning/getting faster a slower bike will force him to carry more speed in the corners and will help him over all be a better/faster rider. It does for me. I have a fmf fatty, fmf shorty, 07 air boot and I ported/matched the stock reed boot. It literally has zero bottom end power but does ok in the mid-top. Very soon I am sending it for a big bore kit. Most likely to hp race development.
Jerkolantern
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Jerkolantern 10/31/2016 11:45am
10/31/2016 11:45am
So is my other sons 03 CR85 but money's hard to come by, so I told him if he can beat kids on this I'll buy him a new scoot, he's learning how to carry speed. I'm well aware of this year's Honda issues, but don't tell me it can't be done, it was only down a few ponies to the yz. Like I said, I'd love to just buy a new bike, but that's not gonna happen just yet
Jerkolantern
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Jerkolantern 10/31/2016 11:46am
10/31/2016 11:46am
mx621 wrote:
I own one. I'm 225lb and hurt a lot of feelings with it. I've had people Come up to me on several occasions and say how...
I own one. I'm 225lb and hurt a lot of feelings with it. I've had people
Come up to me on several occasions and say how the hell in I even moving on that thing, let alone passing them on there brand new 450, slowest 125 ever etc... If your boy is still learning/getting faster a slower bike will force him to carry more speed in the corners and will help him over all be a better/faster rider. It does for me. I have a fmf fatty, fmf shorty, 07 air boot and I ported/matched the stock reed boot. It literally has zero bottom end power but does ok in the mid-top. Very soon I am sending it for a big bore kit. Most likely to hp race development.
This ^

The Shop

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seth505
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seth505 10/31/2016 12:45pm
10/31/2016 12:45pm
Very similar thoughts to mx621. I just rebuilt an 03 that I bought of friends for a project to do. I just posted the build if you want to look at the full list of stuff I did.
http://www.vitalmx.com/forums/Bike-Builds,46/03-CR-125-rebuild-restore,…

Like mentioned, it has ZERO bottom end but who cares. Mine is a 134cc, porting, vforce reed vavle with intake port matched, 07 airboot/airbox mods, Bud racing/HGS exhaust. I just rode mine for the first time yesterday after the ground up rebuild and it was a blast. I also rode it in power robbing sand which is annoying when you don't have lots of power but still fun as hell.
Tracktor
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Tracktor 10/31/2016 2:20pm
10/31/2016 2:20pm
We have an '02 CR125 which gives up nothing to the newer YZ/KTM & it doesn't cost much to do-

96 CR125 HPP cylinder
Gorr 144 kit ( even in 125 form with the HPP cylinder it's fast)
38mm PWK Air Stryker carb with 6.0 Slide
05+ Air boot
03 KX125 pipe with PC Shorty

2015 TX race plastics
B-kit Suspension

On a budget start with Carb, air boot & pipe. For a couple hundred bucks it will rip.

My kid has a new KX250f and he rides this bike more. He has ridden new YZ's and 17 Huskys and the only thing motor wise he says is the Husky is smoother. YZ is a tank...............(Yes, I am sure I will catch shit from the YZ faithful for these claims)....



Tracktor
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Tracktor 10/31/2016 2:22pm
10/31/2016 2:22pm
pete24 wrote:
sell it, there is no way to make it fast, a god dam kx85 is faster
Pete, usually you know your stuff but you are way off base on this one. Can be done & we have done it. Anytime you are in the NW it's here to test.............
MotoX85
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MotoX85 10/31/2016 2:26pm
10/31/2016 2:26pm
pete24 wrote:
sell it, there is no way to make it fast, a god dam kx85 is faster
What he said. No way

YZ is a tank, omg that's hilarious.

JWACK
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JWACK 10/31/2016 2:46pm
10/31/2016 2:46pm
500 dollar budget. I do my own work so this wouldn't cost me hardly anything but time. Not sure what your capable or have the time to do yourself. I don't mind the stock exhaust to start off. These bikes love a good port and polish. Case match. Intake match and reed stuffer port job. Exhaust manifold and pipe match. Makes a huge difference on these bikes. Fresh reeds as well. One up on the rear sprocket. Still won't be a Yz on bottom but mid and top won't give up anything.
Kx125rider 10/31/2016 2:52pm
10/31/2016 2:52pm
I bought one that had a pc pipe and silencer(shorty) and vforce, and it wasnt that bad.
JWACK
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JWACK 10/31/2016 2:56pm
10/31/2016 2:56pm
rongi#401 wrote:
[img]https://p.vitalmx.com/photos/forums/2016/10/31/158348/s1200_Trash_Can.jpg[/img]


Wow what a nice smile you have.
Jerkolantern
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Jerkolantern 10/31/2016 4:19pm
10/31/2016 4:19pm
OK, I'll do exactly what you guys did, including the part for more low end. JWACK would you be interested in doing those mods to our motor? I'd pay you for your time of course.
Frodad78
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Frodad78 10/31/2016 4:29pm
10/31/2016 4:29pm
I have a fresh PWK for that thing that I can't seem to sell for the life of me!
Derek Harris 10/31/2016 4:59pm
10/31/2016 4:59pm
In our latest pipe dyno test the pc and shorty drastically outperformed the fmf on an 03, which very very similar to the 02.

outside of that, remove the stator lock plates so you can move timing, a vforce, some time on jetting with 50/50 race fuel, and you will be competive in peak hp with a yz easily.

sadly the curve isnt as good but its not bad.


Motor work wise we can get a couple additional ponies more from 9k-12, we use a different piston and if you splurge a little we do some transfer tunnel epoxy work that helps the front side of curve.

The honda 03 chassis is quite good


DTHA70
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DTHA70 10/31/2016 5:26pm
10/31/2016 5:26pm
99 cylinder, take 10 thou off the bottom, simple port job, pipe and shorty silencer, taper bore 36-40mm carb, run on c12, itll be 40+hp for about 20 hrs at a time before it needs rings!

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JWACK
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JWACK 10/31/2016 5:44pm
10/31/2016 5:44pm
Jerkolantern wrote:
OK, I'll do exactly what you guys did, including the part for more low end. JWACK would you be interested in doing those mods to our...
OK, I'll do exactly what you guys did, including the part for more low end. JWACK would you be interested in doing those mods to our motor? I'd pay you for your time of course.
Right now I'm not able to. I just moved to Texas from New Mexico and I do not have my belongings yet. No tools or work bench at the moment. Later on in the future I would gladly help out though.
JWACK
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JWACK 10/31/2016 5:49pm
10/31/2016 5:49pm
One more important thing that some folks just don't do and it's free horsepower. Match your base gasket to your cylinder. How old is your kid? And what kind of riding are you/him doing? When was the last time you did a rebuild and cleaned up the power valve?
BobPA
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BobPA 10/31/2016 5:56pm
10/31/2016 5:56pm
I have ridden a descent amount on Honda 125's through the years, from a variety of engine builders...and they just never seem to have it.....best one I rode was a 134 with a home brew port job, race gas compression, and a pro circuit pipe....and I think it ran as well as a stock yamaha
TX_187
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TX_187 10/31/2016 6:51pm
10/31/2016 6:51pm
The Honda will never blow you away with bottom but they're still fun bikes to ride. Match base gasket to cylinder, get 05-07 air boot, pipe and shorty silencer, up 2 teeth in the rear, run a 50/50 mix of race fuel, air striker carb, and get some decent valving on the suspension.

The yz is better in stock form, but the cr can get there with a few tweaks. I've had both bikes.
mx621
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mx621 10/31/2016 7:06pm
10/31/2016 7:06pm
Derek Harris wrote:
In our latest pipe dyno test the pc and shorty drastically outperformed the fmf on an 03, which very very similar to the 02. outside of...
In our latest pipe dyno test the pc and shorty drastically outperformed the fmf on an 03, which very very similar to the 02.

outside of that, remove the stator lock plates so you can move timing, a vforce, some time on jetting with 50/50 race fuel, and you will be competive in peak hp with a yz easily.

sadly the curve isnt as good but its not bad.


Motor work wise we can get a couple additional ponies more from 9k-12, we use a different piston and if you splurge a little we do some transfer tunnel epoxy work that helps the front side of curve.

The honda 03 chassis is quite good


I plan on going with your 134 big bore on my 02 cr125 very soon. Straight vp110 setup. How do you feel about the older HPP cyl vs the 00-03 style rc valve cylinder? I have a 95 complete cyl sitting on my shelf. Which do u recommend? 225lb B rider. ( yea I know I'm to heavy but I love riding it) lol. I have a 450 too btw.





bsharkey
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bsharkey 10/31/2016 7:10pm
10/31/2016 7:10pm
Tracktor wrote:
We have an '02 CR125 which gives up nothing to the newer YZ/KTM & it doesn't cost much to do- 96 CR125 HPP cylinder Gorr 144...
We have an '02 CR125 which gives up nothing to the newer YZ/KTM & it doesn't cost much to do-

96 CR125 HPP cylinder
Gorr 144 kit ( even in 125 form with the HPP cylinder it's fast)
38mm PWK Air Stryker carb with 6.0 Slide
05+ Air boot
03 KX125 pipe with PC Shorty

2015 TX race plastics
B-kit Suspension

On a budget start with Carb, air boot & pipe. For a couple hundred bucks it will rip.

My kid has a new KX250f and he rides this bike more. He has ridden new YZ's and 17 Huskys and the only thing motor wise he says is the Husky is smoother. YZ is a tank...............(Yes, I am sure I will catch shit from the YZ faithful for these claims)....



ill put my bike up against that any day
bsharkey
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bsharkey 10/31/2016 7:13pm
10/31/2016 7:13pm
mrxo2 race fuel and rejet will do amazing things for any of these bikes but its $$$$. not really cost effective but fun
Braaaphole
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Braaaphole 10/31/2016 7:22pm
10/31/2016 7:22pm
The 96 cylinder is the go to on the CR125. The FMF team ran the 96 cylinders for years in outdoors. I ran one on my 99 and 01 race bikes and it really wakes the bike up.
96 cylinder, larger air boot, v force reeds, and PC pipe is what I ran back then and the bike was pretty quick.
inthebadboycorner 10/31/2016 11:41pm
10/31/2016 11:41pm
I had great success on my 2001 with an FMF Fatty, standard length silencer, Boysen Reeds and had the cylinder head squish adjusted.

This was a boost in power across the low and mid, the top end felt the same with a bit more over rev.

There is your $500
MotoX85
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MotoX85 10/31/2016 11:47pm
10/31/2016 11:47pm
DTHA70 wrote:
99 cylinder, take 10 thou off the bottom, simple port job, pipe and shorty silencer, taper bore 36-40mm carb, run on c12, itll be 40+hp for...
99 cylinder, take 10 thou off the bottom, simple port job, pipe and shorty silencer, taper bore 36-40mm carb, run on c12, itll be 40+hp for about 20 hrs at a time before it needs rings!
You show me the dyno of this on a 02 Honda 125 bore and I'll buy 10 of them. Holy cow that's more HP than a Honda, Suzuki and Kawasaki 250F.

You can get that and a little more out of a new YZ or KTM, but you will never see those numbers on an 02 Honda 125 not overbored.
MotoX85
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MotoX85 10/31/2016 11:48pm
10/31/2016 11:48pm
BobPA wrote:
I have ridden a descent amount on Honda 125's through the years, from a variety of engine builders...and they just never seem to have it.....best one...
I have ridden a descent amount on Honda 125's through the years, from a variety of engine builders...and they just never seem to have it.....best one I rode was a 134 with a home brew port job, race gas compression, and a pro circuit pipe....and I think it ran as well as a stock yamaha
This
Jerkolantern
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Jerkolantern 11/1/2016 6:16am
11/1/2016 6:16am
Frodad78 wrote:
I have a fresh PWK for that thing that I can't seem to sell for the life of me!
Well I'm your man. I looked on ebay and they're going ten to fifteen bucks..... haha just kidding, what do you want for it? And what kind of shape is it in? We definitely need one. My email is messed up, could you possibly text me at 507-461-0317 or just respond here? We have PayPal, or I could send a check / cash, money order, cc. Whatever works for you

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