suggestions on my kids 02 CR 125 motor

Jerkolantern
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Jerkolantern 11/1/2016 6:21am
11/1/2016 6:21am
seth505 wrote:
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...
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.
Holy cow- that's a beautiful bike- I hope ours is as nice some day.
Jerkolantern
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Jerkolantern 11/1/2016 6:33am
11/1/2016 6:33am Edited Date/Time 11/1/2016 6:42am
JWACK wrote:
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...
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?
We haven't really touched the motor yet, we did install a boysen Reed block, and went up a tooth in the rear, the kid is 5-9 and about 180# he's not fat, he's like da old man, strong like bull. Or bullshitter. I forget which one. He rides moto, and skill level at good c rider or noob b rider, but he's got me riding his ass, he does cornering practice and body placement practice a lot so he's not at the track as much as maybe he should be. He's getting really good at the basics though and already keeps up with most of the guys on 250f's at his skill level and his bike is soooooo slow right now, I'm a land whale and I smoked him on my younger sons 03 CR 85 and I mean I smoked him- once we get this bike sorted I think I'm going to turn him loose, he rides safely, is getting good at keeping it on the pipe, and getting better at clutching for power. I actually bought this bike to keep him at a disadvantage, I figure if he can win on this, then he can have a new bike. I've been saving for years for him and my other boy. Hunter, who rides the 125 gets straight A's and busts his butt at work. The younger one not so much, but we're working on it...
Jerkolantern
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Jerkolantern 11/1/2016 6:41am
11/1/2016 6:41am
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


Are you a shop? Can I send my motor off to you? Or is this easy stuff to do, I'm a decent mechanic but I've never torn a bike motor down, more heavy equipment service and repair knowledge. If you are can you text me your # or just reply here? Brad 507-461-0317
HenryA
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HenryA 11/1/2016 6:43am
11/1/2016 6:43am
Vforce, VHM head, 05-07 airboot, HGS/PC/KX pipe + silencer, a new piston and jet it correctly. You should be able to get that for about 500$

The Shop

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mx621
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mx621 11/1/2016 6:59am
11/1/2016 6:59am
Jerkolantern wrote:
Are you a shop? Can I send my motor off to you? Or is this easy stuff to do, I'm a decent mechanic but I've never...
Are you a shop? Can I send my motor off to you? Or is this easy stuff to do, I'm a decent mechanic but I've never torn a bike motor down, more heavy equipment service and repair knowledge. If you are can you text me your # or just reply here? Brad 507-461-0317
http://www.hpracedevelopment.com

Derek seems to be the go to guy after researching for the last year. Not the cheapest option, but you get what you pay for. I'm finally gonna tear my bike apart and sent it in. it's due for a top end anyway.
Crush
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Crush 11/1/2016 7:08am
11/1/2016 7:08am
Just remember. Anything is possible!

Although I did remember reading that once they brought the ali frame in, that bike's intake got choked off because of space... so maybe that's the answer, get it breathing.



JWACK
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JWACK 11/1/2016 7:34am
11/1/2016 7:34am
JWACK wrote:
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...
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?
Jerkolantern wrote:
We haven't really touched the motor yet, we did install a boysen Reed block, and went up a tooth in the rear, the kid is 5-9...
We haven't really touched the motor yet, we did install a boysen Reed block, and went up a tooth in the rear, the kid is 5-9 and about 180# he's not fat, he's like da old man, strong like bull. Or bullshitter. I forget which one. He rides moto, and skill level at good c rider or noob b rider, but he's got me riding his ass, he does cornering practice and body placement practice a lot so he's not at the track as much as maybe he should be. He's getting really good at the basics though and already keeps up with most of the guys on 250f's at his skill level and his bike is soooooo slow right now, I'm a land whale and I smoked him on my younger sons 03 CR 85 and I mean I smoked him- once we get this bike sorted I think I'm going to turn him loose, he rides safely, is getting good at keeping it on the pipe, and getting better at clutching for power. I actually bought this bike to keep him at a disadvantage, I figure if he can win on this, then he can have a new bike. I've been saving for years for him and my other boy. Hunter, who rides the 125 gets straight A's and busts his butt at work. The younger one not so much, but we're working on it...
If you haven't touched the motor yet I would recommend just doing a fresh topend, good powervalve clean and a base gasket match. Something easy to start with would be the exhaust port polish. A sand paper verity pack would do the job. It will turn into a mirror if the time is spent on it. And it does make a difference. I always recomend starting by hand with no power tools if you haven't had experience. Mistakes are made really easy with power tools and porting. Your boy could do it by hand with sand paper and time. It's good learning. An 85 should not be keeping up with that bike.
Derek Harris 11/1/2016 7:46am
11/1/2016 7:46am
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!
Id pay to see 40 from that combo.

We have 40 + yz 125 combos and 45 144-150 combos, the the ktm can easily crank out mid 40s on their 125, but it isnt easy by any stretch to achieve for a moto bike.


The hpp cylinder is held in high esteem, and its not bad by any stretch, but the 01-03 stuff wasnt as bad as the honda faithful say.
In fact the 01-03 in karting worlds with totally stock cylinder has been capable of 40 hp in recent years.

I have a customer who recently had 40+ hopes for his full blown 92 or 93 (cant recall) mitch payton build that he was assured was the same piston, porting, and head combo they had.

After some tuning it made 35 or so. damn respectable for 23 year old bike.
Shortly there after the racer x article came out where mitch said the honda was around 35.5 when pc had to switch to kawi, verfiying his build.

The biggest issues on the 01-03 include the heavily angled intake tract, and reed block. If honda had copied the 05+ yz here it would nearly match the yz. not much you can do... although with big budget you can tweak the reed stiffness across the petals and make good gains.
Tracktor
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Tracktor 11/1/2016 8:43am
11/1/2016 8:43am
bsharkey wrote:
ill put my bike up against that any day
Good for you. Sign up for 250/450b and you can as that's what he usually races & often runs the CR just for fun. I am sure there are much faster bikes out there so what's the point of a dick measuring contest? My original point is for relatively cheap you can get the '02 (not commenting on newer years) Cr125's to run well. I figured that pisses of the YZ masses. Funny thing is I offered to buy him a new Husky but he likes riding something different that we built together. You know, cause it's "more funner"...............
Jerkolantern
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Jerkolantern 11/1/2016 9:40am
11/1/2016 9:40am Edited Date/Time 11/1/2016 9:41am
bsharkey wrote:
ill put my bike up against that any day
Tracktor wrote:
Good for you. Sign up for 250/450b and you can as that's what he usually races & often runs the CR just for fun. I am...
Good for you. Sign up for 250/450b and you can as that's what he usually races & often runs the CR just for fun. I am sure there are much faster bikes out there so what's the point of a dick measuring contest? My original point is for relatively cheap you can get the '02 (not commenting on newer years) Cr125's to run well. I figured that pisses of the YZ masses. Funny thing is I offered to buy him a new Husky but he likes riding something different that we built together. You know, cause it's "more funner"...............
So true, most of the fun is in working with your kids making an ugly duckling nobody wants into a rad bike almost everyone thinks can't be competitive. I don't know if it's true, but the guy who got me into bikes always told me 90% rider 10% bike
-eagle-
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-eagle- 11/1/2016 10:37am
11/1/2016 10:37am Edited Date/Time 11/1/2016 10:42am


bll
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bll 11/1/2016 11:19am
11/1/2016 11:19am
As long as your motor is tight, do what I did, trim the airbox for better flow and get a JD Jet kit.
BroFoSho
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BroFoSho 11/1/2016 12:31pm
11/1/2016 12:31pm
I had an 02.
I messed with different pipe/exhaust combos, reeds, etc. made some difference but not a ton. 2 best things you can do to the bike...

1.) one tooth bigger front sprocket. It kills what little bottom end the bike does have, but it pulls sooooo much further up top. As long as you keep it above 8k RPM, it'll rip

2.) Keep the motor fresh. I was doing rings every 5-7 hours and a piston every 10-14 hours.

At the end of the day, it's a 125... all 125s are slow as shit. But as long as you twist the grip off the throttle it'll beat 450s
Kx125rider 11/1/2016 3:08pm
11/1/2016 3:08pm
Jerkolantern wrote:
So true, most of the fun is in working with your kids making an ugly duckling nobody wants into a rad bike almost everyone thinks can't...
So true, most of the fun is in working with your kids making an ugly duckling nobody wants into a rad bike almost everyone thinks can't be competitive. I don't know if it's true, but the guy who got me into bikes always told me 90% rider 10% bike
Ive always thought that too. Its fun passing brand new bikes on your 10 year old bike.

Pit Row

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