Making more power from an 04' CR125

BrodieBiking
Edited Date/Time 5/3/2021 8:29am
Hey,

I have a 2004 CR125 with all the common go fast parts... Pro circuit exhaust, v-force reeds, suspension work... but it doesn't have enough power.

Are there any reputable machining companies within Ontario/Canada?
If not, who is the "go to" guy in the states for a cylinder bore?

I see that the most you can bore out a 125 cylinder is to 134cc... Is it worth the $500? Would 9cc really make much difference?

I realise that buying a 250 would probably be the smarter option, but i've put way to much money into this bike to sell it now.

Any help is appreciated,

Thanks


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jj welks
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jj welks 4/28/2016 4:21pm
4/28/2016 4:21pm Edited Date/Time 4/28/2016 4:22pm
build thread for a baddd 250 on page #1 might be useful
Crisp BRAAAP! 4/28/2016 4:31pm
4/28/2016 4:31pm
I am pretty sure if you had Gorr do it with porting and head mods that it'd be really fast. Run race gas in it and make the mods wild.
pete24
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pete24 4/28/2016 5:46pm
4/28/2016 5:46pm
you can do whatever u want to that thing , its a glorified vacum cleaner, my buddy had one had rpm bore it to 151 was about as fast as a stock yz 125
Tbteam
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Tbteam 4/28/2016 5:58pm
4/28/2016 5:58pm Edited Date/Time 4/28/2016 5:59pm
You can pick up another 3-4HP just by fixing the numbers on your side plates Dizzy
14

The Shop

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BrodieBiking 4/28/2016 6:07pm
4/28/2016 6:07pm
Tbteam wrote:
You can pick up another 3-4HP just by fixing the numbers on your side plates Dizzy
Yes yes... I know I know
BrodieBiking 4/28/2016 6:08pm
4/28/2016 6:08pm
pete24 wrote:
you can do whatever u want to that thing , its a glorified vacum cleaner, my buddy had one had rpm bore it to 151 was...
you can do whatever u want to that thing , its a glorified vacum cleaner, my buddy had one had rpm bore it to 151 was about as fast as a stock yz 125
That's what I'm worried about. I do have an 04 YZ125 that I just picked up for $500. She's seized so it'll need motor work anyways haha
Flatliner
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Flatliner 4/28/2016 6:27pm
4/28/2016 6:27pm
Machine racing used to make a potent 125 back in the day.

Buddy also had an RM by Reynard mods that ripped.
bd
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bd 4/28/2016 6:52pm
4/28/2016 6:52pm
Hard bike to make fast. If you have cash, send the engine (complete) and carb to Watts Perfections. Start with the following:

- PC Pipe With Shorty
- 2005 to 2007 Air Boot
- V Force
- Race Gas (50/50)
- Jetting Critical

http://www.vitalmx.com/forums/MotoRelated,20/2004-Honda-CR-125,543763

http://www.vitalmx.com/forums/Moto-Related,20/05-CR125-Decent-bike,1265…
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nascarnate326
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nascarnate326 4/28/2016 6:55pm
4/28/2016 6:55pm
What fuel are you using?
peelout
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peelout 4/28/2016 7:02pm
4/28/2016 7:02pm
'04 CR125 and "power" don't belong in the same sentence let alone the same discussion.

Hate to be the dick here but sell that fuckin turd and get the YZ running and freshened up and thank me later. I had that year CR125 after coming off a YZ and it was the biggest mistake I ever made with racing. I struggled and spent way too much money trying to get it back to the level of the YZ and never got close. Worst 125 made in my opinion.

Good luck bro, you're going to need it
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LungButter
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LungButter 4/28/2016 7:05pm
4/28/2016 7:05pm
Good luck, your gonna need it.

Is the chassis on the YZ in good shape? You might be better off putting the money into that motor if your looking for a "fast" 125. That generation of Honda 125s just didn't have it in the motor department.
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garagedog 4/28/2016 7:10pm
4/28/2016 7:10pm
I had a 04 with a 134cc kit by Gorr. Also a 06 with a 144 kit. And a 05yz stock. YZ had a much better spread of power , was easier to ride and would wind out much longer. Those Hondas Are just not a good platform, especially the 04 because of the RC power alive. It's a mid range only motor. Carburation is horribly frustrating.
Camp332
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Camp332 4/28/2016 7:24pm
4/28/2016 7:24pm

I see that the most you can bore out a 125 cylinder is to 134cc... Is it worth the $500? Would [b]14cc really make much ?[/b]

I dont want to be a math teacher Brodie. Is that 14, or 9 CC's?

ledger
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ledger 4/28/2016 7:28pm
4/28/2016 7:28pm
I'm surprised no one has mentioned anything about the YZ.... Huh Dats whut I wud doo. Whistling
JM485
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JM485 4/28/2016 7:43pm
4/28/2016 7:43pm
Don't let these guys ruin that bike for you, I have an 04 and absolutely love it. Mine is stock with nothing but a V-force reed cage + fmf pipe, and when I rode it back to back with a new yz at a demo day I didn't feel like the power gap was absolutely earth shattering like people claim. While the yz was a LOT easier to keep in the powerband, I didn't feel like my Honda was down a whole lot on peak power. Maybe it was just because I was more comfortable on my familiar bike, but I remember being surprised how well my Honda held its own. If anyone had dyno charts from a bike test or something I would love to see them, just to see if I'm crazy or if the Honda really isn't down all that much on peak power.

My plans for mine this summer include swapping to an 02 or older bottom end to mate with the 93 top end I bought off a member here. I'm going to keep my 04 motor completely stock as a back-up, and use the older motor to experiment with a little. Might go with the 6 speed trans if I can find one in decent condition, as well as the newer air boot and a general cleaning up of the ports. I still haven't found a bike that turns better than my cr125, not even the fabled rm250, so I say just ride it and enjoy it. If you want a way faster bike, jump up to a 250, but I'd keep the 125 just for fun.
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CrGuy2T
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CrGuy2T 4/28/2016 8:17pm
4/28/2016 8:17pm Edited Date/Time 4/28/2016 8:18pm
04 was a one year 125 with electronic powervalve. Change to a mechanical powervalve and it will help immediately. I think you can just use an 03 Pv but you may have to swap the cylinder.
BrodieBiking 4/28/2016 8:46pm
4/28/2016 8:46pm
nascarnate326 wrote:
What fuel are you using?
Just pump gas, 93... Just because it's readily available
BrodieBiking 4/28/2016 8:47pm
4/28/2016 8:47pm
Camp332 wrote:
[b]I see that the most you can bore out a 125 cylinder is to 134cc... Is it worth the $500? Would [b]14cc[/b] really make much ?[/b]...

I see that the most you can bore out a 125 cylinder is to 134cc... Is it worth the $500? Would [b]14cc really make much ?[/b]

I dont want to be a math teacher Brodie. Is that 14, or 9 CC's?

Hahaha Jesus Christ... I must be tired.

Pit Row

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BrodieBiking 4/28/2016 8:49pm
4/28/2016 8:49pm
Hmmmm, maybe I sell my CR125, fix the YZ for a quick flip and buy a newer bike.......
BrodieBiking 4/28/2016 8:53pm
4/28/2016 8:53pm
Flatliner wrote:
Machine racing used to make a potent 125 back in the day.

Buddy also had an RM by Reynard mods that ripped.
Oh geez I wish I knew that before they closed up aha
Dirtysmile56
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Dirtysmile56 4/28/2016 8:56pm
4/28/2016 8:56pm
Sell it for as much as possible and buy a stock YZ 125. It will be much faster..,,,
Piston Slap
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Piston Slap 4/28/2016 9:10pm
4/28/2016 9:10pm

There is a thing on the right side handle bar. IT's called a throttle assembly.

I guarantee you twist that thing to the stops, and be able to handle the buckking thing beneath you,

you will win.

All the motor mods in the world will not make you a winner.

The connection/disconnection between the throttle hand and the brain will/willnot enable you to be a winner.

"If you don't twist it, you can't win it."
1
BrodieBiking 4/28/2016 9:16pm
4/28/2016 9:16pm
Piston Slap wrote:
There is a thing on the right side handle bar. IT's called a throttle assembly. I guarantee you twist that thing to the stops, and be...

There is a thing on the right side handle bar. IT's called a throttle assembly.

I guarantee you twist that thing to the stops, and be able to handle the buckking thing beneath you,

you will win.

All the motor mods in the world will not make you a winner.

The connection/disconnection between the throttle hand and the brain will/willnot enable you to be a winner.

"If you don't twist it, you can't win it."
yessssir you are right aha... But most of us don't have balls big enough to hold it wide open 99% of the time haha..... Maybe that's the issue Laughing
JMX82
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JMX82 4/28/2016 9:36pm
4/28/2016 9:36pm
Could there be done same thing to electronic power valve 125 what has Blackdiamond done to his 250? I think there might be lot of unused potential with that engine.
jeffro503
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jeffro503 4/28/2016 10:58pm
4/28/2016 10:58pm
Wasn't the 04' the odd year on the CR 125's? Was thinking so. I thought the 05' - 07' bikes was where they changed the power valve? I also thought the 01' , 02' and 03' had stronger motors. 04' was a weird year for the CRF's as well. I remember riding an 04' CRF450 and it was a complete and utter turd compared to the 05' when it came out. ( which was an awesome bike btw )
HenryA
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HenryA 4/29/2016 12:17am
4/29/2016 12:17am
Seems like you're missing porting work on the engine. After that, install a VHM head to raise the compression. Buy race fuel and jet it perfectly and let it siiiiiiiiing
Frodad78
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Frodad78 4/29/2016 4:07am
4/29/2016 4:07am
I posted this on another thread, I'll just leave it here. I feel they are awesome bikes as long as you don't want to race. It would also make a great beginner or trail bike.

I had an 01 CR125

I did the

05 airboot
Drilled out the side panels for air flow
Rad Valve
PV mod
02 Power Valve flaps
PC pipe and silencer.
decked the head
Ported it
Put a PWK on it

then I bought a bone stock 05 YZ125 and it walked away from the CR. I traded it for a KDX lol

The best part about them is the way the handle, they turn on a dime. I still have the PWK if you are interested. Good luck
BrodieBiking 4/29/2016 4:53am
4/29/2016 4:53am
Frodad78 wrote:
I posted this on another thread, I'll just leave it here. I feel they are awesome bikes as long as you don't want to race. It...
I posted this on another thread, I'll just leave it here. I feel they are awesome bikes as long as you don't want to race. It would also make a great beginner or trail bike.

I had an 01 CR125

I did the

05 airboot
Drilled out the side panels for air flow
Rad Valve
PV mod
02 Power Valve flaps
PC pipe and silencer.
decked the head
Ported it
Put a PWK on it

then I bought a bone stock 05 YZ125 and it walked away from the CR. I traded it for a KDX lol

The best part about them is the way the handle, they turn on a dime. I still have the PWK if you are interested. Good luck
What's a pwk?
Frodad78
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Frodad78 4/29/2016 6:31am
4/29/2016 6:31am
36mm Keihin PWK Airstriker Carburetor. The Mikuni TMX carb on my CR was very temperamental. It always needed adjustment and from what I gathered from others was just sub par compared to the PWK. I did the swap and had it jetted by a local shop and I was pretty happy with it.

With the TMX the bike had a good low to mid power, The PWK took away a little of that low and let it Rev a bit more on top. I put the TMX back on after I got the YZ because the CR became my trail bike and preferred the low end snap from the TMX even though it always needed adjustment. By this time my jetting skills were pretty good considering I was always fooling with the TMX. If anything I learned a hell of alot about jetting and how to tune the power of a 125 with that Honda because there wasn't a whole hell of alot to work with.

I played with gearing alot too. When I was in the woods with it I ran a 12T up front, on the Track I ran a 14. For a 125 it made alot of low and mid, People would say the power was like a mini 250. I just had no use for the bike once the YZ showed up.
mx621
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mx621 4/29/2016 6:39am
4/29/2016 6:39am Edited Date/Time 4/29/2016 6:42am
BrodieBiking wrote:
What's a pwk?
its a keihin 38mm carb that came on some 250cc two strokes. easier to jet and they make better power.

the Honda 125's are what they are.. great chassis, but weak motors.. I ride a 02, and while it makes ok peak power it takes a lot to keep it alive as it has ZERO bottom end, and a little mid range.. but if u keep shifting and keep corner speed up its fine.. i actually enjoy riding a bike everyone thinks is a turd, cause when you pass them they have nothing to say. throwing a bunch of money at it will frustrate you.

last summer I parked next to a guy at the track, he had a 2015 crf450, susp valved, yosh exhaust, black wheels, fresh gear/helmet etc.. I had only taken my 125 that day.. before we went out he was literally laughing at me and couldn't believe I was gonna ride it. (im 6'3 225lb) " idk how you ride that thing?" " my buddy had one,they are so slow". Well he changed his tone when we came back... I caught and passed him on an inside corner and pulled away... it stayed that way rest of the day.. I don't consider myself fast by any means.. im a average B rider at best. point is if you like the bike just ride it.. you getting better will be the best mod you can do.

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