05-07 cr125 talk

yz133rider
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Avondale, PA US
7/26/2022 5:45am Edited Date/Time 8/18/2022 10:08am
Anyone have some good info on these bikes?

Should I look for 08 crf450r forks to swap on the front?
Any go to set up or mods? I saw boyesen makes replacement stock style reeds to replace the stock or should I just get Oem?

Any piston worth getting or just go with stock?

I just got a low hour bike but want to go thru it lightly and have it ready to rip.

A lot of the info I’ve come across is to make the 02-04s run decent but it seems the 05-07s make relatively decent power.



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dmm698
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NY US
7/26/2022 6:24am Edited Date/Time 7/26/2022 6:25am
If I was goign to do a fork swap on that bike I'd just hold out and buy a set of production 17+ CRF 450 forks - 49mm showa units that are darn good and as good or better than most of the 10 year old A kit stuff you see people posting.

Profeshenal has no problem landing tons of chicks with those bikes so you should be golden with it as is....
6
7/26/2022 7:00am
Finally a good thread. 1 of my Stolen 06,s I had a rad valve, iKat, 03 kx125 hgs pipe get it from mxa in the UK. I did a lot of research on who has the pipe the US distributor does not A little bending , cutting off the back and pound room for the kick starter. I pounded the pipe in for clearance for a radiator hose on a 04 the 06 doesn’t hv that hose. Off idle snap much improved into a stronger mid that pulls to aprox 11k top end more ovr rev.this pipe has a huge cone section similar to what and oil team used. It runs like a ported engine. On a 04 the pipe runs totally diff , slower to hit once it does it’s much stronger in the mid with 2k more ove rev. I used a reg pc silencer. I was shocked by the improvement. Use kx pipe springs. Stock reeds r a 6 pedal they flutter getting on the pipe. Boyeseen sells carbon tech reeds I hv not tried them in a cr but they worked great on a rm. my 04,s 1 has a new RV the other has I think Boyeseen carbon reeds this bike runs better. Racers choice piston is a close mirror to a srs piston. Stock suspension is good for a 172lb rider go up on spring rate. Valving is really good except for jumping in clay whoops .a fc Revalve fixed that. I noticed throttle response improvement with power flow twin air cage the 04 ran a little stronger. I drilled 3 1 in holes in air box all that improved a little more. It was a tough decision to not use the 05 engine in the 04 chassis because it’s stronger coming on the pipe and ovr all. But I like the way a 04 runs better it forces you to ride hard.

7/26/2022 7:14am Edited Date/Time 7/26/2022 7:18am
yz133rider wrote:
Anyone have some good info on these bikes? Should I look for 08 crf450r forks to swap on the front? Any go to set up or...
Anyone have some good info on these bikes?

Should I look for 08 crf450r forks to swap on the front?
Any go to set up or mods? I saw boyesen makes replacement stock style reeds to replace the stock or should I just get Oem?

Any piston worth getting or just go with stock?

I just got a low hour bike but want to go thru it lightly and have it ready to rip.

A lot of the info I’ve come across is to make the 02-04s run decent but it seems the 05-07s make relatively decent power.



My friend had one of these from 06 until about 2 years ago. First thing I would do is ditch the tmx for a pwk yes it's really that much better in this bike.

Boyesen rad valve over vforce

Fmf is broader power band the pc is more top end.
It's power band is mostly mid
This bike vs my 06 yz125 it really favors an aggressive riding style.

The Shop

b_kowalsk
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Thomaston, CT US
7/26/2022 7:15am
Stock suspension is very good on these bikes. I actually prefer it over my YZ. Both the handling and suspension.
Mostly a midrange focused engine, they do fall a little flat on top. It will never have the power spread or run quite as cleanly as a YZ. Jetting is quite a bit off from the factory so there is some rideability to be gained be spending some time sorting that out.

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Sandusky26
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7/26/2022 7:24am
A CR125 is the best handling MX bike.
1
7/26/2022 7:29am
Paging Profeshanal.
Right here Man. Haha I had 2 attorneys call me this morning 1st one will not represent me for the labor dispute . Chicago co.s owe me ovr 45k. But good news a attorney is covering me for the injuries. 3 months of a nightmare. There is a programmable toggle ignition available in Europe for the 05-07. There’s a thread on here somewhere. Wc radiator braces avail yet. No pc alum throttle pipe avail for 02-07. I went with a pro taper it’s pretty good. The 03 hgs kx pipe is really good , you short shift in the mid range or let it rev out. Prob 38 hp but there’s power everywhere. Stock pipe power pulling range is short the kx pipe is a very wide pulling range and much stronger.

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1
7/26/2022 7:58am
Sandusky26 wrote:
A CR125 is the best handling MX bike.
Yeah it is. So crazy on how well a 04 handles . 12 yrs with no riding on the 1st lap I jumped everything. 2nd lap cleaned it up and put some speed down . 2nd ride I had to ride 30 + minutes straight . In a lot of hip and knee pain actually my knee gave out a few times both rides. I got tired so I relaxed more and let the bike work under me. There so easy and fun to ride. It’s hard to make mistakes.
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yota
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7/26/2022 12:25pm
the stock forks are surprisingly good.
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mattyhamz2
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7/26/2022 12:28pm
Stock suspension was pretty good.

Get a PWK and a 134cc kit. If I remember correctly, they really benefited from the 134.
JMCR250
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Chesterfield, MO US
7/26/2022 12:32pm Edited Date/Time 7/26/2022 12:33pm
We own an '07. It's a fast, very good handling bike. We've done these mods:

Revalve forks and shock with springs to suit my son's weight. Front and back are both very plush.

Pro Circuit Works pipe and Shorty silencer; stock motor.

JD Jetting kit on the stock Mikuni. Runs perfectly, tan plug, never fouls.

That's it. Ride the hell out of it. Reliable as a rock.
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sandman768
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Saratoga Springs, NY US
7/27/2022 4:29am
I have the MXA test of the 05-07… I can post it up if you like… they basically state, everything is very good, accept the engine is lacking compared to the other 125”s…I would keep it stock, go up a tooth or 2 on the rear, work on the jetting & ride it…. I have been riding my 93 CR125 lately….they are a blast but my brain cannot function that quick anymore😂
4
Richy
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UK GB
7/27/2022 5:02am
How do they stack up against the earlier ones from that generation? My '03 was flat as a pancake from new, but it handled sweet.
early
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OH US
7/27/2022 6:36am
Richy wrote:
How do they stack up against the earlier ones from that generation? My '03 was flat as a pancake from new, but it handled sweet.
The air boot is a little less restrictive than the earlier ones, the mod for those is to graft the last gen airboot onto the earlier airbox. Supposedly the powerband is wider but as others have said it's mostly a midrange motor. '04 had a servo controlled power valve, 05-07 they went back to a mechanical pv. Chassis is more refined in the later generations, similar to crf250 from that era, less like the original wide spar AL hondas.
1
Richy
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7/27/2022 6:40am Edited Date/Time 7/27/2022 6:42am
Nice, thanks, always feel like I have unfinished business with that bike but with the price of them now and how good the modern stuff is, it'd be real hard for me to not just buy a YZ.

Got to admire the guys who know that but still choose to build pure passion projects and still go and wring them out on the weekend.
3
7/27/2022 6:46am
Richy wrote:
How do they stack up against the earlier ones from that generation? My '03 was flat as a pancake from new, but it handled sweet.
Quite a bit better. My 1st 04 with decked and ported cylinder, bored carb 36.6 hp with a much stronger and longer mid into a flat ovr rev. A 06 with RV, iKat, 03 kx hgs pipe was stronger ovr all and had great snap off idle. I think stock gearing is great. No problems getting on the mid quick or short shifting on the center of the mid. In a week or so I should hv my 04 Tara Gieger LL championship spec engine back. Quick responding with a potent mid pull.
1
7/27/2022 6:57am
Richy wrote:
How do they stack up against the earlier ones from that generation? My '03 was flat as a pancake from new, but it handled sweet.
early wrote:
The air boot is a little less restrictive than the earlier ones, the mod for those is to graft the last gen airboot onto the earlier...
The air boot is a little less restrictive than the earlier ones, the mod for those is to graft the last gen airboot onto the earlier airbox. Supposedly the powerband is wider but as others have said it's mostly a midrange motor. '04 had a servo controlled power valve, 05-07 they went back to a mechanical pv. Chassis is more refined in the later generations, similar to crf250 from that era, less like the original wide spar AL hondas.
04 to 05 air boot has a straighter shot to the carb and smoother mold on the rt side. You get better throttle response on a 04 and it runs out cleaner. But it has less of a hit , there’s still a hit there it’s just lessened. I never heard of anyone trying a 04 boot on a 05. But it should improve the hit, if that’s what you like.


1
7/27/2022 7:14am
Richy wrote:
How do they stack up against the earlier ones from that generation? My '03 was flat as a pancake from new, but it handled sweet.
early wrote:
The air boot is a little less restrictive than the earlier ones, the mod for those is to graft the last gen airboot onto the earlier...
The air boot is a little less restrictive than the earlier ones, the mod for those is to graft the last gen airboot onto the earlier airbox. Supposedly the powerband is wider but as others have said it's mostly a midrange motor. '04 had a servo controlled power valve, 05-07 they went back to a mechanical pv. Chassis is more refined in the later generations, similar to crf250 from that era, less like the original wide spar AL hondas.
04 to 05 air boot has a straighter shot to the carb and smoother mold on the rt side. You get better throttle response on a...
04 to 05 air boot has a straighter shot to the carb and smoother mold on the rt side. You get better throttle response on a 04 and it runs out cleaner. But it has less of a hit , there’s still a hit there it’s just lessened. I never heard of anyone trying a 04 boot on a 05. But it should improve the hit, if that’s what you like.


I use nu car finish wax and spray silicone in the wax bottle. Wax the inside for a smooth air flow. Get that air to the carb quicker Yo.
2
crc245
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7/28/2022 7:37pm Edited Date/Time 7/28/2022 7:44pm
53T sprocket, VForce3, leaner pilot/clip position, fresh top ends/rings, good fuel (110 leaded/pump split for us), fresh tires (100/90-19 rears on the 1.85” rim), proper spring rates on stock components, and lots of flow make the 05-07’s FUN! Don’t be afraid of 1st gear in certain turns (remember, it’s a 5-speed), and stay away from any 08’ CRF fork swaps, even though they bolt right on; 2008 was a one year 12.5mm cartridge that never worked as well as the prior 12mm’s. Also, the 4T forks were shorter than the 2T’s these years. If the 46mm KYB’s aren’t good enough once sprung for you (I’d give em’ a shot first!), 02-07 CR250 Showa suspenders are easy to dial in, and they bolt right up.

I dropped the disc guards on mine and updated the 240mm front rotor/hanger; 240 was good at the time and on such a light bike, but there are better options with 04-14’ fitment that are direct fits. Also, that hybrid steel/aluminum rear sprocket lasts, but at the expense of pulling power. All aluminum is noticeable on the small-bore CR’s!

MXA was pretty on-point with their assessment:

https://motocrossactionmag.com/amp/on-the-record-complete-test-of-the-2…
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7/29/2022 7:31am
crc245 wrote:
53T sprocket, VForce3, leaner pilot/clip position, fresh top ends/rings, good fuel (110 leaded/pump split for us), fresh tires (100/90-19 rears on the 1.85” rim), proper spring...
53T sprocket, VForce3, leaner pilot/clip position, fresh top ends/rings, good fuel (110 leaded/pump split for us), fresh tires (100/90-19 rears on the 1.85” rim), proper spring rates on stock components, and lots of flow make the 05-07’s FUN! Don’t be afraid of 1st gear in certain turns (remember, it’s a 5-speed), and stay away from any 08’ CRF fork swaps, even though they bolt right on; 2008 was a one year 12.5mm cartridge that never worked as well as the prior 12mm’s. Also, the 4T forks were shorter than the 2T’s these years. If the 46mm KYB’s aren’t good enough once sprung for you (I’d give em’ a shot first!), 02-07 CR250 Showa suspenders are easy to dial in, and they bolt right up.

I dropped the disc guards on mine and updated the 240mm front rotor/hanger; 240 was good at the time and on such a light bike, but there are better options with 04-14’ fitment that are direct fits. Also, that hybrid steel/aluminum rear sprocket lasts, but at the expense of pulling power. All aluminum is noticeable on the small-bore CR’s!

MXA was pretty on-point with their assessment:

https://motocrossactionmag.com/amp/on-the-record-complete-test-of-the-2…
Yeah fork length I wouldn’t change that. Say a crf forks r shorter that would throw the handling off. The 04 and 05 shocks r s diff length. I fitted a 05 swingarm on a 04 and vise versa. There’s a diff gap on the mount . Blue spring is 05.

Sc2
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7/30/2022 1:14am
I have an 07, spent ages trying to get the jetting rite with the mikuni, gave up in the end and swapped for pwk, mate of mine has 07, with mikuni and his runs spot on
BTW, I find it PIA to work on pwk carb in situ, lack of space as its a tight fit and usually end up swinging the sub frame out the way

I have the vortex ignition switch fitted and tbh it's not night and day difference, it may need setting up (if you can) properly, but for me I wouldn't miss it if wasn't there

These bikes still turn heads at tracks and ritely so, they was well a head of their time in the looks department

@profeshenal125 what's you're story, I must of mist it, did you have a prang on you'res, do you have a build thread

Where you guys picking up bits for it, I did have some original stuff sent over from the states, partzillia I think
5
7/30/2022 7:07am
Sc2 wrote:
I have an 07, spent ages trying to get the jetting rite with the mikuni, gave up in the end and swapped for pwk, mate of...
I have an 07, spent ages trying to get the jetting rite with the mikuni, gave up in the end and swapped for pwk, mate of mine has 07, with mikuni and his runs spot on
BTW, I find it PIA to work on pwk carb in situ, lack of space as its a tight fit and usually end up swinging the sub frame out the way

I have the vortex ignition switch fitted and tbh it's not night and day difference, it may need setting up (if you can) properly, but for me I wouldn't miss it if wasn't there

These bikes still turn heads at tracks and ritely so, they was well a head of their time in the looks department

@profeshenal125 what's you're story, I must of mist it, did you have a prang on you'res, do you have a build thread

Where you guys picking up bits for it, I did have some original stuff sent over from the states, partzillia I think
That yellow plate with the hgs pipe was stroker crank ,2mm Ovr bore= rocket with 23+ ft lbs of torque. That and 2 other clean 06,s where stolen in 13. 45k of industrial mechanic tools also which I had a big loan on. It took me a few yrs to get 3 cr,s again. The cr,s are out there somewhere.
7/30/2022 7:16am Edited Date/Time 7/30/2022 7:46am
everytime i read about hot rod cr125s, the conclusion is that when its all said and done its more or less as fast as a stock yz125 and still quite a bit off a ktm125

def a good bike to teach you how to go fast!


is bolting on the showas off the cr250 worth it? i hear the kyb stuff stock is just as good.

or the real question is...is putting the kyb stuff on a cr250 an upgrade? the TC showas of this era had midstroke harshness
1
7/30/2022 8:06am
everytime i read about hot rod cr125s, the conclusion is that when its all said and done its more or less as fast as a stock...
everytime i read about hot rod cr125s, the conclusion is that when its all said and done its more or less as fast as a stock yz125 and still quite a bit off a ktm125

def a good bike to teach you how to go fast!


is bolting on the showas off the cr250 worth it? i hear the kyb stuff stock is just as good.

or the real question is...is putting the kyb stuff on a cr250 an upgrade? the TC showas of this era had midstroke harshness
Stock suspension is very good get the spring rate correct. Jumping into clay whoops a revalve is needed. 1st ride in 12 yrs I passed a new yz on the 1st lap and jumped everything. I,m sure the yz is much faster on top than a stock 04 with a stock pipe. A yz has 8 more on top. They handle better and make jumps easy. IMO 36 hp is all you need all tho 38 would b nice. Stewart only had 36 hp and he ripped. Get a 125 to run responsive-quick then quick shifts on the strong part of the mid.
7/30/2022 8:57am
Stock suspension is very good get the spring rate correct. Jumping into clay whoops a revalve is needed. 1st ride in 12 yrs I passed a...
Stock suspension is very good get the spring rate correct. Jumping into clay whoops a revalve is needed. 1st ride in 12 yrs I passed a new yz on the 1st lap and jumped everything. I,m sure the yz is much faster on top than a stock 04 with a stock pipe. A yz has 8 more on top. They handle better and make jumps easy. IMO 36 hp is all you need all tho 38 would b nice. Stewart only had 36 hp and he ripped. Get a 125 to run responsive-quick then quick shifts on the strong part of the mid.
my 2004 rm125 was around 30 hp on a good day and id be surprised if the cr125s of those eras were anywhere near 30. maybe 28?

a hot rod stock bore cr125 prob made 35 hp perfectly jetted

i know the shifter cart cr125 guys made big hp but those engines were all top end
yz133rider
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7/30/2022 9:00am
So far I ordered Dunlop 952 tires, stock top end, boyesen reeds, aluminum 53t rear sprocket, and some air filters and shock bearings since they’re clanking around.

Gonna change the fluids, change the top end, and the other parts and see what she’s got next weekend!
3
digger
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Upstate, NY US
7/30/2022 9:53am
everytime i read about hot rod cr125s, the conclusion is that when its all said and done its more or less as fast as a stock...
everytime i read about hot rod cr125s, the conclusion is that when its all said and done its more or less as fast as a stock yz125 and still quite a bit off a ktm125

def a good bike to teach you how to go fast!


is bolting on the showas off the cr250 worth it? i hear the kyb stuff stock is just as good.

or the real question is...is putting the kyb stuff on a cr250 an upgrade? the TC showas of this era had midstroke harshness
You're pretty much spot on here.
I owned a pretty good running 07' cr125 for a while, and it was by no means fast. It was super fun to ride though. I felt like a hero on that bike, but the race results didn't show it.
I never really like the stock KYB forks. I just could never get them to work the way I wanted them to, so I swapped them out for a set of Showas from an 08' crf250, along with the rear shock as well. I was able to get the Showa stuff to work soooo much better than the oem KYB components. After I made those changes, it was the best handling bike I have ever been on. I couldn't do anything wrong, handling wise, probably because the engine was so weak, but what a fun bike to ride.
GnccDE
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Milton, DE US
7/30/2022 10:13am
yz133rider wrote:
So far I ordered Dunlop 952 tires, stock top end, boyesen reeds, aluminum 53t rear sprocket, and some air filters and shock bearings since they’re clanking...
So far I ordered Dunlop 952 tires, stock top end, boyesen reeds, aluminum 53t rear sprocket, and some air filters and shock bearings since they’re clanking around.

Gonna change the fluids, change the top end, and the other parts and see what she’s got next weekend!
Are the 952 tires lighter Weight? When they wear out maybe try Hoosier or another light weight tire within Weight tubes, ert3 chain etc.
JMCR250
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Location
Chesterfield, MO US
7/30/2022 1:47pm
We did put a 53 sprocket on my son's bike. Seemed to make a positive difference. He has no problem keeping up with other 125s on straights and hills.

I have an 05 CR250 with the TC Showas. My son's CR125 with revalved KYBs is plusher and transmits less chop to the rider. I think my bike handles big hits better.

Unless you're a top level pro, I'd leave the KYBs on and just revalve/respring for your weight. They are light and work amazingly well.
3
Tumic
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SE
7/30/2022 2:07pm
I bought a -07 for my girlfriend a couple of months ago. I have never owned a 05-07 but 3 02’s and 1 -03.

So i started going through some old threads about the last generation engine and saw that Derek Harris? Claimed that the 05-07 cylinder were more or less a YZ clone when it comes to the port design.

So what is the problem then on the last generation? Still to much crank case volume or what?.

I told my self to keep this bike stock, but i saw that the nicasil are starting to show some wear and will soon need a re-plating and that got my head spinning.

It’s rare to see a full blown build when it comes to the engine on the last generation.
1

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