Cr125 00-03 best upgrade parts.

Tumic
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Tumic
Edited Date/Time 2/6/2022 12:16am
So, short story long.

About 10 years ago i decided to build a balls out cr125 build on my -02 chassis.

I made a HPP cylinder conversion, sent the engine to Eric Gorr, went for a big bore/stroker kit ported for mid-top and race fuel so it ended up being a 155cc engine.

Got it back, the cylinder was un ported and the engine had a 2mm squish gap…

I then went for another route, let another tuner correct the head and port the cylinder.
The problem is that the porting was corrected to the new 58.5mm stroke and the port floors were lowered 2mm to compensate for the 2mm further down that the piston goes at BDC with the stroker crank.
But when the port floors were lowered, the piston skirt ended up being to short and exposes the crankcase to pipe at TDC as you can see here.




After that i put the bike away since it performed really bad and bought a sx150 instead.
But now i have started to give the CR another chance and sent a -02 cylinder for a new 56mm bore and plating so with the 56/58,5mm bore/stroke combo it will be a true 144cc and using a cylinder spacer to raise the cylinder to compensate for the changed stroke.

So the thing i looking for now is some dyno graphs if some of you guys have tested different exhausts on the 00-03 engine and same with different intakes.

I currently own PC, FMF and Dep pipes as far as exhausts goes and Boyesen rad valve and stock intakes.

Just looking for every little bit of extra HP for this build. I have a programmable CDI and the 05-07 air boot before someone mention that.

I have went through pretty much every thread out there on both Vital and Thumper talk from the past 10-12 years, so now in looking for information that some might have but not have posted here before.

And no, i dont want to swap to a ktm engine or ”just buy a 250” since i own both of those to.

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MxKing809
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MxKing809 1/30/2022 7:07am
1/30/2022 7:07am
Good luck. They were slow in 02…… imagine trying to make an 04 CRF250 “fast” today.

I built mine with a HPP, KX pipe and had Chad Watts work the carb, cdi, race gas, 07 air boot - and it was sill a dog.

As a wise person once said - “don’t go chasin’ waterfalls”.







In all seriousness, good luck. I gave up and sold mine when *I hit the realization it looked way better than *I was ever going to make it run. Hopefully you have better luck, and find the missing link, that it sounds like we were/are both searching for.
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Tumic
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Tumic 1/30/2022 7:24am
1/30/2022 7:24am
MxKing809 wrote:
Good luck. They were slow in 02…… imagine trying to make an 04 CRF250 “fast” today. I built mine with a HPP, KX pipe and had...
Good luck. They were slow in 02…… imagine trying to make an 04 CRF250 “fast” today.

I built mine with a HPP, KX pipe and had Chad Watts work the carb, cdi, race gas, 07 air boot - and it was sill a dog.

As a wise person once said - “don’t go chasin’ waterfalls”.







In all seriousness, good luck. I gave up and sold mine when *I hit the realization it looked way better than *I was ever going to make it run. Hopefully you have better luck, and find the missing link, that it sounds like we were/are both searching for.
This bike is a ex 125 gp bike that were built for Eric Sorby to run in the 02 world championship before he left europe in the last second and went to PC Kawi in US. A couple of those bikes ended up here in Sweden in -02 and i had one of then as my race bike that season and it ran really well, no other Honda 125 have been close in performance to that bike.

Back in -08 i found another of those team bikes for sale on the internet, the seller did not know what he had and i bought it cheap with really low hours on it.
That bike never ran as good as my first one i had in -02 so it was then i decided to do the 155cc build.

But even with the 155cc it did not run as good as my first 125. Now i have found some reasons for it, but if i could get the CR with full race prep and 144 or 155cc to run as a stock sx150 i would be more than happy.

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brocster
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brocster 1/30/2022 8:29am
1/30/2022 8:29am
Power valve mod
Air Stryker carb
Rad valve
Swede tech exhaust manifold
FMF fatty and shorty combo
Up a tooth on the rear
My 2000 hauls my 190# ass around pretty well
Zero head or port work. Stock head, stock cylinder

My son has an 04 and we like my motor over his which has nearly the same set up but performs differently which I account to that stupid servo operated RC valve.
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yz133rider
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yz133rider 1/30/2022 8:33am
1/30/2022 8:33am
MxKing809 wrote:
Good luck. They were slow in 02…… imagine trying to make an 04 CRF250 “fast” today. I built mine with a HPP, KX pipe and had...
Good luck. They were slow in 02…… imagine trying to make an 04 CRF250 “fast” today.

I built mine with a HPP, KX pipe and had Chad Watts work the carb, cdi, race gas, 07 air boot - and it was sill a dog.

As a wise person once said - “don’t go chasin’ waterfalls”.







In all seriousness, good luck. I gave up and sold mine when *I hit the realization it looked way better than *I was ever going to make it run. Hopefully you have better luck, and find the missing link, that it sounds like we were/are both searching for.
Tumic wrote:
This bike is a ex 125 gp bike that were built for Eric Sorby to run in the 02 world championship before he left europe in...
This bike is a ex 125 gp bike that were built for Eric Sorby to run in the 02 world championship before he left europe in the last second and went to PC Kawi in US. A couple of those bikes ended up here in Sweden in -02 and i had one of then as my race bike that season and it ran really well, no other Honda 125 have been close in performance to that bike.

Back in -08 i found another of those team bikes for sale on the internet, the seller did not know what he had and i bought it cheap with really low hours on it.
That bike never ran as good as my first one i had in -02 so it was then i decided to do the 155cc build.

But even with the 155cc it did not run as good as my first 125. Now i have found some reasons for it, but if i could get the CR with full race prep and 144 or 155cc to run as a stock sx150 i would be more than happy.

Put the ktm engine in the cr chassis.
Or just keep dialing the ktm and live happily ever after.
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Tumic
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Tumic 1/30/2022 9:23am
1/30/2022 9:23am
brocster wrote:
Power valve mod Air Stryker carb Rad valve Swede tech exhaust manifold FMF fatty and shorty combo Up a tooth on the rear My 2000 hauls...
Power valve mod
Air Stryker carb
Rad valve
Swede tech exhaust manifold
FMF fatty and shorty combo
Up a tooth on the rear
My 2000 hauls my 190# ass around pretty well
Zero head or port work. Stock head, stock cylinder

My son has an 04 and we like my motor over his which has nearly the same set up but performs differently which I account to that stupid servo operated RC valve.
Yeah i have the 7mm stop pin in my 02 cylinders to and both a 38mm TMX and a 38mm airstryker. But i have been thinking about testing a 36x38mm oval bore carb to.

I have bought exhaust flange spacers that i will try but i have yet to decide if i should buy swedetech, PC or the Boyesen exhaust flange.

I have also speaked to Hygge about letting him make a custom pipe for the engine as soon as it’s back togeather so i can give him the port timing and maps for it.
Tumic
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Tumic 1/30/2022 12:09pm
1/30/2022 12:09pm
JOE_SPROCKETS#1 wrote:
Why do ppl go the hpp cylinder Route all the time?
I did it for the 58mm bore. The 00-03 cylinders can only be bored to 56mm unless you offset bore the cylinder towards the intake side.

Other than that i am pretty sure that it is just a internet thing that people belive that a -95 HPP cylinder is better than the newer style.

At the dyno the HPP and newer style cylinders perform the same.
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NHtoWA421
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NHtoWA421 1/30/2022 3:29pm
1/30/2022 3:29pm
Carson Brown has spent a lot of time on these. I'm sure he and his dad have a pretty good set up for these. I would reach out to him on Instagram.
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Bruce372
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Bruce372 1/30/2022 4:49pm
1/30/2022 4:49pm Edited Date/Time 1/30/2022 4:55pm
With all the carbs, reeds, ignitions and pipes and combinations, the best thing you could do is find someone with a dyno, prepare to throw lots of money at setting up the engine and be prepared for major disappointment when it doesn't meet up to other Japanese 125s, let alone rhe new Austrian 125s.

Sorry, not trying to be negative, but rather realistic and pragmatic. How much, is your time and sanity worth? The cr125 was slow 20 years ago, and probably wouldn't out perform a ktm85 today.

I am sure there are plenty of people will come here and say you need this crank case, that cylinder, this carb, this air boot and I am sorry but I don't think they are in reality or able to separate fantasy with objectivity.
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yota
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yota 1/30/2022 5:40pm
1/30/2022 5:40pm
had my 03 for 10 or 12 years. love the handling, hated the lack of power. had the 134cc mod, port work, power valve mod, V-Force, air striker then later Lectron, 07 airbox boot, vented the airbox. got pretty fast on top but had zero low and mid. I also have an 05 YZ125, think I'll drop that engine in the CR. the stock YZ engine is better than the fully modded CR. I also have a 21 TC125 which is just way better than them both so the CR doesn't get used anymore.

here's the best mod I've done for my 2003 CR125R.


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brocster
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brocster 1/30/2022 6:41pm
1/30/2022 6:41pm
Bruce372 wrote:
With all the carbs, reeds, ignitions and pipes and combinations, the best thing you could do is find someone with a dyno, prepare to throw lots...
With all the carbs, reeds, ignitions and pipes and combinations, the best thing you could do is find someone with a dyno, prepare to throw lots of money at setting up the engine and be prepared for major disappointment when it doesn't meet up to other Japanese 125s, let alone rhe new Austrian 125s.

Sorry, not trying to be negative, but rather realistic and pragmatic. How much, is your time and sanity worth? The cr125 was slow 20 years ago, and probably wouldn't out perform a ktm85 today.

I am sure there are plenty of people will come here and say you need this crank case, that cylinder, this carb, this air boot and I am sorry but I don't think they are in reality or able to separate fantasy with objectivity.
I agree with this. Funny that I have some pretty in expensive “mods” on my ole CR but there’s something about the frame, suspension and handling that works for me. However, I did ride a 21 YZ125 at a demo day last year and in stock form the engine/power made my bike feel like an 85. Ha! No worries though, taking her out for a shred tomorrow to sneak some garage queen 450’s.
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Tumic
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Tumic 1/30/2022 9:47pm
1/30/2022 9:47pm
This is just about making the cr125 as fast as it can be. As i have stated earlier, i own a couple of other bikes and are well aware of the CR’s flaws.

But it can be done, the 134cc that Leib ran at RBSR put out 38 on the dyno so i can’t see why 40hp out of a 144/155cc should be a problem.

Just trying to narrow down the parts list a little bit.
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plano67
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plano67 1/30/2022 9:56pm
1/30/2022 9:56pm Edited Date/Time 1/30/2022 9:56pm
My 2001 CR125 with my 1994 cylinder bored out to a 144cc.

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NorCalRedRyder 1/30/2022 10:16pm
1/30/2022 10:16pm Edited Date/Time 1/30/2022 10:18pm
I'm not very technically inclined like my Dad was, he was an engineer and built/ repaired all the cars, boats, and mx bikes he raced. When I got into the big bikes and he didn't have the time to work on them, we had JN Innovations up here in Norcal do the suspension on all of our bikes. He would then send the motors up to Steve Lamsons dad in the Sacramento area to port and polish them. He did an 01 Cr125 that was just a dud and slow af. Once we got it back and slapped a pipe (not sure which one, but I think FMF), I was faster on that then I was my pimped out CR 250. That 125 had power for days and the suspension was amazing. JN would come out to Club Moto after he did the suspension work, after working all day mind you, it make sure it was completely dialed in to my weight, height, and ability. I was 6'3" and about 165 at the time, but he got it dialed in. Wish I still had that 125, it handled like a mountain bike and hauled the mail. RIP Mr. Lamson.
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Chris99Flannery 1/31/2022 3:06am
1/31/2022 3:06am Edited Date/Time 1/31/2022 3:11am
Bruce372 wrote:
With all the carbs, reeds, ignitions and pipes and combinations, the best thing you could do is find someone with a dyno, prepare to throw lots...
With all the carbs, reeds, ignitions and pipes and combinations, the best thing you could do is find someone with a dyno, prepare to throw lots of money at setting up the engine and be prepared for major disappointment when it doesn't meet up to other Japanese 125s, let alone rhe new Austrian 125s.

Sorry, not trying to be negative, but rather realistic and pragmatic. How much, is your time and sanity worth? The cr125 was slow 20 years ago, and probably wouldn't out perform a ktm85 today.

I am sure there are plenty of people will come here and say you need this crank case, that cylinder, this carb, this air boot and I am sorry but I don't think they are in reality or able to separate fantasy with objectivity.
It would easily out perform a ktm85sx with just fresh build with head and jetting. Not hard to get to 35hp region with some effort. No cooling on exhaust spigot and the 5spd box is not ideal,
Chris99Flannery 1/31/2022 3:09am
1/31/2022 3:09am
Chris99Flannery wrote:
It would easily out perform a ktm85sx with just fresh build with head and jetting. Not hard to get to 35hp region with some effort. No...
It would easily out perform a ktm85sx with just fresh build with head and jetting. Not hard to get to 35hp region with some effort. No cooling on exhaust spigot and the 5spd box is not ideal,
Really need to bias the flow out of the reeds asymmetrically upwards with custom reeds and manifold.

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nascarnate326 1/31/2022 6:27am
1/31/2022 6:27am
Ill be the one to state the obvious, this isn't going to be cheap but a good start is VP fuel and a Lectron carb for 98% of people.

From there an extremely clean/ recently rebuilt/ well running engine, not some 28 hour clapped out special (what I had lol)

I found that a 100 rear tire made the bike feel noticeably faster than the 120 that was on the bike when I got it. Use a normal chain, not something with x or o ring that robs power. Basically limit everything that robs power before trying to make the CR125 engine a screamer IMO. Check to make sure the flywheel is the stock flywheel and not something heavier that a previous owner installed. Also dropping some weight on the riders part is almost always the most effective mod.
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Tumic
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Tumic 1/31/2022 7:29am
1/31/2022 7:29am
nascarnate326 wrote:
Ill be the one to state the obvious, this isn't going to be cheap but a good start is VP fuel and a Lectron carb for...
Ill be the one to state the obvious, this isn't going to be cheap but a good start is VP fuel and a Lectron carb for 98% of people.

From there an extremely clean/ recently rebuilt/ well running engine, not some 28 hour clapped out special (what I had lol)

I found that a 100 rear tire made the bike feel noticeably faster than the 120 that was on the bike when I got it. Use a normal chain, not something with x or o ring that robs power. Basically limit everything that robs power before trying to make the CR125 engine a screamer IMO. Check to make sure the flywheel is the stock flywheel and not something heavier that a previous owner installed. Also dropping some weight on the riders part is almost always the most effective mod.
Maybe i should have wrote more about the bike but this is a build with no expenses spared. KYB Kit suspension, larger radiators, triple clamps, haan wheels with a60 rims etc.

All those things is pretty obvious part from the Lectron carb that all the VET riders around the world praises but you never see one on a 125 race bike for some reason.



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homerdaman
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homerdaman 1/31/2022 8:45am
1/31/2022 8:45am
have you reached out to Tom Morgan? He builds some amazing 144 kits that come with a complete owners manual that he wrote up. Might be a solution?
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NoMuff2Tuff
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NoMuff2Tuff 1/31/2022 9:03am
1/31/2022 9:03am
If your running a Keihin carb the STIC metering block makes a good gain especially on top with better over rev but you will have to run some good fuel and spend time dialing it in. I ran one on a 07 and it really made a difference. I'm in the process of building a 6mm long rod 144, hopefully in the next few months I can have it running to give some feedback.
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Tumic
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Tumic 1/31/2022 9:04am
1/31/2022 9:04am
homerdaman wrote:
have you reached out to Tom Morgan? He builds some amazing 144 kits that come with a complete owners manual that he wrote up. Might be...
have you reached out to Tom Morgan? He builds some amazing 144 kits that come with a complete owners manual that he wrote up. Might be a solution?
Yeah, i have talked to him. Fast response in the mail conversions and a really humble guy.

The thing is that after had my parts over the sea two times with a so-so result i wanted to try my luck here in Sweden this time.

I don’t doubt Morgans skill in any way, just want to be closer to the tuner this time.
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Tumic
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Tumic 1/31/2022 9:29am
1/31/2022 9:29am
NoMuff2Tuff wrote:
If your running a Keihin carb the STIC metering block makes a good gain especially on top with better over rev but you will have to...
If your running a Keihin carb the STIC metering block makes a good gain especially on top with better over rev but you will have to run some good fuel and spend time dialing it in. I ran one on a 07 and it really made a difference. I'm in the process of building a 6mm long rod 144, hopefully in the next few months I can have it running to give some feedback.
I have been looking at those and will probably order one.

What rod are you using for the long rod conversion?
Tumic
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Tumic 1/31/2022 11:24am
1/31/2022 11:24am
NoMuff2Tuff wrote:
Pro X KTM rod part # 03.6220
Have been looking for a longer rod for my stroker crank to get a better piston/rod angle.
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yota
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yota 1/31/2022 12:20pm
1/31/2022 12:20pm

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NoMuff2Tuff
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NoMuff2Tuff 1/31/2022 12:23pm
1/31/2022 12:23pm
NoMuff2Tuff wrote:
Pro X KTM rod part # 03.6220
Tumic wrote:
Have been looking for a longer rod for my stroker crank to get a better piston/rod angle.
I sent you a PM
profeshenal125 2/3/2022 5:10pm
2/3/2022 5:10pm
Dirt.Squirt wrote:
Where’s profeshenal when you need him
Right here Man. JM racing decked the cylinder a lot, porting was just basically widening the exhaust port, head mod, bored carb. Pc pipe pc long silencer, v force , iKat is really livens it up. Aprox 36.5 + hp but a very wide mid that went to a flat ovr rev. I Loved it and it sounded super sick. But I wanted more I told him I need a set up for Millville. 2mm stroker crank 1 up 1 down and 2 mm ovr bore, no case mods. The head is machined for the 1 mm up. It would easily pull a 2012 250f, 22-23 ft lbs torque. Tara Gieger ran the standard bore with a 2 mm stroker . Same setup she hole shot and won pro races in her 1st yr. On the 04. John worked with SRS to develop the 02 or 03 when that Tx. Rider raced the GP,s . The whole chassis was stock that tells you how well they handle. John stuffed the cases on 02, 03,s. No need to on the 04.
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profeshenal125 2/3/2022 5:24pm
2/3/2022 5:24pm
Dirt.Squirt wrote:
Where’s profeshenal when you need him
profeshenal125 wrote:
Right here Man. JM racing decked the cylinder a lot, porting was just basically widening the exhaust port, head mod, bored carb. Pc pipe pc long...
Right here Man. JM racing decked the cylinder a lot, porting was just basically widening the exhaust port, head mod, bored carb. Pc pipe pc long silencer, v force , iKat is really livens it up. Aprox 36.5 + hp but a very wide mid that went to a flat ovr rev. I Loved it and it sounded super sick. But I wanted more I told him I need a set up for Millville. 2mm stroker crank 1 up 1 down and 2 mm ovr bore, no case mods. The head is machined for the 1 mm up. It would easily pull a 2012 250f, 22-23 ft lbs torque. Tara Gieger ran the standard bore with a 2 mm stroker . Same setup she hole shot and won pro races in her 1st yr. On the 04. John worked with SRS to develop the 02 or 03 when that Tx. Rider raced the GP,s . The whole chassis was stock that tells you how well they handle. John stuffed the cases on 02, 03,s. No need to on the 04.
Jeff Dement raced for srs on cr125 there pistons where the best. Team Suzuki used them. I,m sure it will b difficult to fing a srs pipe but I think HGS made them for srs. A 03 kx hgs budd pipe would add a lot. Probably the best. The pipe was slower coming on the pipe not a good thing on a 04. Once it hit it pulled hard with 2 k more rpm. The same pipe on a 06 is the opposite . Rt off idle it’s very snappy strong and long mid range with 1,500 more rpm. Freakin perfect.


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