With all the talk of how slow and outdated the cr125 engines are i thought i’d share this after todays dyno session.
i bought this bike two years ago in pieces as a project bike and did a complete frame up resto.
The nicasil was worn out so i went for a big bore since it needed a re-plate. The cylinder and carb was sent to VHS tuning in Holland and got bored/plated and a light porting. VHS then provided a VHM head with a insert for race gas and bored my carb as i asked them to.
The carb is a 99-00 KX125 36mm PWK carb with a power jet solenoid that VHS oval bored to 36x38.5mm so i could keep as much low end grunt as possible on it.
To being able to control the power jet i bought a HPI ignition cdi from Belgium that is programmable and can be bought with a power jet port built in to it.
After today when we had the bike on the dyno, programming the CDI and powerjet we ended up with 41whp/29wnm (rounded numbers and corrected).
For a reference a stock carbed sx150 lands at 38whp on the same dyno.
Would a sx150 have done better with the same mods? - fuck yes.. is this great numbers for a cr125(144) from 2005-07? FUCK YES.
This was never ment as a bike for chasing HP with, i wanted a broad power curve so my GF can ride it to. In the dyno chart it’s two different curves we did. I always said that if this engine could land at numbers close to a stock sx150 i would be happy, and we met that goal.
Complete engine specs:
*58mm Vertex YZ125/144cc piston
*VHS tuning ported cylinder
*VHM head with race gas insert
*V-force 3 intake
*PWK KX125 -99 carb oval bored
*HPI ignition programmable CDI
*DEP pipe
*10mm exhaust spacer
*BUD racing silencer
Chassis:
*Öhlins GP forks
*Öhlins GP shock with TI spring
*Zeta triple clamp
*CRF wheels
*X-fun aluminium tank
*TX race restyle kit
*Magura Hymec clutch
*Titanium footpegs
*Race radiators
*Renthal full diamond grips
Well done! The 2007”s have a great chassis…I throughly enjoy riding my pretty much stock 93CR125..I see a visit from Professional125 soon…
Thanks. Yeah, this is my 4th 02-07 cr125 and still today they have a modern feel to them.
And yes, i guess we will hear about Tara’s 04 again 😅
Very Kool to see the 3rd gen AF 02-07 CR125 & 250 getting positive reviews. They take minor mods to get the engines to run very well.
The chassis as mentioned is as good as modern bikes when set up properly.
I always felt that these bikes got negative reviews & were underrated when they 1st came out. I found out the true potential after doing my own tinkering in the mid 2K’s.
Enjoy !
There is no denying that there is better 125’s out there, but the cr’s are not as bad as the internet VET rider reputation.
Back in 02/03 i raced cr125’s and in 02 i had a bike built by a world championship team and that bike was really good. Eric Sorby should have raced for that team but jumped ship the last minute and went to the US and rode for PC instead. The suspension on that bike was marked with Sorbys name.
In 03 i had a SRS A kit (head, cylinder, reeds, cdi, exhaust and transmission gear). SRS also had a GP team but i doubt that the team used the same parts that they sold to the customers. But that bike was also fast enough but not as good as the 02 i had.
So it has always been possible to make them run okay, but put out KTM numbers has been a tough task.
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Looks like you got good numbers bottom to top. Install the stock plastic & drill some holes in the air box. I think your gal would like the seat better too. The bike isn’t getting any air with that kit. Power flow cage helps too , you can feel a difference . Dep has a long header for a broader power band. A 03 hgs kx pipe would probably pu 2 1/2 - 3 on top, less of a hit on my 04. That pipe worked Awesome on my 06 stock cylinder. Like a Real good port job on a RM. you might want to try the stock carb with a different taper bore. That’s what JM racing does . My jetting is clean with the mod cylinder . My mod bike from the hit to the ovr rev . Is a quick torque ripper aprox 39. 9 but I didn’t go for peak numbers. I wanted a quick responsive with strong & long mid to ovr rev. JM worked with SRS & there engine. Jeff Dement ride for SRS he,s from TX. Too. I bought the srs piston Very good, head, pipe& silencer . The Ny. Importer went out of buisness then. It was tested against a pc bike on C12. The it’s bike was faster with bolt . Srs used a customer pipe what anyone could buy. Tallon Viohlznd ran a SRS engine at fmf . JM racing is the 85,125 gurew.
It did nothing on the dyno when we did some pulls without the seat so i doubt that it’s to resteicted regarding the air. We even did some pulls without the subframe on and no gains there either. The TX kit is more open at places around the rear fender than the stock plastic…
The TX seat has a flatter foam and we prefere that modern feel over the oem seat.
Regarding the carb i value the powerjet and throttle response of a PWK higher than 0.5 extra HP on top from a TMX carb. We also live in a part of the world where we ride within a 55 degrees celsius temperature span over the year and having a PWK that is less weather sensitive also trumps the TMX there.
Regarding the pipes we tried some different ones, 4 different silencers.
If you know how much it takes to gain 2.5-3hp out of a 125 engine where you scavange 0.5 hp here and there over all the places you modify, you would realize that there is nothing as a 3HP gain out of a single pipe.
Yeah I tried a few pipes the 03 hgs kx works best on a 05-06. I haven’t tried it with the mod engine yet only a stocker. Less of a hit more clutch to get going but then more mid with 2k+ more pull on top. Even tried a 04 pc pipe on a 06. That was funny low end snap into the mid was exciting. Then it fell flat at 9k & wouldn’t rev. But you could hit 5th gear in a few feet speed shifting. Stock Honda pipes r actually Very good. I really want to try the correct hgs budd pipe on my 04, the pipe is for 03,04. The 04 should hv it’s own pipe the engine is nothing like a 03. Messico is supposed to be a strong mid to top end pipe . From what I heard. Strange on how restrictive a 04 silencer is. If I ever hv time I would like to cut 2 1/2 + inches off it. The 06 works great. Shorty pc sounds the best but the fmf. Shorty is great too. Hgs budd silencers are a bit longer right ? I like the stainless 1 with the carbon cap.
As soon as you touch the inside of the engine the whole ”this pipe works great on this engine” goes out the window since the porting and the pipe works togeather.
The Messico talk is from Nino Fenaroli that swears by them for the HPP engines.
A member in here had a 05-07 engine built by Chad Watts and then tried 4 or 5 different pipes and siliencers on a dyno here in Sweden where the PC pipe ended up working best for his engine spec.
I think he tried Bills, PC, Messico, Scalvini and maybe HGS.
While in my case with my porting and bore the DEP pipe worked way better than the PC pipe.
As for silencers i tested stock, PC enduro, PC shorty and the Bud silencer. On the dyno neither made any difference in numbers, so changing the silencer would just alter the feel of the powerband when you ride it. But not provide any real HP numbers, so i went for the ”medium” length of a silencer that BUD is. I would say that it’s somewhere in the middle of a r304 and a r304 shorty.
When it comes to silencers many people fool them self just because how they sound and think the bike becomes faster just because of a higher sound.
Bud makes their own silencers, HGS has nothing to do with them, only the pipes. And the HGS BUD pipes are just regular HGS pipes with a BUD stamp on them.
But this is why i bought a programmable CDI so we could work around some things. The DEP pipe had more front side and over rev on the dyno than the PC but were like 0.2 HP off on peak HP, but after some ignition adjustment we surpassed the PC pipe on peak and kept the bottom and over rev.
It becomes clear that small mods on a bike can alter how the engine likes the ignition curve set up to generate the right amount of heat so the pipe can work as it should.
Yup. The JD ign. made a noticeable difference on an 03 PC cyl. & head mods.. Also, an 07 with Chad Watts engine mods..
Both being CR250’s..
These case reed engines respond very well to engine mods & an aftermarket ignition with good fuel like VP..
I have a JD box on another cr125 build, i would guess it’s the one with the plano Honda cr125 curves since i bought it from PC many years ago.
But that made no improvement to speak of on that bike, probably because the engine spec was so far out of the window compared to a regular 125.
But what i have found out through the years is that if you are gonna put out the money and buy a CDI/ECU you should invest in a day on the dyno to, otherwise you can just use the stock stuff imo.
I ran a crf250 on the dyno a couple of years ago and compared a Vortex ECU to stock and no pre-set curve in that box gave anything compared to the stock ECU and that was a built engine with ported head, cam, hi comp, exhaust and air boot mod.
Sure ju can get some gains from a bought ECU, but considering how much they cost, the gains are small out of the box but can be really good given the right time.
I can’t speak on a 125 or crf250, but on a 250 2T there were noticeable gains. This is on a stock CR engine & a modified one. The same JD ign. used back to back on an 03 engine, I was fortunate to buy the last unit from PC that had a programmed map to compliment their cyl. & head specs.
When testing an 05-07 stock ecu vs. the JD there was a noticeable difference in performance as well on a stock engine.
Same with the 07 stock ecu vs. JD with a Chad Watts engine specs..
The aftermarket JD ign. made a difference on both stock & modified CR 250r case reed engines from my experience.
I heard tuners say the c125 stock ignition is good. Not much to gain with a aftermarket. I think unless your going for more top with a spec to replace a piston every 4-5 hrs. Aftermarket usually has better snap & hyper pull with a higher rev ceiling. My engine is Real quick with a iKat. They work Awesome on a 04. How much do you think it would cost to make them ?
Cost to make what?.
At peak HP we made around 1hp compared to stock CDI, but gained around 1hp on the frontside of the curve and around 1500rpm of over rev with the custom curve.
And with the powerjet enabled by the HPI cdi, we got another 1hp on the frontside compared to stock. So 2-2.5HP gained on front side of the curve thanks to custom map and PJ.
here is a picture of the gains on the backside of the curve compared to stock.
Once again it always comes down to how far out of the window of the stock ignition your other mods have caused. On a stock engine i doubt you would se any large gains if you were to try to make a custom mapping.
IDK how much it cost to make one, but I’d suggest buying one.
I hadn’t been on their website in many years since I bought the 03 CR JD ign about 20 yrs. ago.
Back then they had a dyno chart of an 02-07 CR250r. It showed gains on a stock engine with a JD ign vs a stock cdi..
Below is a dyno chart of a YZ125 they currently have on their website. You can see a difference between the stock vs JD ign..
I believe that is also on a stock YZ125 engine as well.
There are less than $100 in component and assembly costs in a CDI/MCU, most of the cost is in design and development.
The iKat like the Roost Boost adds no measurable performance increase, if it can't be measured is it real?
I hv the 1st generation iKat on my 04, trust me it works like a great ignition. I had the 2nd gen iKat the skinny one on a 06 cr125. It worked great to. The 04 really gets a boost tho. Mxa said the Ikat works really good too. You think it would cost 100 bucks to make a ikat ? Where would I buy the parts to make 1 ?
That’s a Great increase . Does Hpi make a ignition for a 04 cr125 ?
These systems have been sold under many different names, there's not much to them, a capacitor, a diode and a resistor...
There is no measurable power increase, if you want a power increase buy a programmable CDI/ECU, Honda's benefit from ignition advances before peak power, if you have a throttle position sensor, further advancing ignition timing at partial throttle openings will make the throttle more sensitive.
Pit Row
No they don’t make one, and neither does another company today.
I don’t know if JD could have made one back in 2004. 04 was the last year SRS offered a engine kit for the cr125 and up to 2003 they always came with a JD cdi, but i can’t find any information now what parts the 04 kit came with.
Zeeltronic have a CDI that would be suitable for a 2004 CR125, but @profeshenal125 would have to develop his own maps...
https://www.zeeltronic.com/page/pdci-11vt.php
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