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If i remember correctly, the SRS piston was a re-branded stock Husqvarna piston at the time.
The SRS hgs exhausts were different from the regular HGS pipes in 03, but the regular HGS pipe for 05-07 cr125 looks identical to the -03 SRS pipe.
When it comes to the BUD/Hgs pipes i am pretty sure that they are regular HGS pipes with just a BUD stamp.
My -02 race bike also had the base of the cylinder cut down a bit and had a wery strong bottom and mid range. It had a 36/38mm oval bored carb, a cut head and a FMF exhaust that i don’t know if it was special or just a Fatty pipe with the team’s name stamped on it.
Any way, it is one of those -02 cylinder that i now have sent to get bored to 56mm and re- plated.
The engine setup im looking at now will probably be:
58.5mm stroke
56mm bore -02 cylinder
109.9mm ktm rod
Cylinder spacer to lift up the cylinder
VHM head
Boyesen rad valve
Stuffed cases with epoxy
PC exhaust flange with spacers for fine tuning
36/38mm oval bore carb
HPI programmable CDI
As it goes for exhausts i will try what ever i get my hands on and with the season of electrical water pumps, i have been looking at a 12v water pump and a lightning stator so i can remove the stock impeller and gain a little there.
My opinion is that when the aluminum frame was introduced on the CR125 in’98, the intake tract was less than ideal. this was the nail in the coffin for an already aged motor. I took a ‘00 CR125 and made a straight intake manifold and gained about 2hp. Due to the shock location, there is no way you could ever run this configuration. In hindsight, I believe the packaging of the aluminum frame and the impacts it had on the intake tract is what made the CR125 suffer.
The ‘00 CR125 saw the first flap flap powervalve. This replaced the HPP setup. It was developed by a HRC engineer from the road race division. It did not seal as well as the HPP valve and functionally, it wasn’t an improvement. Plano Honda tried to rectify the intake tract issue by cutting and welding a completely new read cage boss onto the cases. This can also be seen on the Amsoil CR125’s in the early 2000’s. By this time Yamaha and KTM were light years ahead in terms of engine development and packaging for optimum intake tract flow. Honda had no choice but to not only retool a whole new motor but also significantly repackage the chassis to provide a straighter intake tract. With the ‘04 CRF250 in work, the CR125 was put out to pasture. We did get a one year only electronic RC valve but that was like throwing pebbles at a battleship. Oh what could have been if Honda did what they needed to do.
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I can’t remember if JD had to them to. JD made the boxes that were included in the SRS A kit and for PC kawi. I think that plano ran used JD to.
Back in 02 i tried a regular HGS on my race bike but that felt really flat and had no hit at all compared to the fmf exhaust.
I had the same feeling with the PC exhaust on my cr155 build compared to the DEP pipe with a BUD racing silencer. The PC just reved but with no hit.
I have been looking at the pics from the epoxy work on the last generation US HRC cases and thinking about doing the same.
A kart tuner also has the reed thickness assymetric to favour flow upwards - I'm guessing that's what the boyeson ports where effectively doing..that's cool to vision.
Did they fade power on the Dyno after multiple runs as the ex port got hot?
The ex height is what the mugen cylinders have in common.
I've seen the Euros had adjustable spring preload on their pv governor through outer cases - don't think I've seen that on Lammy's bike?
Do you know what carb they used?
Also were they 5 or 6 speed?
Cheers for the goodstuff DynoDan!!
Tumic. I'd also get your gearbox ISF'd. My back wheel spins very free.
Man it's actually endless, like using roller mains with a slip-fit, Det ring machined into top of the cylinder, polishing the pistons you use to a mirror finish, crank maintaining a couple mm bigger gap so there's no viscous friction with case, R7376 spark plug.
You need a good tuning simulator and theorise for a bunch and I'd reckon with custom pipes, ignitions etc and piles of Cash, you could get mid 40's.
Or get a TM or KTM motor who've done 3/4's for you already... but I agree where's the fun in that!
The map switch is included and i think the total cost ends up at between 250-300€ if you go for all the options.
I don’t know how good the base maps is, but this is the cheapest box i have seen for sale with a decent price on the programming tool. One of the most respected tuners here in Sweden used HPI before he had a stroke and had to close shop.
I have found that some for some CDI brands you need to be a dealer to get your hands on the programming stuff but not with HPI.
Kidding of course.
https://youtu.be/WeYsTmIzjkw
Not apples for apples but your fairytale 38hp is easily attainable for a tuner who's willing to put the time in.
The Hondas faults are all fixable to an extent. Two strokes are a sum of all equations and there’s way more than just the antiquated cylinder/case design of the Honda.
It’s like NA pushrod engines are limited but people love trying to get more from them. So why mock this guy??
I don't think 38hp is obtainable from a bike that starts out below 30. Sorry. You ever opened up a sx150 after 40 hours? That twin ring piston still look new. On a bridge port engine, the piston won't last 5 or 10hours on a big bore if you want major power. (I've had them as well).
The other part of the equation is fuel, that sx150 is running all day on pump gas. Put $40 gallon VP and the Japanese bikes have another 2hp to catch up.
We all enjoy riding, and some of us enjoy wrenching... if a 125 isn't fast enough, just get a bigger engine... or if you want expend hours of time and thousands of dollars then that's cool as well.
Pit Row
Interesting stuff,
built an 03 from the ground up a couple years ago. I wanted to do the extended connecting rod but didn’t know where to start. I saw it in an article someone did on Micheal Byrnes 03 factory bike.
have you done this? Was it successful?
https://youtu.be/4iEdDytXj4s BUT can you just have a great time riding it? Yes
https://youtu.be/4iEdDytXj4s
I got my 03 running REALLY great after installing a STIC metering bloc in my Keihin PWK. Freshly rebuilt stock motor with FMF fatty and silencer and I feel like this is the mod that made the greatest difference. The bike runs much better from bottom to top with a nice gain in top end power. 100 octane at 32:1 and it screams. I'm impressed with this STIC! I don't feel like I'm at a power disadvantage anymore.
03 vs 07 airbox boot. 07 on the left.
A blast from the past. Travis Preston’s 02 bike. Any idea what the purpose of that spacer is?
long rod motor
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