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You note that you are making port programs etc, can you calculate the difference when ports are lowered by 0.5 and 1.0mm as done by these professional tuners.
I appreciate it! How much more hp did you get out of it if you had to estimate, or whittle of power and where whether down low or up top. Thanks a lot.
What gas and oil do you run?
I had 2 04 cylinders decked & ported. JM racing did both. The 1st 04 was decked, ported , diff carb taper. Then I had a 2 mm stroker crank& 2 mm ovr bore. 23 ft lbs of torque it would pull a 250f in 2012. It was stolen. The 2nd cylinder I got back in the fall. I haven’t ridden it yet. But I wanted quick responseding with a strong and long mid into the top end. I hv Tara Gieger,s LL championship replica porting with a little more torque since I,m bigger than a chic. Max hp is 38 maybe 39 the mid should be really strong with quick response to get out of corners quick. I just wish the 04 had its own pipe. It’s the same as a 03
but the cylinder is much better on a 04. Best sounding 125 when it’s pulling a hill. I never heard a 125 like it.
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Picked up an 02 also some time back and just now getting around to restoring it. I spent a little time researching before I purchased it, but don't really remember alot of what I read. I do seem to remember someone saying to run an 07 crank.. as it had plastic stuffers in the crank wheels(maybe?) that reduced some of the volume in the crankcase compared to the 02 crank. Also maybe the 07 manifold.. as it was supposedly and improvement as well... again, my memory is fuzzy on this. Also to vent the airbox as much as possible.
profeshenal125 or tracktor... you guys ever spend much time with an 02? what where your mods?
Gavan.... if I am understanding correctly.. taking 1mm off the bottom of the cylinder and then recutting the head for .8-.9mm squish (and of course cleaning and matching the ports), along with the PC pipe and silencer makes a noticeable improvement in the performance.. almost to the point of being somewhat competitive on power? The other option is to run a suzuki piston which, I assume because of the pin bore location and piston height, gives the effect of lowering the cylinder by .5mm?.. so you get some of the benefit for less work. Curious as to how that mod compares to the '98 HPP cylinder swap that was somewhat popular.
Does anyone have any thoughts on the 5 speed transmission? I seem to remember some people swapping out to the early model 6 speed.
Yes I have heard of the 07 crank and 05-07 intake boot but I have never tried. People say the intake boot works pretty good but haven’t seen to much feedback on the 07 crank. I have a feeling people just see the plastic fillers and assume it’s lighter and somehow better (I could be wrong though). Building a 99 right now I bought in pieces and recently bought a 6 speed for it as people say the 5 speed is no where new as good, so I will be trying that out as well. Also thought off trying the 99 top end on the 02 but I decided not to because I don’t have the time to be experimenting with stuff like that lol. I have heard that the port is better on the 90’s 125s and that the 00-03 have ports that are slightly a little large and placed a little high.
I ran 98 pump, then with octane booster and then with Avgas a low lead 100 octane. The avgas was best. Ben_Tukes 2ml over probably gives added mid range which i would do but stuck with it being a 125 to be the same as my old bike and able to compare to my yz125, the yz definately pulls like a 250 from low to mid which is nice, top end is about the same. I want to get it out on an mx track and see the difference as you really need to ride a 125 hard on either bike to get the fastest speed.
In relation to gearing i did change that, i think i went 1 tooth up on rear which helped too.
02 ,03 pro bikes ran a 99 cylinder. Those that didn’t had the cases stufffed like Jeff dements srs cr125 for the 125 gp,s. He ran a stock frame swing arm & linkage. No works chassis parts like all the other 125,s. Means the chassis is Great. I run a 05 air boot with twin air power flow cage. I tested them separately. The 05 boot on a 04 has better throttle response with more bottom & run very clean to the ovr rev. With power flow cage add a better throttle response and bottom stronger mid and top end pulled a little longer . Ran Great bottom to top. 04 has its own air boot . Off idle it’s dead more clutch is needed the lower mid hit is stronger along with the mid range , top end is flatter. If you like a strong hit & mid range the 04 air boot is Great. I drilled 3 holes on each side of air box . Bike ran a little stronger. Wiseco top piston racers choice is really good.
Thanks profeshenal125.. some good info there. What carb did the race bikes run?.. or what carb do you prefer for those bikes. Did they run the 5 speed trans in the race bikes?
On a separate note... has anyone run a big bore on the 02 bikes... 134cc. Would the larger displacement help any with the oversized volume in the cases and ports that plagues the 02 cylinders. I've always heard the big bores don't typically feel as lively or rev out quite like the 125's, but I am sure some of that is dependent on how the engine is configured, exhaust, etc.
I have a 134 and it definitely adds to the mid power. Did not make any jetting changes either
I was partial to the 1995 cyl. myself but have built many many CR125's over the years. Honda used to sell CR125 kit motors to dealers in the late 90's/ early 2000's for shifter kart racing applications, they they came completely dissasembled and used the six speed gear box from the steel frame era as that worked better for kart drivers. We sold a bunch for sure and they were all assembled by us at the dealer I worked for with a healthy go kart scene in Colorado at the time. I have used shifter kart sites and forums to find parts I would need still tucked away, just a heads up if anybody here is looking for parts.
Stock carb makes the most power,RC tested diff carbs on his 250 he ran the stocker. I hv a diff taper mod JM racing did. My opinion John builds the strongest cr125,s. In 98 fmf used a works trans with a taller 2nd gear to close the gap between 2nd & 3rd. Srs used to sell the 2nd gear.
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Post a reply to: Possible group buy: 98-02, 03-04 CR125 replacement cylinder with corrected port and transfer layout