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Mugen cr 125 cylinders
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I have no personal experience with mugen, altho i am looking for a 90s Mugen CR125 kit for my 91.
I have spoken about them with different people and a fair bit with Nino, and i think he was saying that yes, they are competitive with modern day 2 strokes!
I guess similar speed to putting a 144 kit onto a cr125? Maybe Nino can answer this
they seem to command some strong money even if you can find one
the last one I had on a bike was in 1987 when I sold an 85 with one on to trade against a new 87
I think i got £800 at the time
I have a 144 kit on my 99 cr 125 and have been very pleased with it along with other mods that I have made to it this year
Just need to learn how to go faster than a snail now
My '91 has a 134cc '92 top end with '99 powervalves and I only run the 36mm carb.
Stomps really hard in the midrange and makes power really fast.
I use a 91/99 mix of gearbox parts to pull 2nd and 3rd closer together too.
It's a great little hare and hounds weapon, but lacks the over Rev you'd want on a fast mx track.
The mugen kitted motors are screamers by all accounts. I passed one up a couple of years back as it's not right for the riding I do or my skill level.
In hindsight I should've bought it and put it on the shelf.
The Shop
Would be interesting to see a port map for a mugen. From what I understand, you just cannot replicate it with a Honda cylinder, no matter how you go about spacing or decking the barrel.
I think it's the port positions you can't subsequently match.
Admittedly, ultimately anything's do-able, but by the time you've done it, you may as well have bought a mugen kit.
In the last 25 years i have seen many 125s with all kind of tuning (big bore as well) but in the end none matches the screaming mid-top of a Mugen. I still have to ride a '16 KTM 125 head to head against my AF with '90 Mugen but from what my friend tells me when he compares it to his 144cc AF i guess mine is still competitive
AND those HPP engines are like tractors...durability is unreal! My '90 Mugen now has 950+ hours and is still on its original Nicasil !! The transmission of those engines is bulletproof as is the clutch and everything else.
While the new '16 KTMs have several issues already: after every couple of hours the exhausts break, there is issues with cracked lower cases and to top it off on most 125s the exhaust valves aren't working properly. They don't open/close freely so they stuck somewhere in the middle which makes for poor low-end or weak top-end...or both
Mugen 1990 ( i actually prefer the '90 over the '91):
Mugen 1991:
CRF chassis, awesome suspension , 1998 lower end with '90 Mugen kit and the weight reduced to the lower limit of 88 kilos / 194 lbs:
It rides like a dream and is a smile machine....it is so much fun to throw that thing around
https://www.youtube.com/watch?v=F8wfkXKrJdg
Aluminium nut:
Stock steel nut:
How hard are these Mugen Cylinders to obtain? Anyone know of a source? They sound Migh-T Nice!
Also, are those X-trig clamps? Loving the drilled out sidewalls
Pit Row
Mugens are very hard to find. They got made up to '91 only and these days they are collectors items with sometimes ridiculous prices.
http://www.thumpertalk.com/topic/993917-my-new-cr-125-afs-aluminium-fra…
On my CR 125 AF you see above i saved a total of 8 kilos / 17,5 lbs!
Bolt tuning is the last to do to save weight.Too costly really. It saved 836g on mine (not replacing wheel and swingarm axles.). Total possible bolt-savings on a bike would be around 1200g.
How ridiculous is ridiculous? $1,000 for a cylinder or $5,000?
I got a lot of flack already in italian forums because of my comments:
Honestly - I was really expecting big things out of the YZ125. You read a lot about how good that engine is even against KTMs (very user friendly low-end with decent top etc). BUT against my '91 Mugen it was really lame. My 24 year old Mugen engine was leaps faster! And even chassis-wise i wasn't impressed at all. It still is a "old" bike. The YZF 4-strokes however were a different thing. Racersharp handling etc...but the '16 125 Yami was not impressing me at all ! I'd prefer my '98 all day. No kidding!!!
My '98 CR 125....'91 Mugen kit....and 17 years in use !! Nowadays it serves me as a spare bike and test-bike to try out things on the engine. But i ride it every time it's a muddy mess to save my nice AF. I raced it twice this year and still won races with it...
I am in the lucky position to have the choice between different bikes with different Mugens
I have a 90 kit and when it comes to peak power it screams especially with DEP pipe, but it is quite weak on the low end. Then I may not have perfect jetting and gearing. My cylinder has slightly modified porting so that may explain the peakyness. I have the intention to take it to a dyno this winter and compare with a stock cylinder. With HGS pipe it gets more bottom but loose some of the hit on top.
Compared to my Rinaldi YZ125 07 it may not differ that much in max power but the YZ reach max power much faster as it pulls much harder from low rpm. Also most tracks I ride are quite soft which makes a narrow powerband more problematic than on hardpack.
I also tried a Pro Circuit but didn't like it at all. It makes just revs but has no torque. Best is the Tomasin R&D which has awesome mid-top just like the Messico and an absolutely insane overrev up top. It wont' stop pulling.
My collection:
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