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How much have you dynoed the 19 150 at? I'm thinking of getting that or tm144.
Steve Clitheroe knows his engines and knows how to make the bike rideable for the average guy which will in turn improve lap times which is what it is all about rather than some top end figures
Aprilia did loads of development in the end
With two stroke tuning them more I know the more I realise I don’t know
the ktm easily goes over 40 stock when tuned in for me
Interestingly - it's more a revver than the 125
Now to direct it back a bit would you change the Hpp head to an O-ringed, 2 piece head and what chamber style do you prefer, flat tub, toroidal, dome?
I like orings - so it just depends on the user, both work fine.
I prefer what works for the engine - often I've used toroids with sucess on flat tops. Sometimes they dont work - usually a flat tub/bath tub/top hat isn't best.
Everything that aprilia pioneered with heads on their engine hasn't translated to many builders on many other projects. Honda and yamaha - and the ktm 85, 125, all have similar heads that all work quite well.
Some heads of honda were like this - and also work well.
It basically the same engine that factory connection ran. Oh and by the way , Honda and Factory Connect Dyno’d the Mugen cylinder and also the SRS racing stuff, and power wise it wasn’t any better than stock, just moved the powerband oneway or the other. But was not more power.
And we ended at a whopping 34 or something like that.
When you look at the mugen cyl - as I told the customer - there was nothing to really seperate it from a std one...as he was certain that bike would go 40.
Don't mean to hate on the mugen parade - as the faithful for that are vicious...but it just wasn't spectacular.
But never do I see!
Knowing what I know - I think a ton of numbers are inflated from the era. No different than the cr500's being total animals and unrideable - and yet vs a modern 450 they are tame.
A production 2005 (to current) yz125 IMHO is as good or better than what lined up and race SX in 96-98 on any color.
Throw the fuel at it they used to run, little ignition timing, pipe silencer of choice, maybe a tiny bit more compression and it would have dominated vs the 90's bikes. Even sadder is how close the 2005 is vs the 96 yz. Not far apart but the changes added up to 3-4 hp at 7000-9000
It may be off a tad of the best peak hp of the era - but it's usable power curve would avg way more power
A producton ktm 125 of today - would have been cheating at the time - and evidence of that is the factory ktm in 2002ish (langston) was so much faster than the others - it was nearly a four stroke 250f. And the ktm 125 of 2019 is ridiculous vs the older ones. The changes that allow it - didn't exist in that former era. It's all in tiny nuances that have evolved in gp racing and karting etc.
And at that time a full factory 250f in 04-05 was lucky to exceed 40hp, I'd bet around 37-38 on the bikes. PC said their 2012 production bike was better than full factory 07-08 of theirs (minus RPM they turned) if you ever need evidence of what Im saying.
My point being - As much as we glorify the era - we glorify it because of how good the racing was, how much we THOUGHT the factory bikes were better than std (likely were), and the sound and smell.
Most of us consumers are blind to the fact the OEM's are the true drivers of development. Case in point - in 2017 and prior I had to do INSANE amounts of work to ktm 105 cylinders to get them where I wanted. tons of epoxy on short side turns and roof angles, HUGE amounts of dyno time, custom pipe, ignition, heads etc.
31-32 hp for more r&D than i ever would like to admit. And our package smoked what was available from anything else we tested - you name it.
The new production 105 cylinder will go those numbers with the proper but minimal effort. KTM has stepped up all the little details we were trying to do
I just built a 112 that knocked down 36 - and a production yz 125 is 34! Had you said in 2 years time - I could leap 4 hp with minimal effort - i'd have laughed at you. Normally hp comes tenths at a time. I'd have also said 36 was impossible from a 29.5mm carb and reeds that are used...but apparently I was wrong.
The OEMS are smart, have huge budget, best test equipment, are well connected to other smart people, and hate losing.
Rant over
to answer - Mugen was very close to production cylinders of the time - pick a year to compare with for the variances...as honda had small tweaks over those years. The ex port was slightly higher, less than 1mm diff, and the transfers for all intents were the same.
On the dyno it moved the power curve 400ish rpm to the right - to be expected on a higher ex port, with a little more peak hp when compared back to back using same pipe, jetting, and ignition at trade of some bottom (not much loss). I think the production cyl we used was a 97 I'd have to ask the owner I can't remember.
With a tiny bit more massage work to the ex port - I think it was capable of 2-3 more hp. Past that would require massive transfer changes with epoxy.
The huge positive of that era honda is the "midrange" as compared to production 00-04. I'd have to double check exactly how much but at 9000 rpm those hondas and mugen were like 4 hp stronger if I remember right. I think it affirms why people say those hondas run better - so much easier to keep on the pipe.
The transfer short side turns on the older hondas is "longer" with more distance from cyl to turn apex. I largely believe this is the major diff in mid range as the honda and current yz are similar in this dimension and shape.
The 00-03 honda has a far different approach in transfer in that area - obviously for the worse.
For 2500 - find a good builder, and a couple cylinders, and youd get farther than a mugen for sure. Definately could spend those bucks in ways that added up to better power.
But it wouldn't be a mugen!
Pit Row
The TM is too...I recently knocked down 42 on a pump gas TM which surprised me for T port...
But at the power it has production - exceeding that of the ktm (or about on par with new 19) I think they don't want the headache of the powervalve complexity...
The transfers are fantastic - and obviously where the power comes from vs a yz or ktm
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