I never ran a moto ride on the dyno with a knobby. SLIPPAGE. I always put a street tire on for optimum grip. I can't tell from the vid what you are using on the rear. It almost looks like a knobby. Can you confirm ?
If you could what size tire is that on the rear? I picked up the 2025 112 yesterday and I want a tire like that asap! Thanks in advance bud love the channel
@HPRaceDevelopment That makes perfect sense, Never too old to learn something new, I've had it wrong for year's so thanks for that handy bit of knowledge much appreciated
What is exhaust port height difference from top of the port to top of cilinder wall? What is difference betwee yz and exc? I cant find messurments anywhere between yz and exc 😅😅 Tnx Sorry for bad english😅
What do you think a 2002 kx 250 would put down for whp stock, I do have vforce reeds, procurcuit pipe and slightly higher compression just curious if you would know
Derek have you had any austrian TBI 2 strokes that require throttle to start when warm? Ever since day 1 with my brand new 250 XC-W it requires ZERO throttle to start when the bike is stone cold, but when it's warmed up it always requires a C-hair of throttle to start. Otherwise the starter will just spin and spin. I always see guys starting their bikes with a split second push of the button. After a TSP medium comp head install and ECU flash it's still the same. Not a big deal, but I was just curious. Funny how some of the TBI bikes you see run great and others run like 💩.
@@K-Rivs carb bikes routinely required some throttle when you kicked or e started. I dont see why thats odd for an efi bike to need same - starting is a complicated challenge on efi people want efi to be magic but its just a fuel delivery system - not magic.
Agreed. I remember riding it for the first time and said man it's so similar to the old school carb'd smokers. I was just curious since it seems like not every TBI smoker is identical running wise. Appreciate it
@@K-Rivs they do seem to vary more but people never appreciated how amazing carbs really are so now i think its a slap in the face when efi is not what people expected.
OP got a question for ya.....as the amount of 2 stroke oil is increased in the fuel mix (richer mix) should ignition be advanced more? In other words does 2 stroke oil make gasoline burn slower or faster > more oil=more ignition advance spark?
Everyone in Japan copied 2stroke engines from eastern europe in the 60s. 2stroke engine is very hard to tune, so why not to copy or just reply anything that somebody had some sucsess. Do the homework and see for yourself who really developed 2strokes as we know them. Latest KTM 250 2stroke Racing bike in MOTO GP made about 150 hp. Think about that.
@@HPRaceDevelopment that's a disappointment, i was thinking about running them in my street 2T supermoto, to hopefully get some protection against E10 fuel
All power valves are a copy of the Kawasaki design. Most brands only get to use one type of the other. Some use the rotors that act as if the header is shortening at rpm. Or a flap to raise the top of the exhaust port with rpm. All designs are a weak 2nd behind the kips system. And everything is a copy of a kawi. Just one half or the other
Bought a used bike, it did not come with the jumper wire for the switch. Can you tell me what two wires need to be jumped for map 2? There are 6 wires in the bundle.
One time I fitted a Yamaha piston to an 80 thou oversize Honda two stroke. Only had to move the ring locator pin, re-shape the combustion chamber squish band, fit a different connecting rod to the crank and make an alloy base gasket plate to get the deck height correct :) Wouldn’t recommend trying this to anyone else unless you are really bored with a stack of time on your hands.
@@HPRaceDevelopment Two strokes are rather sensitive to compression ratio as well. Very high compression requires a strange amount of ignition timing advance.
Interesting information on those dark marks in the bore. Highland cycle on RU-vid overheated his TBI 300 really bad and the black lines in the bore match the bolt holes all the way around. Interesting, thanks for the explanation and great content
Also, the 2004+ rm125 cylinders are a direct copy of the ktm 125 cylinders of the time. Might I add though that the late rm125’s are a fantastic engine, if anything they improved on KTMs design
How impressive do u think these engines would be in terms of tech and hp if the oems still put all there r&d into there 2 strokes as they are with there 4 strokes as of rn?
im actually curious what year kawasaki did this? and this is pretty funny considering one of Hondas builders stole kawis port designs back in the day to build big bore cylinders and they still failed.
@@HPRaceDevelopment there's only so much to change. Not really a copy when they feel completely different to the rider and have different head tube angles
YAMAHA WAS ADDING THE REED TRANSFER BACK PORTS N THE EARLY 80S LOOK UP THE YAMAHA WRENCH REPORTS .......... IN FACT THEY ADDED IT ON 77-79 DEF YZ125 N PORTING SPEC. THEY DID NOT STEEL ANYTHING.....I HAVE ONE WITH IT AND THE CASE MODS TO, THE BACK CYLINDER AND CASE BOOST PORT...ON MY 78 YZ125 I RACED IN PRO CLASS AND STILL HAVE THAT BIKE... AND YAMAH HAD CHROME CYLINDERS TO ON NOGUCHIE KITS........AND HONDA HAD MUGEN KITS ... WITH I ALSO HAVE 1976 CR125M
Sleds are certainly the most modern kept up with two stroke tech in many aspects by oems - but per cc 155 hp at a single clutched rpm isn't that impressive. A 40hp 125 cc - which isn't all that impressive for a 125 - would a 250HP 850cc sled. A 50 hp 250 two stroke - easily already done on a dirtbike would be 170 hp at 850cc. If sled guys wanted to actually be impressive that number would need to be around 200, which for a 275cc triple would be neat.
Drop the 125 down to 8000rpm & it's NOT impressive. 8000rpm (& lower) is where those sleds run. Gotta keep apples to apples. RPM is how you make the comparison. We build race sled 440's that make over 130hp at 10,500rpm on 34mm carbs (rules on the carbs). Just say'n.
Theres only 1 way to get results, they all end up there sooner or later. Just change 10% of the design, not too hard to add minor features to avoid legal procedures.
And who was the rider that developed the YZ like the CR, Jeremy Mgrath, and who won on those YZ’s and CR’s after Jeremy, Ricky Carmichael and Chad Reed.
@@MichaelMiethke well the yz was in progress well before mcgrath came to yamaha. His involvement was after it was already a production item. His race team bike certainly had his touch and Im sure was fantastic for the era as all the yamaha guys were good. I think they slept on their work a bit allowing suzuki factory team to take the next leap on their race package for a bit - which reed said he was blown away how good it was
I think they’re the same also as the 250 R Honda Four trax. Sphinx makes big bore cylinders for those Honda four trax . I wonder if one of those big bore cylinders would drop right on the YZ 250??
@@HPRaceDevelopment I was just curious cause it looks very similar. I wonder if it’s close enough that the Sphinx cylinder could be modified to pick to fit the YZ 250. That would be a cool way to have a big bore YZ 250.
it has already been done. you can look up eddie sanders racing he developed a big bore kit for the yz using his honda big bore. plus a builder by the name of bubba ramsey did this with honda jug on yz cases. its fully custom and looks cool as all get out. the info is out there you just have to dig for it.
@@randytidwell5836 They interchange - we sell our custom yz250 piston for rm and kx - and it works in the older cr with a head cut for the dome vs std oem flat top (honda had both at various years)
@@marcozuffada not really. They have about the same port timings, intended rpm range and target power delivery. Combined with a low power output per cc because mx bikes are all about power width at these power levels - the pipes are really geared towards good power at early rpm with powervalves down that rev well but arent geared towards high power narrow rpm window. additionally the pipe has to fit the bike and not be in the way. If it were an all out drag race engine or similar hell ya its crazy to be same
I think if you are racing competitively then that may be reasonable, but for general use, that's way too frequent (in my opinion). How often do pistons get changed in roadbikes or jet skis etc. If compression is getting low or it's noisy then yes, but otherwise I wouldn't.
@@julianholley2358 My thoughts exactly. Roadbikes though, have 2 piston rings as opposed to the single one on mine and jet skis are 2 stroke (single ring?)
if you riding hard on mx track, 80 hours should be okay, but if you are doing slower trails, enduro etc. you could go even to 150 hours on this thing with no problem, i'm rebuilng mu husqy fe 250 every 120 hours of riding fast cc, trails, enduro and mx, so mix of everything
I have a crf450r and haven't changed the piston in the 6 years I've had it. Not noisy, no smoke, good compression. Will be replacing the piston soon as part of a rebuild do will see what it looks like. My son's KTM 2 stroke, I replaced the piston when it starts making noise or compression low. Must have 60 hours on current piston and it's still all good, aim for once per year replacement. Guess it's down to personal choice / risk appetite.
I’m looking into getting a pipe and silencer setup on my KTM 300sx 2023. I’m on the fence between the bills setup or the fmf fatty with the blue 2.1 they look amazing but I want best for performance. If you have a suggestion lmk. Thanks
Unfortunately, even though the KTM 250 makes more HP its actually in a very narrow portion of the rev range well in stock trim (and the YZ250 out performs it in the other 2/3rds of the useable rev range 😉) Hence why alot of the magazine testers and other 2-stroke diehards still choose the "old as the hills" YZ250 platform over the KTM as their favourite 👌🏻
@@Wilkesy259 thats not even remotely accurate. Why people like to spew bullshit will never make sense to me, why you wish to spew it also doesnt make sense to me. the ktm makes more power at every throttle position and every rpm. magazines say “it revs out quick” which happens when you make more power than your competition with a lighter bike. The solution - is gear it taller - which happens to work fantastically but goes against the add a tooth mantra they all have. If you wish to proof me wrong, post up a video of both bikes on the dyno at 5 throttle positions compared, then go drag race them equal rider weight. Its no contest - the ktm crushes the yz. The yz is just fast enough off bottom and has a nice “hit” to it early enough in the power to feel quick, then noses over and holds flat on power just long enough to feel like it revs far because it cant pull itself to the end hard enough to feel a quick sign off. i owned 5 of them - i know the bike well.
If pipe temps are that critical why aren’t all 2 stroke exhaust double walled. And why don’t woods racers experience a big drop in power even momentarily after splashing through a puddle as nd finally why doesn’t anyone wrap pipes with the header insulation except the hillbilly guy on the edge of the pits.
@@brianpatterson5058 I dont think your grasping what im saying. Pipe gas temperature inside the pipe is what determines sound speed. The pipe wall temperature plays a small role in that compared to ignition, head, port, and fueling. Woods racers DO experience changes in running when splashing through water - if the scenario is right. But achieving a high pipe gas temp all the time is not desireable, and a low pipe gas temp all the time is not desire able. As explained in the video
You have to remember R&D progresses as time goes on. Ktm had to start somewhere, every company does this, a little innovation at a time, monitor reliability and such. If you want to be riding a 2 stroke for the foreseeable future, then get on board with efi. The govt is cracking down on this stuff. Look at all other 2 stroke markets. They've all went efi and they all started off stupid and "dumb". In 10yrs time youll see 2 stroke bikes running at the complexity level of marine and sled engines. Also for the average rider, peak hp doesn't matter as much as wanting, consistent low and mid speed rideability. No boggy spots, clean idle indefinitely, inconsistent temp and environments etc etc. theres so many benefits. max hp matters too dont get me wrong. But i dont think your looking at the bigger picture here. The average guy wouldn't know what to do with a carb if his or her life depended on it anway. So tuning it to their conditions is outta the question.
KTM had a long time to get this ready - it wasn't some 1 year overnight whim. I have friends in various departments - it's been an over 15 year program.
Amazing video, thanks for your time and dedication for the motocross community. One recommendation I have for you is to clean the cam lens before filming to fix the blur on the video that happens to me all the time. Thanks again.
thx - sadly the phone is getting old and the blur is becoming a part of it. we switched to led lights in the shop and for whatever reason it has made glare and reflections way worse
