Something so satisfying about that built yz250 coming on the pipe. Reminds you of all the crazy motor work done by race teams in the 90s, experimenting and learning as they went. Occasionally someone would get those ports JUST right, and it would rip as good or better than the setup here; being the envy of the entire MX park that weekend.... good stuff :)

You could hear it rev out mire and keep building power impressive

Nice. New room looks good too

That’s insanely impressive!

Nice work! Fun to see the dyno numbers too ... I don't know why, but I've been wanting a yz250 again ... I almost bought a 2019 used a few months ago. I don't do motocross - just trail riding (58 years old) in the mountains. But, I love how light they are, and fun when they get on the pipe. But, my last one just sat a lot, because 4 strokes pull from lower, and are a little smoother, which makes riding slow easier.

@Dallasdeckard

Ай бұрын

I'm 62 and maybe like you used to love to blow blue smoke and tear the earth up. When I hit 50, though, I started wanting a smoother ride and the ability to ride slower (through the woods and so forth). If I rode a YZ250 the way I drive my WR250F, I'd be fouling plugs all day and it just wouldn't do what I want to do now. Pride, ego and love of riding on the thin edge gets me wishing I had a YZ once in a while, but the WR is just too much fun for how I ride now and I don't worry my wife and two adults sons now like I used to. I get it, believe me, but I'd rather ride longer (into my 70's) than risk injury and get my wife and sons on my azz to stop riding. I raced a bit when I was in my teens and early 20's, while my two sons have always just been leisure riders. So, they aren't used to, nor do they enjoy, wide-open riding. When they were young I kept it tame so they could ride with me. When they got older, I found it hard to get them to go with me very often. When i bought the WR and their mom told them I'd slowed it down a lot, they expressed an interest in riding again. Since then, they both bought WR's like mine and we go riding quite a bit, so it was definitely worth dialing it back.

@bennyblanko3

Ай бұрын

@@Dallasdeckard Thanks! I appreciate the comment and wisdom. You are absolutely correct. And, I'm going to quit dreaming about a 2 stroke ripper, and enjoy the various 4 strokes that I now ride. I do see WR's come up quite a bit in Idaho. But, I already have a plated DR350, KLR650, TW200 and TTR125 (all plated) and the DR is fast enough and fun to rip around on. Sometimes even though we get older physically, it takes a while for our brains to catch up that we aren't 20 anymore. Anyway, really appreciate the comment, and it really hit for me.

Good job not dropping off too much in the mid.. thats as impressive as the big gains up top. Sweet

@HPRaceDevelopment

Жыл бұрын

bike will be back for a head more my normal route - i think we will get the mid back

@yamaha4902

6 ай бұрын

​@HPRaceDevelopment new video?

Wow that’s crazy how big of a difference it made on the dyno. I could hear the difference also. I have got to have you do some work to the cylinder or either have you set a cdi for my sons ktm 125

Great video thanks mate!

True story, Red Bud Michigan MX national. I think it was around 92 or a bit later when Kawasaki was first to switch from box vans to a semi team trailer. One of the crew members said he would give my buddy and I a tour of the trailer, after some of the fans getting autographs cleared out, so we came back an hour later, and he took us in----and left us alone in there. And there is was, a cylinder sitting on the bench with the name "Laracco" on it for a KX250. So I pick it up to look at the port work, and to my slight amazement, very little work was done. Then Big Laracco, (Mikes dad), walked into the trailer and caught me red handed looking at the jug. So out we went. :)

@HPRaceDevelopment

Жыл бұрын

It's "small things" that make nice differenes. The evolution from a 1985 250 to a 2005 is a bunch of small things that add up quite a bit!

I started racing in 1975 and it was so secret what to do FMF was big help they built my 1976 CR125 and it was fast but frequent ring change required today the bikes so good and knowledge shared am very jealous. Although I raced whole season on YZ250f with zero failures.

@HPRaceDevelopment

10 ай бұрын

The secret for the last 20 years is there is no secret. The have and have nots is just time and money to give someone what they really like. Factroy racing has some secrets today in 4 strokes - related to valve train and camshafts. But the pistons, ports, bearings, rods etc are very standard.

The fact about yz250 parts fitting onto cr250 cases is crazy, I have an old cr250 and am now convinced to put a Yamaha top end on it cause it’s weird and interesting.

@HPRaceDevelopment

Жыл бұрын

It would take some creative engineering to make the powervalve work or go to an e power valve

Great information and thanks for showing charts!

Yes MC made that yamaha into as close a replica of his beloved cr as they could do. Steel framed cr and yz 250ts are some of the most sought out bikes amongst 2 stroke fans. They were so ahead of their time and well liked by many riders. While YZs cant compete with stock KTMs off the showroom floor anymore, they are very easy to add hp onto with a design nearly 2 decades old

Hey been so impressed with Matty Burkeen racing 2stroke would luv to see ya be able to give him little more...... Bbbbrraaaapppp!

@HPRaceDevelopment

Жыл бұрын

Im sure he already has it built

@bustedford

Жыл бұрын

Matty should have a way a guy could donate a buck or 2 so he could get some speed parts and shocks👍🏻

@superfan311

2 ай бұрын

Matty B uses a JMS ported cylinder and OEM modded head , ran the Phathead at Budds and it worked very well .

Impressive

This is awesome.

Great video and very informative. I came across this video because I was searching to see if a newer 99+ cylinder would fit on a 1986 YZ250 bottom end. Cylinders are getting very hard to come by and it would be great if I can swap a newer cylinder and head on it. Any idea if this would work? Thanks!

@dormantmenace

Жыл бұрын

No way. I have a 86 yz 125. Completly different power valves in the least.

its crazy to actually see the swingarm fall over when you get over the hp peak. very nice to see it visually

@HPRaceDevelopment

Жыл бұрын

Good observation. You are actually watching the torque curve..and you could measure torque of a bike purely by putting a scale (more advanced one) under the front tire and properly calibrated plus knowing engine rpm could measure power this way. But it would need a load - like we have - and measuring power with the load is easier...so it's done that way.

really nice tech videos !! the dyno graphs are wheel horse power or crank hp ?? i subscribed 😉

@HPRaceDevelopment

Жыл бұрын

wheel

can you make a video comparing different mixing ratios of oil with stock tunning. cheers from argentina

Looking at the dyno sheet I see pc in there listed as well did this have a pro circuit pipe added as well as the porting mods & stic vs stock setup?

@HPRaceDevelopment

Жыл бұрын

both bikes, as shown, have pc pipe and silencer - only changes in chart are porting and head

Derek,s IN the house, to many good things said about your work. Lets support derek, like he supports the sport ,come on ladies and gentlemen

I believe so on local tracks

Man you’re definitely the YZ doctor. Could you give me some advice on what mix fuel to oil ratio for a brand new motor for break in would appreciate your input

@HPRaceDevelopment

7 ай бұрын

Manual suggests 20:1 You wont hurt anything if you followed that

@motomatt6752

7 ай бұрын

Sounds good that’s what I’ll do thanks again

Does increasing the power/rpm like that significantly shorten bottom end and gearbox life, all else being equal?

@HPRaceDevelopment

Жыл бұрын

YZ250's have weak gear boxes, RPM doesn't effect their life, just time on the gears. While the power is placed higher on this, it is still signed off similarly in "extreme" over rev. On track, people rev a stock or mod engine in the air and before shifting to 11-12000 rpm so rod life is about the same.

9cv emis Very good

Hi there, Thank you for the video great content, what sort of dyno are you using in these videos. Jacob

@HPRaceDevelopment

Жыл бұрын

In house designed and built, using performance trends software

@JESMotorsportsMechanical

Жыл бұрын

@@HPRaceDevelopment nice man, love seeing people make their own tools makes it more affordable for sure

Hey great work. So cool to see the old YZ motor tuned perfectly. Do you have a good 2008 RM 250 jetting you can recommend or sell? I think these engines are quite similar.

@HPRaceDevelopment

Жыл бұрын

Not really, off memory the RM ran far leaner main jet sizes than the yz. It uses a slgihtly richer needle. If I remember right, buy the yz reed spacer and 2 gaskets, and run a little race gas (if it's stock) and it will really run good

@Dierk200185

Жыл бұрын

@@HPRaceDevelopment Thanks for the tip!

@ghostrt1608

Жыл бұрын

@@HPRaceDevelopment ... what brand of premix do you like to use for the YZ250 2-stroke

@HPRaceDevelopment

Жыл бұрын

@@ghostrt1608 Lot's of brands are great!

do the knobs on the tires not make the reading innacurate since the tire bounces more?

@HPRaceDevelopment

Жыл бұрын

no knobs on that tire..we use street tires for all dyno runs

@FreDEV_OFFICIAL

Жыл бұрын

@@HPRaceDevelopment ahh sorry haha, i saw the beginning of the video and was like, wait but there knobs on that tire. My bad!

I'm in the process of rebuilding a 2000 RM250 and I'm trying to get power delivery more like my old YZ250X. Is it even possible on this ancient bike? I don't mind spending some money on the top end while the bike is apart but I don't want to waste money if it's still going to hit like a freight train.

@HPRaceDevelopment

Жыл бұрын

not sure. My understanding the 2000 rm was considered slow and not too aggressive. maybe the powervalve isnt working right

Impressive. I have a question. What aftermarket reed petals would u recommend for a stock cage .. also my bike is a 2001 with no reed plate Spacer. Is it true Yamaha made a mistake with the reeds blocking the rear boost ports or do the 2002 to current engines have this spacer for another reason . ? Hit me back. Thanks

@HPRaceDevelopment

Жыл бұрын

with Spacer is 1 hp better everywhere. Ive published this online years ago. I suggesg oem reed petals in oem cage

@carlmackenzie6430

Жыл бұрын

@@HPRaceDevelopment what other reed combinations have u tried ?

@HPRaceDevelopment

Жыл бұрын

@@carlmackenzie6430 all of them

@carlmackenzie6430

Жыл бұрын

Thanks 🙏

Could I just send a cylinder for porting? Whats approximate cost for this service? Love the results

@HPRaceDevelopment

Жыл бұрын

yep. 400 for the cylinder alone

What piston did you end up using ?

How do you plug the ecu into the computer and what software is going to show how many total hours are on the engine. Can’t find any information on this anywhere unfortunately

@HPRaceDevelopment

10 ай бұрын

You dont with stock ecus on 2 strokes. You can on 4 stroke ecus with the proper cables and software - usually lots of money

@colinchilds

10 ай бұрын

@@HPRaceDevelopment got it man. That’s unfortunate… I’ll be taking a rough estimate then inventing in an hour meter! I appreciate the speedy reply

What numbers do you think that Star Yamaha 250 would make?

@HPRaceDevelopment

Жыл бұрын

47-48 on my dyno

On the dyno around the 9 min mark, as you get to max rpm, am I seeing things, or is that rear tire expanding,----with the rim? Is it just climbing up on the roller a bit higger?

@HPRaceDevelopment

Жыл бұрын

Probably just climbing, we track calculated gear ratio to make sure no clutch slip or tire slip, and it doesnt vary much

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment It might be some kind of optical illusion too.

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment I have a little land and sea water brake dyno I use for 30cc engines, and I use a centrifugal clutch, (modified to expand earlier). If that clutch slips,--a huge warning flashes on the screen. It has not slipped since I modified the clutch.

Hi! Very good and interesting videos. I just subscribed to your channel. How much HP you get from a highly modified Husqvarna TC 250 2018? I have this bike with modified Mikuni TMX 38 carb, better breathing modified airbox, Boyesen Rad Valve intake, Wiseco 1-ring piston, stock cylinder porting, slightly more compression with a modified stock cylinderhead (tighter squish band), FMF Fatty pipe and Pro Circuit R304 shorty silencer. I run it with 32:1 mix for better lubrication and to have better pistonring ”seal” from the extra oil. These 250’s have 72 mm stroke and the maximum piston speed exceeds 85-125 cc piston speeds because of the longer stroke. Because of this I think 1-ring forged piston is needed. I use red powervalve spring (softest and wildest one). Can a highly modified 250 2-stroke get the same HP as stock 500 2-stroke?

@HPRaceDevelopment

11 ай бұрын

A well done ktm/husky can make about what a stock 500 makes Id guess you are currently around 50 on our dyno, you would need around 55 to be at a stock cr500

I want a new yz250 but should I even bother or find 06+ I would like to know your opinion! I race a 01’ cr250 and would be coming off that.

@HPRaceDevelopment

Жыл бұрын

hard to say! Honda is good motor in 2001 off memory

@eaglemx45

Жыл бұрын

@@HPRaceDevelopment very fast motor no issue pulling hole-shots on 450s just seriously lacking in frame/suspension. had my fun with it!

I port/stroke small 2-stroke engines for a living, (30cc approx, and sell them all over the world), that I learned how to do in my older dirt bike days. I have a head design for the YZ250 (I have a 2019, after almost 2 decades off a bike,---and lowered it), and I am wondering if I can hire you to do some comparative dyno work. I made a head for my last bike (1997 KX250) that i rode a lot, (knew the bike well), and I felt more power there. If it works, maybe we can do some good business with each other? Doug in Michigan

@HPRaceDevelopment

Жыл бұрын

sure send it i've got a bike here

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment Ohh, I just have the heads. I have to develop it and prove it out on my bike first, and I hope to get to that next summer. Porting these little engines keeps me real busy. I might be the first person in the world to port 2-stroke engines with CNC milling, because with RC cars, I do a case of 36 top end kits at a time. The finish hand work drives me nuts, (but I can't cut corners because I love quality)--and takes most of my time. I would love to find somebody to make pipes for me. I have a great reputation in the world for RC gas cars/boats, like Mitch Payton, and a great distributor. I am sure I could keep a guy busy and prosperous if we make good stuff. :)

@SL4US

Жыл бұрын

​@@EarthSurferUSA dude go for it

NICE RESULTS CONSIDERING YAMAHA'S 45HP DOESN'T LEAVE MUCH ROOM FOR IMPROVEMENT WHILE RETAINING RIDEABILITY.

Sorry to bother anyone with this question But.. I had let a buddy borrow my crf450r. (Mistake) and he took off with it for a few hours! Only to bring it back locked up. I can break it free and start it.. but I licks up after just a bit of time? Any tips? I much appreciate it. 🙏

@HPRaceDevelopment

Жыл бұрын

needs a rebuild Im sure

@michaeljohnson4004

Жыл бұрын

@@HPRaceDevelopment thanks for the reply. Bummer on the rebuild tho. 😞

You mentioned the bike is running a STIC. What is your opinion on it?

@HPRaceDevelopment

Жыл бұрын

we like them

@keithpeterson6108

Жыл бұрын

He likes being able to sell them. 😉

What's the break-in process for a new 2 stroke top end?

@HPRaceDevelopment

Жыл бұрын

We have a video in progress hopefully to drop soon! Great question

@gaara10122

Жыл бұрын

Pin the throttle for about 2 minutes and dump the clutch

Did both bikes have stic mod or just the ported one?

@keithpeterson6108

Жыл бұрын

He fluffs his numbers & the stock bike was stock.

I'm very green but like speed and engine sounds like most so stupid questions are , as a kid race development garage Maxwill Racing Engines Pty Ltd down the road used chains to secure V8 dirt machines , do straps have some give and possibly affect readings ? If you swap pistons and the top [crown ?] is shaped differently does that affect squish and compression ? Do you guys use wideband or WOT on a 2t always reads rich no matter ? I know there are dumb questions , thanks anyway .

@HPRaceDevelopment

3 ай бұрын

Straps not really - if the tire slips obviously power reads low but we track tire and clutch slip in data and know if we have any. Tire pressure will alter power reading - too low and you loose power, too high and likely to slip tire more if the dome is different it will alter the squish and compression. Depends what sort of different as to what you gotta change. Wideband on a 2 stroke is essentially worthless. Depending where you put it can alter its readings a lot, but also when you are not at peak torque rpm the afr sensor reading is no even close to actual true afr in the combustion chamber.

@johncoscia5258

3 ай бұрын

Thanks , very interesting .@@HPRaceDevelopment

Is it OK to run Avgas in two-strokes been told it helps with lubrication or is it just a waste of time and money

@daviddavidson4496

3 ай бұрын

Avgas still has lead in it Lead is a great lubricant

Am I missing something? No before and after the porting- just two different bikes? I want to know what differences the porting makes.

@HPRaceDevelopment

Жыл бұрын

You are seeing before and after

@keithpeterson6108

Жыл бұрын

Fudged numbers

Stock jetting?

Hello, I have mounted a fatty and shorty fmf exhaust on my yz 250 23, my question is is it protected with the 50 n3ew pos 2 series carburetion and 178 main jet, or should it go up to 180, thanks in advance

@HPRaceDevelopment

6 ай бұрын

Don't know what you mean by protected. If you want power from a yz the stock jetting is too rich. But - you can't run pump gas if you wish to make it run right.

@Liliros

6 ай бұрын

@@HPRaceDevelopment thank you so much

I would think you have to be losing power with the transfers backed up with exhaust gasses, (which may be a very narrow RPM range when it happens), because it is mixing exhaust gasses with the next charge. I could agree that happens with sustained wide open throttle, (250 2-stroke on a modern 4-stroke track, no doubt,--or just down a road,--lol), and I doubt it made much more RPM after it starts happening, (signs off). I am going the other direction for my bike, woods ricing sand whoops.berms, 3rd.4th gear stuff mostly. Want to boost the lower rpm's. These guys are wringing the guts out of a 250 2-stroke like a 125 on these fast tracks. I am too old for that stuff. :)

@HPRaceDevelopment

Жыл бұрын

In MX, people ride well beyond where power signs off..both just in the air and some on the ground. You can't build in enough blow down to solve the "issue" without killing power. KTM is now implenting a rev limiter on their new CDI's 2 strokes and EFI 2 strokes, it sounds at a "low" RPM but is 2000 RPM past total sign off. And yet people hit it all the time - just how the sport "style" has evolved despite it being wrong

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment "In MX, people ride well beyond where power signs off". I know, today. The faster 4-strokes made the tracks faster. That is what happens with any motor sport with corners when you add power. There is no such thing as "squaring off a corner" anymore,--like road racing. lol I don't have any experience on a 4-stroke. 80's and 90's were my hey day (59 next month). Compared to most tracks in the 2-stroke days, today's tracks are faster and less dimensional. I remember when you had to have great corner speed to clear the next jump, and people mastering clay off cambers, (for examples).

@skyhawk409

Жыл бұрын

A good port job won't sign off till 11500rpm stock 9500rpm 2 stroke sign off is the engines natural rev limiter.change gear or shut the gas.

@skyhawk409

Жыл бұрын

A good port job won't sign off till 11500rpm stock 9500rpm 2 stroke sign off is the engines natural rev limiter.change gear or shut the gas.

Does the stic metering rod make a difference on the dyno on the yz250?

@HPRaceDevelopment

Жыл бұрын

yes

@TheAyoubh

Жыл бұрын

@@HPRaceDevelopment how much more hp? Debating if i should drop 300$ on one

@HPRaceDevelopment

Жыл бұрын

@@TheAyoubh More than a pipe and silencer.

@keithpeterson6108

Жыл бұрын

@Huda Ayoub Pipe & silencer is about 1hp

Oi gostaria de saber se é real que essa moto atinge mais de 15 mil rpm?

What sprocket combo are they running?

@HPRaceDevelopment

Жыл бұрын

50 rear

New shop?

@HPRaceDevelopment

Жыл бұрын

new room

Is this rear wheel hp or the crank? Preety sure 250 2 strokes have 55 ish crank hp? Not sure why the lower rear wheel numbers are always used

@HPRaceDevelopment

6 ай бұрын

These types of comments are ignorant - or dumb. Go design and build a dyno - then measure what “you are sure of” Maybe you will learn a lot along the way. If you wish to measure crank power, then your dyno design will have to remove the clutch and transmission from the crankshaft, and the dyno will need to measure directly off the crankshaft. What makes a bike win races is how much power it makes at the tire…people like to win races so thats what we measure and work on

@justcrapclips4214

6 ай бұрын

@@HPRaceDevelopment I have no experience with engine dyno’s or how their used exactly , I just used numbers which are widely spread by everyone, which don’t make them correct obvs but so how can this be a stupid question ? You haven’t just invented fire or anything new so don’t act like it

@HPRaceDevelopment

6 ай бұрын

@@justcrapclips4214 You asserted a statement as “fact” and provide no evidence or understanding to support it. Meanwhile - I - built this dyno, I - understand how it works, I - know the physics behind it, I - test on the daily, I publish this info for you to consume and maybe inprove what you “think” you know. Maybe - you should appreciate that and update what it is you think you know

Well, you got some good over rev out of it with out losing mid or bottom end and the peak power is impressive. But,--(yea, you knew it. Sorry.), if the stock head is the same as my 2019, it is pretty low compression. I am thinking you put a higher compression head on it, (to retain the mid range/low end), and it probably helped it rev too. I am thinking 2014, (not sure. Would have to look it up), Yamaha lowed the compression to burn any junk fuel in the world. Would my guess be right that you can still run 93 octane gas with those mods? If you actually lowered the compression, you should try one of the earlier heads. I bought both of them. The only difference is .0085" more material on the gasket surface for my low compression head, easy to cut and run again, and still run 93. For the guy who has to hang it open, that is a great mod. Doug in Michigan

@HPRaceDevelopment

Жыл бұрын

I have a long history of development on these. Have tested a lot of cylinders and heads… The yz, if jetted for best power, will detonate on pump gas with stock head. They are “high” comp vs the KTM’s which make a solid 5-6 more hp on my dyno. I’ve found that if the pipe design and cylinder are really good, usually more compression wont help, and often lower compression is best. On the yz, I’ve found more compression feels snappy/good on track but it doesn’t do a lot on the dyno curve

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment "The yz, if jetted for best power, will detonate on pump gas with stock head." I have been getting the bike lowered a bit properly. Stock jetting is very rich, have not touched the engine yet. What do you think of my set up. I want more low end power, the closer to my 1997 KX250 the better, (which was a blast in my favorite trails.). I picked up a v-force reed valve, jetting, have an older head with more compression if needed, but plan on lowering the cylinder about .5mm to lower the exhaust port, (get a lower rpm pipe. Does FMF still make good ones?), and raise the compression, jet it well, (using needle shims for fine tuning), and try a head design I am slowly tinkering with. Sand the head design, what else could you suggest for closer power to the KX? Thanks. That is all I read of your post so far,---lol

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment "I’ve found that if the pipe design and cylinder are really good, usually more compression wont help." I understand that too, good pipe effects. But to the premise of our engine building, I think we are after 2 different applications, and you are racing against 450 4-strokes on a fast MX track. Personally, I think we need to start a new series and drop the FIM/AMA from MX/SX. I am also quite sure the factories are sick of the FIM also, (wasting the industries resources in places like Turkey, where they buy no bikes, for reasons of political "inclusion" only,--for one example.). So lets start a movement, a good one with the track owners and the factories running the racing. They won't waste money, and we can race the 250 2-stroke with the 250 4-strtoke---and grow the darn sport by reducing racing costs, at least a bit. Oh yea. I need more mid range. :)

@HPRaceDevelopment

Жыл бұрын

@@EarthSurferUSA right, well usa clearly is corrupt, now that I've seen behind the curtain, the OEMS and feld, mx sports are all in it together. OEMS don't want 2 strokes, and mxsports agrees. The sport long ago didn't need 450's and yet here we still are

@EarthSurferUSA

Жыл бұрын

@@HPRaceDevelopment Hmmmm. I don't quite agree that OEM's don't want to make 2-strokes. I know they must miss a lot of the market share they once had when more people could afford a bike, (and had more places to ride). I don't think the factories had any intention of making a 10 grand bike in 1997. It was pressure from environmental government dictator groups, the EPA and such, who forced the 4-stroke on the industry. That is what they use, force. Not only in MX, but the entire world today IMO, lives under a dictatorship. Freedom is a funny thing. You have to try to do something with your life in private business to find out what we have lost. And still, many private business owners do not get it, as if government intervention is part of free enterprise. It is not. It is part of communism, who stole our free enterprise to fund itself, and end our liberty to compete. They already took everything, and left us some recreational industry to play with. Kids in school today, are taught to get into sports and get a job with the state. I would really like to try Laissez-faire economics with a good court system so we can't screw each other. We are freaking slaves again! I see it.

What squish clearance/piston deck height were you running on this engine? And what did you do to lower the compression?

@HPRaceDevelopment

6 ай бұрын

Dont take this offensively but why would I publish any of that? Since our ports aren’t* at stock heights - deck height isnt something of relatable relevance to someone without our set up…

@mozer30

6 ай бұрын

@@HPRaceDevelopment I don’t take offence at all, just wondering what works for people as the internet gives mixed results. Yamaha obviously err on the side of caution when it comes to squish clearance, so I have some work to do. Thanks for the reply though 👍

@HPRaceDevelopment

6 ай бұрын

@@mozer30 ports arent*

@HPRaceDevelopment

6 ай бұрын

@@mozer30 you will loose power if you tighten stock squish or increase compression or both. The question becomes what do you want in power character

@2strokewilson46

3 ай бұрын

Iv done my own head work I tightened up squish and lowered compression and it definetly makes more power

How much Torque does a stock yz 250 make?

@HPRaceDevelopment

3 ай бұрын

around 30 lb ft torque and hp are connected via math - take any point of the hp curve say 7000 rpm it makes and 41hp that rpm, multiple 41 by 5250 and divide it all by the rpm point you picked - 7000 - 30.7ft lb of torque To find peak torque you have to do a couple points to see where torque is highest value - dyno software does this automatically for you at all rpm points. Power is all that matters from a racing standpoint and average power is also important.

I ported two strokes for 30 years, it’s a leaky crank seal you should have done a leak down test that was all ways the first thing a did it’s two strokes biggest problem sucking air

@HPRaceDevelopment

Жыл бұрын

Im 100 percent sure it isnt.

@HPRaceDevelopment

Жыл бұрын

The black isn't oil. It's burnt carbon. It doesn't wipe off or come off easily.

Hey man just wondering what rear tire is that

@HPRaceDevelopment

Ай бұрын

Cheap brand harley tire

@Queloqueloco

Ай бұрын

@@HPRaceDevelopment thank you man I just like the look of it. I do a lot of track racing, and that Tire for some odd reason caught my eye if you ever find out the exact model of that tire, please let me know. It would be highly appreciated.

@HPRaceDevelopment

Ай бұрын

@@Queloqueloco I'll try to remember to look tomorrow

How do I get the most mid range out of a yz250x?

@HPRaceDevelopment

Жыл бұрын

depends on what you call midrange

Transfers don't make power? Tell Jan Thiel that. Doing this without at least a good 1D simulation like ENGMOD2T might yield a bit more power, but I made 89 rwhp using a disc valve intake, porting - extremely aggressive - a SOTA pipe and a bunch of other junk to a KTM SX 300(250 with big bore kit) It took a couple of years to develop the little dragbike, but it flies on both dirt and pavement.

@HPRaceDevelopment

7 ай бұрын

i own engmod big dog and have been fortuneate enough to message with jan- for about 15 years now. Mx engines and platforms are constrained in ways drag applications and road applicaTions are not - or your stock 300 would make 65 hp. And yes - raise the transfers on the yz and you will crush the power on the front side with a huge hole/dip as well. If you spend a little more time in your sim, using a powervalve design like the yz has (which isnt simulated accurately from a flow perspective either) you will quickly see the pipe designs work extremely well when the valve is down and when its up - and provide wide power. As you go to a larger belly design that doesnt fit on the bike without causing riding issues - the front side power falls off bad.

i have never seen that black coating on any of my bikes, but never had a yz, only tm, and gasgas

@HPRaceDevelopment

7 ай бұрын

If you don't over rev a lot, you wont see it.

@markilleen4027

7 ай бұрын

@@HPRaceDevelopment im on the road most of the time banging it out

@HPRaceDevelopment

7 ай бұрын

@@markilleen4027 definately not revving very high then some motocrosses will rev their bike under no load like a jump as high as it will go

@markilleen4027

7 ай бұрын

@@HPRaceDevelopment oh no she be getting banged out trying to keep up with me friends on street bikes, the bike would spend most of it's time pinned in fifth and forth on back roads, no jumps,

@HPRaceDevelopment

7 ай бұрын

Yeah it wont rev high enough under load @@markilleen4027

37.5-40.3?! Apparently I don't rev that hard, I've never seen that carbon build up all the way back to the Reed's?!

@HPRaceDevelopment

10 ай бұрын

37.5-40.3?

why not show the graph of the same bake before and after the changes you made?

@HPRaceDevelopment

4 ай бұрын

That bike was never here in stock form initially - got it for a dyno tune after the work had been installed and he had some power shift requests We have in the thousands of yz250 dyno pulls - stock ones as shown with the bike we did show

@chyrt

4 ай бұрын

@@HPRaceDevelopment You do good work, it seems. And know what you are talking about. But what I mean is the dyno pull of the bike when you got it in vs when you were done with the modifications you made. Sure the yz250's you showed in this video are theoretically almost the same, I just prefer a more scientific approach. Your video's are of a quite high standard, I'll keep on watching you

@HPRaceDevelopment

4 ай бұрын

As I said - on this bike we didn't have it here stock. I lucked into having the other bike here at the same time - and shot the video...If you don't trust our work or content - sorry. We are the ONLY shop publishing ANYTHING and we do our best to be fully honest and transperent on all subjects we decide to show. What we don't show is how HORRIBLE the vast majority of what is sold by what are considered "good shops" truly is. @@chyrt

@HPRaceDevelopment

4 ай бұрын

We could have just shown NO stock bike for reference - as that's how it would have been shot had the other bike not been here to show a same day same tire/wheel same make and model bike. The other bike had a fresh crank, top end, cylinder and that vhm head, pc pipe and silencer and all new electrical system we had just installed. I'd say a pretty good representatin of a "not so" stock bike@@chyrt

@chyrt

4 ай бұрын

@@HPRaceDevelopment Truly, I believe you. I learn a lot from you video's and am grateful to be able to watch them.

3.5hp

The black oil in the cylinder is from the right side crank seal leaking

@HPRaceDevelopment

Жыл бұрын

This is just factually innacurate. Its from the fresh charge burning inside the cases during over rev.

having sut in your ports isn't DUE to a rider that revs his bike a lot that's what you get when you try to baby a 2 stroke like a 4 stroke that's why you have to run 2 strokes hard or else, they will foul up.

@HPRaceDevelopment

Жыл бұрын

Sadly that's completely innacurate. This particular owner is proof of that - he's a pro and LOVES to rev. With owners that rev a lot, on a 2 stroke, the exhaust gasses don’t have enough time to get out, and enter into the transfers. When this becomes extremely, they actually burn into the transfers the fresh charge. But it burns poorly and is overly rich due to inert exhaust gas dilution and it’s really sooty. We have hundreds of example historically of this behavior. Owners that baby their bikes and don’t rev enough have squeaky clean cases and transfers. The fresh fuel is a great solvent and cleans everything

Oh come on, not even showing the port work?

@HPRaceDevelopment

Жыл бұрын

The point of that would be?

10hp is too much

@HPRaceDevelopment

Жыл бұрын

Im lost… but 10 would be a huge improvement!

kill the music mate

@HPRaceDevelopment

7 ай бұрын

You can thank youtube amigo

Just buy a stock ktm 250sx 53 horsepower better Engineering .

@HPRaceDevelopment

10 ай бұрын

not 53 - but yes more power stock by a large margin.

Does this dude have instagram

Get it up to 13.5k RPM and then let's talk. Kids play in the dirt, men ride MotoGP

@HPRaceDevelopment

Жыл бұрын

13.5 on a 250 two stroke doesn’t exist for any single…sorry. that would exceed any piston speed ever used in F1….or moto GP…just saying.. Our 250f packages exceed 15k….in pro racing where budgets are bigger they exceed 17000.

@ahole5407

Жыл бұрын

@@HPRaceDevelopment you might want to look into what the guys over at ESR have done with these MX motors. Also BRC, Seay Performance, or ProKart and Steve Gleasons PK 250. 85hp and 13,500rpm. And with potential for more Tuning an engine means that the only stock part of the motor you have left is the cases and they will be modified or CNC billet. Seems like ppl have become lazy and think that throwing a pipe on, a rejet and chamfering the ports is considered a "high state of tune" No, custom pipes, programmable digital ignition, custom balanced crank, high end bearings, piston, cylinder, tranny, intake, reeds carb, ect... You get the picture. And top end rebuilds every 6hrs and bottom end every 18-24hrs Easily $10k in the motor and most dirt rider will bitch about buying parts that cost more than $500. We don't care about the frame. We use the motors. And the reason they don't get developed more is because there are not many of us doing it. Two strokes were banned on the street due to emissions. I own an Aprilia RS and still ride it. But taking a kart engine and shoving it into something like a RS50 or Honda rs125 both weighing under 190lbs wet and being street legal is the goal. The top superbikes in the world have a HP to weight of about .5 HP per pound. You see where this is going. We've already proved the 150 kart motor in the swaps. Now it's time to build the fastest street legal two-stroke that isn't just a drag bike.

@HPRaceDevelopment

Жыл бұрын

@@ahole5407 I am very familiar with both BRC and ESR, assuming you are not referring to the USA ESR (also familiar). I've had multiple talks with - as well as seen the stuff that BRC did before BRC was a company. When Riley was building 125s cloned from the leaked aprilia RSA images I knew every internal detail. I still have the pictures floating around. Additionally - the absolute MOST powerful mx based 250 makes around 62 hp on our dyno used in world karting. It's all custom, one off. You will NOT find an mx 250 that will peak at 12500. It will REV that high - for very short durations of rod life. Simple basic math can easily tell you these things - it's just NOT reasonable with a 72mm stroke - or a 68mm stroke if you build an overbored, under stroke version of the mx 250. Just leave it be my man - if you want to actually contribute - then why don't you bring one of your high fabled motor builders packages by - and I'll post it up for the you tube world to see. I've had all of europe's "best offerings" for the mx world on the dyno, and we EASILY have it matched or covered. We build MX bikes for MX applications. Occasionally we build karting engines for karting applciations. The requirements are far different. The budgets are far different. You want to pay my fee to build a 13500 rpm 85cc that peaks at over 30 horse, be my guest. Been there - done that.

@VitaliyKhomich

Жыл бұрын

​@@HPRaceDevelopment @ahole is a keyboard warrior

@HPRaceDevelopment

Жыл бұрын

@@VitaliyKhomich He is lacking some brain cells

Does this dude have instagram