Yamaha had that progressive PV design in the RZ350 and TZR250 in the mid 80's. Not sure why they went guillotine here.

Great video, thank you for sharing!! Just some feedback, I wish the camera angles were closer and covering exactly what you are doing and was slower paced too. Clearly you’re a professional, but for us watching for the first time, it’s overwhelmingly fast and unclear. Thank you again for sharing and uploading, I hope the feedback helps for future content :)

How about trying a lectron carburetor and also a smart carb SC2

Less music. More bike

Have you ever dynoed 1989-1990 yz 125?

Hi guys it's me again to let you know that one of my ideas (butterfly baffle in the exhaust for shorter tuned length) has been built and tested please search "Two Stroke 3,5 HP to 28 HP in 7 minutes". Bear in mind I and the builder had never had any conversation about the subject so I don't know how he had a similar idea.

I love the no BS approach. I called for a motor build and derek flat out told me what is a waste of money. He couldve charged and made money on these things but he told me they make no more power. Hes been a gentleman to work with

I’m glad I stumbled on this video, 2hrs later I think I have watched all the relevant videos. Great info, and lots of it!, and thanks for taking the time to reply (you have answered many of my questions). Pity we are opposite ends of the world, otherwise my head was going to be in your hands already, although… the wold is a small place after all. G’day from down under.

Your videos are extremely interesting so I have three questions to ask. There’s been so much talk about a straight 250 vs 250 class. From what you’ve seen and tested, what is the most peak HP you can extract from a 250 2T vs a 250F and do you think it would be fair? Also I’ve been comparing the 300SX vs the 350s as I’m considering it for a next bike. In terms of peak HP what do they make on your dyno?

What an amazing video i would love to be an apprentice under you

Amazing videos am a fan and about to my own yz250 build thanks to you

😎🤙🔥

dude... you're awesome. take a break on making us all feel like students and post a video of you riding! 🤘

dude...amazing stuff

You still left a lot of material

What about octane i got an mc125 its hard to get 98 around here. Also concern bout plugs getting redish from experience on cars. Or try 91 or 93 as lomg as dont detonate

I have a 19 husky 300 tpi with 300 hours and I’ve loved every minute on it, runs perfect all the time. I have a 23 125xc tbi with 10 hours and so far it runs just as good as the 300. My main issue with the carbs is the crappy gas we have nowadays, if my bike sat for more than a couple weeks I’d have to clean the pilot jet even if I drained the carb. Now I just hit the button and go. I could see serous racers preferring a carb but for a weekend warrior I’ve been very happy with the efi.

Thank you so much for making this. I've been struggling with my mapping and I thought it was all in my head that stock felt better but clearly it's legit

Thanks for sharing, I learned a lot in 10 minutes.

Hey Derek, what’s your favorite exhaust system for the 23+ KTM 450s? Which ones have you tested?

You deserve more views than you're getting. Love what you're doing demystifying everything.

I think you better pull a few shock low speed clickers fully apart! I mean unscrew the blue anodised section of the high speed adjuster out of the compression adjuster ring nut assembly. You’ll find that the slow speed clicker needle bottoms in the blue section and not the port on the high speed clamp post. The clamp post has an oring on it…so where is the oil going to flow?? There is a small hole from inside to the outside of the blue section of the low speed clicker that allows the fluid to flow through. The high speed adjuster does not change the slow speed needle position! The high speed collar works as others have stated below.

Watching Gomer Balls Unbolt that Head made me Cringe…I would Never have him do Any work on my Bike after Watching That🤦‍♂️

🍀🍀💚💚

Ya, but why did added cc’s not benefit? That would have been nice to hear about.

Those barrel studs could of been cleaned before final assembly , @ 12.02 gunge in the threads (especially the long stud) will affect final torque for sure, great vid however

Is that with the euro map on stock ecu? Cuz there’s no way my 2015 500 is making close to that power and it’s fully desmogged.

What kind of hp do you think the Pro Circuit 112 have?

Stupid question. YZ85cc really picked up the pace. Yes absolutely 100% yz85 are competitive. My son is winning almost every race with yz85

@hp race development my kx85 2017 with a 100 cylinder and fresh crank seals is running scorching hot on the exhaust and cylinder after quick 3 min ride or just idling?

Hey man just wondering what rear tire is that

Has there ever been a good explanation as to why the new 2 stroke KTM EFI system doesn’t have a sensor somewhere inside the exhaust? There has to be a good reason as to why the aftermarket hasn’t cracked this code yet. Is it because the factory stuff is just impossible to crack, or is it just not worth trying based on the system as a whole?

Thanks Craig

Or put it in a drill....

Awesome stuff. Very informative. Soooooooooo much money for those cone valves. How much money is that per second gained on a track for a old fat vet? Lol.

Thanks, useful information. I'm running out of juice at high rpm

Is the cylinder liner made from cast iron?

The elephant in the room here is there was zero measurable wear on that piston. Don't change it if it an't broke. Maybe put rings in it but I bet there would be zero compression increase once the new piston and rings are broken in. 300's can do 200-300 hours on the factory piston. Most of the wear in happening in the barrel. If you want that fresh factory feel - replace the piston and barrel. Otherwise leave well alone - spend time getting jetting perfectly right for the day and you will get more out of the bike.

Thanks for sharing your hard earned information we are a third generation moto family and are struggling with getting our 2024 GAS GAS 65 to perform well some are better than others we have two and several of the people we race with are having the same issues the 23 didn’t seem to have these issues. My grandson is 9 recently got off the 50s he was super confident in Cobra it was consistent in the performance area he has to ride his butt off because he’s 105 Lbs so kids65-70 Lbs usually get to the first turn ahead naturally, I’ve been watching your stuff since I first found you when you got pulled into the claim gate debacle ( you guys got hosed for no VALID reason) now after a very long winded explanation have you had the time to develop a great top level race package for the 2024 65s yet? Have you found any of the bike oddities and what is the root cause, we have a few friends at KTM Daniel Blair and Justin Musket and they haven’t found the root cause but acknowledge it a valid issue. We may need a good race engine soon & maybe our WP cone valve kit sprung and valved for him, he’s really good but the new bike keeps us from letting him push to his ability it’s soft and scary because the way it runs and bogs intermittently. His Cobra 65s were good runners but he fits the GAS GAS better. Can you help? ❤🙏

Great video! What gearing would recommend on this bike?

After all these mods what would you say the CCs are now?

What's the maximum amount of fuel that the tuner can add? Is the fuel increment a percent change and the spark a degree of advance?

Fantastic job on illustrating

Absolutely love the in depth tech talk and explanation of engine theory and application, I can geek out on this stuff all day long and I learn so much from your videos.

Very cool video dude!

Bull shit

So is stock map zeros across the board ?

Was the tranny gears polished or anything done to them ?

How close is the crank hp compared to wheel hp on the dyno?

Did anyone see how the pipe is worth buying?