[morgan]

^^^^^^ Slotted mandrel, 6 bucks from CC Specialty.

 

[mixxer]

Projects I have been on lately have been building a 05 KTM 450 SX for my 16 year old sonny boy... He has ridden a bit his whole life but was just ho hum about it until I bought the KTM to build for myself... He wanted to take a ride on it and I told him to be careful and told him it will probably scare the crap out of him... Oddly enough it was love and lust at first ride... So I told him it was his and he was going to strip it to the bare frame and rebuild it with me...

It was a great father son experience !! The KTM rfs engines have some of the best ports around , probably THE best , for making a hvp down draught intake port... And the dual exhaust ports are excellent also...

I have done a lot of KTM rfs engines over the years... Lots of them for tt racers... Always wanted one of my own... So I scored a heavy discontinued 14oz flywheel weight and went to town on a hvp raised floor epoxy port setup...

I have owned and modded crf450s.... And they were impressive... But this KTM setup is without a doubt the hardest pulling 450 I have ever owned.... The order of the day is short shift it and sit forward to fight the front end lift.... Sam thinks its a thrill... I think its obscene... Lol.... Above my skill level to make use of for sure...

Sam liked the idea of a father and son KTM clan... So I bought a fairly abused 02 KTM 250 exc 2 stroke..... Dads going retro with a 2 smoke...lol.... Found a rare NOS German DOMA KTM factory race pipe for it... So far that's the best thing about it...lol... Lots of work ahead...

Also new on the yfzcentral forum I wanted to show people in my how to port thread that 80% of the power gain comes from 50% of the port work....

I asked if any members had dyno tuned a carb and fuel injected model yfz and would be willing to send the heads to me in the name of technical info sharing.... A couple guys had and agreed and did send me heads... Minimal work for maximum gain.... I asked if they would photo document the heads when they got them back and then post dyno sheets after the re tuning post porting.... Agreed.... Heads are back in the mail this week...

Lots of fun stuff

 

[duke416ex]

I found a couple heads at home I will try to post up soon. One is fairly stock and one came off a blown engine that was ported wanted to see opinions. Plus got a couple heads I want to try.

 

[gboezio]

I love KTM's too, I have a few freinds that bleeds orange
I'm into chassis and suspension, but I will come back for more power, waay more !!

Thumbs up for beeing a super cool dad !!

 

[mixxer]

Good to hear from both of you guys... !!

I'm hoping to post up some of the KTM head mods when I get a block of time...

The guys testing the Yamaha heads that have only the work done that will make the majority of the gains will be quite interesting..

 

[mixxer]

Mods to my KTM 250 engine.... Miracle of miracles I found a new old stock DOMA KTM race pipe for my 02 on eBay... Doma is out of Germany and they make KTM pipes that KTM themselves uses as upgrades and as KTM race accessories.... Dirt Rider magazine did a big pipe shootout for 2 strokes and the Doma pipe took top honors.... They haven't made any for.my bike for years since its a 2002.... So once I got the pipe, it made the rest of the restoration of this bike seem worthwhile... But boy oh boy.... Hillbillies like the term "good enuff" to describe everything that isn't repaired correctly.... The project is more of hillbilly erasing than it is a rebuild / Restoration.... My son sam likened my bike project to one of the abused animal rescue shows... And it seems like a good comparison... So... Got the Doma pipe... Ported the cylinder for more midrange.... Upped compression with a thinner base gasket (moose gasket kits give you 3 different thickness base gaskets, from 3rd world country use, to jetted correctly with good fuel use compression choices) steahly heavy flywheel weight (came with bike) ... Original reed cage did not need replacing... Excellent design for velocity and longevity of reeds...

Maybe just a couple weeks before restoration of my KTM 2 smoke is complete...

 

[mixxer]

Update.... Doma pipe hits way too hard on the 2 stroke for woods use... Might as well replace the throttle with an on/ off switch...lol... FMF Gnarly pipe on order

 

[mixxer]

I just finished setting up another trx head for Josh Romero ... Multi time kicker arenacross pro champion... I think it's going to be his 7th pro championship...

 

[mixxer]

It doesn't matter if I use the Doma or the fmf gnarly pipe...

The Ktm 2 stroke is just too violent of a power delivery for me

A few weeks ago I traded the Ktm for a yz450... I have had several yfz450's.. But this is my first 5 valve / 2 wheel Yamaha...

The guy I traded with said it was his first 4 stroke and while he knew it was more powerful overall compared to a 250 2 stroke, he thought the power delivery was too boring...

I actually love the yz... Much more rideable ... I'm going to mod it for max torque... A project is born

 

[mixxer]

The real advantage of 5 valves is they can make tremendous torque and midrange.... But if you focus on top end, you give up the real advantage... With the 230 pound weight of the yz, I'm going to focus on early torque and gearing to let the bike pull

 

[duke416ex]

So are we about ready to start the online porting class?


I have a trx head and a yfz head to play with.

 

[mixxer]

I have complete pics up and info for a 4 valve here ... And the same thing for the 5 valves on the Yamaha forum... As far as I know, nobody has put up more info than that anywhere

 

[mixxer]

I have to add in that the best heads I have ever worked on in the off road world are the beads on the newest crop of yz250f fuel injected heads... 2015 and 2016 models...

They are crazy good castings on all fronts.... If anyone gets a chance to study them...do it...

 

[mixxer]

"#VenomPower..Appreciate you,went with a Stage 2 Cam over the HRC.Wow.Won all 3 championships with that latest motor,People think I have a Big Bore all the time,funny sh!t."

That was yesterday's text message from multi time Kicker Arenacross Champion #44 Josh Romero....

I don't think Josh has never not won a championship since I have been setting up heads for him... Racers need throttle response you can use to control a machine with... Instant hit... Killer torque... And solid over rev to the limiter...all in endurance engines with long term reliability

Just the kind of engines I like to make....

 

[duke416ex]

Thoughts?

 

[socksandammo]

Thoughts? Ya, MAX turbulence! I wonder if its effective though, never seen that before.

Sent from my HTC using tapatalk.

 

[mixxer]

That is extra work for no advantage over simpler setups....

The deal is that you don't want a smooth surface on your intake port.... air behaves like a fluid and fluid sticks to smooth surfaces...

Fish have scales and bird feathers have a similar texture to break surface tension and grip of both air and water ... so either can move faster and more efficiently through the "fluid" they move through...

That's why you don't want a smooth intake port... air will stick and move slowly at the boundary layer of the surface.... less flow.... like how you can drive 70mph through rain, yet it sticks and moves slowly over your smooth windshield...

Using rough Sanding rolls ... or better yet.... using your carbide cutter to leave a rougher finish on the intake port .... makes for more and faster airflow....

The whole golf ball thing was done years ago... and never caught on... because it is more work for no more advantage....

I actually posted pics almost 10 years back of me dimpling a port surface to allow for epoxy adhesion... but said that I was doing golf ball port for massive flow instead of what I was actually using it for .... the world went mad....lol... that's when I first saw that pic Duke posted...

 

[duke416ex]

I came across it on a car page, looks awesome, like a good background shot. I remember several years ago a few motox companies selling dimple valves but they didn't catch on that I know of. Idk, maybe all the pros have them.

 

[Redrider7]

I know this is a resurrection but felt like I should add my story. I read this post about 6 months ago when I was really wanting to do some power mods to my 05.. Finally had to put a crank in last month so went ahead and did some port work as well. I used the info in this post to shape the intakes, I went wider on the port floor, a little reshape of the ssr, and just a little straightening of the sides, and just clean up and guide treatment to the exhaust side. I rounded up the guides and spring humps so there is a nice little track all around them. Blended the bowls to the seats and did a fair amount of unshrouding in the chamber.
Results
I noticed a huge improvement in low end response time and it never stalls in the low rpms anymore. Pulls harder without question in the whole rpm range. I ride trails 90%. I don't have access to a dyno for power results, but it's much more fun to ride. Just wanted to say thanks mixxer.

 

[bowlingarage622]

That is extra work for no advantage over simpler setups....

The deal is that you don't want a smooth surface on your intake port.... air behaves like a fluid and fluid sticks to smooth surfaces...

Fish have scales and bird feathers have a similar texture to break surface tension and grip of both air and water ... so either can move faster and more efficiently through the "fluid" they move through...

That's why you don't want a smooth intake port... air will stick and move slowly at the boundary layer of the surface.... less flow.... like how you can drive 70mph through rain, yet it sticks and moves slowly over your smooth windshield...

Using rough Sanding rolls ... or better yet.... using your carbide cutter to leave a rougher finish on the intake port .... makes for more and faster airflow....

The whole golf ball thing was done years ago... and never caught on... because it is more work for no more advantage....

I actually posted pics almost 10 years back of me dimpling a port surface to allow for epoxy adhesion... but said that I was doing golf ball port for massive flow instead of what I was actually using it for .... the world went mad....lol... that's when I first saw that pic Duke posted...

Mixer how much to port my head for me sent u a pm


Sent from my iPhone using Tapatalk