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mixxer

Doogee's Bro's Hawk Porting

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Big topic.... Can't get into it all now... Just start it...

Bottom line... Doesn't matter what you buy or do to your engine... Every single piece breathes through the ports...

Everything is either handicapped or enhanced by the porting dynamics.. 

 

Porting IS a science... It is physics and fluid flow ... Pure... But only simple if you understand the basics that govern all of this... And a buttload of time and experience doesn't hurt either... But the knowledge is first... Otherwise you are playing a game of darts in a pitch black room....

Next up... It doesn't matter how much money you pay ... You have zero guarantee that you are getting real enhanced airflow... More than you will ever believe ... The majority of port work you get is amateur ... Big/ shiny holes are not magic of any sort... Plenty of places actually hinder the performance...

On and on... It's gross... And it's true....

The big magic is to deliver responsive , high volume, high VELOCITY flow ... That adheres to corners / radius/ changes in direction... And circumnavigates obstacles efficiency....

I will come back into this...

Just wanted to post some pics of Two Brother's Racing "port work"...

You can buy a hammer... It doesn't make you a carpenter... You can buy a grinder..  doesn't mean you know shit about porting ...

These ports are huge... Slow... Poorly contoured.. 

Bowls are too big to make adequate seat cuts for low lift flow gains... Etc etc etc...

Doogee is going to get bigger valves... Not to make bigger bowls... But to correct the seats and gain flow...

I really wanted to assess the ports and change the intake geometry...

Plexiglass over combustion chamber...

Shop vac nozzle in exhaust port..

Swingarm lamps throw light through plexiglass and into port from behind me... Vacuum pulls all chips the funk out of my way so I always have a 100% clear port picture...

I'm soooooooo picky about seeing a clear pic at every second....  And I'm not sucking chips and port debris into my lungs either

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Hogged out sewer pipe porting...

No Venturi...

No velocity....

Just a hole....

Port walls were too smooth...

Rough walls break surfuace tension and make laminar flow increases at port wall boundary layer... I'm roughing up and leaving double cut carbide texture...

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Edited by mixxer
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Shit short side radius/ SSR work...

High speed airflow will not adhere and overshoot the short side .... Choking airflow with the airflow itself... No feed to back side of valve...

I have seen worse..  but this isn't good...

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Another view of shop vac and plexiglass... Clear / well lit ports to work on

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Bowl diameter too large...

No room for extra seat cuts to enhance flow around valves at lower lifts... 

Just changing Port texture with carbide burr...

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Enormous and inefficient low velocity ports...

But now cleaned / contoured/ and with correct surface texture ...

Ready for the magic....

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More after the epoxy fully hardens to the point where I can finish it....

This setup is going to make more power at every single point in the rpm band...

More bottom end...

More midrange...

More top end....

More horsepower.... 

And a shitload more TORQUE and RESPONSE ... across the entire range ... from Idle to where the rev limiter pulls the plug on the party...

Bet on it...

More pics after I can finish it all up....

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Love learning this stuff.
Soaking it up as much as possible.
Thank you Mixer

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  Dang mix, That's awesome. Guess I'm gonna have to send you the front head too. I'm going to get some new intake boots and blend them into the ports. As to the intake valves I'm thinking Chris Schumann could make some but I'd really like to avoid lash caps. Both Ferrea and Kibblewhite have said they can make some but they want exact detailed drawings. Measuring the valves isn't too hard except for the keeper area. I don't know the radius and it's very hard to accurately measure without an 'optical comparator'. I've checked the parts fiche and about "50 million" Honda's use that same keeper pair. I could send an existing valve off and say; "duplicate this except for a 28-28.5mm head, but if they lose it I'm hosed. Stock valves are no longer available and the special, 27mm, one's that are in there can't be found anywhere. JD Hord told me he uses "Rev" for his 28mm valves. I've also contacted them but they haven't replied with a positive response, said they couldn't find his specs/records. I'm kinda at the "good grief" point. I'd like to say; "Look guys I want a Hawk GT valve, standard Honda keeper groove, "x" distance from the end, "x" stem diameter, "x" overall length" with a 28mm head. I've actually tried to find a stock valve to send off and say duplicate this except for a 28mm head, but I haven't been able to source one.

Edited by Doogee57
punctuation, spelling
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  Ok John, I did a little checking on the compression ratio. The Honda manual shows it at 9.4 to 1. That's for 647cc. Doing the math shows that at 698cc (82mm bore) it works out to 10.15 to 1. That's theoretical using a flat top piston like stock. As you can see from the piston I sent you the wiseco pistons have a substantial dome. Wiseco is claiming 11 to 1. That's seems about right. The area/volume near the intake valve looks to be about 20-25% of the dome. If I shave that off to improve the chamber/piston relationship it calculates out to 10.78 to 1. That's not too bad. I'll think I'll do it.

  Welding up the chamber in that area (a major, major undertaking) and cutting the piston for an .032"-.035" squish I "guesstimate" might get me 11.3 to 1 or so. I don't think it's worth the hassle for a street build. Now, if I was building an unlimited budget, billet crank, titanium rod, 11,000 rpm, full race, motor,,, yeah, then I think I'd go for it.

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   And by the way John, what did you think of the exhaust port? I did a little work in there. There was a big flat spot between the guide and the seat area. I rounded that off and streamlined it like I've seen in the pics of your Venom CRF250r head as well as some of Ron Hamp's CRF250r heads. Also, the hump where the guide boss blends into the port further downstream doesn't look like it can be smoothed down much because of how close you would come to breaking thru into the spring seat. I went as much as I dared there.

   To me, the exhaust ports look like 2 Bros didn't do anything. They looked pretty much stock, although I don't have a stock one to compare. Surely if they had done any work in there they would have done something around the guide boss area. It looked virtually untouched.

Edited by Doogee57
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Yeah Doug, you don't have to make this an enormous undertaking .... The bike is going to work so much better with the easy changes, even without changing valves out...

I like the idea of the piston cutting mod a lot... You won't miss the compression at all ... Especially since it's going to be packing in more intake charge..

Fresh pistons with your mod will even scavenge the cylinder better for a more powerful/ less diluted burn...

Add in the porting changes...

And if you can make the smaller diameter initial headpipe pieces...

What a tremendous change all that will make.... No downside...

Don't break the bank or drive yourself crazy... It's going to be an awesome re do...

And...

You sir are a master of all fabrication... You are going to have this head to use as a model for the other one 😀

I'm far too lazy to do 2 ...lol..

But I really really wanted to get into one of them after you posted those first pics...!! 

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The exhaust port has quite a bit of volume to it... And the work you did already looks good... I wouldn't want to slow velocity by taking much more material out anywhere...

The biggest help the exhaust port will get is if you can not have it step out into the oversize headpipe arrangement and lose more velocity and vacuum ...

Edited by mixxer
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As a side note...

All the work we are talking about will make for a much stronger vacuum signal operating on those CV carbs...

It will sharpen throttle response markedly....

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2 hours ago, mixxer said:

. I wouldn't want to slow velocity by taking much more material out anywhere...

   Yeah, that was my thinking. And I was also thinking that with the mods we're doing that sticking with the existing valves wouldn't be too much of a compromise. The gains available in just the ports and the head tubes look to be pretty substantial. The 2 Bros work is decidedly "old school". You and Ron Hamp (and even Honda) have proven (on the carbed CRF250's) that there is power to be gained across the board with a more sophisticated, high velocity port design. I greatly appreciate your help on this project.

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Very glad to be part of it Doug...!

BTW, your brother is very fortunate to have you as his sibling... I don't know how many of us have kin spinning wrenches and worrying about our rides...but it's gotta be nice..

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7 hours ago, mixxer said:

I don't know how many of us have kin spinning wrenches and worrying about our rides...but it's gotta be nice..

   It kinda works both ways. He's also got a CRF250X and he called me asking about an 05 "R" (just like mine). Said the guy wanted 400 bucks. Had the rod sticking thru the cases. The rest of the bike was primo. I told him snag it. Then when he got it I said; "Send me the forks. Send me the shock". So now I have 2 sets of suspension for my 05 "R". I re-valve the spare set at my leisure then take em to the track. Ride a session, pull off for the kids/80's to go out, swap the fork or shock, and then the kids are flagged off after 20-25 minutes. Go back out and test. Got my "R" workin really sweet now. It's kind of a luxury.

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   It kinda works both ways. He's also got a CRF250X and he called me asking about an 05 "R" (just like mine). Said the guy wanted 400 bucks. Had the rod sticking thru the cases. The rest of the bike was primo. I told him snag it. Then when he got it I said; "Send me the forks. Send me the shock". So now I have 2 sets of suspension for my 05 "R". I re-valve the spare set at my leisure then take em to the track. Ride a session, pull off for the kids/80's to go out, swap the fork or shock, and then the kids are flagged off after 20-25 minutes. Go back out and test. Got my "R" workin really sweet now. It's kind of a luxury.

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The only real way to know if what you are doing is improving the flow and not hindering, is with a flow bench. Costly and takes a lot of time to make the stands for every head. I ended up using plexiglass. Especially if your working on a twin 4 stroke. It’s the only way to make sure that they are flowing equally and find the max lift for calculating a cam. The pic is of the exhaust port on my own bike. I had a shop cut the seats for oversized valves. I port and polish the exhaust as smooth as possible, but the intake is a different story. As I’m sure you all know about this, but it is for those who don’t. Intake needs to be rough, not smooth. The gas needs turbulence. It’s a real slow process and that’s why it cost so much. Now they can be machined, but not entirely.IMG_1161.JPG

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29 minutes ago, Contractor said:


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Good of you to point out and old fallacy that has nothing to do with port flow...

Shiny ports... 

I will polish an exhaust port just to make clean up easier...

And sometimes I will semi polish just to make irregularities in the wall apparent... Fix that...and then go for the 50 Grit or carbide finish that actually improves wall flow by breaking surface tension...

The reason to be ok with polishing an exhaust port... And we all secretly want to shine up our work... Is that the shiny surface doesn't impede flow for long.... Carbon will coat it up naturally... And the flow will increase on it's own...

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Good of you to point out and old fallacy that has nothing to do with port flow...
Shiny ports... 
I will polish an exhaust port just to make clean up easier...
And sometimes I will semi polish just to make irregularities in the wall apparent... Fix that...and then go for the 50 Grit or carbide finish that actually improves wall flow by breaking surface tension...
The reason to be ok with polishing an exhaust port... And we all secretly want to shine up our work... Is that the shiny surface doesn't impede flow for long.... Carbon will coat it up naturally... And the flow will increase on it's own...

Pretty much everything you do on a engine will eventually breakdown. The valves, the spark plugs, the exhaust header etc. That polished port will remain clean for way long. It’s kind of like saying that there is no good reason to crosshatch the cylinder because it will diminish anyway. Everybody does things differently, I prefer to take the time to polish the port until there is nothing possible to restrict flow. If I have the bike, I also match up the intake and exhaust as well. This how I was taught and have always done. I don’t tell anybody to do anything my way. That is the best way I look at things. Happy porting. Lol

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