Gary,Jim, Mailman, and other members please accept my apologies


XS650 Guru
Reaction score
North carolina
It has been brought to my attention, which could have been done privately but it wasn't, that my porting numbers were off which I truly had no idea they were inflated. When I first started my porting adventure I searched the web for a porter to flow my work and I found a guy who became a very good friend, who I thought was my friend. On the very first head that I had him flow, I asked him if his calibrations for flow conversion were accurate because I became suspicious the numbers seemed high but no other Xs head flow comparisons existed to confront him because no one was posting flow data, even Bob Bertaut(spelling) who was using a Super flo 110 at the time refused to share his flow data,he would share porting photos but that's the extent of it, so I just continued to have my friend do to my testing and that his conversions were accurate. Later Jack
Last edited:
So with that, I'm asking the moderators to delete all my porting threads as it was never my intent to mislead any of the members of this forum. Later Jack

I think that would be a drastic response Jack, you’re among friends here, we are all ( for the most part ) just hobbyists. Your experiments with head flowing was very informative and interesting to read. It would be a shame to delete it.
My opinion….Bob 😉
I feel that is quite drastic Jack.
Your thread has been and will no doubt continue to be inspirational.
I would hope that you would reconsider...

Espeacially since that is incorrect...
I didn't say anything about your numbers Jack.
I was talking about MY numbers on MY bench.

As I stated, the two are not comparable. From the beginning I have said that the only intereest in in percentage of gains.
It was coincidental perhaps that the numbers aligned initially.
I have not once said anything about your numbers being wrong.
I made the error in my original calibration using the coefficient of the orifice plate because that was how it was initially explained to me. There were issues with the numbers. I owned it and demonstrated the how and why in the recalibration video. The testing doesn't lie.
Everything I have presented not only can be but has been repeated and repeated.
Everything I do is based on data which is specific to MY bench.
I have made it abundantly clear that I have NOT tested your head, only a copy that was obviously not built to your standards.
Your head's flow numbers are correct on the bench it was flowed on. That bench was a calibrated Superflow.
Your head tests repeatedly the same so I see no issue. If you are happy it is all that matters.
Of all the testing I do the CFM numbers are the LEAST important data.
For some people it is the only data and the only data that matters.
There are many ways to skin a cat.

This posting is not about your head or your numbers. It is an explanation of how I arrived at the correct calibration for MY bench and how those numbers are verified using standard formulas utilized by almost everyone in the porting world. Formulas which have been created and tested by SAE among others.
My numbers are correct on my bench. I can verify my numbers in numerous ways and have done so.
It is unfortunate that you choose to take the approach that I have said anything about your numbers being misleading.
All I have done is present factually the journey I have undertaken in making certain that my bench is accurate and I have data that is reliable.
I didn't create the formulas or the laws of fluid dynamics. They exist.
Reconciling your head's performance with those realities is up to you.
I prefer ALL the data to be in alignment when porting a head.
If something is standing alone way out of the box it is an issue that should require more investigation and be resolved.
If you take offense to me sharing data and explaning how it is inter-related, I apologize.
I don't understand how that becomes personal for you.
But that is what this is going to be about. DATA. Formulas used for verification or to identify issues.
Porting... it's complicated... .. I know a fellow who has "salt fever "... Bonneville... he built a flow meter... to measure the speed of the air.... also filled the ports with rubber.... let it cure... then placed in water so that they are equal with the fluid displacement measurement... then he raised the top of the head.. for longer valves to match the higher lift cam had had made.... I wonder how they ported King Kenny's Xs heads.... 😎
Hazy memory; lore had Lisle? port Yamaha heads for flat track, then yamaha sent one back to have a short run of race heads made to match his work?

From the factory racing guide;
An Open Apology....
I am honestly set back by this.
It has affected me. Jack is one of my most revered members.
I made it clear many times over his epic thread has been my inspiration.
I sent him the following apology in a private message which really doesn't contain anything that can't be shared.
I got to thinking that giving him the aplogy in "Private" wasn't enough.
There may be members that don't actually realize my admiration for this man.
So I would like to publicly apologize for not finding a way to make this better.

You have been the very inspiration for what I do.
My posting/thread wasn't and never has been in any way an effort to diminish your hallmark work regarding the D Port.
I realize you had hoped that my testing would verify your work but it has never been about verifying any concept or idea.
It has truly just been an attempt at discovering factual information and using that information to move air..
I believe that just like myself, you attached too much weight to the initial flow numbers being so close.
You must realize how difficult it was for me to move away from that position once I understood that the numbers simply did not align.
Especially since I had pronounced them publicly. Even in the beginning I emphasized that as close as they were the numbers were not truly comparable as they were flowed on seperate benches (calibrated or not).
This last posting that upset you off was not an effort to say your numbers are inflated. It was an explanation of the process I went through and how I resolved it. There are others that may find that information useful when calibrating their benches.
I don't see how I could possibly have tiptoed around the subject.
You can absolutely believe me when I say I wish I could have. I truly have great respect for you and what you have accomplished as well as how you shared your information and knowledge. I believe the information I posted is useful to others and it needed to be posted within the thread.
I could have privately messaged you with a heads up I suppose but would that have really changed the way you reacted?
Hindsight now says that I wish I had at least tried that route. If I took a misstep there I am truly sorry.
I try my very best to be as accurate as possible in my testing and in presenting it.
We obviously have different viewpoints on how we approach moving air through a head.
I have always thought that should be okay. I have always tried to be very respectful to you. You have earned it.
I ask that you please do not remove your epic thread. It carries great weight and I personally think it should have been a sticky.
Even if one were to think your numbers are high and I am NOT saying they are; it has absolutely no bearing on the reality of the gains you made.
The percentages of gains would not change. Since the stock head and the D Port were tested on the same bench the relationship/percentages of gain would be unchanged.
In other words the magnificence of your work is in no way diminished either way.
I am really at a loss as to how you think I should have gone forward in my thread.
The math says 200CFM is too high. It says that in each and every instance.
A 150 CFM through an engine with anxs specs and 750cc is shown to be enough air for around 73hp at around 7200-8700 rpm
200 CFM is calculates to about 95hp at around 9800-11,300 rpm.
The first one is in line with a high performance xs650 with a 750 bbk.
The last one is not achievable. Every single formula used within the industry says the same thing.
Since the head has been ran and has had glowing reports about the power created we know something is amiss.
I never mentioned your 200+CFM in the posting that upset you. I only discussed MY numbers and tried to demonstrate how they were invalid.
In my opinion which you may not think much of, your work is nothing short of amazing and I hate that you feel it has been dimished in some way.
Obviously I alsways ask for correctness and if there is something that you know that tells me all these standard tests and formulas are wrong I would want to know.
Lastly I just want to say that I am sorry if you have felt attacked or hurt in any way. My only intent from the start has been to share information and discovery. I do not concern myself with trying to look good which is why I can accept and correct my errors whether discovered by myself or brought to my attention by others. I hope you will accept my apology and know I understand if you choose to no longer interact with me. I really would like to get beyond it together.
I am honestly one of your biggest fans even though we have never really been "friends"
Thank you for all you have shared.

Wallace 153.jpg
Wallace 200.jpg
Last edited:
I just want to make it clear, that I'm not upset with anyone for anything. When Bluz mention that his calibrations were off,a bell went off knowing
that no two benches could possibly be this far off in CFMs, it is just impossible to have one bench so far out of calibration and I'm just totally devastated
with all the hard work I put into this head I'll never know the true actual gains made. After doing some deep research, I now know what a stock XS head
flows on a Super Flo 600 at 28".There will be no deletions of my porting post.
Your true actual gains have not changed.
The actual CFM numbers yes.
Applying your gains percentages to the flow numbers you have for a stock head should get you pretty close to what the D Port flowed.
If you so desired.
Jack I could not care less what the actual numbers are, gains yes. Your thread has encouraged me to attempt porting it is very useful. In fact without your thread I would not do anything more than a casting cleanup.
I am greatly relieved you are not deleting your posts, thank you for posting them.
Guys, as i usually do not get too much, or don't feel a high affinity to forum small talk, but as being said one bench measures this one bench measures that!
Repeatability and measuring tolerance are the key words here, at least, in my book.
Furthermore it also always depends what orifice coefficient gets used and how the to and fro conduct at/around the orifice/vena contracta is designed as this can change measurent data also distinctively
Everything else can be read in books about fluid mechanics.
I usually on purpose do not post pictures about my numbers as:

1. They mostly serve me, (among other measurements) just for interpretations and approximations and,

2. Most important is that they're reliable and repeatable with emphasis on a high repeatability and low error tolerance.

Kind regards and good evening to all of you

Last edited:
Your true actual gains have not changed.
The actual CFM numbers yes.
Applying your gains percentages to the flow numbers you have for a stock head should get you pretty close to what the D Port flowed.
If you so desired.

Your true actual gains have not changed.
The actual CFM numbers yes.
Applying your gains percentages to the flow numbers you have for a stock head should get you pretty close to what the D Port flowed.
If you so desired.
Years ago I was given a flow data sheet of one particular head that some considered the holy grail XS head but not me because no one head fits all
applications despite what some think and Shell Theut(SP) knew that also. Max flow came in at 181+CFMs at 500 lift I believe and exhaust came in around 140 CFM if my memory is correct, Flow on the intake came in hard around 225 to 300 lift, low lift was nothing to brag about, can't remember the exhaust cuz the data is on my old hard drive which can't be retrieved. I said to myself that no matter what it takes I have to at least come close to those numbers as possible as a goal motivator. That D port and exhaust belched out the smoothest flowing port sound that I've ever experienced and I knew right then I reached my goal when my friend said damn. Yes I understand the gains haven't changed but what has changed is that special moment of
reaching my goal finally. I have no beef with you Bluz.
It is a huge relief to hear you say that Jack.
It has been weighing heavy on me.
I know how shattered and conflicted I was when I made the realization.
I spent many hours trying to make those numbers work...
I was devastated for a bit. But I finally accepted and it made improvements to my work.
I have read some of that history but know that I am not flowing for motors built to that extreme.
MUCH much work with access to the best machining and tech. A mountain I doubt I'll climb.
There is the occasional nuggett to grasp.

I would say that you did reach a grail of sorts. Your numbers (gains) are VERY impressive.
I can say with certainty that they are not easy to duplicate. At least not with a different design.
It is the extra milling and the intake matching that has led me to the designs I;ve been working on.
The intake match isn't that difficult but some may wish to try different length intakes for tuning.
Just easier to be able to mate it stock. Part of the give and take.
If I remember correctly Spungle reported that his did not fit and he ran without them.
The head I have that Hugh ported did not ever have any I do not believe.
It was also ran without them. My numbers (gain wise) are approaching yours and I am still tweaking.
Although the approach is a bit different I am applying many of your basic principles.
Where the porters of those great heads of history inspired you to pursue this endeaver with passionl
I can say with absolute certainty that it has been YOUR work... YOUR head that has given me that same inspiration.
It is YOUR head that is the standard I personally have been using as the holy grail.
I am absolutely certain that I am not the only one.
You went beyond those that were an inspiration to you.
You have freely shared your knowledge, techniques, everything.
Your epic thread is a step by step guide that you gifted the entire forum with.
I do not need to tell you how secretive most every porter is.
Your willingness to share that knowledge and experience is unique.
It inspired me beyond just having a desire to start porting again (from my primitive days long ago);
It inspired me to follow you in sharing my journey... hopefully helping others as well.
Furthermore, I could not be more greatful that beyond your thread you have freely given me nuggetts of information directly and indirectly by pointing me to other sources and opening my thoughts to new ideas I hadn't considered. Some of which have been very promising.
You did that knowing I was going in a slightly different direction. You are a stand up, stand out guy.

And yes you can absolutely tell a great deal just by listening
You know quickly when it's off the track and it sounds so sweet when it is getting into the zone.
It is that sound that makes the work worth the while.
I could hear it in the video.
I am always beyond belief what you accomplished without access to the equipment I am blessed to have.

For me personally, the absolute fact that you have sprung up others to follow your path in porting these bikes is an even far greater accomplishment than the D Port which has in itself become something of legend in these pages. I know Signal and myself are at least two members that are doing this as a direct result of your efforts. There may or may not be others.. But I firmly believe there will be more. And that is because of YOU.
Creating a new batch of porters may not have been a goal, may not have even been a thought, but to have that effect is quite an accomplishment.
That is something you should be proud of. You are one of the forum's most repected members, especially when it comes to matters of porting.
Thanks again for sharing,
Last edited: