Re: Porting For XStreme Power

[jack]

In this picture you'll notice arrows on the outside of the spigot area and what you wanna do is match up the inside of the port with the inside of the spigot manifold to avoid any disruption in the flow to cause turbulance with cost HP in the long run.

You'll find that the stock spigot area the size of 34mm,perfect for 34mm R/S or Flatside carbs and depending on which carb you choice to use,take this area out to match you carburators spigot inside diameter. Again you'll find flow in the areas of the XS inatke port in the
1) Guide boss area ,so lightly trim this area you can either round it of put a sharp feather edge to it.( Use caution in removing material) better to remove alittle at first,then to have to return to replace because to much was removed then should of.

2) the bottom of the guide itself,just take a carbite cutter and round the guide to the back as far as it allows or lathe cut it for a professional appearance.

3) the spigot area is an area that holds back CFM and you can really enlarge this section beyond the standard route but again you must use a judgemental call here as to how much to remove cause it can and will slow the "Velocity " down and hurt filling the cylinder,throttle responce and low to mid range performance. On my personnal heads I'll take it to the edge to gain all I can get to make HP and Torque......Jack

4) the pocket itself, is the real key in my opinion to unleashing the CFMs and along with the SS Radious Turn. Work this area right up to bottom throat cut 60 degree cut ( it's dowm from the 46 degree seat angle) and blend it. You want a smooth transition from that point down to the guide and up to the roof sections. Look at third picture down for an example of this discription.

[jack]

This is a shot of the opposite port to show in detail what my ports looked like after porting. Just glance at the wall and the floor section and "REMEMBER" when working the "FLOOR and SS RADIOUS" just remove enough to get the a decent finish. If you remove to much from the floor section, you'll slow the air speed down at the SS Radious.

[jack]

This is the best example shot of the SS Radious and runner or wall I've got. Just take notice as to how smooth the turn of SS radious is leading into the seat area and the furthest section to left to right of the picture as to how the wall feathers down to the seat. This heads is HookTools and is probably my best work yet to working the SS Radiou and the floor.



In the first picture below ,I've high lighted the location where that big dip is and just smooth this area as best as you can but work this dip from the pocket out to the spigot point and you won't remove all of it but you'll remove a big portion and this will relief some air disturbance which could cause a stall motion decreasing the amount of CFMs at certain RPM ranges which leads to a drop in "POWER"




In the picture below, it fully shows how I worked the pocket,floor and SS Raious. You too can achieve the same results and even top mine,it just takes time and some patience. So go slow and easy and you'll all do fine.

This concludes my efforts to show how easy it is to port the XS head and to open the "Window " to the dark side of porting and I hope you'll take the opportunity to follow through in porting your own heads to further expand your knowledge and to help others who seek it.

I'd like to thank the following member for helping me in this thread, 50Gary for suppling a donar head for flow comparisons against a stock head VS a modified head

HookTool for allowing me to modify his XS head and take pictures for this project but most important to get real testimony from a true member to what can be achieved.

I would like to take this opportunity to thank Bob Bertaut in his efforts to passing along imformation to me opening the window even further in increasing the CFMs. I'm still in the experimenting stages with this vailuable imformation and the results will be posted at a later date.

But most important I'd like to thank the members of this board for being patient with me in getting this imformation posted,being it took longer than expected. Thanks Jack




In these two shots below are the methods of which I used to modified the SS Radious.I used a long cartridge roll mandrel to reach down in the port,then I proceed to use a light touch and worked the shortside in a manner of a side to side motion untill i achieved the profile I was looking for.



In this shot,I'm working the SS Radious from the combustion chamber to gain better access to work this area and to address the cap lip that sometimes is present(Just run your finger in this area to feel for a really sharpe edge and where there's little aluminum build up from the factory) and provide a smoother transition from the floor leading towards the seat area,to further enhance CFMs from dropping off at higher RPMs by reducing turbulance.

[mental]

Jack, again, absolutely awsome bit of tech. Thank you for taking the time to photograph and document this whole proccess. I hope to put it to good use some day.

Mental

[50gary]

Great job Jack! To many of the guys that have never done any of this type of work it's a god send to see it display and described like this. Most guys would be intimidated by this porting thing but you have taken the guess work out by a bunch. Thanks from a friend and board member. This series would be good to save and post in a "How To" section when we get the updated web site. Cheers, 50gary

[hooktool]

And I get to run the head!!! ;D ;D ;D I'll post results as soon as it's going. Getting pretty close. After I got the head on, I couldn't find the cam chain link that I put where I could find it. Got a new one today and hope to get the motor in this weekend. Still short an ignition system.

Thanks, Jack!

John

[Burns]

Did you end up putting a motor with this head on a dyno? I'd sure like to see those numbers.

I just scanned your amazing piece of work and am in awe at your dedication and the fantastic contribution that you have made to all xs lovers!

Unfortunately, rather than the "sculpter's touch," I have the fine motor control of a drunken hippo, so I won't be using any power tools on my own heads. But, I'll be taking this piece to the guy I locate who actually does have those kinds of skills.

If you have a recomendation for someone in this line of work please let me know. You have convinced me that a good porting job is absolutely the best thing that can be done to this motor no matter what the intended use for the bike.

thank you

[Burns]

I think you misunderwstood my question Jack. I wouldn't expect anyone who has busted his hump though the endless hours of work and study needed to master something as artful as porting to share his trade secrets. I wasn't asking that.

What I was asking is, can you recommend someone that I can send my head to? That is, someone who is in that line of work whose work you respect.

I've seen in your other posts that you are not taking that kind of work yourself.

[xsroy]

hi,,, jack,, anything on larger vavles? say 3mm larger intakes and 2mm larger exhausts? what is your email?, i'd like to talk with you further on this,,as to your work schedual and pricing< thank you

[xsroy]

ya i know bigger is not always better,,and the conservative approach usually beats hogged out anytime,, but was reading "building a better twin" article the other day where branch did a head for a magazine with bigger valves and 36 miks, 750 kit, , 1 1/2" dia headers 32" long,,shell #1 cam where they wanted it to have the braodest band possible,,,that was done around 1980,,now i know for the street is dosnt make sense to scream a 650,go for the torque and gear it up,,,anyways,,just gathering as much info i can when i can,thanks xsroy

[mercurymorse]

While it's not always a absolute must to install larger valves to increase a head's volumetric efficiency to make HP, in the case of the XS head, the valve throats are too large for the stock valves and smaller seats are not an option on this head. 2mm larger IN and EX valves will optimise this ratio. 750 Virago valves drop in. This will compromise your choice of camshaft lobe centers. Removing the valve pocket ridge, as shown in the Yamaha Racing Tips, is not recommended, as it hurts low and mid-lift flow. I would always choose better heads over bigger cams.

[crazypj22]

Virago 750( XV750) valves dont drop right in, if you fit them to stock head the installed height is too short and the springs get coilbound before full lift. (not good for valve train) you have to cut the valve seats oversize and for correct installed height. Its possible to cut seats so that the spring height is correct with 0.040" between coils and the actual installed height is slightly less than stock
PJ

[jack]

PJ........As for for inlarging the valves seats in order for correct spring height for the Virago valves due to the shorter stem,that's a really bad move,you do not want to sink the valve,you'll disrupts the fuel flow and speed to the seat,effecting how it enters the combustion chamber and cylinder decreasing preformance. Either install a valve with the correct stem height or stay with a stock valve or have a custom valve made.......... Just passing along a tip from what I've seen through flow bench testing ............Jack

[crazypj22]

Hi Jack,
if you sink valve into head it will only be in the same place as a stock valve (XV valve is exactly the same length as XS650) you do have to reprofile the combustion chamber to match the original configuration though. ( easy if you have the right cutters- I used Neway)
PJ

[superelbert]

One thing is to do a job such as this, another thing is to take the time to stop and document it underway!

I can only take my hat off!

Excellent work!

Having just got my XS, seeing the before-after pics was a real revelation as to the potential for improvement!!

After I found my compressio to be 152-3 psi on both cylinders, I decided not to touch the engine, but after looking through this post, well lets just say I got some inspiration!! ;D


Now, to my point...

Surface finish and port jobs seems to be a forever on-going discussion.

When it comes to fuel distribution, we have all heard the argument that a slightly uneven surface creates some turbulence helping to keep the fuel droplets in suuspension.

When I try to visualise a port with engine temperature walls and iar rushing down at several hundred feet per second, I struggle to visualize all that fuel drizzling down from the polished port walls thereafter to collect in various pools throughout the intake port! ;D

OK, there is of course something to this, but I suspect the significance (if any) may be overrated.
Would be usefull if someone told us otherwise!

Anyway, when it comes to flow, we like it to be laminar.
Smooth strata of moving gass slipping over a non disruptive smooth surface, that's the best.

But what can happen is this:
As the flow passes over an abrupt change of some sort, the smooth laminar flow may de-laminate it self from the adjacent surface.
This causes turbulence.. sometimes a lot.

The interesting thing is that if there is moderate ammounts of turbulence present in an area suceptible to flow de-lamination, this may actually cause the separated flow to re attach it self.

If you look at some aircraft, some of them have a number of very small finns distributed in certain areas over the wings.

This is to create that moderate turbulence in order to help re-attach laminar flow across the wing section ehich might otherwise be separated and cause the wing to stall.

Earlier in this thread i read about making small slotts on/by the short side radius, and I think we can start to see the rationale for these here...

So, what I would probably do, would be to make the ports as smooth as possible where uninterrupted laminar flow could be expected, and leave some rough areas where it would be reasonable to expect the air to "lose contact" with the adjacent wall boundary, typically the SS radius.


Some fod for thought here??