Jack's Information on Head Porting

I have to say, when I recently rebuilt my stock XS2 motor, I never even considered cleaning up the head, but now I’m beginning to wish that I would’ve given it at least some minimal port work. Something I’m curious about, some of these photos show a lot of material removed around the exhaust port valve guide. Is there any concern about creating a hot spot on those valve guides? I can certainly see how gas flow would increase.
Anyways, I’m enjoying following along and learning something new. Thanks!
Actually the hot spot is the stock bulging guide protrusion which acts as heat sink and the valve stem absorbs all that heat. By reducing the guide length and working the guide boss, you reduce heat absorption to the valve and the exhaust port its self from a faster flowing port. Pictures can be very deceiving particularly in port images, not alot material is removed from the guide boss, there's plenty of meat in the roof supporting the guide. Haven't had one complaint yet regarding valve heating issues in the EP. You don't need oversize valves in the EP (with the exception of a bad seat)to get it to flow, you gotta work it.
 
All I ever used was a Dremel as well. I find the sanding rolls good for the initial cleanup and knocking off the big casting flaws. I use the ball cutters (mostly #191 and #192) for removing and blending the machining marks around the seats, also to smooth out the spot where the valve guide "bulge" meets the port wall .....

OYfwNUg.jpg


What I use most for smoothing the ports out are Cratex wheels or bits. These are made from grit impregnated rubber and come in all different grits and shapes. I use the plain wheels for most of the port's main walls, cone shaped ones to get into the tighter nooks and crannies .....

LAoKPvJ.jpg


You can get a pretty good high polish finish with these, and that's fine for the exhaust port, but for the intake it's better to have a textured finish. This agitates the fuel/air mix a bit as it flows through and keeps the gas droplets from dropping out of it. So, after I smooth and blend the intakes, I go back with a sanding roll and texture them up a bit .....

VFCgqJt.jpg


For me, the big thing is removing and blending all these factory machining and "chatter" marks around the valve seats .....

sM6a1gQ.jpg


..... and removing the casting flaws .....

yaHx9rC.jpg


QzaWAum.jpg


These things are awful from the factory. It looks like the Lunar landscape in there, lol.

Thanks 5twins! That’s super helpful!

I’ve just ordered a #191 & #192 cutting ball, I already have heaps of sandling rolls, do you use a longer shank on your Dremel to get into the ports when using the sanding rolls or does the standard length suffice?

I just need to build a head stand now, hopefully get this done in the next couple weeks. What do you recommend for illumination, what are you using to light the head whilst porting?

I’m assuming any vapour blasting can happen before or after the port work, it won’t make any difference will it?

Daniel.
 
All I ever used was a Dremel as well. I find the sanding rolls good for the initial cleanup and knocking off the big casting flaws. I use the ball cutters (mostly #191 and #192) for removing and blending the machining marks around the seats, also to smooth out the spot where the valve guide "bulge" meets the port wall .....

OYfwNUg.jpg


What I use most for smoothing the ports out are Cratex wheels or bits. These are made from grit impregnated rubber and come in all different grits and shapes. I use the plain wheels for most of the port's main walls, cone shaped ones to get into the tighter nooks and crannies .....

LAoKPvJ.jpg


You can get a pretty good high polish finish with these, and that's fine for the exhaust port, but for the intake it's better to have a textured finish. This agitates the fuel/air mix a bit as it flows through and keeps the gas droplets from dropping out of it. So, after I smooth and blend the intakes, I go back with a sanding roll and texture them up a bit .....

VFCgqJt.jpg


For me, the big thing is removing and blending all these factory machining and "chatter" marks around the valve seats .....

sM6a1gQ.jpg


..... and removing the casting flaws .....

yaHx9rC.jpg


QzaWAum.jpg


These things are awful from the factory. It looks like the Lunar landscape in there, lol.

DE84A5C5-BC32-4772-8E2B-DD7E9EA7E0F1.jpeg


Are these guys the type of grit impregnated rubber I should be looking to use?
 
Yes, those look like the ones. I use mostly the coarser grits. Most of the port can be accessed with the bits right in the regular Dremel tool. To get in deeper, I have the flex shaft attachment.
 
Yes, those look like the ones. I use mostly the coarser grits. Most of the port can be accessed with the bits right in the regular Dremel tool. To get in deeper, I have the flex shaft attachment.

Great, I’ll order some of those as well.

I have the flex shaft attachment for my Dremel tool too.

In regards to speed settings, what should I be looking for with each attachment?
 
I don't use anything special for lighting, just one of those clip-on trouble or work lights placed close to the head. To protect the insides of the guides and keep all the grinding dust out of them, I thread strips of oil soaked rags through them.

Another great piece of advice, so just soak a few strips of rags in motor oil and thread them through the guides?

I can’t thank you and everyone else on this thread enough!

It seems like quite a daunting process attempting this but all the help & advice I’m receiving is making me a little more confident!

Cheers. Daniel.
 
Yes, strips of oiled up rags. They needn't be dripping wet, ring them out so they're basically just all oiled up. When I'm done and remove them, I swab the guides out with Q-tips to ensure they're clean before installing the valves.

I'm not sure about the speed, I'd say medium-fast. Not full speed but not below medium. You'll see what works good as you try it.
 
Yes, strips of oiled up rags. They needn't be dripping wet, ring them out so they're basically just all oiled up. When I'm done and remove them, I swab the guides out with Q-tips to ensure they're clean before installing the valves.

I'm not sure about the speed, I'd say medium-fast. Not full speed but not below medium. You'll see what works good as you try it.

One more question 5twins... for now at least. Sorry!

Do you use any kind of compound/fluid when working the ports? When I’ve been polishing parts I’ve taken to using GT86/WD40 as a kind of lubricant if you will?

Daniel.
 
No, I never used anything, just did them "dry". I think you'll be surprised how nice and shiny those Cratex bits will get things. I don't go for nor get a mirror-like finish here, just a pretty shiny, blended and smooth port .....

G4Pqad4.jpg


These ports are supposedly borderline too big to begin with so you don't want to be taking too much material out of them and enlarging them more. I think just the basic clean-up I do helps. I know it altered the flow somewhat because when I put it back together I had to tweak the jetting slightly. I was able to decrease the pilots one size (I was up 2) and increase the mains one more size (I was up one).
 
No, I never used anything, just did them "dry". I think you'll be surprised how nice and shiny those Cratex bits will get things. I don't go for nor get a mirror-like finish here, just a pretty shiny, blended and smooth port .....

G4Pqad4.jpg


These ports are supposedly borderline too big to begin with so you don't want to be taking too much material out of them and enlarging them more. I think just the basic clean-up I do helps. I know it altered the flow somewhat because when I put it back together I had to tweak the jetting slightly. I was able to decrease the pilots one size (I was up 2) and increase the mains one more size (I was up one).

I’ve read that time and time again, that the ports are too big and ideally need material added for optimal performance.

I have considered sending one off to have this work done but I’m not really building a full-race XS so perhaps this would be OTT? I think matching manifolds to intakes and cleaning up the head will need my needs at the moments

Anyway I’m fascinating by the whole concept and it’s something I would love to learn more about and be able to carry out myself and perhaps to more complex port work in the future. I’ve even sourced another head so I can do another!

Daniel.
 
I’ve read that time and time again, that the ports are too big and ideally need material added for optimal performance.

I have considered sending one off to have this work done but I’m not really building a full-race XS so perhaps this would be OTT? I think matching manifolds to intakes and cleaning up the head will need my needs at the moments

Anyway I’m fascinating by the whole concept and it’s something I would love to learn more about and be able to carry out myself and perhaps to more complex port work in the future. I’ve even sourced another head so I can do another!

Daniel.
When you have XS 650 knocking down 48 to near 60 MPGs the hear say of the port volumes are to big is total BS! Do these ports have flaws regarding insufficient flow to support certain megacycle high lift cams, absolutely and this were the hear say comes into play. Ask Griz1 want his Xs 700 is knocking down with that ported head I did for him. Now can you improve the ports performance by epoxying the intakes , absolutely and there isn't a intake port on this planet that wouldn't benefit by reshaping it's port. The ports on a stock xs with the exception of the EP supplies exceptional flow for stock low lift cam, shell 1 and megacycle 250-00. You wanna talk about excessively big ports, Shell ports would be at the top of the list but they were set up to certain track conditions for cushioning power delivery.
Porting these heads to the next level doesn't take much effort and the rewards of doing it yourself are very gratifying
 
In regards to working the guide boss area when working around the outer diameter ends, you do not want any flat areas or resistance points that'll cause turbulence in the port hindering flow. You need to work those areas at the angle of the roof as best as you can, the exhaust pressure flows up the roof and deflections will slow it down by turbulence. The two outer arrows are the areas I'm speaking off and attention to details will pay off big time. The middle arrow is the guide, if you'll look down the guide you'll notice a lip or ridge where the valve stem makes no contact and if the lip extends further down than the casting surrounding the guide,cut that guide end flush to the casting but keep in mind you need to, leave enough to round profile-radius the guide end, again to reduce turbulence. Now you guys can do it your way but I'm just pointing out areas that need alittle more detailing to enhance flow. Can you see the differences
in these two images .
5twinns.jpg

ehaust boss 4.jpg
 
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When you have XS 650 knocking down 48 to near 60 MPGs the hear say of the port volumes are to big is total BS! Do these ports have flaws regarding insufficient flow to support certain megacycle high lift cams, absolutely and this were the hear say comes into play. Ask Griz1 want his Xs 700 is knocking down with that ported head I did for him. Now can you improve the ports performance by epoxying the intakes , absolutely and there isn't a intake port on this planet that wouldn't benefit by reshaping it's port. The ports on a stock xs with the exception of the EP supplies exceptional flow for stock low lift cam, shell 1 and megacycle 250-00. You wanna talk about excessively big ports, Shell ports would be at the top of the list but they were set up to certain track conditions for cushioning power delivery.
Porting these heads to the next level doesn't take much effort and the rewards of doing it yourself are very gratifying

I’m using a cam with a 250-30 profile and valves that are +1mm on the intake and +0.75mm on the exhaust.

Daniel.
 
Are you sure you wanna use that particular grind for street use? Heres a dyno graph of it's power curve.

I’m not 100% set which on cam profile I will go with although the 250-30 is what I’m leaning towards.

This is how Howard Smedley, ex-proprietor of Smedspeed describes the 250-30 profile

“Megacycle 250-30
A really good hot/wild street cam. 0.440’’ lift, needs 10:1 compression to work well, but gives very strong midrange and top end, and can be adjusted to give stronger bottom end too at the expense of some top end loss. Really good hot street cam for 750 cc and bigger engines. Needs shorter valve guides/valves recessing, and good valve springs.”

I’ve studied Craig Weekes Peformance Guide extensively, I read it three times by the pool whilst on vacation in Florida.

It’s probably worth mentioning that I intend on track day use with my bike.

Daniel.
 
I would get with Jay760 and build the motor around his combination as it seems to run real strong. You'll need to install bronze guides to prevent seizing or galling of the valves stems,iron guides are a no no in this type of racing and i would'nt use a guide seal on the exhaust guide either,you'll want all the oiling that guide can receive for lubrication,but thats my opinion. As for the port work the intake is fine but me personally I would work the exhaust port differently in getting the E to I flow ratio down to around 70 to 75% to prevent over scavenging but again that's my opinion cuz if you get that port right it'll flow big time right with the intake at certain lifts. Anyway I hope it all comes together with that 250-30 for you.
 
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