Power

And Merry Christmas to you also. I am unable to test is port heads since I lost my sight. I had a lot of work in that head, if the numbers are wrong then they are wrong. I observed the numbers in my prime. The engine ran well and the customer was very happy. With two moves I have no idea where the data sheet is. I remember the numbers because of their unusual fit to the application and the years of experimenting with various port shapes and coefficients to simulate overlapping effects on the off the seat air speed and velocity. These were the best I had ever done. And it was an XS head. Not a 427 Cammer, I studied what the cammer liked at low lift.
 
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The only thing that I would have done is that used Virago 920 XV1100 intake valves and I had to clearance the block sleeves and I used the Virago exhaust valves too. I used a bowl hog to get 100% valve and bowl size, I did end up with a wider SSR, and a wider LSR. As far as I can remember that is it. I don’t if that’s a help or not. As I said before Merrry Christmas. And I really want to be sure that it is understood that I hold ethics and the truth highly. I really wish that I had the data handy to share and I would like to. Bless you.
 
@Oldnwiser

With all due respect and i almost regret to say but if you measured 242cfm@0,3" at 28" with a 43mm ish intake valve then according to my experience i feel there is something wrong with your measured numbers in particular regarding the fact that the D-shape on your intake port is as i understand on the long turn side and not on the short side where the majority of flow goes (thus where the highest velocity is to be found and where there is the need to lower the velocity by increase of surface). I'm purposely not citing at this point the findings of eg Jerry branch or CR Axtell but it's just what I measured with a velocity probe in the intake port on a SF600 type flowbench.

Considering that a stock TT500/Xt500 head with the later 47mm valve flows bout 179cfm@25" at Maximum lift 242 seems to me sky high numbers.

I would have to look for my measurements of a stock xs head but I'm inclined to remember that the XS numbers were proportionally lower and worse due to a worse port shape in comparison to the XT500.

Kind regards and merry x-mas to everybody

Christian

Kind regards christian
I had an 1100 Virago that had been wrecked and used it for parts. I don’t remember the diameters it’s all in the box with the built specifications, close to 800 ccs of overbore and the heads came out well. But I was as surprised as anyone, the power it made was impressive according to the customer. I really don’t know what to say. Call me a liar, set me on fire. I used to build SOHC 427 Fords and learned a thing or two from that. But, I would rather not share what took me 35 years to learn. I’m a bald faced liar if it makes you sleep better. 179 is good enough.
 
What size are xv1100 valves, my other head has xv750 valves
 

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@Oldnwiser

Hey no reason to get upset as i purposely uttered my opinion in the most diplomatic and jovial tone that i could find with no whatsoever intention to criticize,or insult somebody as a liar that i don't even know!
Anybody can do as he is happy with and to his liking as long as he wishes.
Point is that the numbers seemed very high to me considering also the total flow potential given (even on a developed port) a certain valve size and it's area at/within the valve throat at a characteristic valve lift.
Anyways if the bike ran well than it ran good and fast, your stated point came through, loud and clear and was understood.
My point was just physical laws are physical laws and maximum flow potential given a certain surface area remains that.
E.g: the top contenders heads of a certain very competitive 2v class in the International speedway league were/are around 230-250ish CFM @25" with about 47-49mm intake valve diameter and pretty radical downdraft intake ports.
Similar numbers can be found on the modern reproduction manx, Goldstar and G50 heads, leading to horsepower figures in the +50 range.

180ish CFM@25" on a xs650 head (imho possible with 44-45mm valves) could highly likely lead to a good +80horses.

Kind regards christian
 
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@FLEA
I'm afraid there won't be too much to follow as my intention was/is not to be controversial, but just to state my admittedly personal opinion based on my experience of porting heads as well as knowing the literature stated by oldnwiser.
As mentioned before, if the power of the bike (btw: @jay760 compliments have been watching some of your videos, very very nice) was good no need to discuss as everybody was happy and satisfied.

It will be interesting to try to build a 880 engine with big approx 44mm valves and a megacycle high lift camshaft with 38/40mm dell'orto pumpers, as I have more experience with the dellortos then with Tm's or Fcr's.
I plan already for a good 2years to do such a project but do have a massive backlog on SR/XT and Guzzi heads and a very demanding and time consuming full time job).

All the best and a happy joyful new year to everyone.

Kind regards christian
 
That 50 hp. claim was gross hp.--measured at the crank with no alternator or drive gear dragging down the numbers. Net (wheel) hp. is lower, usually low to mid 40's on a stock motor. Regarding makers' advertised power back in the day, our thinking was that the Japanese raised pretty small horses....
@Oldnwiser

Hey no reason to get upset as i purposely uttered my opinion in the most diplomatic and jovial tone that i could find with no whatsoever intention to criticize,or insult somebody as a liar that i don't even know!
Anybody can do as he is happy with and to his liking as long as he wishes.
Point is that the numbers seemed very high to me considering also the total flow potential given (even on a developed port) a certain valve size and it's area at/within the valve throat at a characteristic valve lift.
Anyways if the bike ran well than it ran good and fast, your stated point came through, loud and clear and was understood.
My point was just physical laws are physical laws and maximum flow potential given a certain surface area remains that.
E.g: the top contenders heads of a certain very competitive 2v class in the International speedway league were/are around 230-250ish CFM @25" with about 47-49mm intake valve diameter and pretty radical downdraft intake ports.
Similar numbers can be found on the modern reproduction manx, Goldstar and G50 heads, leading to horsepower figures in the +50 range.

180ish CFM@25" on a xs650 head (imho possible with 44-45mm valves) could highly likely lead to a good +80horses.

Kind regards christian
I don’t want to be contrary, I apologize for being so. I appreciate all good information. I won’t be spreading bad information. That was what I came with. The combination is closely related to David Vizards design principles and the Shell Thuet racing design. The XS650 with a big big bore 750 and the 1100 cc Virago I had for parts had nice valves. The port in the head is really nice . The SF 1020 bench really allows you to find eddies in the flow that are similar in recoil to any forced round port that has a small SSR, and it radiates upwards to the long side creating swirl and small eddies that act as a brake in the atmospheric pressure. You have to really work for every cfm by reducing the things that slam on the brakes on atmospheric smoothness at such low lift. It’s easy to get big numbers on.600 lift cams but using overlapping exhaust to get the pressure smooth enough that it doesn’t recoil, and sound waves even affect the flow. A happy port is a quiet port. It is really hard to get that flow at off the seat and using overlap to get the train moving quickly and efficiently is as much an art as a science, The sound of good flow is a when you have to stop and realize that you are flowing beyond the edge of your ability and one more touch of the burr is going to disrupt it. Any way that is where I am coming from. And I apologize for snapping back. I can’t do it anymore because I shattered my left shoulder and my mojo is gone. I can’t even play the guitar anymore.
 
I personally am not too big a fan of low lift flow on street used engines as i do not like the fact that low lift flow usually makes engines more prone to being pipey (being more dependent on correct exhaust length, etc, etc).
For my part, i usually try to on various, similar time period, heads that i work on, to raise the intake floor and lay back the SSR in order to shift Eddy flow/turbulent vortices on the SSR up to higher gas velocities/rpm range, while at the same time keeping in consideration the fact that the fuel mist/droplets follow/s a different flow path then the lighter air.
This (personal taste) approach is based on maximizing flow and coeff of flow in the mid to 80% valve lift range and use, if available, cams with steep ramps and moderate overlap lift(overlap area) while keeping the gas velocity high in less critical areas of the intake port.
For that reason I ordered myself a while back the 250-40 cam for my personal engine build in order to also gain on the valve lift offered by that profile coupled with early intake closing in order to achieve a nicely tractable engine.
The overlap flow area will get quite increased anyways with bigger valves hence in my experience better to stay with somewhat moderate overlap duration.
Furthermore I made in a lot(actually most ports i work on ) of cases good experience with intake floors that are at the SSR apex as wide as possible, hence classic d-port shape
One has to watch out in my experience in order not to overdo it and create dead areas in one of the most sensitive areas of the intake port and also to not create an intake port that somewhat behaves like a straight bottom 2stroke piston port intake (thus instantaneous pressure release making imho the engine once again pipey).
So given the above mentioned facts i usually spend the most time on new port shapes (according to used cam profile) with a venturi/prandtl tube probing the ports in order to find (based on experience and software simulations) out what suits the port/cam combo the best.
The exhaust port on the Xs as is, is already pretty huge so I plan to level it a little out with slightly larger exhaust valves and trying to find out a more homogenous port shape, but being honest, given the pressure difference between intake and exhaust and the importance of the intake port i usually spend the most time on the intake port.
One will see (as mentioned did not have fully time yet to investigate) how much room is in the exhaust port to operate with the Tig torch as i would be tempted to raise the port floor there by welding in order to get a nice d-port there as well, but as mentioned that will be definitely of non priority as for such a build there are other things that are of far higher priority (eg valve reangleing given the cam profile and planned valve sizes).
I'm for my part will stay with the 360°twin crank lay out as i like the engine characteristics besides being already the happy owner of two 90°twins, and vibrations do not really scare me as i do not plan to ride to Patagonia or cape north on that bike anyways hahaha.

Hope that explained in brief a hint my philosophy.

Happy new year and kind greetings to all of you!

Christian

Ps: @Oldnwiser
No reason to apologize for anything, in particular not for technical discussions, don't worry :)
 
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No, I only do local sprints, just for fun,

I am not a technical person regards to engines a lot of the posts on here go straight over my head just go by trial and error some things work others don't, I spend most winters thinking of something else to try, mostly I am better off leaving it alone,

The one thing I do know is the cam I use is almost as good as a 250-40 but low lift long duration 

Mine is on the left the 250-40 is in the middle, shell #3 on the right
 

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@jay760
Hey pity as i would have loved to listen to some wild stories from Santa pod (would love to go there someday with one of my future projects (have roots supercharger in need of M20 Beezer:laughing:).
Anyways watched some of your YouTube videos and loved the wheelying starts of yours, big friggin compliment.
For the rest i will write you a PM within the next couple days.
Thanks for the comprehensive pictures.

Kind greet'z from Italy
Christian
 
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I personally am not too big a fan of low lift flow on street used engines as i do not like the fact that low lift flow usually makes engines more prone to being pipey (being more dependent on correct exhaust length, etc, etc).
For my part, i usually try to on various, similar time period, heads that i work on, to raise the intake floor and lay back the SSR in order to shift Eddy flow/turbulent vortices on the SSR up to higher gas velocities/rpm range, while at the same time keeping in consideration the fact that the fuel mist/droplets follow/s a different flow path then the lighter air.
This (personal taste) approach is based on maximizing flow and coeff of flow in the mid to 80% valve lift range and use, if available, cams with steep ramps and moderate overlap lift(overlap area) while keeping the gas velocity high in less critical areas of the intake port.
For that reason I ordered myself a while back the 250-40 cam for my personal engine build in order to also gain on the valve lift offered by that profile coupled with early intake closing in order to achieve a nicely tractable engine.
The overlap flow area will get quite increased anyways with bigger valves hence in my experience better to stay with somewhat moderate overlap duration.
Furthermore I made in a lot(actually most ports i work on ) of cases good experience with intake floors that are at the SSR apex as wide as possible, hence classic d-port shape
One has to watch out in my experience in order not to overdo it and create dead areas in one of the most sensitive areas of the intake port and also to not create an intake port that somewhat behaves like a straight bottom 2stroke piston port intake (thus instantaneous pressure release making imho the engine once again pipey).
So given the above mentioned facts i usually spend the most time on new port shapes (according to used cam profile) with a venturi/prandtl tube probing the ports in order to find (based on experience and software simulations) out what suits the port/cam combo the best.
The exhaust port on the Xs as is, is already pretty huge so I plan to level it a little out with slightly larger exhaust valves and trying to find out a more homogenous port shape, but being honest, given the pressure difference between intake and exhaust and the importance of the intake port i usually spend the most time on the intake port.
One will see (as mentioned did not have fully time yet to investigate) how much room is in the exhaust port to operate with the Tig torch as i would be tempted to raise the port floor there by welding in order to get a nice d-port there as well, but as mentioned that will be definitely of non priority as for such a build there are other things that are of far higher priority (eg valve reangleing given the cam profile and planned valve sizes).
I'm for my part will stay with the 360°twin crank lay out as i like the engine characteristics besides being already the happy owner of two 90°twins, and vibrations do not really scare me as i do not plan to ride to Patagonia or cape north on that bike anyways hahaha.

Hope that explained in brief a hint my philosophy.

Happy new year and kind greetings to all of you!

Christian

Ps: @Oldnwiser
No reason to apologize for anything, in particular not for technical discussions, don't worry :)
The valve lift is a big limitation of the original design. If I had .500 to work with I definitely would fill in the SSR and widen it and make the port cross the guide to make the mixture feed the plug like a cigarette and shorten overlap. A Hemi likes that. I had a friend with a 505 ci FE SOHC and I learned a lot from Fords original design. It is really hard to get the lift you need. The 650 seems that with the tie down cam bearings and the springs that .500 at the valve can be done, so 236/230@.050 on an 100LSA and.500 would work for the street with adequate compression. I d like to figure 8 the chambers to create a squish area to keep the mixture focused on the plug it is too bad that a twin plug per cylinder couldn’t be arranged. If you could have individual cam stubs for each cylinder and a 4 plug arrangement, 2 per cylinder facing each other would require a redesign of the head. I drew it out once but I have no idea where it went.
 
@Oldnwiser

Hi there and seasons greetings,
From the 250-40 on (0,480 lift) megacycle offers profiles with lift up to 0,550".
Also given the fact that most of my(i convert them) TT/XT/Sr heads are combustion chamber and at times port weld ups i can assure you that even a XS head can be converted to squish combustion chamber lay out.
I did not yet bother (due to time issues as mentioned) to measure compression on my 880 motor but I'd reckon that with heftier squish areas that one would get into the twilight zone regarding even dynamic compression with early intake closing like on the 250-40 and a built up combustion chamber.
I want to mention though, (although for several reasons I personally don't like the resulting Guzzi/ducati style squish type) that with 87mm the xs has already if paired with correct piston dome shape a usable squish area.
Although i'm pretty convinced that with bigger (I'm focusing on 44mm for now) intake valves and the needed reliefs in the valve seat pockets that one could substitute lost compr.ratio through lateral squish build up on the cast iron combustion chamber calotte.
But with 87mm pistons there is already a (even though for some

My conclusion in brief is:
Considering that the XS in 880 displacement is basically a short stroke TT and that one can find on early XT's still with 45 intake valves a good usable +40 streetable horses that one could go up to +80 if one can work around some of the peculiarities of the XS head

Happy new year to everyone
 
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I like that strategy, even the early Hemi suffered mixture speed changes that affected fuel atomization. The use of squish to keep the fuel atomized and the air moving at the speed needed to get a clean burn is what makes this engine happy. I like the 360 degree rawness, but the 270 degree smoothness. Is that conversion worth the effort? Is your 880 a 270/90 or 277/83? As I understand only the 533 can handle the 880cc displacement. Is it a 270 or 277 conversion?
 
@Oldnwiser

I assume considering that i live in Europe and since it's one of the last non custom classic XS' with flanged rims that it is a 533 but will open investigate when I hopefully get done with my back Log on XT/Sr heads/cylinders.
Engine is definitely a 360 as the work was done by previous German owner (up to the time the v twin configuration got popular most big bores in Germany were 360's afaik also given that 360's were widely used to my knowledge for sidecar-mx over here)
From what I could tell ports had already work done but I always use on the top end my own stuff as i have my own ideas for engine combos (eg the 250-40 with reangled larger valves).
Crucial point is mostly when I will find the time to work on it.
For now I will do with restoring the rolling chassis, bodywork.

Kind regards
Christian
 
I wish that a U.S. company would reproduce the XS2 with the 533 engine and a modern head configuration. The engine could easily support a 3 valve system on each cylinder by splitting the port on the intake side and using a forked shaft rocker that can operate two smaller valves on the intake side. The velocity and flow would be much greater and would burn cleaner to satisfy emissions standards without sacrificing power. If you squeezed 4 individual carbs in with the same can and the forked rocker for each cylinder it would be a neat package either carb or fuel injection and the ports could also be siamesed to allow a DelOrto carb to feed each cylinder and large enough to feed 2 intake valves on each cylinder with the long tube intake manifolds . The casting would have to be designed to do it but should fit the cylinder of the existing architecture. The exhaust could be slightly a slightly larger valve and the port optimized. Would that be neat or what? A 533 crank and a 3 valve head that looks like a stock engine, OHC design is begging for that , light titanium valves filling the intake side of the chamber and 1.75 exhausts and an oval intake port for each cylinder and heck a round 40 mm carb into the intake that’s longer. The intake port couldn’t even be a round port with a separated wall downstream.
 
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@Oldnwiser
I ain't no big fan of one carb for two cylinders as one get tangled up in gas resonance issues, and independent runner with carb the maximum is.
About the 3valve lay out, yup that would be interesting (i once started on a similar project for the xt500 but got as usual tangled up in time issues, don't forget I'm not a business shop, thus i have a pretty busy day time job), but and that is a big buuuut, I'm convinced that 3valves are not necessary also considering that from 80horses on the cases supposedly dont take more increases that lightly.
Considering that with a 87mm bore short stroke and let's say up to 47mm one should, in my experience, get a good usable +80 horses.
That in all honesty would be for me already plenty of usable juice if the engine delivers in a good mannered way.

Kind greetings Christian
 
Not many air cooled 3V engines have ever been made, but Honda did make some. And Ducati made a prototype 3V Pantah/ F1 at some point in time, with quite good results.
 
@arcticXS
Yes but Ducati actually built an imho quite sweet 3v (ST3)engine in the already water-cooled years. AJS as well built the 2cylinder (G45 and I think also a 7R) in its race version as 3 valver.
I have to admit that the Hondas never intriguede too much besides the turbo bike.
Sweet bikes but research points in the direction that an efficient 2 valve head is in its highest state of tune already quite good.

Kind greet'z
Christian
 
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