POWER POWER???

Good comments, guys. Scabber, you and I see eye-to-eye on priorities--chassis first. Burns, that's a good summary of the basic tweaks, though I'd recommend welding up the crank with any significant mods.
 
Thank you for the hat-tip.

It seems to me that it is a good thing that there is a clear point of diminishing returns on modifying this motor. This motorcycle is "the people's classic" and it is fitting that its design limits discourage the "money pit" approach to hyper-modification.
 
Are you aware that there's a bolt on 750 kit? I think Mike's sells a version that people are happy with. Regarding all the porting and polishing and tuning and swapping parts, and the more radical strategies, I've yet to see one dyno result from it posted here, and that can only be because it would be embarrassing considering the time and or money invested.

It occurs to me that personal satisfaction and "racing" are the only two reasons people do just about anything :) The actual general consensus is if power for its own sake is the thing you're after, consider a bike that fits your style better. I ride an XS650 because it's easy and cheap to keep it running. And good-looking, to me. And interesting to other riders who see it. And...

What is embarrassing is not knowing what Bob Bertaut,Craig Hanson,3M,Johnny Issacs,Harry Lillie,Shell Thuet, Jerry Branch and the numerous other XS enthusiasts had in common when it came to pushing the XS head to another level beyond stock state without the the use of a dyno for comparison of a modified Vs stock head ( for some ). A mild clean up can and will yield positive gains and if you decide to go outside the box in completely re-altering the ports,the rewards of even higher engine performance are endless with the right touch in tuning. The XS head has the flow capability to support 100HP and has done so in the past with 1000CC stroked motors.
Unlike some engine performance upgrades,porting adds nothing to engine stress that could otherwise diminish life expectancy to certain parts. In the right hands, porting the head will yield the best bang for the buck,regardless of engine displacement.
 
^That's not my field, so I needn't be embarrassed. But I'll tell you, I notice there's still no dyno chart. I think we came to this before and eventually just dropped it. You couldn't or wouldn't tell me how much of a hp gain you got from porting. There's nothing outrageous about that request.

Objective measurements is in my field, and also I know how deceiving the senses alone can be. My XS has twice the horsepower some days. But I know it's just me. If you now want to call me names just call me a skeptic. :) Nothing personal. Truly.
 
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cool and ya im still here in the backround sifting through the bullshit answers of people who dont have a clue on how to answer the question. Thanks to all who did answer, that all pointed me in the right direction
 
It was true in 1950 and it's true today---
" Speed Costs Money, How Fast Do You Want To Go ?" tim
 
OK, Mitch, now we have a performance goal. And the bottom line is--you can get that out of the engine, reliably. To mods recommended in PM and by Burns, add the higher 5th gear from Mike's XS to 17/32 sprocket combination and an oil cooler. You'll still have plenty of go off the line and be nowhere near full throttle or redline at the ton.

Get ready for some noise here; some of these guys think the motor will disintegrate if it's wound higher than 5K, and in some cases they may be right.
 
^That's not my field, so I needn't be embarrassed. But I'll tell you, I notice there's still no dyno chart. I think we came to this before and eventually just dropped it. You couldn't or wouldn't tell me how much of a hp gain you got from porting. There's nothing outrageous about that request.

Objective measurements is in my field, and also I know how deceiving the senses alone can be. My XS has twice the horsepower some days. But I know it's just me. If you now want to call me names just call me a skeptic. :) Nothing personal. Truly.[/QUOTE
And you will never see a dyno run from me either,waist of time and money as I know what to expect but every combination will yield different outcomes due to varibles in parts selection,etc but if you're looking for specifics contact Craig Weeks. If porting yields a flow gain,typically you can take the flow percentage and rough estimate the power gains over stock,there are formulas to do just about any calculation to theroize.
 
Gee, Jack, when it comes to porting outcomes, wouldn't dyno numbers influenced by a whole slew of factors be a whole lot more objective and informative than those subjective, impressionistic flow bench numbers you put up? You know, dyno numbers, like those charts from Jerry Heiden that show all the fine results you aren't gonna see? ROFLMAO!

Gents, when Jack puts up flow figures that make Craig's jaw drop, he's got nothing more to prove.
 
I like my 650s with their top ends mildly modded - just like my women, lol.
 
The limiting factor is not the heads it is the cases. If you get a set-up that puts out 100 h.p. the motor won't last long enough to go through a set of tires.

And flow bench numbers are all well and good but show me the torque curve with the carbs and exhausts you are going to bolt to that head. Those are real world numbers.

Last thing. Going down the road on this motorcycle for an extended period of time ("crusing") at 100 mph ain't gonna be any fun. Once again it is not just making power - it is the whole package. An XS650 is a Route 66 kinda bike and you can't make it be a Goldwing.

IMHO
 
the 1000cc XS650 on the MADRacing Tovami dyno, sound is INCREDIBLE in real life, 70HP is not amazing but the torque numbers ARE! 106 Nm of torque!

Supposedly...


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680cc, dellorto phf36 carb kit, open exhaust = 47 HP ..again supposedly


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XS650SE Chopper on the Dynojet at Heiden Tuning doing a nice steady curve with a peak of 48.05 Max power and 56.57 Torque.

supposedly

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not a single screen shot from the monitor on the dyno for any of these ..
 
id like the option to cruise at 100 but dont want to sacrifice getting to that number

100 MPH on an XS is not what I would call a cruise. I went out on a gumball, No rules no speed limit. Did 100 and more for about 10 miles and on my XS and you have got your hands full. The power and tork can be felt transmited through the frame. Feals like the motor wants to rip it's self out of the frame. Dyno run, I don't need no stinking dyno run to tell me I'am building power. The sound of the exaust makes it even better. Now you can call me stupid but I call it crazy. Why did I do it because I can. If you build it right you wont sacrifice mutch but your wallet and loot that was in it. Or your life if you don't get it to handle and and stop first and lose controll of the bike. If the man don't get you first. Run it till it quits then build a better one. Nothing lives forever. I don't plan to. 1 gumball in a lifetime should do it for you. Your choice. 650 CC head work and the right cam really enough power for an XS. :D
 
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Gee, Jack, when it comes to porting outcomes, wouldn't dyno numbers influenced by a whole slew of factors be a whole lot more objective and informative than those subjective, impressionistic flow bench numbers you put up? You know, dyno numbers, like those charts from Jerry Heiden that show all the fine results you aren't gonna see? ROFLMAO!

Gents, when Jack puts up flow figures that make Craig's jaw drop, he's got nothing more to prove.
:laugh: Marketing parts isn't one of my specialties:wink2: nor do I care about the skeptics who've never attempted a DIY porting job nor understand that these XS"s are a high revving power plant air pump and any attempt to maximize flow or velocity can be beneficial in building Hp, keeping the power drive sustained for racing purposes or what ever.

Haven't had much time to touch up that D port head for Craig,he's made arrangements to get it flowed on the house:thumbsup:
 
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