How much power?

billyfrank · Posted: September 11, 2006, 8:04 pm Post subject: How much power?

What can be gained out of these motors? I have a 72 XS650 that I want to build into a Thruxton killer, or at least be able to run with them. Is that a conceivable aspiration.
y buddy just forked out for a new Thruxton and its nice but, with a baby on the way I think I will work with what I got.
Can 70hp be obtained from these motors and still be streetable? or will it turn into a grenade? Anybody have dyno experience?
Thanks,
Billy

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Billy..you simply can't argue with displacement and modern technology and the Thruxton has them both. Even with a displacement of 840cc Xs,you'd be lucky to squeeze 68 hp from the old dinosaur. It takes money and a lot of internal modifications to prevent the old Xs from exploding. your best bet is power to weight ratio in dusting off the Thruxton..................Jack

billyfrank · Posted: September 12, 2006, 7:16 pm Post subject: Re: How much power?

Yeah that is what I was afraid of, but you never know until you ask.

Does anyone know if the 750 big bore kit is available for the early 72 motor? I believe it is a 300 series.

Thanks,
Billy

royfisk · Posted: September 15, 2006, 4:07 pm Post subject: Re: How much power?

650 central has a dino run posted showing roughly 55 hp and 92ft lbs of torque from a 752 cc motor. This is rear wheel horsepower .

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Roy............. A well tuned XS with an aftermarket exhaust system and caburetors will get ya around 48 hp and that's without head work and replacing the camshaft which should net ya in the end with about a mid 50 rear hp figure and all without spending over $700 for a 750 kit of course you won't reap the stump pulling torque of a big bore kit either but ya saved a bunch of money for other idems................Jack

royfisk · Posted: September 16, 2006, 7:39 am Post subject: Re: How much power?

Jack; Thats where I am at, I was just posting a dyno run for the purpose of answering billiefranks question . I am sure that the bike on that run is not a real streetable engine.

royfisk · Posted: September 16, 2006, 7:57 am Post subject: Re: How much power?

Jack how much torque can one expect from a 650 top end done with heads exhaust and cams,carb? I am guessing here of about60-65. would that be reasonable assumption? More then likely the stock ignition needs to go away also. I havent had any ignition problems on either the points type or the electronic, but also know that issues with coils do exsist. Ive been meaning to ask your thoughts on ignition systems.

billyfrank · Posted: September 16, 2006, 11:07 am Post subject: Re: How much power?

Thanks for the info.

I have seen the big bore kits listed only for the later model engines as well as the aftermarket electronic ignitions. If I can get 70 ft/lbs of torque I would be very happy, especially if it is all in the midrange.

Thanks again,
Billy

royfisk · Posted: September 17, 2006, 6:56 am Post subject: Re: How much power?

Your torque range would depend on cams carburators and exhaust pipe, jack can give you more info on these subjects.

Barrett · Posted: January 22, 2007, 10:59 pm Post subject: Re: How much power?

billyfrank,
I would first ask if your friend is a good enough rider to dust you on your XS 650. I mean a GSX-R 1000 makes gobbs of power and corners like an Xacto Knife, but, me on my Buell, can wear out the Gixxer guy from work...because he doesn't have the riding skill. Drag racing and road racing, so far.
Then tune or change for results in that area...corners/handling, acceleration, braking, top speed...
You can then go with sticky tires, shocks, carbs, jets, cam, exhaust, fork brace, high flow filters, new brake pads or late model calipers...

xsjohn · Posted: January 22, 2007, 11:20 pm Post subject: Re: How much power?

XS1100's run pretty good and you can still say you ride an XS. Lots of parts out there and they are about as cheap as a XS650. Just fixed one for a friend. Got rid of the vacuum advance to save the electronic ignition. 90 some horses. It will roll on.

John

billyfrank · Posted: January 26, 2007, 11:47 pm Post subject: Re: How much power?

Barrett- My buddy is actually a better rider than I am, he has alot more experience. You are right on the money as far as skills go, and hopefully someday I will have sharpened mine up some. In the twistes I do expect him to whoop me, but on the freeway I would like to keep up.

I am building a 72 XS650 into a cafe bike mostely to be different and also because it looks cool. If it can be quik and reliable to boot that would be great. I will definately be picking peoples brains as the projct progresses.

Thanks for the input,
Billy

xsjohn · Posted: January 27, 2007, 2:51 am Post subject: Re: How much power?

The faster it runs the faster it dies.

John

tudawgs · Posted: January 27, 2007, 11:55 am Post subject: Re: How much power?

The Xs motor rephased, with the 750 kit and an upgraded cam will put you you right along side the Thruxton. You won't beat it but you will stay right along with it.

billyfrank · Posted: January 27, 2007, 12:54 pm Post subject: Re: How much power?

John- This is my fun bike so I expect it to be broke a bunch(learning curve) Laughing

I never have built a real motorcycle, plenty of Vespa's and a few cars. I have a second bike that is a good runner(VX800 Suzuki), so if the 650 is down I wont be out.
I will build the motor out pretty mellow to start and then go from there. I ahve a couple other projects to finish before march and then it will be next in line.
Thanks,
Billy

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

People are always quoting HP numbers from minton's among other sources....my question is: has anyone dynoed a 650 with real compression? The 750 big bore kit is 10.25 to 1....what about a 750 with 12 to 1 or better...I've seen plenty of Triumphs with compression rates like those....I realize fuel becomes a problem but they still sell lead additive....yes, it may be a grenade but it is fun while it lasts...I'm starting to think that the cheapest power modification to be made is a thin copper head gasket on stock or slightly oversized pistons and a shot of lead....

yamaman · Posted: January 27, 2007, 10:28 pm Post subject: Re: How much power?

You want power? How about Ross 840cc pistons at 12:1 comp, carrillo rods, stainless valves, h duty valve springs with titanium keepers?
That oughta pump some ponies!

www.users.bigpond.net.au/dave650/

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

That's a big ripoff....stainless valves don't build power but would be nice...titanium keepers are unecessary and don't build power...mikesxs valve spring set would do fine....any motor could be made to 12:1 via millwork so I don't see the point in any of this high priced junk aside from the carillo rods...

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Your cheapest power upgrade would be to port the cylinder head over increasing the compression ratio. You might increase your combustion efficiency but the extra bang will no doubt put extra stress loads on the weak stock rods,you'll just beat out the bottom end over time.The head is the heart and soul of any air pump. Stainless valves won't increase the HP #s but different valve arrangements will increase the flow efficiency by a small perecntage and with the XS head you take what ever you can get to increase the engines volumetric efficiency..............Jack

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

Jack, good to see you back at the post....are the stock rods that weaK? I've never seen one give way except on those machines that were ridden foolishly...I would like to put in carillos as a long term investment but I imagine they are pretty pricey....my only point in the above post was that half of those super-pricey parts weren't really required...Jack, I'm dying to see the final results of those flow numbers from that head you've been working on.....ttmaniac

yamaman · Posted: January 28, 2007, 9:41 am Post subject: Re: How much power?

Yeah, theres not much in stainless valves, but hey if your gunna chuck in some bigger 1's, hey why not?????
Titanium keepers, once again if your buying new 1's what the hell. run them. But the 840cc pistons has gota get your blood up!!!!!!!

Carrillo rods are worth the expense, if your going to the expense of a bottom end rebuild, it's always going to be an expensive exersise, and 1 you only ever want to do once!

Dont forget the link I posted is a Aussie site priced in Aussie$$$ I think that $US would help in the aquisition!!!

Lastly, yep it's all in the head! Have what ever you want, but it's still gota breathe!......................enjoy! Very Happy

PS went to see Paul Kelly and The Pretenders just now, free booze, VIP tickets AWESOME!!!!!!!!!!!!!!!!!!!!!

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

Can the clutch stand up to the torque? The xs has a decent clutch (not a diaphragm junker) but I don't know how well it would stand up to that kind of torque....I'm willing to bet you would see 80+ HP from a 12 to 1 840 kit well built....it would be the bomb fo' sho'....no one ever posts dyno results for such an engine which is a bummer....I waiting on the day of solid billet xs heads and cases....couldn't afford em but it's fun to dream!

tudawgs · Posted: January 28, 2007, 2:06 pm Post subject: Re: How much power?

I think eveyone isrunning alittle off track when it comes to running with the crotch rockets. As we all know the sport bike motors develop horsepower through rpm not torque. The 650 motor rephased will give an extra 2000 + RPM to bring closer to the sport bike RPM range. The 750 cc gives you the horsepower(torque) and the higher lift cam shaft and heavier valve springs allows it all to happen. This is a fairly inexpensive solution if tou want your classic bike to run with the modern machines.

ttmaniac · Full Member Joined: Dec 22, 2006 Posts: 468

What happens to the torque when you rephase?....since when did rephasing become cheap? Pound for pound, dollar for dollar THE cheapest way to power is in your gas tank.....fuel.....oxygenated garbage fuel won't make power like the good ol leaded race fuel.....hobby shops around the country have shelves stocked with extremely high performance fuel...glo-fuel....what this is is a mixture of nitromethane and castor oil....nitro for power and castor oil for lubrication....mix in a little of this stuff with each tank of gas and boom, you've got power...major power....mix in alot and boom, you have no engine...it'll blow the head off your xs as though it wasn't there....I've contemplated a glo-fuel injection system whereby the fuel is dispersed into the carb via jetted nozzles (so you can control flow)...you can purchase mini fuel pumps for model airplanes that run off 12 volt power..you CANNOT start your bike on it....bike must be warm and running max throttle unless you were using VERY small amounts....I don't see why this wouldn't work...I don't think anyone has tried it.....yes, I know it'll grenade my motor but I have access to 5 or 6 spare bottom ends so who cares....I just don't want to blow my balls off in the process so, little by little is how you experiment....yes, fuels are the cheap way to power.. a gallon of glo-fuel is 60-80 bucks I think depending on grade....just a thought

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