8 valve head ?

[floris]

Hello,
I wonder if there has ever been anyone whome tried to fix a 8 valve head to the XS engine.
I know for fact that Kawasaki has also a 650 cc paralel twin, and yes with a 8 valve head.
Would it be possible to make that work for our XS ? with a Kawasaki head i mean.

The why is simple.
The XS is a strong engine with not to many HP.
Currently mine is in good hands with Jerry v d Heiden for a big tune up.

BUT, a want more !!!

If possible a 8 valve head.

Anyone ?

 

[arcticXS]

Floris,
I went to Jerry Heidens shop in 2011, and saw an experimental 8-valve XS engine on the bench there. I believe the head was from a Laverda 668. I guess you could enquire about how this project went.The Yamaha TX/XS 500 was also an 8-valve, but only 48 hp or so. I am afraid this is the closest to an 8-valve XS you can get for sensible money...
And then there is NRE (Nourish) engines, which are based on the pre-unit Triumph design, or as cylinder and heads for upgrading unit Triumph twins. Fast, but expensive, and possibly fragile and maintenance intensive....
In any circumstance, a 8-valve aircooled twin needs quite a large valve angle for sufficient cooling. For a really hot parallel twin, a BMW800/Husky900 or Kawasaki 650 (ER-6) would be a better starting point. I personally would LOVE an ER-6 based street tracker or bobber. Low weight and potential for 70-80 hp........

 

[gggGary]

IMHO (and no experience) the XS will never rev high enough to need all that breathing.
You can make more horsepower than the XS cases can take with a very lightly breathed on 2 valve cylinder. Now if you want the bling no one else has, well then, have at it! Post up pics on how it goes.

 

[floris]

it's not just the bling, actually, it's not the bling at all.
Like to see how far it can go with the XS.
Just thaught about a 8 valve head and if it may work.

In case it's impossible or difficult, hey, that'll be the answer why it's never done.
Thanks for that.

In case you may wonder, i'm a painter not a tecnician.
take a looksee at www.feniks-decorations.nl


Floris.

 

[crashcourse]

I may be mistaken, but I believe I read somewhere that two valves can breathe better than four at moderate rpms. I wish I could cite a source for that. Sportbikes use four because the reduced mass of the valves allows higher rpms, and thus more power. The xs crankshaft isn't balanced enough to rev that high even if it had four valves.

That said, if you have a fancy-shmancy rephased crankshaft, maybe you really could take advantage of the extra valves. I've toyed with the idea myself, keep us posted!

 

[jay760]

I think there was somebody running one on a sidecar x outfit in Holland,

 

[XSLeo]

Anything can be done with enough money.
The cases are the weak point when going over about 70-75 hp. Over these levels the cases can't take it.
Leo

 

[weaselbeak]

"I may be mistaken, but I believe I read somewhere that two valves can breathe better than four at moderate rpms."

No. 4 valves open a larger area earlier giving a wider powerband, for starters. Do the math, 4 circles in a given area cover more square inches than you can with 2. It is true that higher RPMs are available with 4 valves, as they are lighter, requiring less energy to lift, and lighter springs to close, a bonus being that they don't have to slap shut so hard. Theoretically, an xs650 would be capable of more RPMs with 4 valves for these reasons. More RPMs equal more oxygen equals more power.

 

[NONclow]

2 valves per cyl, small port volume, benefits from higher intake velocity at lower rpms. 4 valves per, larger intake volume, but lower velocity, untill it can breathe better. Two different animals. If I wanna cruise, it's the 1B. Speed... out comes the NINJA, where the sweet spot is between 5000 and 11,000! Unless in a low gear, anything below 5K it's like WFO on the 1B in fifth at 20mph Spring pressure isn't too much lower with the potential for 50-80% more revs, they have to close that much quicker. H*nda tried making a wider powerband with the VFR800 Vtec, 2 valve operation untill 5K when electricly activated hydraulic pressure opens the other two achieving high velocity down low with the breathing of four on top. Talk about complex and expensive.

 

[weaselbeak]

That's more in the cams. My gs 1100 4 valve was a torque monster, redline 9K. Any gear, any time. Downshifting completely optional.

 

[650Skull]

scroll down and read what Craig Weeks has to say

 

[NONclow]

My gs 1100 4 valve was a torque monster, redline 9K. Any gear, any time. Downshifting completely optional.

That's because of large displacement heavy flywheel inertia, and plain bearings on the crank instead of rollers. Like Leo said the cases can't handle the higher revs and a 4 valve head would move the powerband higher. Not to mention 4 valves usually mean DOHC, so the cam chain system and top engine mount (all that extra power compromising the lower end, I definately want the extra mount!) would need to be modified. The only way you could move it back is with custom cams with shorter duration and overlap. How many will you have to try before an adequate set is stumbled upon? The frame downtubes might even have to be modded to a single tube to clear the exhaust. And then there's carburation...

Maybe I should think about putting a 2 valve head on my NINJA for better low end...... Naaaa I'll just ride the 1B

 

[gggGary]

Skull thanks for that link! It's must read for anyone new to the XS650 fold. AND a good review for us old farts that think we know everything.

 

[member3480]

I build a lot of race motors and there are problems that you have to face with each motor you build.
Someone talked about a GS1100 motor and two things jump out right away when you increase horsepower. CLUTCH BASKET CAN'T hold up blows up easy...TRANSMISSION another week point...CRANK needs to be welded up and balanced also.
Two valve versus four valve has been a fight for years which is better and what flows more. Most of you newer motors are 4 valve for performance right out of the showroom. I have just done some Busa motors and they again have week points to get that horsepower to the ground and rev past 14 grand. But you can put larger valves bigger springs better cams and bronze the valve bucket and make crazy horsepower.
A twin motor has much more week points and there is just so much you can get out of one without blowing it up between your legs. Turbo or a quick shot of NOS is a easy way but again TRANS/CRANK/CLUTCH/CASES are they going to take it plus the oil volume. Most cranks go because of oil volume you can go super fast but if the oil all runs to the back of the motor very little is on the crank and boom there goes the crank. That's why most performance bikes have windage trays to keep oil in front. Can that be done in those little cases. Bike was built to ride and have fun with and I know there are some die hard guys who may or may not try and get the most out of a xs motor. BUT there is a VERY big difference between a RACE MOTOR and one rode on the street. ME if I was going to build the all out xs motor I would go with big cam big bore big carbs bigger valves and port the head . Have crank balanced and welded and also have clutch basket welded and upgrade springs and last undercut trans so it shifts easy. Maybe I will get some real horsepower out of it but it sure as hell will run better than stock.

 

[weaselbeak]

My GS1100 came from the factory with a welded crank. The clutch was one of the best to begin with, but beefing it up was easy and inexpensive. I've not personally ever seen one with a broken tranny, but have heard of it. I beat mine pretty hard ,too.

 

[floris]

This morning visited Jerry vd Heiden.
It's clear now.

Indeed it's complicated.
The reving is an issue, even as finding a suitable head.

If you want this, it can be done.
But the cost and effort are way bigger than the result.
This engine is simply not designed for that kind of technical studies.
I know now.

I will go as far as 1000 cc with a long stroke.
270 crank.
Big carbs.
Electronic ignition.
Oil kooler
Megaphone exhaust.
Hot cam.

Wil give me enough torque.

;-)

Floris.

 

[CDNTX650]

Id say that it was pretty obvious the minute it was thought of..even 1000cc with all the work pretty much takes any streetability right out of it...

 

[floris]

Say you !
Do you even know Jerry v d Heiden ?
The man is God in XS country.

If Jerry says that snow is black, i believe him.

End of discussion.

Sorry.

 

[gggGary]

If you talk to Mr. Heiden again I'd be interested to hear his take on crank welding.

 

[member3480]

NEVER has Suzuki welded a crank at the factory. I owned more than 15 of them and all were pin cranks and clutch basket were the worst. Springs flew out of them all the time . So someone pulled the wool over your eyes saying it was welded.
When a GS1100 or 1150 done both you welded up the pins so the crank could not turn. I use to go to Canada and buy GS1100 up there because they had 25 more horsepower than the ones in the US. All GS1100 in the US had there cams set back for less horsepower and all you needed to do was put slotted gears in and degree in cam to get more power. I had a 1982 Blue GS1100 and only had 125 miles on bike tore it down put slotted gears in and ran no base gasket and a V&H pipe and broke the A stock MPH record at a track in CONN. We had one run 10:30 1/4 mile with stock exhaust. I have a GS motor and frame sitting here in my garage to one day hit the street.
Gary I don't think welding a XS crank is going to do anything because it will never rev that high to spin in the pins. I had to weld cranks because of the 14,000 to 16,000 RPM runs at the track. I never tried but I don't think a XS motor will go past 9,000. You can rev way past you power band so high rev is not all that it takes. I also would love to hear what he says on the xs motor.