Big valve GS1000 head

[rapidray]

torque does the work, horsepower is how fast the level of work can be done.

This is why I keep telling people that just about NOTHING is as fun as a 16 valve, 1400cc GS street motor! YEEEEHAAAAAAAAA!!!! Lol!!
Ray.

[GregT]

my approach will work with any displacement-of N/A GS1000 chain drive - using a small port head, carb size diameter relative to intake valve diameter, light crafty porting , big valves, long duration medium to hi lift cams and 4-1 exhaust relative to exhaust cam timing are just the way I prefer to make things happen from idle to redline.

matching and balancing everything makes a flatter smoother torque line and more horse power is a by product -- torque does the work, horsepower is how fast the level of work can be done.

I tend to agree with your approach for my application - Roadracing on short circuits. Torque is of primary importance where you don't have the room to wind up to a high top speed. We've used a small port head with OE valves with good results. Then we went to the big port head with big valves...and lost a heap of HP in the midrange to the point where the rider couldn't steer it on the throttle as he had been doing previously.And yes, it was quicker up top - but on our circuits that doesn't mean a lot. Daytona, Philip Island, the IOM, yes maybe for those who go there.
Now we're about to go to one of our biggest local meetings with a small port head fitted with the big valves. I'm optimistic...
Let you know how it works in a couple of weeks.

[John Kat]

first I love your project gs in gsxr frame..john kat a tuned exhaust is more about sound waves than volume.

matching and balancing everything makes a flatter smoother torque line and more horse power is a by product -- torque does the work, horsepower is how fast the level of work can be done.

Thanks!
That's why I love my 1290 KTM Superduke: no need to rev the engine, it just pulls you out of the bends like there was no end.
On top the gigantic torque has only 210 kg fully gassed to move...

[trippivot]

This is why I keep telling people that just about NOTHING is as fun as a 16 valve, 1400cc GS street motor! YEEEEHAAAAAAAAA!!!! Lol!!
Ray.

yep ray, new term - " low lift flow " because TSCC is just a sales slogan lol

I'll always like 2 valve GSs' - my next one will be a hard tail chopper - or a methanol burning hill climber. !! big port hemi power!!

greg T - like to hear how it goes,, small port, big valve combination

jon kat - I read the whole thing a few times after I came across a pair of 89 GSXR1100 chassis, thought about a GS / gsxr DOT head hybrid amalgamation - but recently saw the 80's katana with a 1127 -ooo weeee !! those chassis are cheap around here!

I hope we didn't scare the OP out of using one of these, the big port GS head works GREAT on top - Just don't do a lot of cutting - except milling - it's perfect to grow into and you cant hurt it.

[BadBillyB]

Having ported quite a few of these 2V heads, The large port head should be used for big motors (1200+) and the small port should be used on smaller motors. Although size does matter, as we all know, the shape of the port is most critical. The factory port shape is awful. The short side turn is way too sharp and abrupt. The short side is also too short. Rounding and raising the short side turn in effect lengthens it. The long side can be raised also but is limited by the proximity of the lifter cavity. On drag motors (which is all I ever built) I went all the way into the lifter cavity, but just barely. A machined aluminum washer (now a spring shim) was then JB welded into the lifter bore to seal up any oil getting sucked in. Attached is a pic from my racing days (80's) showing what the end result would look like. I used Manley A&B two part epoxy to raise and contour the short side radius.....Billy
IMG_0520.jpg
To the OP, 38mm/32mm valves are already very generous size, the Kaws had 36/30 valves . And props to A. Graham Bell (Performance Tuning book) for the original illustration that I scribbled all over

[GregT]

I was in at one of our local speed shops last week and the owner was showing me his CNC porting setup...He brought up, as an example, an inlet port from a head imported from the US which he'd probed and copied...I don't know what it was or who had produced it but the port angles were pretty well identical to the GS1000 setup.I asked if his software had a scaling function. The answer was yes. Hmmm, one day when finance allows...Sure beats hours of peering down a die grinder.

[GregT]

greg T - like to hear how it goes,, small port, big valve combination

The answer is - very well indeed. Owner came out to take it up the road for a systems check. I watched as he went over a small bridge and opened it up as he saw the open road...Gave it a handful and it went about a foot sideways, LOL. Only supposed to be a quiet run.
At the track it had all it's lost midrange back plus a better top end.
I'd told him it really needed fresh rubber for the weekend, but no...So while he led several races, all they had to do was wait till he was well sideways and go underneath him.
Rider's comment - I like the usual option of dialling up wheelspin when I need it - not every time I open the throttle.....
FWIW it's running a 160/60 17 Michelin rear. We really need to look at a legal 5 inch rim and go to a 180.

[trippivot]

that is great - give a guy what he asks for , and then he wants what he used to have lol!

[GregT]

that is great - give a guy what he asks for , and then he wants what he used to have lol!

It was self inflicted...When he came back from the test ride up the road, he looked thoughtful and said "it's got a bit of an edge now, hasn't it..."
Which was when I told him it needed rubber....
At the track, there's a series of lefts which tighten slightly as they go on. One of his competitors remarked to me in passing on the Saturday that I should go down and have a look at the GS there as it was spectacular from his viewpoint behind...I wasn't game to go look. Apparently by the last left it was nearly full opposite lock....