I'm an airbox believer

[nvr2old]

I got my '79 GS1000S to a stage where I could finally test ride it this past weekend. I had removed the airbox and installed velocity stacks, purely for aesthetics. In the garage it would fire up and idle, and rev nicely. Cool. The first time I slipped into gear and rolled away I could tell there was something wrong. It flat fell on it's face under load. It ran like total crap. My (Honda) certified technician friend and I went through the whole process of checking timing, spark, coils, spark plug caps, float settings, clogged jets..nothing. Everything was right on the money. As a last resort, mostly, we hooked the airbox back up..turned the key on, touched the starter and it lit right off. Runs absolutely perfect now. Took the airbox off again..what a pain..started it..ran like crap again. Re-installed the airbox again..what a pain..runs beautifully. Dumped the velocity stacks (sadly) but the bike just will not run with them. Good lesson. The airbox is what creates the velocity needed for these bikes...so, ironically, the velocity stacks proved to be "non-velocity" stacks. I've always been a strong advocate for airboxs on all my Hondas, and now I'm a confirmed believer with my first Suzuki also.

The moral of my story..I'll never stray from the box again.

[tkent02]

The moral of my story..I'll never stray from the box again.

Or you could jet it properly for whatever intake/exhaust you are running.

[nvr2old]

Or you could jet it properly for whatever intake/exhaust you are running.

I'd be curious to know how many people have had success re-jetting with stacks and a race pipe. I see dozens of threads where people really struggle with it. There never seems to be a perfect formula for any particular application, and I'm not sure if I should expect there to be. The way it runs with the airbox is so incredibly better, that I wonder if there's any advantage to messing with it just to have the "look" with velocity stacks.

[blowerbike]

the VM's are do-able.
the vaccum carbs require a recalibration kit.
any mechanic should have known that if the air flow is increased and extra fuel is not added to rebalance the formula for the entire rev range...
lean conditions happen and the ridability is gone.
im a firm believer in hands on learning experiances.
although i do have a piece of paper that says i "gadeatedd hi-skooll"

[nvr2old]

the VM's are do-able.
the vaccum carbs require a recalibration kit.
any mechanic should have known that if the air flow is increased and extra fuel is not added to rebalance the formula for the entire rev range...
lean conditions happen and the ridability is gone.
im a firm believer in hands on learning experiances.
although i do have a piece of paper that says i "gadeatedd hi-skooll"

There just never seemed to be a lack of fuel, that's what we struggled with. It "felt" like it was starving under load, but every test we did seemed to prove to us that it was getting more than enough for all four cylinders. The plugs, if anything, showed it was running a little rich, perfectly even color across the four. Rode it with the airbox, did a throttle chop-plug test, and that beautiful brownish-tan color had re-appeared.

[srsupertrap]

Suzuki described those 1979 GS1000 VM26 as "EPA carbs" which meant they were cold blooded right from the factory. The were a big rideability difference between the 1978 & 1979 version which Cycle magazine documented in their test of the 1978 GS1000C and 1979 GS1000EN. So there should be no surprise that your Yoshi & velocity stacked GS1000S carbs fall flat on their face. The Yosh pipe was never known as a mid range pipe and it was also designed for racing. Looks cool but favors the top end. Pardon the pun but there is no free lunch.

Nvr2old, unless someone has adjusted the VM pilot fuel & air screw to compensate and that might not be enough, I can understand your point. The fastest way to make it run with the way cool velocity stacks is install DJ Stage III kit. Then search the forum for "Keith Krause GS1000 jetting recommendation" which covers this topic in depth, again and again.

I personally use the VM29 Smoothbores and my GS1000/Supertrap 4 into 1/K&N equipped starts right up, idles fine and is ready to ride before I get the gloves on. More importantly its ridable throughout the rpm range with no flat spots, backfires etc.

IMO, here is an article that should be permanently stickied in the Performance section.

Steve

http://www.thegsresources.com/_forum...rch+free+lunch

[doctorgonzo]

I'd be curious to know how many people have had success re-jetting with stacks and a race pipe. I see dozens of threads where people really struggle with it. There never seems to be a perfect formula for any particular application, and I'm not sure if I should expect there to be. The way it runs with the airbox is so incredibly better, that I wonder if there's any advantage to messing with it just to have the "look" with velocity stacks.

Mine runs great. It's called a dynojet kit, about $120.00. I'm actually in the near future going to dump the pods some people refer to as velocity stacks for REAL velocity stacks. Bigger fish to fry at the moment.

[TheCafeKid]

Mine runs great. It's called a dynojet kit, about $120.00. I'm actually in the near future going to dump the pods some people refer to as velocity stacks for REAL velocity stacks. Bigger fish to fry at the moment.

WHy would you do that?? Honestly? Are you planning on racing it? Have you ever seen what happens to a street motor when Vstacks have been run on it for long periods of time? The airbox, and even pod filters do just that. They filter out the CRAP in the air and keep it out of your motor. I just dont know why anyone would run velocity stacks on an every day rider. If its something that you built to go ALL OUT on the track, or out in the middle of nowhere once in a while, fine, i guess, but not a regularly ridden bike. Just my opinion however.

[seuadr]

my bike ran like **** even after i cleaned up the carbs, replaced the orings and boots etc etc etc etc

one day, i had the airbox out for yet another carb cleaning thinking that was the problem.

that's when i noticed the airbox snorkle was not fully on the airbox.

i put it back on, then epoxied it into place.

bike ran great after that.

[nvr2old]

My friend and I were almost incredulous. We've always known that stock air boxes are hard to improve on. Even on our race bikes of that era we ran stock boxes, but the complete black and white transformation in this case, blew us away. We worked together at a Honda dealership when these bikes were new. He was the Service Mgr, and I was a painter. He's a great guy to have in your corner when it comes to diagnostics, and then the mechanical skills to do what's necessary. Methodically re-checking things off that it could/might be..to then simply bolting the air box back on to totally cure the problem. That's why I took it off again to replicate the crap-fest, and sure enough.. Now, it runs up through the rpms smooth as silk, great power right off idle. We laughed and shook our heads, had a beer, and chalked it up to another learning experience. It's time to start putting some miles on it!

[KEITH KRAUSE]

nvr2old, your bike was simply running too lean. One of the basic rules of thumb is if a bike will rev' OK without a load but bog down when under load, you have fuel starvation. In your case, very lean.
Nothing wrong with liking airboxes but you CAN pick up enough HP with a basic K&N pod/quality pipe/jetting kit combo to take off a full second from stock 1/4 mile time. Not just in your head, but significantly quicker. Will that matter much? Depends what you like. One second won't make your bike a world beater but it IS a little more fun to hear the 4-1 howl.
As for velocity stacks, they don't exactly go hand in hand with long engine life. Why take time and money to fix up a bike just to let huge amounts of grit slowly destroy what you built?? And I've seen a chart around here awhile back that showed stacks add maybe 1 more HP over quality pods. The chart was from a respected magazine many years ago that tested your bike with various intake changes including stock airbox, pods, no filters at all, and stacks. Only if every single ounce of HP was needed would someone run stacks. For an older bike, on the street, it makes no sense.
Now if you MUST have that look, then go ahead. The DJ3 kit will work well enough but you may have to bump up the main a little more than what they provide. Keep in mind that only at the range of 7,500 rpm's to 8,500 rpm's will your motor make that 1 extra HP. The stacks will have no benefit anywhere else. In fact, if you install the larger main to compliment the stacks at the very top of the powerband, you'll most likely NOT like how the main mixes at any other time.

[Nessism]

No way pods, pipe and jetting will take a full second off a GS bikes 1/4 mile time. You'd be luck to get 1/2 second.

[49er]

No way pods, pipe and jetting will take a full second off a GS bikes 1/4 mile time. You'd be luck to get 1/2 second.

Now,now. Let's not burst the bubble here!

The stock air box is fitted with adequately tuned rubber velocity stacks. Sure you can't stand there and admire them, but they're there and do a fantastic job.

The real trick with our road going GS's is to get more air into them at a controlled rate, through a modified stock airbox !!!!

[nvr2old]

To be honest with you guys, I was only going for the look with v.stacks. From the start, the vision of this bike that's been burning in my brain for 30 years, was of the Superbikes of the day, and they all had those beautiful velocity stacks. To me, they really added a period performance look that along with the Yoshimura pipe and rear sets, just gave it the correct attitude. Shaving off time on high speed runs isn't as important to me as dependability and rideability. The stacks I used did have a real fine mesh screen over the ends, and I was hoping that would suffice. The last thing in the world I want to do is ruin the engine just for the sake of a look. This bike is going to see a lot of street use and a fair share of 80-100mph. It runs so nice now, that I'm going to leave it alone at this point. I admire anyone who'se been able to dial one of these babies in to an all around performer in all conditions with the velocity stacks and pipe combo. God knows it sure looks bad-ass-cool.

[cyclefvr2]

i wouldnt run v stacks if they gave'm to me, on vm carbs the backpressure from stock exhaust is needed, with stock springs as well
its all figured from the factory, thats why they run so good
take the air box off ,and theyll never run right with out a lot of work
plus you get caught in the rain, your motor is drownded out, i preferr the k&n stock style filters, or pods with the outside covers on them, my bike runs good, but power is like **** since i drilled out the pipes, (end of them)
they were rotting anyway
i would like a vance repackable kit , or stock ones again, its a sweet bike stock,and performs like crazy!!