I'm new to the GS twin world. I want to race my bike at the track this weekend, but I'm not sure what the best sprocket size (front or rear) for making the best out of what power I have.  What's the best combination? I have heard from many diffferent people, many of whom say it can run a 1/4 mile time in the mid 14's, but also many more have said it can run in the 13's. I ride a 2004 Gs500F that's all stock and has only 1200 miles on it. what can I realistically expect? I'm an experienced rider and I know how to get a good holeshot and fly thru the gears (I know my powerband well). Who do I believe?

Not many drag racers here i would presume since most are noobs, but if your serious about racing it even though you will get beat by most bikes, do the simple bolt ons: filter/exhaust/rejet, add weight reduction, a slick in the rear and run a 14 or even a 13t front sprocket with a wheelie bar and launch at 8k you should be able to hit 12's depending on your riding skill.  A stock gs will run mid 13's all day long.

13t is a pretty sharp turn on the front, I would suggust a combo of down in the front and up in the back to reach your desired gear ratio, also remember to take into account the sidewall of the tire your running, it plays a big role too.  I found this site to be of great help when I wanted to see what combination of front and rear sprockets would get me.   Remember stock is 16 front and 39 rear.

http://www.cyclelandspeedway.com/kart/forms/gearchart.htm

can a stock gs really run 13's?

Quote from: bcutrufellican a stock gs really run 13's?

seems like a bit of too much optimism to me.....I would guess that 180 lb guy will never get anything lower than low 14s......if you are 120 lbs, then maybe

I drag race exclusively (corners scare my knees  :lol: ).  I think I am one of two active drag racers here (Greg Gabis was racing a GS450 in stock class a while back).

Yes, a stock bike can run 13's but you have to know what you're doing.  Don't expect to just go out and run the number.

I have run the stock gearing and also the 15 tooth.  The 15 tooth REALLY wakes the bike up off the line but you have to know your clutch/throttle feed or you end up staring at the sky and dragging your feet off the back end of the bike to the 60ft marker.  Running the 15 tooth front, I cross the finish line at 11,000 in 4th gear.  I think the stock front sprocket had me crossing the finish line at roughly 10,500 in 4th (little foggy, that was a while back).  I'd like to try a 14 tooth with a shift to 5th and see what that nets me.  Without an air shifter you pay a premium price for each shift...  5th and 6th are overdrive gears but the overall ratio of 5th is still roughly in the ball park.

While you're waiting in the pits to race, sit on the bike and get in your tuck and adjust your mirrors.  If you're racing brackets, you will leave first because your bike will be slower than every bike out there.  You will want to watch your opponent approach you in your mirrors and then the end-of-strip games begin.  If you've previously adjusted your mirrors in a tuck then you have complete control of the motorcycle and a full view of your opponent without leaving your tuck.

(I'm rambling but it's lonely being the only one at the tree) Be prepared to smoke everybody off the line.  For whatever reason, the GS ROCKS off the line.  I regularly CLOBBER Hyabusas, GSXR's, CBR RRRRR's - the little GS COMMANDS and nobody will be able to take you.  Start dirt bike style (pretend you're on the starting gate of a 125cc moto and get your elbows out).  Let your clutch out to the friction zone and then pull it in a mm.  grab a big ol' handful of gas (big elbows) and get er done.

I haven't posted my drag results since last year so the data is old but if you search for "Race Report" you will find my old drag times and bikes I put on the trailer.

Any other drag questions you have, please post them - I was beginning to feel like the only one...  Let me know what track you're racing at!

Weather will also play a large role in how the bike performs, as does the launch. Launch is key in drag racing, as if you screw up your first 60' you might as well cruise down because you can never really make up for it. Roughly every tenth lost in the 60' is two tenths lost in the overall run. If you're just going to a test and tune, your reaction time does not matter, as it does not affect your overall posted times, but shallow staging can help out a little bit. Worrying too much about your reaction times will do nothing but kill your launch as you will be too concerned about the tree and not your bike.

I have never drag raced on a bike before (although I plan on doing it very soon), but I have done quite a lot of it in cars. Most of my knowledge comes from that, but I'm sure it all applies to bikes as well. I also agree that a stock GS has the potential to run 13's, based on my feel for it so far.

pinto, i know this topic has come up before and i dont recall a definite answer.  wouldnt shifting at red be a detriment to your time?  shouldnt shifting occur at max hp peak?

Yep, I think you're probably right.

I've never been able to really nail that one down and in brackets, consistency wins the game so I just pick an RPM that I can hit the same every single time.  Also, rpm through the traps might be different than your shift points.  In top gear, your ET will suffer more if you shift and only get a few hundred rpm out of the next gear vs exceeding your power peak in the current gear by a few hundred rpm.

Really the only time I have experimented with shift RPM was in a car.  I was racing a friend's Monte Carlo SS (the cool one with the Nascar back window).  Racing the car in DRIVE netted a 15.8 ET with the engine shifting at ~5,250.  When I shifted manually I ran a 15.4 (I over-revved it in 1st and floated the valves).  Shifting manually, my RPM was 5,500.

Sooooooo.... I dunno...   :dunno:

At SOME POINT this year, I will do a valve job on my GS (33,000 miles) and then I'll dyno it.  When I have a dyno sheet for the motor I'll be able to experiment with the shift points.

Quote from: weaselnozepinto, i know this topic has come up before and i dont recall a definite answer.  wouldnt shifting at red be a detriment to your time?  shouldnt shifting occur at max hp peak?

It depends on the power curve. You never want to shift at your peak though. All that would do is drop you to a RPM that is much lower in power. You want to shift to get the most power down. Therefore, go PAST your peak then shift where the current power level roughly equals the power level on the other end of the curve. The middle spot or 2/3 spot should be where peak is. If you shift too fast at peak you'll miss an opportunity to keep the power up to close to the peak and instead go too far back down and have to work its way back up.

Then again, red is never the peak on an engine (at least, it shouldnt be) so for most engines peak and red are two different RPM spots.

Quote from: weaselnozeshouldnt shifting occur at max hp peak?

Well...  You want to keep the HP as high as you can, so shifting right at the peak might actually make you a little slower.

I'm not all that familiar with the HP curve on a GS, but you want to shift when your current HP is about to be lower than post-shift HP (from what I've seen, it's usually pretty close to red-line).

Not really sure on a GS though.   :dunno:

Quote from: The Lazy DestroyerThen again, red is never the peak on an engine (at least, it shouldnt be) so for most engines peak and red are two different RPM spots.

for vtec engines max hp is at red.  now that i shift at red sometimes a lil after.

Quote from: weaselnoze

Quote from: The Lazy Destroyer
Then again, red is never the peak on an engine (at least, it shouldnt be) so for most engines peak and red are two different RPM spots.

for vtec engines max hp is at red.  now that i shift at red sometimes a lil after.

Yea but dont those have some wacky dual cam setup, where one cam is below 4000 rpm's and the other kicks in for the rpm's above that.

last year i had my gs run 14.2@92 mph...it wasn't stock but it wasn't modified that much...just a 15t sprocket, stock gsxr canister and jetting....and i weigh 210

Quote from: sprint_9

Quote from: weaselnoze

Quote from: The Lazy Destroyer
Then again, red is never the peak on an engine (at least, it shouldnt be) so for most engines peak and red are two different RPM spots.

for vtec engines max hp is at red.  now that i shift at red sometimes a lil after.

Yea but dont those have some wacky dual cam setup, where one cam is below 4000 rpm's and the other kicks in for the rpm's above that.

taken from insightcentral.net:
{Variable-Timing & lift, Electronically Controlled: This is Honda's term for their technology that adjusts the amount that intake/exhaust valves are opened based on the current engine speed. The Insight uses a variation of the VTEC system that Honda calls VTEC-E ("E" standing for efficiency), that operates only on the intake valves.}

now i believe in my car vtec kicks in at 4200 rpms.  it also has to do with how much trottle is applied.  if i remember correctly a different sized cam lobe shifts into place to adjust the timing.  eh its late and i dont feel like reading.. go here

It would be interesting to see the cams in one of those engines.

I had a run at the drags last week, 90% stock bike, full tank of gas (doh!), I weigh about 165 without gear. 1st run I got 15.247s, 2nd was 15.117, 3rd 14.789s, 4th run was 14.791s. Weather was 10C, 90%+ relative humidity.

Plan on going out again in a month or two with some mates once I've got a new air filter and the jets worked out properly, they are a mess atm. I'm hoping to crack into the 13's once I find out the power band and this time I'll run with less fuel in the tank.

I didn't bother doing a burnout on the pad, doubt it'll do anything worthwhile with the Dunlop GT501's I've got on the bike.

I have yet to take my bike to the dragstrip but I know it is faster than my car.  My cars best time 14.8 @ 92 mph with a avg 60 ft time of around 2.2 seconds.  Street tires and a 2900 rpm launch, launch any higher and she breaks loose.  

Eventually I will get the GS to the dragstrip, curiousity is getting the best of me.

Quote from: brembo90% stock bike, full tank of gas (doh!), I weigh about 165 without gear. 1st run I got 15.247s, 2nd was 15.117, 3rd 14.789s, 4th run was 14.791s. Weather was 10C, 90%+ relative humidity.

I didn't bother doing a burnout on the pad, doubt it'll do anything worthwhile with the Dunlop GT501's I've got on the bike.

Right on!  I don't bother doing a burnout either.  There's really no need with the GS.  You're not going to spin the rear before you wheelie so...

Definitely run with less fuel in the tank.  I don't know what gas weighs (probably less than water?) but water is 7lbs./gallon.  If you went with only one gallon in the tank vs. 3 well...that's some good weight reduction.

How much time did you have in between each run?  I ask because your runs trended faster.  As eliminations progress, the time between each run gets less.  I've noticed that if I come in hot of the freeway, get through tech, and make a pass (lots of heat in the engine) my time is quick.  Then the bike cools for 30 minutes or so and the bike slows.  Then there's less and less time between runs and the bike keeps picking up.  

Just wondering if you saw the same thing.  If so, then idling in the staging lanes to keep the engine warm is probably a good thing for ET on the GS.  It's exactly opposite of what I do with my car - I try to keep all heat out - but if it works I'll do it!

Quote from: V8Pinto

Quote from: brembo....  I don't know what gas weighs (probably less than water?) but water is 7lbs./gallon. ...

8 lbs/gallon for water