Just as the title asks, what would be the ideal RPM range for a hard launch off the line? Was experimenting a bit today, tried at around 8K but still feels a bit bogged down, maybe I need to ride the clutch for a bit longer?

Don't want to experiment too much as I don't want to unnecessarily wear the clutch down, 99% of the time no car even bothers trying to jump a bike off the lights anyway.

Stock everything by the way, 2004 GS500F, Pirelli Sport Demon tyres.

  ooooooh controversial topic right here!! 

Watch some stock bike proper drag race vids... Not the super fast ones .. Just the 'wed night fun' type..

It seems to be more as you said... Good clutch control rather than sheer revs ..

I'd maybe think around 6-8k rpm .. You want the clutch slip to get the bike moving as much as you can without the bogging ... Then get out of first and let the clutch engage fully to put all the available gs500 'power' down to the road..

But yes you will give your clutch a beating! ... Practice if you must ... But real close to home or a ferry vehicle ... So if you blow the thing out you CAN get it back to garage easy!

Ideally you want to use a 'beater' spare bike to get your technique down ... So you not bike-less if you break it ... 

.... Oil/tyres/fuel .... And now hard launches ... Controversy! 

rejetting the carbs gives it a lot more power off the line for hard launches and acceleration.  I actually replaced the stock air filter with a K&N drop-in and went from the stock 17.5/60/130 to 20/62.5/142.5 jets and it's waaaay better for off the line acceleration.  Now The Buddha first thought this jetting was too rich, but ironically now he says it's too lean 

thats true too Rado! ..  .. you got a different can on too yeah?

im not knocking that theory at all... but launches .. while power is an important factor for sure.. technique is very important .. 

not everyone is a fan of drag racing... fair enough... and i certainly am not the 'go to guru' on the topic.. but for a lot of years i have watched and heard people talk about.. 'losing the race off the line' .. a bad launch can kill the run! ..

now.. OP .. so the anti's dont want to crucify me for encouraging bike abuse!! .. i really dont mean to push the idea that hard launches are the best thing since sliced bread... as i said before... they are HARD on many parts of the bike....

however... having the technique sorted out properly to 'minimise' the potential for breakage is STILL important! ..

i dont think there is a rider on here that hasn't belted it off the lights/line at some point! .. (someone honestly tell me they havent!!) 

.. thinking... maybe ask burning1 and a few others that (dirt or road) circuit race too... getting your shaZam! together on the start and getting that hole shot can also make a big difference...

sure overall riding skill/technique counts more in the long run ... but if you must hard launch .. then make sure its smooth!!!

Quote from: Janx101 on October 10, 2013, 03:54:35 PM
thats true too Rado! ..  .. you got a different can on too yeah?

Actually I've got the stock exhaust 

I personally like having a peppy vehicle that can scoot and pull off the line if I need it; but I don't normally ride super aggressively, though I'm not laid back and slow either.

ok, first, off, change front sprocket, go one tooth down. much better drive off line and through mid range.  jetting the carbs is good but the stock exhaust doesnt help for mid to upper RPM power. the extra back pressure helps with the lower RPM torque a little. by helping the engine wind up rpm's faster you can use the HP in mid to upper rpms sooner.   launching is mostly about technique true, but its a culmination of the whole package. and......the package constantly changes, fuel,oil, wear and tear, temp C/F, weather, what you ate for dinner (think im kidding?) the GS isnt a torque monster but does well for what it is.  if your bracket raceing it might be ok ONCE you have everything dialed in.

Quote from: Blueknyt on October 10, 2013, 05:23:00 PMjetting the carbs is good but the stock exhaust doesnt help for mid to upper RPM power.

...

the GS isnt a torque monster but does well for what it is.  if your bracket raceing it might be ok ONCE you have everything dialed in.

With the stock jetting this was true, but now it's very torquey throughout; especially in the top end.

Getting a good launch is extremely not trivial.

First, start by redlining the engine. We aren't looking for peak torque, we're looking to build as much momentum in the crank as we possibly can.

Start of launch is the hardest part. We need to simultaniously roll on to WOT, and to get the clutch into the right spot in the friction zone. Ideally, we want to dump as much of that crank energy into the wheel as possible, we do *NOT* want to over-rev the engine, and we do not want to bog the engine down. Aim to get to WOT immediately, and to drop the engine RPMs down to 8 or 9K RPM.

From here, feather the clutch out. Your throttle needs to stay wide open. RPMs should stay at 8-9K RPM. Use the clutch, and the clutch only to maintain engine speed. Eventually the clutch will be completely released, and the launch is complete.

FWIW: Getting a good launch is very very hard. I got an ideal launch once, and ended up beating some 90HP 450cc I4s into the first corner.

A 2 stage rev limiter will help. On those, you can set the RPM limit to about 10.5K with the clutch applied. It eliminates the need to modulate the throttle during your launch.

now THAT .. is some good info!! 

Quote from: radodrill on October 10, 2013, 07:36:13 PM

Quote from: Blueknyt on October 10, 2013, 05:23:00 PMjetting the carbs is good but the stock exhaust doesnt help for mid to upper RPM power.

...

the GS isnt a torque monster but does well for what it is.  if your bracket raceing it might be ok ONCE you have everything dialed in.

With the stock jetting this was true, but now it's very torquey throughout; especially in the top end.

i think what you noticed is the engine isnt running lean anymore. if you uncork the exhuast, you will have to jet again. you will notice it really wakes up from 6-9k. still falls on its ass at 10k but gets there faster. stock jeting, filter and exhaust it is alittle peppy from 3-6k but tapers off 6-8k and then splats Wile E coyote style at 9-10k, sure it will rev higher but all bark no bite.  NOW, this is for the 2 jet carbs,  ive not played with a set of 3 jet carbs yet.

it can be a torque monster!! .... just more of a wazowski instead of a sullivan! 

Quote from: burning1 on October 10, 2013, 08:49:30 PM
Getting a good launch is extremely not trivial.

First, start by redlining the engine. We aren't looking for peak torque, we're looking to build as much momentum in the crank as we possibly can.

Start of launch is the hardest part. We need to simultaniously roll on to WOT, and to get the clutch into the right spot in the friction zone. Ideally, we want to dump as much of that crank energy into the wheel as possible, we do *NOT* want to over-rev the engine, and we do not want to bog the engine down. Aim to get to WOT immediately, and to drop the engine RPMs down to 8 or 9K RPM.

From here, feather the clutch out. Your throttle needs to stay wide open. RPMs should stay at 8-9K RPM. Use the clutch, and the clutch only to maintain engine speed. Eventually the clutch will be completely released, and the launch is complete.

FWIW: Getting a good launch is very very hard. I got an ideal launch once, and ended up beating some 90HP 450cc I4s into the first corner.

A 2 stage rev limiter will help. On those, you can set the RPM limit to about 10.5K with the clutch applied. It eliminates the need to modulate the throttle during your launch.

Wow, excellent post! I will follow this advice the next time I try this!

Quote from: Janx101 on October 10, 2013, 01:45:19 PM
ooooooh controversial topic right here!! 

Watch some stock bike proper drag race vids... Not the super fast ones .. Just the 'wed night fun' type..

It seems to be more as you said... Good clutch control rather than sheer revs ..

I'd maybe think around 6-8k rpm .. You want the clutch slip to get the bike moving as much as you can without the bogging ... Then get out of first and let the clutch engage fully to put all the available gs500 'power' down to the road..

But yes you will give your clutch a beating! ... Practice if you must ... But real close to home or a ferry vehicle ... So if you blow the thing out you CAN get it back to garage easy!

Ideally you want to use a 'beater' spare bike to get your technique down ... So you not bike-less if you break it ... 

.... Oil/tyres/fuel .... And now hard launches ... Controversy! 

If I burn my clutch on the GS, I think I'll give up riding, lol.

It's pretty hard to burn up the clutch on the GS500. The clutch seems to be designed for the 1000cc I4s, not the twin.

I managed to over-heat mine by doing 3-4 race passes without a break. It went back to normal as soon as it cooled down.

+1

Hard to burn a GS clutch with abuse, saw the clutch parts out of my 97 and with 90k hard miles on it and they looked good as new.  Weak spot if any is the too weak springs that allow too much clutch chatter on fast uphill clutch slipping starts with heavy rider.  The 97 engine was replaced by son when he took it for a commuter due to high oil consumption and not clutch problems.

going one tooth smaller on the front sprocket will REALLY help with the traffic light battles. They can be had for $40 delivered on ebay and fitted in about 15 mins with a socket set and a pair of circlip pliers (then a chain adjustment after fitting)

Jetting is a bit of a touch-n-go affair with sizes and mixed results but there appears to be gains to be had vs the stock carbs... Im running 20/60/142.5 with a K&N in box filter but its too rich in the mid (more power than stock but poor throttle roll off)... Fitting a pipe soon so this may change it however I expect it needs the needles adjusted to fine tune it.

I had an 89 GS500 with over 100,000 kms and im sure the clutch had never been replaced. When the bike was cold the clutch would slip when accelerating up hill (100km/h zone, steep hill, 95kg rider) 

Being a wet clutch they really can cop a flogging without too much stress and there is a lovley youtube clip on how to replace it

Importantly always have fresh, good oil, and a well adjusted chain if you intend on flogging the bike