Suzuki GSX650F Forum - www.GSX650F.biz

Just wondering if there is something wrong with my bike, or whether this is normal. If I'm at the lights, and try to pull away quickly while the bike is just idling, the acceleration kind of lags for about a second or two before it delivers any power. If I keep the revs up to about 2-3k then slip the clutch it's not so bad but still noticeable. I'm sure it only started doing this after the first service, but maybe it's just all in my head.

There is a combination of factors to why it happens but there is nothing wrong with your bike, and it's not all in your head. It is normal.

I'd say the same. With the small displacement of bike engines, they need moderate revs to make much power. Our bike isn't nearly as bad as some sport bikes though. I rode an R6 a while back that needed to be revved like mad to get power, it felt like it was a 250cc before you hit 8,000rpm LOL

ah ok no probs

how far along (milage/Km) wise after the first service? I had to retension my chain after i got the first service done. to me it felt like it picked up a little better

you can get the bike to take off like a rocket from the lights from idle. it takes good throttle/clutch manipulation and control tho

practice and you'll get it to happen

What he said.

Below is a dyno of a 650F, they don't even bother measuring below 3500rpm.



The "lag" is most likely a result of you loading up the engine while it's rpm is too low. With an inline 4 it is to be expected that the "oomph" climbs with rpm, up to a certain point (on the 650F this is somewhere above 8000 rpm).

I believe there are members who frequent drag strips, they would be the best to advise you on your take-off technique, but to summarise, as you slowly release the clutch lever, you should try to maintain the rpm that is providing you with the acceleration you desire by increasing throttle (and obviously, once your clutch is fully engaged, the rpm increases with throttle up until you decide to change gears up.)

Hmm, that sounds kind of complicated but it's all a matter of feel...

If you want to see what a 650F is like below the 3000rpm mark, here is a copy of my dyno chart measured from idle.
It does not show the torque curve but if you want to work it out
the formula is;

5252 x HP = (x)
(x) / rpm = lb/ft

eg: 5252 x 22 = 115,544.
115,544 / 3000rpm = 38.51 lb/ft

so at 3000rpm I've got aproximately 22Hp and 38.51 lb/ft of torque at the rear wheel.
What you will also notice is the air/fuel ratio below 3000rpm. The bike runs lean.
Run 1 (red) is prior to having the power commander installed to remap the Air/fuel and Run 2 (Blue) is after.

(basically eloborating on what Human Potato also just said )
One thing you also need to consider for a quick take off (and the lag) from a complete standstill is the laws of physics applied to the bike.
You are effectively trying to shift weight and a body of mass that has zero momentum instantly down the road.
To do it quickly you need to have a large amount of force behind it to start with - basically have it built up and ready to go.
Then you've got the time it takes to apply that force from the combustion chamber through the transmission, through the drive chain, through to the back wheel and down on to road.
As soon as the force starts to shift the mass, it will decrease under load and also through various elements of friction.
To keep going you need to maintain an equal amount of force against the mass or to speed up keep multiplying that force.

From idle you simply dont have enough force to shift the bike instantly without lag.
You will never see a drag bike sit in the staging area at idle waiting for the green light.

thanks for all the advice everyone, I've always thought that I take it very easy on my bike maybe ill try giving it some at the lights, and turning up the throttle more as i let the clutch out. On a side note, my bike has now been relegated to second place in my main form of transport, because I just got a car (at long last) which makes me very happy, mainly because now my bike is just for fun! not for all the boring transport tasks as well, like going to work etc. I have noticed, my enjoyment of the bike is much higher when I haven't been out on it for a while, feels like almost a new experience again