Ok some may think this Q is pointless because its a cruiser not a Hayabusa....BUT....I have a nightster and now that I have been riding for a few months I am wondering the best way to take off if you were looking for fastest acceleration- but safely. (they forgot that part in the riders course!). This is my first bike and as you know the N doesnt have a tach...so I have been shifting on feel/engine sound etc....would you stay in the lower gears longer or get through them quicker to take off quick??? Just need a little 101 schooling...

 

Yeah... you're right... but if you're that new... I'd say take your time... you'll learn all those bad things yourself in time...

Charlie D.

 

A quick take off has nothing to do with higher gears, it is done only in first gear. Shifting gears will come after you've mastered the take off (or launch).

You WILL NEED TO BUY A TACHOMETER. You can't launch without one and you can't shift gears without one.

Traction is paramount. It is the most important thing to launching a vehicle. You generally run a little lower rear tire pressure to increase it's traction. For the street maybe 28 psi, for the dragstrip maybe 20 psi. Unfortunately Harley’s don't come with high traction tires, they come with bias ply tires where as Buells come with sticky road racing tires that have way more traction than your Harley has. So you might consider buying different tires (and possibly wheels).

You must keep the rpms high by slipping the clutch. Usually the launch rpm is about 1000 rpms above the rpm that the engine makes it's peak torque at (this is why you must have a tachometer to launch with). When you take off you have to have the engine already revving and you open the throttle wide and let the clutch out just enough to keep the engine's rpms at (or slighly above) peak torque rpms. You continue to slip the clutch (a little bit less slipping as the road speed increases and the rpms drop - but never let the rpms drop below peak torque rpms) until the road speed of the bike is a match for the engine rpms, then let the clutch out completely. At least it's a lot easier on your Harley than it is on a 600cc Jap bike with they're 16,000 rpm red lines and absolutley no bottom end torque. If you let your clutch out too soon you loose only a little bit of acceleration but on a 600cc bike you'll bog the engine down and it won't get going until it's going at least 10,000 rpms.

You may bring the front wheel off of the ground. If the bike isn't going to flip over, don't worry about it. If the bike is going to flip over, you must back off of the throttle, though not necessarily closing it. Just back off enough to slowly let the front tire back on the ground then open it wide after the wheelee (sp?) is over.

All of this will take some practice to get it right so I would start practicing at less than wide open throttle to get used to what your bike is going to do. Try some quick starts at 1/3 throttle to begin with then increase the amount of throttle (a little bit with each launch) as you get better at launching your bike.

There is a cost in worn clutches with quick launches. You can reduce this cost by lowering the overall gear ratio of the bike and not slipping the clutch so much. You can go bigger on the rear pulley and if you have to you can go smaller on the front pulley (though lowering the front pulley size will increase the load on the drive belt and lessen it's life). I used to drive a '66 Mustang on the street and was always looking for a way to launch quicker. I changed the rear gears from 3.00 to 5.14 and it allowed the car to launch very quickly. Those gears were a little extreme for street driving, but, hey, I was a kid, what can I say.

If I were building a bike to "Street Race" I'd put a sticky radial tire on the back and lower the gearing as much as possible. Also, when hot rodding the engine, I would never over cam the engine. Power Bandwidth is key to good street performance and it comes only with low rpm engines. If you put too much cam in the engine you loose too much low end power to do a good launch without slipping the heck out of the clutch (this is what's wrong with launching a 600cc Jap bike over and over again on the street). Street races are done at much lower speed than you would ever do at the dragstrip (well, most of the time) so lowering the gearing isn't going to hurt that much.

If you're going to race at the dragstrip then things change a little and it will cost you a lot more money.

Rod

 

Is that why I just sit at the light With the motor SCREAMING in NEUTRAL?

I can launch and shift WITHOUT a Tach as I have EARS. Before you go out and buy a tach I suggest you go out and purchase some ears...they come in handy!

 

Your question is only valid against other Harley's if you're trying to do 0 to 60 against a metric you will lose. what's the point, like you said it's a cruiser.

 

You're not giong to get the best launch or times without one. You need to know the exact RPM for peak torque.

 

I have observed that just about any post generates controversy.

I had the same initial responses. However:

If you are going to do starts using this method, you will need a tachometer to do it optimally. You will also need to understand the power curve of the motor very well. If you really don't want to optimize performance, it could very well be done by "ear", and some might be very good at that.

With regard to the second comment, it is absolutely true that a Sportster won't be competitive against a new sportbike. But then again, racing is done in classes. There is nothing wrong with competing against those in the same class/style of bike.

 

True on all counts, but we're talkin' stop light fun, not Drag Strip fun.
imho ya don't need a tach to go fast, just experience and feel.

By the way, EXPERIENCE is the key word there, so for the initial poster, if your a newbie ya might not wanna get too crazy as BAD things can happen IN A HURRY that way.

Have fun & stay WITHIN your LIMITS.

Like they say, A man's gotta know his limitations.

 

Both rfranz1952 and creekhed1 have important things to say about "having fun".

When you're "having fun" on the street you have an advantage with your Harley that the small Jap bikes don't have - a low rpm engine with lots of bottom end torque. You can beat a lot of guys on Jap bikes off the line and across the intersection because they will bog they're engines during the launch. Back in the '80s I raced a Suzuki 1100cc 4 cyl with my Yamaha 920cc twin and beat him across a six lane intersection because my 920 had lots of low end power and he wasn't able to get his bike going because of his bike's lack of low end power. Sure, once I reached 45 miles an hour and had just shifted into 2nd gear he went by me at 70 mph but as far as I was concerned I had won the race off of the line.

You must stay within your limits, that's why I recommended 1/3 throttle to start learning how to launch your bike. It will take many months to really learn how to launch a bike if you are new to motorcycling. And you don't have to take it to perfection. You can bypass the clutch slipping if you keep your engine in a state of tune that keeps your low end power high and just reley on the pulling power down low to get you going.

When you race on the street you get to choose the bikes you're going to race against, there for setting the class rules. When I used to dragrace on Mulhuland Drive, a little bit beyond the Rock Store, I had the most trouble with bikes like Ducatis. Unlike the Jap bikes, the Ducatis also have lots of low end torque and they make up for inexperience in launching abillity of the rider (they don't bog the engine down). Today the Japanesse also build big displacement twins which would give you quite a run off of the line, until they're higher horsepower finally wins the race for them. You can't beat a 12 second bike with your Sportster in the quarter mile but you can beat them in a short street race if your good at launching and the other guy is not.

And sure your bike is a cruiser but we all like to "have fun" once in a while.

Rod

 

One more thing. There are other countries besides Japan and USA. And there are other bikes.

BMW, Aprilia, Ducati, Triumph, KTM, Moto Guzzi and Victory (our second USA bike) are all big displacement twin cylinder engined bikes that will give you more trouble in "Having Fun" than most small Japaneese bikes. And I'd consider them all in the same class, they all will run 12 to 13 second quarter mile times, just like your Harley. Well, some will run 11 second, and a few will actually run 10 second et's but you'll loose that race imidiatley with no chance at all.

Rod