Riding skills: How to get a good race start

By Michael Neeves -

Riding Skills

 11 November 2010 13:15

Most top-level racing bikes (including the fabulous new Aprilia RSV4 Factory APRC SE road bike) equipped with cutting-edge electronics packages will have some form of launch control. 
The very best of these systems will let you pin the throttle, dump the clutch and off you go with the perfect start. The electronics prevent the bike from bogging down or pulling massive wheelies.  
But for the rest of us with no electronics to rely on, race starts are a balancing act between clutch, throttle, body position and nerves. I’ve been racing for over 20 years and can get off the line pretty well, but I’ve been known to make some real howlers, spectacularly jumping starts or bogging down and going backwards. 
The start of a race is everything. It’s the easiest time to overtake and get ahead of your rivals. If you muck it up, it’ll take you all race to recover…if you ever do.
Here are some race start tips:

• Don’t panic! Try to stay as calm as possible. It’s the most stressful time of the race and it’s hard to even hear your own bike. I try and ignore I’m in a race for a split second and imagine I’m just pulling away swiftly from a set of traffic lights. Left foot goes on the peg for instant gear changes, right foot on the ground to stop you falling over.
• Set your revs. At the point where the meat of your power starts. It’s usually around 9000-10,000rpm on an inline four-cylinder superbike or supersports machine. Whether you blip the throttle around these revs, or hold a constant the throttle is down to whatever you feel most comfortable with. If you have too few revs and you let the clutch out too fast, you’ll bog down.
• Let the clutch out progressively. Do it too fast and you run the risk of lurching forward and pulling a big wheelie. Let the clutch out slowly at first to get the bike rolling, then progressively feed the clutch out as your speed builds.
• Apply more throttle. Once you’re rolling and the clutch is almost fully out, it’s time to give it more gas. Again, smoothness is the key as too much throttle will result in a big wheelie.
• Lean right over the front wheel. In the dry you can stop wheelies by leaning over the front of the bike, which will let you apply more throttle and achieve a faster start. In slippery conditions there’s a chance of wheelspin, so adopt a more neutral stance on the bike to transfer more weight to the rear of the bike to aid rear traction.  
• Second gear. Clutchless change (or quickshift) into second gear. Powerful machines will still want to wheelie, so stay hunched over the front of the bike to keep the front wheel down and keep moderating the throttle. 
• Braking point for first turn. Will more than likely be different to normal as you’re approaching it at a slower speed. Try to establish a marker (which will normally be further down the track towards the corner) on your sighting lap.

How to Slide like a SuperMoto Racer

February 10, 2014 by Brian Christner 

How many people would love to slide their motorcycle into a corner like a SuperMoto?  Me me me!!  That is what I said the first time I witnessed a SuperMoto race.  Something that sparked my interest immediately.
Sliding like SuperMoto  is something that takes practice preferably in a parking lot away from cars.  But as soon as you experience it you are hooked.  When I raced SuperMoto I loved it and miss it still.
Why does a SuperMoto bike slide you ask?  Well the slide going into a corner occurs when you load the front of the bike during heavy braking transitioning the weight from the rear of the bike to the front wheel.  During the weight transition we are also downshifting to a lower gear and then letting the clutch out in a lower gear thus making the rear wheel turn at a slower speed than the front.  With a little lean angle the rear end starts stepping out and WALA we are sliding.  Now the details

How to Slide like a SuperMoto

1. Setup a reference point for breaking and a couple more for the turn into the corner and the apex (middle of the corner).  Try to use something that is easy to spot like cones, T-shirts, or something else that you won’t mind running over.
2. Shift your weight as far forward as possible.
3. Ride a couple times into the corner to find the right speed for the corner and start picking up the pace and focus on hard braking with the front and rear brakes starting at your braking point.
4. Downshift to the gear you want  exit the corner with.  Stomp on that gear shifter like you are putting out a fire.
5. Let off the brakes slowly and let the clutch out slowly.  If you let it out too fast and don’t have a slipper clutch you will experience the rear wheel hopping.  No Problem if that happens.  Pull the clutch in just a little bit to get the hopping under control then let the clutch out again.
6. Lean.  Start leaning into the corner and push the bike down.  If you want to try dangling a leg put your leg out and as far out and forward as possible.
7. Now put it all together and focus on being smooth.  Smooth off the brakes and clutch.  Lean into the corner and control the slide with the rear brake or add some throttle.
8. Repeat these steps and slowly increase speed but not to much.

Repeat these steps and try to control the huge smile that will appear under your helmet.

How to Launch your Motorcycle like a Drag Racer

june 10, 2010 by Brian Christner 

 

  Quick launching your motorcycle is used in multiple different ways from racing your buddy from a stop light to motorcycle racing both on the drag strip and the road course.  A good launch is a coordination between throttle and clutch control while managing wheel spin and wheelies.  This technique works on any type of bike from cruiser, motocross, or superbike.  The number one tip of learning how to launch your motorcycle is practice, practice, practice!
So now down to the mechanics of launching your motorcycle quickly.  You already have the fundamentals of launching a motorcycle from a stand still as you do it every time you start your motorcycle.  You add throttle, let the clutch out, and then start moving while adding more throttle while releasing the clutch fully.  The same applies to race starting/launching your motorcycle.  Check out the steps below on how to race start/launch your motorcycle like a drag racer.

Body Position

Many people don’t realize the importance of body position on your motorcycle for successful launches.  The more weight you move over the front wheel the more throttle you can apply and the faster your start.
Move as far forward on  your seat as possible until your belly button is resting on the gas tank.  Now lean low and forward on the bike until you helmet visor is almost touching the windshield of your motorcycle.  Next, is matter of preference or comfort is the position of your feet.  I prefer to keep my left foot on the peg while only keeping my right foot on the ground.  It is also possible to have both feet down which requires fast reactions to get your feet up and get ready for the gear change.  Also some people prefer to keep the right foot on the peg and left foot on the ground in order to cover the rear brake pedal to control wheelies.  Whatever foot position makes you comfortable should be used just ensure that your body weight is distributed equally on your feet.  Be cautious of pressing  hard on one foot as it can actually steer the motorcycle off course. 

Throttle and Clutch Work


It is best to practice this next step in either a big open parking lot or a deserted road.  With your body in position  bring your revs up about 2,000 RPM more than what you normally would launch your motorcycle from a standing start.  Keep the rpm’s steady and avoid varying the rpm’s.  The correct launch RPM will depend on the bike you are using.  If you are riding a big 1000 CC bike like a Suzuki GSXR then you will need less RPM in comparison to a Yamaha R6.
Once you’ve decided to go start  faster starts start feeding the throttle and gradually release the clutch so that your bike stays at the launch rpm until road speed matches the engine speed. At that point, you should have the clutch out and be on the way to full throttle. Smaller bikes will require a lot of throttle and a lot of clutch slip, whereas on bigger bikes you will have the clutch out before you’re at half throttle in general. Experienced riders will want to work toward using full throttle right from the start, even on a big bike, and using only the clutch to modulate the power delivery. If the front end comes up or the rear tire starts to spin, keep that in check by pulling the clutch in a tad rather than backing out of the throttle. Closing the throttle will drop the revs enough that it will be difficult to recover, whereas pulling the clutch in keeps the engine spinning hard for when you have things back under control. Many riders keep the throttle steady through the whole sequence until it’s time to shift to second gear, but keep feeding in the throttle once the clutch is out until it’s at the stop. On a big bike that still has lots of speed in first gear to go even after the clutch is out, there’s lots of time to be made.
Now take a moment and analyse your start.  Did the engine bog down or the front wheel come off the ground too much?  Start adjusting your launch rpm, throttle, and clutch inputs and try again.  Keep adding launch rpm until you feel comfortable with the launch and attitude of the launch.  Remember you are not Valentino Rossi or Nicky Hayden so start out with low launch rpm’s and gradually increase them as you get comfortable with the process.
Take the opportunity and head down to your local drag strip.  You will be amazed on how much you will learn by doing a couple runs and watching the other riders.  Let us know how you do with your new riding tip.

MENGUKUR PERBANDINGAN KOMPRESI

MENGUKUR PERBANDINGAN KOMPRESI

TEKNIK DASAR MENGUKUR PERBANDINGAN KOMPRESI


Nah...ini dia mekanik dan biker suka pada salah persepsi, bahwa perbandigan kompresi disamakan dengan tekanan kompresi. Berikut kita bahas tentang hal ini.

TEKANAN KOMPRESI
Tekanan kompresi dipakai untuk mengukur tekanan yang terjadi diruang bakar.
Tujuan :
1. Untuk mengetahui tekanan kompresi motor sehat (standar)
2. Lalu membandingkan dengan tekanan kompresi yang udah terpakai.

Jika tekanan kompresi udah berkurang maka, kemungkinan disebabkan beberapa hal :
1. Ring piston bocor/sudah aus
2. Klep juga bocor
3. Gasket head bocor
4. Terjadi kebocoran di dalam ruang bakar tetapi tdk keluar melainkan ke dalam mesin itu sendiri, terutama pada bagian sebelah timing chain (keteng)

Ada kemungkinan lain yang membuat tekanan kompresi naik, yaitu :
1. Ruang bakar kotor dan penuh dengan karbon.

Nah...silakan diperiksa dengan teliti kondisi mesin anda.

Alat ukur tekanana kompresi bisa dibuat sendiri melalui alat bantu tekanan yang dipakai pada pengukuran tekanan angin ban. Hanya saja harus dibuatkan alat bantu seperti busi yg berlubang dan hubungkan ke meter tersebut dengan selang anti panas.

PERBANDINGAN KOMPRESI

Istilah ini lebih dikenal dengan Static Compression ratio (SCR) atau perbandingan kompresis statis.

SCR harus ditentukan sesuai dengan oktan bahan bakar yang akan dipakai. Jika SCR terlalu tinggi maka akan terjadi detonasi atau ngelitik. Hal ini akan menyebabkan mesin over head dan tenaga mesin menjadi drop.
Dan yang lebih fatal, maka piston akan pecah.

Berikut data bahan bakar dan aplikasinya :


Ada 2 metoda pengujian untuk menentukan besaran oktan
suatu bahan bakar,yaitu :
1.  Research Methode (Metoda Research)  Nilai oktan ditentukan dengan uji klinis di laboratorium,
  hasilnya dinamakan RON (Research Octane Number)
2.   Motor Methode (Metoda Motor)   Nilai oktan diuji melalui aplikasi langsung ke motor bakar yaitu campuran bakar pada inlet( lubang masuk)  yang  bersuhu tinggi  dan berkecepatan  tinggi. Hasil pengukuran disebut Motor Octane Number (MON)

Pengukuran SCR:


Rumus Dasar :




LANGKAH :
1. Siapkan alat ukur berupa Gelas Ukur (buret)

2. Buatlah mesin seperti pada posisi gambar di bawah



Mengukur Volume Ruang Bakar :

3. Letakkan posisi piston pada  titik mati atas (TMA
4. Isi cairan bensin + oil kedalam ruang bakar melalui busi sampai batas lubang busi

            Hasil yang didapat = Volume Ruang Bakar (V1)
5. Setelah langkah 4,  langsung piston diletakkan pada posisi titik mati bawah (TMB)
6. Tambahkan isi cairan tadi sampai batas lubang busi .
Hasil yang didapat = Volume Total (Vtotal)
              Mengukur Volume Total (Ruang Bakar + Cylinder)

7. Hitunglah perbandingan kompresi menggunakan rumus dasar.
CONTOH :
Dari hasil pengukuran didapatkan hasil sebagai berikut :
- Volume Ruang Bakar   =  9 cc  (langkah 4)
- Volume Total              =  124 cc  (langkah 6)

Maka, perbandingan kompresi  adalah :
V1 : Vtotal  =  9 : 124 (Semua bagian di bagi 9)

Hasilnya  : Perbandingan Kompresi = 1 : 13.8

Bahan bakar yang dipakai harus beroktan MON minimal 100 yaitu : Avgas

sumber  http://www.bintangracingteam.com/pintar.php?id=17

Cara Menghitung Over Lap Cam

Sebelum mengitung over lap cam/noken as. Kita harus harus mengetahui dulu tentang LSA atau Lobe Separation Angle. LSA adalah sejumlah angka derajat yang diperoleh dari jarak antara titik tengah ujung bubungan lobe-in dan pucuk bubungan lobe-exhaust. Berdasarkan pengalaman saya jika kita hanya menggunakan cam atau noken as mentah memudahkan mekanik menghitung angka LSA makin ekstrem. Karena saya bisa membuatnya sesuai spek yang aku inginkan dari sebuah motor. Jika angka LSA  yang ingin kita capai adalah kecil tentunga gampang kita buat, ini disebabkan profil kem masih bebas dan leluasa kita kreasikan. Bisa dari kepala, pinggang, sampai pantat, semua bisa kita papas sesuai karakter yang akan kita buat.
Hal ini tentu berbeda dengan cam atau noken as standar yang perlu tambahan las untuk membuatnya tinggi/tebal kembali, dan bahan biasanya mudah aus tergerus. Resiko durasi berubah sudahlah pasti. Hal yang perlu kita ketahui tentang LSA adalah semakin kecil LSA, berakibat semakin besar overlap. Ini sangat cocok untuk putaran atas. Karena tingginya resiko overlap membuat pembilasan makin sempurna pada mesin motor diputaran atas, seperti yang kita ketahui proses pembilasan terjadi pada saat overlap. Karena klep in dan klep ex membuka secara bersamaan di TMA (Titik Mati Atas).
Hal lain adalah LSA menentukan Power Band. Walaupun memiliki durasi yang sama, Jika LSA dirubah akan membuat karakter mesin juga akan berubah. Oleh karena itu,agar dapat mengusai trek balap, kita harus merubah LSA tanpa mengubah durasi cam. Secara teori jika trek balap panjang memerlukan LSA yang kecil.
Cara menghitung LSA dan Overlap.
Berikut adalah conto perhitungan LSA, jika sebuah cam atau noken as pada klep in membuka di 25° sebelum TMA. Dan klep out terus terbuka sampai 30° setelah TMA. Kita dapat peroleh angka overlap adalah 25°+30°=55° .
Cara menghitung LSA nya adalah :
((Durasi in / 2) – angka bukaan in) + (durasi exhaust / 2) – (angka tutup exhaust) / 2) = LSA. Cth; durasi in 270° , bukaan in 25°, durasi exhaust 270° , tutup exhaust 30° . Maka LSA = ((270°/2) – 25°) + (270°/2)-30°) /2) = 110° + 105° = 215°/2 = 107,5° .
Dan hasil dari contoh perhitungan LSA diatas adalah = 107,5°
Demikianlah cara menghitung LSA dan Overlap. Semoga bermanfaat untuk anda semua dalam memodifikasi cam balap anda.

sumber http://www.seputar-motor.com/cara-menghitung-over-lap-cam/