DirtRider . Net MX, SX, Arena Cross, Off-Road Community
Dirt Rider . Net Text Version Home
Dirt Bike Dirt Bike Dirt Bike Dirt Bike

This is the text version of DirtRider.Net
Click Here for the Full Version


Pages: 1

starting bike

(Click here to view the original thread with full colors/images)

Posted by: levistibby---------------------

hey guys quik question. somebody asked me if i was taught the proper way to start it up? i dont know but he just told me to kick it hard. then they told me its best to wait till dead center then kick it. what does this mean?


Posted by: rmc_olderthandirt---------------------

There are techniques that vary depending on if the bike is a two stroke or four stroke and then there are techniques that vary with the specific bike.

On a two stroke the bike can start on any revolution. As far as the kick is concerned you just get a good bite with the kick start lever and kick it hard. A small motor, sucha as a 125, kicking it anywhere in the cycle is fine. For a larger motor you may want to bring it up on compression then get a new bite (ratchet the kickstarter back up to the top) so you can give it a hard long kick.

On a four stroke the engine will only fire on every other revolution. You have to bring it up on the compression stroke, get a full bite with the kickstarter and then kick it. If you kick it on the exhaust cycle instead it probably won't have enough momentum by the time it gets around to the compression stroke.

How you deal with the throttle varys from bike to bike, how the carburetor is jetted, how warm the bike is, etc. If my bike is warm (like when I restart after shutting it off to talk with my riding buddies) I will crank the throttle 1/4 to 1/3 open and kick.

If my bike is cold I will leave the throttle closed and kick it until I get any kind of response then crack the throttle just barely open. I can generally get my bike started in less than a half dozen kicks, which is far better then when I used to crank it WOT from the first kick....

Rod


Posted by: mox69---------------------

I'm going to guess he meant wait until the piston is top dead center (TDC) to kick it. I'm not sure that is necessary, but if you want to try heres how.

Start by putting pressure (with your foot) slowly on the kickstarter until the it is really hard to push. The hardest point is TDC (or close) if it gets easier to push you are past TDC.

So basically before giving the engine a good kick, put some pressure on the kickstarter with your foot and move it into this hard spot. Let the kickstarter coil backup, and then kick it.


Posted by: Octane250F---------------------

I never made sure that my 250F was at TDC when I kicked it. I just gave it a few kicks and it always started on 3-6 kicks.
I know that on the older 4-strokes (especially the YZ 400 and YZ 426) you had to make sure you had them at TDC, but it seems like with the newer 250Fs and 450s that you dont need to.
Also, with a 4-stroke you NEVER want to have the throttle open when you kick it, because the engine can kick back on you and you can get injured. Trust me, Ive seen it happen.


Posted by: rmc_olderthandirt---------------------

Quote:
Originally Posted by mox69
The hardest point is TDC (or close) if it gets easier to push you are past TDC.



Actually, as you approach TDC the effort to rotate goes to a minimum. Exactly at TDC the only effort required is the drag from the bearings. Just past TDC it will go on its own without any effort at all.

The greatest effort is somewere a little past halfway up the compression stroke. At exactly half way up the forces on the piston has the greatest leverage against you (the crank journal is at 90 degrees) but the pressure in the cylinder is still fairly low. As you continue the pressure in the cylinder goes up but the leverage goes down.

You want to rotate the engine slowly until you have a firm amount of resistance, which indicates that you are on the compression stroke. Then you want to kick it hard so that it is turning fast as it passes TDC as you need the rotational speed to generate the spark.

Rod


Posted by: levistibby---------------------

ok thx guys. kinda new to all this so tryin to take as much in as i can. see u guys around


Posted by: halfastowens---------------------

so i just messed up my ankle that was previosly broke this year, all from the kickstarter kicking back. i've been starting this bike the same way ever since i got it and it is just now that it kicked back on me. I'm still kinda confused on the tdc. i've read the manual up and down and all it says on tdc is when you are trying to rebuild the top end. well at least that i can remember. I'm not to good with understanding things untill i see it done, reading about this gets confusing. I do appreciate any advice though


Posted by: High Lord Gomer---------------------

Quote:
Originally Posted by rmc_olderthandirt
On a four stroke the engine will only fire on every other revolution. You have to bring it up on the compression stroke, get a full bite with the kickstarter and then kick it. If you kick it on the exhaust cycle instead it probably won't have enough momentum by the time it gets around to the compression stroke.
I have always started 4 strokes beginning just after the end of the compression stroke. On older bikes without auto-decompression, you *had* to do this. On those, you slowly kicked through until the piston came up on the compression stroke and it got very hard to kick. At that point you would pull the manual compression release and gently nudge the kickstarter to get the engine just past TDC. Then you would let the kickstarter come all the way back up and take a full kick all the way to the bottom. That ensured that you had the momentum of (almost) 4 complete cycles of the engine before it got back on the compression stroke.


Posted by: digifox---------------------

Good tuning and a good leg...

Seriously if you get a bike tuned near perfect it will start first kick no matter what!
and if you have a good leg, its even easier to start..

*Shrug*
you all can say 500 2T are hard but try a 650 2 cylinder 4T..
"I" can start it on 2-3rd kick

All i can say is Tune and kick hard
and if its a 4T and you kick-it over and it doesn't start, For the love of your leg..SLOWLY turn it over to make sure its not going to kick back....(like gomer said)


Posted by: DirtDomain---------------------

Quote:
Originally Posted by Octane250F
with a 4-stroke you NEVER want to have the throttle open when you kick it, because the engine can kick back on you and you can get injured. Trust me, Ive seen it happen.


what happens now?, because i can't start my dirtbike unless i have a little throttle going and then i put it in first and then ease off of the clutch and give it gas but now i am afraid to...


Posted by: J-man---------------------

when i start my 250F i go a little bit past TDC that thing wont start at all in TDC



Text Version Home





vBulletin Copyright ©2000 - 2009, Jelsoft Enterprises Limited.
vB Easy Archive Final ©2000 - 2009 - Created by Stefan "Xenon" Kaeser