Hard to start = how many kicks?


40 replies to this topic
  • roylo

Posted July 21, 2009 - 12:44 PM

#21

Hopefully, I will be able to fix it this afternoon.




Get the piston at the top of the compression stroke? Forgive me of my ignorance, but how do you know when the piston is at the top of the compression stroke?



When your about to start you bike push the kick starter down until you come up against the hardest point or resistance felt throughout the stroke. Sometimes you have to push the starter down a few times to find it, other times its at the top already. Then you bring the starter ALL the way to the top and kick down hard to do your start against this hard point.
After some time on the bike you will get to know how hard the resistance feels and know straight up if you are at that point or not.
Kick starting from this point gives the engine the best chance to fire up compared to any other point in the stroke :worthy:

  • YamahaRocker

Posted July 21, 2009 - 12:47 PM

#22

Lol. It's kinda funny b/c my 2001 WR426 starts with just one kick. Cold or hot. :worthy:

  • guitarnut57

Posted July 21, 2009 - 12:55 PM

#23

When your about to start you bike push the kick starter down until you come up against the hardest point or resistance felt throughout the stroke. Sometimes you have to push the starter down a few times to find it, other times its at the top already. Then you bring the starter ALL the way to the top and kick down hard to do your start against this hard point.
After some time on the bike you will get to know how hard the resistance feels and know straight up if you are at that point or not.
Kick starting from this point gives the engine the best chance to fire up compared to any other point in the stroke :worthy:


I can't wait to try this next time I ride. Thanks

  • sketchyhayde

Posted July 21, 2009 - 04:06 PM

#24

ive read somthing simalar to this about anther 07 yz450 when it was cold no problem running warm not bad some back fires then hot wouldnt run i figurred carb problems or plug problems

  • guitarnut57

Posted July 21, 2009 - 06:02 PM

#25

ive read somthing simalar to this about anther 07 yz450 when it was cold no problem running warm not bad some back fires then hot wouldnt run i figurred carb problems or plug problems


That is exactly what my bike does!

  • grayracer513

Posted July 21, 2009 - 06:07 PM

#26

When your about to start you bike push the kick starter down until you come up against the hardest point or resistance felt throughout the stroke.

That's not the top of the compression stroke, that's the beginning of it. :worthy:

It is nevertheless best to start from the point where compression is felt.

  • roylo

Posted July 22, 2009 - 12:02 AM

#27

That's not the top of the compression stroke, that's the beginning of it. :worthy:

It is nevertheless best to start from the point where compression is felt.



Top, beginning whatever its called you know what I mean. What I explained is the correct position to start from.

  • Aka.Goose

Posted August 05, 2009 - 07:36 PM

#28

Hopefully, I will be able to fix it this afternoon.

Get the piston at the top of the compression stroke? Forgive me of my ignorance, but how do you know when the piston is at the top of the compression stroke?


So have you got it dialed in?
What seems to be the steps that work for you?

  • guitarnut57

Posted August 06, 2009 - 08:35 AM

#29

So have you got it dialed in?
What seems to be the steps that work for you?


I was going to wait a few weeks before giving you guys an update to make sure it wasn't luck, but I think I've figured out a way to start it when it's hot. I think my biggest problem was that I wasn't getting a full, forceful kick in (I'm kind of short), so now I walk my bike over to a berm or jump and lean against it. Then I blip the throttle about 1/8 of a turn for a second or two. Then I find the top of the stroke and kick. After 3 or 4 kicks, she fires right up.

You guys really helped me out on this one :thumbsup:

  • grayracer513

Posted August 06, 2009 - 09:07 AM

#30

.. I find the top of the stroke and kick.

If you mean "the hard spot", once again, that's the bottom of the compression stroke, where the piston is starting up against the air trapped by the closed valves.

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  • guitarnut57

Posted August 06, 2009 - 09:42 AM

#31

If you mean "the hard spot", once again, that's the bottom of the compression stroke, where the piston is starting up against the air trapped by the closed valves.


Oh yeah I forgot about that little debate a few posts up :worthy:. Yes, the bottom of the compression stroke, or that point where the compression is so strong that it's very difficult to initiate the kick. It fires right up when I start from that point :thumbsup:

  • grayracer513

Posted August 06, 2009 - 12:36 PM

#32

There's a reason for being picky about that. From a technical standpoint, "top" is just that, the top of the stroke, where the piston is at TDC. If you were to use the beginning of the compression stroke as the point at which to set the valves, for instance, rather than the mark indicating Top Dead Center, you'd have the crank about 80 degrees out of place, and you could get the wrong readings. Calling the start of the compression stroke the top can lead to confusion.

Plus, when you keep your references straight, it helps you understand what's happening within the machine as it works. The true top of the compression stroke can be felt through the starter too. If you bring the crank up against compression and apply a steady pressure to push slowly through the stroke, there is a point at which the resistance briefly disappears, the starter jumps downward a bit, and you feel what seems like a second compression stroke. The sudden drop in resistance was TDC. The "second compression stroke" is actually the piston, having pushed all the air past the rings, pulling a vacuum in the combustion chamber as it moves down the bore on the power stroke. The top of the compression stroke is where it ends, not where it starts.

When starting a manual decompression YZF, you are told to push the crank until you hit compression. This will occur in that engine at somewhere around 120 degrees BTDC, when the intake valves close. Then, you're told to pull the compression release and move the lever about an inch farther to stage the engine for starting. That moves the piston farther up the bore, but not past TDC, so that the remainder of the compression stroke is only about 70-80 degrees of crank travel, instead of 120, and you will be able to push it through that past the ignition point, and start it.

In an auto decompression engine, the AD mechanism holds an exhaust valve off its seat until the engine is at the aforementioned 70-80 degrees before top, so it sets things up for you just by running up against compression.

  • guitarnut57

Posted August 06, 2009 - 12:49 PM

#33

After reading that, I am thankful that my bike has AD. Thanks for explaining how it works.

  • saccityfire

Posted August 06, 2009 - 06:33 PM

#34

My head hurts after that thorough explanation GR. I am really thankful that you keep that locked up in your head for us to access form time to time. I need a beer now!

  • Slick_Nick

Posted August 06, 2009 - 06:39 PM

#35

My bike starts in zero kicks. (Majic button.) :thumbsup:

  • grayracer513

Posted August 06, 2009 - 07:06 PM

#36

My bike starts in zero kicks. (Majic button.) :thumbsup:

Thanks for sharing that.

  • Slick_Nick

Posted August 06, 2009 - 08:40 PM

#37

Thanks for sharing that.


I was just trying to joke...

  • grayracer513

Posted August 06, 2009 - 08:57 PM

#38

I was just trying to joke...


Try this forum instead

  • USED YZ426F

Posted August 08, 2009 - 10:54 AM

#39

Experiment and find the sweet spot?


That is the answer. Everyone's bike is a little different. Took me a while, but I figured out what my 426 likes and now I can start it hot or cold in 1-3 kicks.

  • guitarnut57

Posted August 10, 2009 - 06:59 AM

#40

That is the answer. Everyone's bike is a little different. Took me a while, but I figured out what my 426 likes and now I can start it hot or cold in 1-3 kicks.


You guys were right on the money. It started on the 1st kick cold turkey (choke was not even on) on Saturday. When it was hot, about 4 kicks turned it over.





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