just got 01 yz 426. acts like it wants to start and fire up but when it dose the kick start shoots back up into my foot so hard it hurts like hell ?


25 replies to this topic
  • Chimpanmoose Mullen

Posted February 03, 2012 - 05:17 PM

#1

it has spark and really sounds great while kicking it and then bam broken ankel lol also the decompression cable is broke i just orederd another. but shouldnt i still be able to start it.

  • OLHILLBILLY

Posted February 03, 2012 - 05:50 PM

#2

Probably got a lot to do with no decompression ability. Fix the decompression cable and I bet it'll start right up with no drama.

  • Chimpanmoose Mullen

Posted February 03, 2012 - 05:59 PM

#3

i hope your right man... im waiting for the new cable in the mail. i just wish sombody else with the same bike could go and try to start it ith no decompression and see if it dose the same thing with the fire up and then break your leg with the kick start

  • 79yamdt

Posted February 03, 2012 - 06:31 PM

#4

Maybe if you asked in the yamaha forum in the yz4xx forum. That's where this should be posted. Hopefully that's all it is. Welcome to the forum hope it helps you as much as it has me. I know trying to kick start my 400cc two stroke without a working decomp makes it very difficult to start because I can't kick it fast enough.

Edited by 79yamdt, February 03, 2012 - 06:34 PM.


  • Chimpanmoose Mullen

Posted February 03, 2012 - 06:36 PM

#5

the decompression cable is broken and i have one on order. but shouldn i still be able to start it? and why is it kicking back like a freight train when it trys to fire? it is a 2001 yz 426 that was just rebuilt.

  • briangriff321

Posted February 03, 2012 - 06:55 PM

#6

Dont touch the gas when you kick it or it will kick you

  • briangriff321

Posted February 03, 2012 - 06:59 PM

#7

And wait till you geta cable before you break something

  • zlathim

Posted February 03, 2012 - 07:06 PM

#8

Put your right hand on the brake master cylinder instead of on the throttle grip when starting the bike. It will eliminate any involuntary twisting of the throttle that you are doing when trying to start the bike.

How are you going about starting the bike? It is usually necessary to get the piston slightly past TDC before trying to give it a good kick. That's what the decomp lever is for, getting it past TDC. I have found that on my bike, I can get it past TDC without using the decomp if I apply medium but constant pressure on the kickstart lever for a little while. It will eventually ease past TDC as the compression bleeds off. Then let the lever return to the top of the stroke and give it a good kick. My 01 WR 426 was tough to start until I got the procedure down. Now I don't have any trouble at all. MX boots will help protect your foot in the case of a kickback.

Edited by zlathim, February 03, 2012 - 07:07 PM.


  • OLHILLBILLY

Posted February 03, 2012 - 07:18 PM

#9

The trick is, to get it past TDC on the compression stroke, then jump on the kicker. That is what you use the decompression lever for, to get it past TDC. If you can get it bumped past TDC without the decompressor, then you should be able to start it as normal. If your at somewhere around the bottom of the exhaust stroke and coming up on compression when you kick it, well.. Without getting everything moving sufficiently fast before it compresses and fires, the spark advance will light the fuel/air mixture ahead of TDC, and there won't be enough centrifical energy to carry the piston past TDC and use the majority of the charge pressure to provide movement in the correct direction, resulting in the piston being slammed back down in the direction it came from, and this is what your feeling in your foot/ankle. All the decompressor system does is let you easily get just past compression TDC, so the kick cycle will have the rest of the ignition stroke and all of the exhaust stroke to get inertia built and everything moving fast enough before it comes around to the compression stroke, it will go on past TDC, and work as a proper fire cycle.
That's an "in a nutshell" idea of what's going on. Get it past compression TDC, then jump on the kicker, and you should be ready to ride without a sore ankle.

  • Lelandjt

Posted February 03, 2012 - 07:18 PM

#10

I think this has nothing to do with the decompression system and is in the kickstarter gearing.

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  • grayracer513

Posted February 03, 2012 - 07:42 PM

#11

The correct way to start the bike is NOT to move it just past TDC. You push the kick starter to the point where the resistance of the compression stroke stops you (which is a good 110-120 degrees before TDC), pull the comp release, and move the lever about an inch farther. This moves the piston about halfway up the bore from where it is, but still BEFORE TDC. Then you let go the release, reset the kick lever, and push it through a full stroke with the throttle closed.

Watch:

http://www.yamaha-mo...troke_vid_a.mpg

http://www.yamaha-mo...troke_vid_b.mpg

If you kick from there as I described, and as demonstrated by Mr. Dubach, you'll force the piston the next 80 degrees past ignition and TDC under direct pressure, and it should fire. If you kick it from "just past TDC", you'll have to turn the engine about 680 degrees (nearly two full revolutions) before it gets back there again, and in so doing you will run into the full compression stroke again, and by that time, the lever will be near the bottom, and your power will be gone.

You really need the decomp lever to make it work conveniently, but you can cheat without it if you just push the lever that inch or so past the point where it comes up against compression. Not past TDC.

A fresh, healthy 426 is nearly impossible to kick through a full compression stroke, and it's way too hard on the starter to try it.

  • chris856

Posted February 03, 2012 - 07:46 PM

#12

Might be a stupid question but are you holding the throttle open. If I kick my bike over and even accidentally crack the throttle it kicks back up into my foot.

  • timmyp8823

Posted February 03, 2012 - 11:48 PM

#13

Put your right hand on the front brake master cylinder while you are kicking it. That way you know you aren't accidentally turning the throttle when you kick. My cold starting ritual went something like this. Pull out choke knob. Slowly push down kickstart lever till you feel heavy resistance. Pull decomp lever and bump piston past TDC. Release decomp lever. Give throttle two quick turns. Take hand off throttle and place it on M/C. Give lever a full weight of your ass man kick. If it doesn't start,repeat except for the two shots of gas. This method got my 98 WR to light nearly as easily as my current 200 smoker does.

  • Lelandjt

Posted February 04, 2012 - 08:59 AM

#14

I can start my 300 2stroke with my hand. I can start my 105 2stroke with my thumb.

  • 79yamdt

Posted February 04, 2012 - 11:25 AM

#15

I can start my 300 2stroke with my hand. I can start my 105 2stroke with my thumb.


Congrats. What does this have to do with his bike?

  • Chimpanmoose Mullen

Posted February 04, 2012 - 11:36 AM

#16

im not giving it any gas and even if im just barley cycling threw sometimes it will fire and kick right back on me. other times ill get it just past tdc and kick it and it will move about an inch and then just lock up. idk im thinking i may need to just take her into the shop

  • Chimpanmoose Mullen

Posted February 04, 2012 - 11:39 AM

#17

any of u guys live close to branson west missouri? and want to see if u can start it? maybe its just me screwing up somthing idk

  • briangriff321

Posted February 04, 2012 - 12:00 PM

#18

Just wait till you get the comp release fixed

  • maverickxp

Posted February 08, 2012 - 01:15 PM

#19

might be a timing issue, if your woodruff key broke and your timing is a hair off she might be firing too early or too late causing her to kick your foots butt. im in st louis, i might be able to check her out for you

  • budda

Posted February 10, 2012 - 10:31 AM

#20

Fix the de-comp cable and then follow the start procedure and it'll be fine, mine was exactly the same.

De-comp lever in and kick it through 5 - 6 times, let lever out then find TDC, lever in a smidge till the Kick start goes through the hard point by about an inch then give it a good boot and off it goes.

If this doesn't work try bump starting it.





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