Won't Start yz426


26 replies to this topic
  • ezzrigby

Posted February 09, 2008 - 11:04 AM

#1

Hi, i have a 2001 yz426, i have totally stripped down the engine/ carb and rebuilt from the bottom up replacing all worn parts. Cost me a fortune.

I just can't get the thing to start. The bike is timed spot on, getting a strong spark, all my electric's test ok but still no go. Can anyone sugest a simple thing that i may be missing.:busted:

all help welcome, i also think i don't have the starting sequence down to an art yet. but i've tried so many ways that surely i would of got it right once:confused:

Thanks

  • knightsofstevenson

Posted February 09, 2008 - 11:08 AM

#2

I can't think of much but is it getting gas into the carb? Also if you have it all torn apart could there be something with the kill switch since that might be taken off right now.

  • YELL-OSNAKE

Posted February 09, 2008 - 12:13 PM

#3

how's the plug look, is it wet with gas??? hopefully so, if not then you have a fuel problem, if it is....it's flooded now. kick over about 20x with decom lever pulled in, DON"T touch the throttle after doing this. bike is prob flooded. did it at least backfire or anything. new engines were always hard starters for me. I usually would get someone to pust start me, because I would get so wore out from kicking, but I don't think that will work on a fresh 426 with good compression. get afew friends, and some beer.

  • ezzrigby

Posted February 10, 2008 - 01:45 AM

#4

The carb is jetting fuel in and the plug seems wet. but for the time i have been trying to start i would of thought it would be alot wetter. The bike won't even back fire which seems odd.

Getting a strong spark so can't be the kill switch or the neutral switch.

checked the timing again, i think it's right line the bottom mark(magneto) with the inspection hole mark. exhaust cam mark (e) with the top of the head the inelet cam mark (i) the same.
My magneto has two marks am i using the right one has a mark like ( I-I ) and also ( I ) i used just the I mark is this the right one?

Tim

  • grayracer513

Posted February 10, 2008 - 10:16 AM

#5

... is this the right one?

Tim

Yes it is.

  • 426boy

Posted February 10, 2008 - 02:40 PM

#6

i have had good spark on my 426, and wouldnt start, threw a new plug in and it fired first kick. i spent along time thinking it has spark why wont this pig start. they are picky with thier plugs i guess. you could always bump start it down a hill, or skitch or a car or quad just put it in second and pull the compression realease then when you are moving let it go and it should pop.

  • todds924

Posted February 10, 2008 - 04:23 PM

#7

The carb is jetting fuel in and the plug seems wet. but for the time i have been trying to start i would of thought it would be alot wetter. The bike won't even back fire which seems odd.

Getting a strong spark so can't be the kill switch or the neutral switch.

checked the timing again, i think it's right line the bottom mark(magneto) with the inspection hole mark. exhaust cam mark (e) with the top of the head the inelet cam mark (i) the same.
My magneto has two marks am i using the right one has a mark like ( I-I ) and also ( I ) i used just the I mark is this the right one?

Tim


Make sure....I mean MAKE SURE! that your carburetor is really cleaned properly..paying special attention to the pilot jet. I cant tell you how many times people have told me they cleaned the carburetor...only to find a plugged pilot jet. If you have spark and your sure your cam timing is correct, you have compression...that only leaves a fuel problem.

  • BASSic

Posted February 10, 2008 - 07:48 PM

#8

I don't know what the weather is like in the UK but I'm guessing it's cold. Try a new plug and if that doesn't work, take your air filter off and put a good shot of ether in there.

I had some trouble getting my 426 to start because it was sitting for a while and there was stale gas in the tank, but ether was enough to get it going. I topped it off with fresh gas and it starts on the first or second kick every time.

  • ezzrigby

Posted February 11, 2008 - 12:46 PM

#9

Thanks for the pointers. Will give it all a go and post an news back as soon as i can.
Thanks
Tim

  • mike_dean

Posted February 11, 2008 - 04:50 PM

#10

Make sure you try fresh fuel, todays gas goes stale very fast in a normal gas can. Mike

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  • 1rkcooper

Posted February 11, 2008 - 06:40 PM

#11

At the top of the YZ forum page is a sticky with common threads. At the bottom of the page are two starting videos, one cold start and one hot start. These are excellent videos for the proper technique, however i think each machine has it's own little quirks.

How to Start a YZ426 (Video with Doug Dubach- Special Thanks to Yamaha Motors, and all the Good People at Dubach Racing Development)
(Requires QuickTime, or a player that will handle QT videos)
Part 1: (Cold Start) http://www.yamaha-mo....roke_vid_a.mpg

Part 2: (Hot Start) http://www.yamaha-mo....roke_vid_b.mpg

Note: Video may take a few minutes to download.

  • BASSic

Posted February 11, 2008 - 08:03 PM

#12

I forgot to mention my super secret trick to getting my 426 started in extreme cold ( less than 35 degrees F ). It's not really my secret because several people here on TT told me this trick - I don't know what I'd do without it:

1. Turn Gas On
2. Pull Choke Out
3. Use decomp lever to get past Top Dead Center (no 03 cam yet...)
4. Give the throttle two good twists
5. Kick

The biggest secret is step 4 - when it's cold outside, ignore anyone who tells you to never touch the throttle on a four stroke. Two twists squirts enough gas to get it to fire up on the first kick. It's easier to start than a cold two-stroke!

  • 426boy

Posted February 11, 2008 - 09:23 PM

#13

I forgot to mention my super secret trick to getting my 426 started in extreme cold ( less than 35 degrees F ). It's not really my secret because several people here on TT told me this trick - I don't know what I'd do without it:

1. Turn Gas On
2. Pull Choke Out
3. Use decomp lever to get past Top Dead Center (no 03 cam yet...)
4. Give the throttle two good twists
5. Kick

The biggest secret is step 4 - when it's cold outside, ignore anyone who tells you to never touch the throttle on a four stroke. Two twists squirts enough gas to get it to fire up on the first kick. It's easier to start than a cold two-stroke!


thats no secret thats how your soposed to do it haha

  • jeeper33

Posted February 12, 2008 - 02:58 PM

#14

I might be going down the wrong road here...but moving away from the bike being the problem, you stated:

"all help welcome, i also think i don't have the starting sequence down to an art yet"

were you able to start it before the rebuild? The Yz426 can be a son of a gun to start, pretty much only if you're new to it. once you get the sequence down, it'll start every time, usually on the first 2 kicks.

The only reason I ask this, is because when I first got mine, I knew how technicially it was supposed to start, but i had problems doing it right off the bat, as many 426 owners have.

Judging from the experience when mine is a pain, change the plug, sometimes even to a used one. 9 times out of 10 shell fire right up, and if she doesnt, shell pop to clear the cylinder, then fire right up ;-)

Another quick tip (i hope youre not bored at this point) if it is cold there, throw a canvas over your bike and put a light under it...just make sure there isnt anything flammable that would drip on the bulb :applause: give it an hour or two to acclimate to the temperature, and it should be easier to start.

if you still have problems, i can give you a whole list of things to check, as im sure most members on here can. I've never been a fan of pull starting it...if youre resorting to that, theres something else going on. With no auto-decomp camp, its a tricky thing to pullstart, and you shouldnt need to do it. look at other possibilities first(the ones stated above)

~jeep

  • ezzrigby

Posted February 13, 2008 - 12:15 PM

#15

I maybe being stupid but when you set the timing you first get the mark on the flywheel lined up at tdc on the compresion stroke then set your cams according. Is it possible to set the cams effectively 180 degrees out?

It's been on my mind cause i've tried most other things surgested now and am strarting to loose my rag. The bike was bought as a bad runner but it did run and my project was to recon it for supermoto use but i'm starting to wish i hadn't.

  • grayracer513

Posted February 13, 2008 - 12:44 PM

#16

I maybe being stupid but when you set the timing you first get the mark on the flywheel lined up at tdc on the compresion stroke then set your cams according. Is it possible to set the cams effectively 180 degrees out?

It's been on my mind cause i've tried most other things surgested now and am strarting to loose my rag. The bike was bought as a bad runner but it did run and my project was to recon it for supermoto use but i'm starting to wish i hadn't.

"180 out" goes to the automotive world, where the cams (usually only one) are timed off the crank and the ignition timed separately off the cam. In that case, you could time the cam, run the engine up to TDC, and put the distributor in with #1 cylinder indexed to the exhaust/intake overlap, rather than the compression/power transition. Even then, it's a misnomer, since when the distributor is 180 out, it's actually timed 360 degrees away from where it belongs.

But give it a little thought: What is it that determines which TDC is exhaust and which is compression? That's right. The cams do. It doesn't make any difference which TDC you choose to set the cams on, because until the cams are in place, they're all the same. Without the cam(s) you can't put it at TDC on the compression stroke because there isn't one. Oh, I suppose you could put one cam in upside down if you were determined to, or install them at BDC instead of TDC, but I don't think you're headed that way.

But what about the ignition? Doesn't it have to fire just before a particular TDC? Yes it does, but it does not harm if it fires on the other one, too, so that's how it sets up on most modern motorcycles. The ignition is triggered by the crank at full engine speed, instead of the old automotive norm of being triggered of the cams at half speed, so it fires every revolution. Because of that, it can never be "180 out".

  • ezzrigby

Posted February 14, 2008 - 10:20 AM

#17

Great news finally got the little bugger to start. Changed the plug, fuel and various other bits, cursed and swore at it then talked nicely to it. Then she thundered into life. Not fully sure what the full problem was maybe just lots of small things making a big problem!!!!

Next fault is that it won't idle without the choke any clue's?
Thanks every one you have all been very helpful.
Tim

  • Socal426f

Posted February 14, 2008 - 11:09 AM

#18

I have a similar method to starting with my 02 426F. Turn the gas on, 2 turns of the throttle, pull the choke and then 1 kick. She fires every single time. It can sit for a month and will still fire no matter what. The scary thing is that I've never checked the valves and recently decided to throw in a new plug, even though the old one was working just fine.

I do jet her with a JD kit after putting on the Yosh pipe and also have one of the Boyseen Quickshot accel. pumps or whatever thos damn things are called.
Also still use the decomp lever since starting has never been an issue. New oil after every 3rd ride trip.

  • BASSic

Posted February 14, 2008 - 02:32 PM

#19

The scary thing is that I've never checked the valves and recently decided to throw in a new plug, even though the old one was working just fine.


Do you have any plans to check the valves any time soon? How often and how hard do you ride? I'm curious to see if they need any adjustment. My 01 YZ426 (newly acquired) has never been checked and runs great - no abnormal noises from the valvetrain. I'm thinking of checking them this weekend. What has me worried is timing chain stretch. My 89 XT350 ate up two sets of intake valves after it jumped time due to a stretched chain (should have changed when I replaced the valves the first time).

Also still use the decomp lever since starting has never been an issue. New oil after every 3rd ride trip.


Same here, though my plan is to see if the valves need to be adjusted. If they're still in spec, then the stock 01 exhaust cam and manual decompression are staying put. If I need to adjust the valves, I'll replace my stock cam with an 03 cam since it needs to be removed for adjustment anyway.

  • grayracer513

Posted February 14, 2008 - 02:36 PM

#20

My 89 XT350 ate up two sets of intake valves after it jumped time due to a stretched chain (should have changed when I replaced the valves the first time).

The two events are purely coincidental, and otherwise unrelated. One will not cause nor prevent the other.





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