2001 YZ426 hard starting

13 replies to this topic
  • Travbisa

Posted March 07, 2009 - 07:48 AM


Shes having a hard time starting. This is what I have done sor far: Replaced gas, cleaned carb, replaced plug. Checked coil .4-.5 ohms. Sometimes she starts, sometimes she don't. Floods easily. Could it be a weak coil? Is that common? :p

  • CyclePro238

Posted March 07, 2009 - 08:26 AM


Maybe you could use a Valve adjustment?

  • Travbisa

Posted March 08, 2009 - 05:47 PM


Valves are all within specs. Any other ideas?

  • mitchicle

Posted March 08, 2009 - 06:15 PM


Whens the last time you replaced/cleaned your air filter?

  • mitchicle

Posted March 08, 2009 - 06:18 PM


Also check your timing, all it takes is being one tooth out. Hope this helps

  • aj_yz426

Posted March 08, 2009 - 06:32 PM


Shes having a hard time starting. This is what I have done sor far: Replaced gas, cleaned carb, replaced plug. Checked coil .4-.5 ohms. Sometimes she starts, sometimes she don't. Floods easily. Could it be a weak coil? Is that common? :p

Manual says primary coil resistance should be 0.2-0.3 ohms at 68F.

I believe colder the temperature the lower the resistance. So if its less than 68F in Maryland then your resistance would be even higher than the measured0.4-0.5 ohms if it were 68F, so maybe its a bad coil.

That being said, the stock AP setting squirts fuel for about 3-5 seconds (mine was around 4-5 range) so they flood easily. After I did the BK mod it doesn't flood so easily and is easier to start. When you start it cold, prime with a couple twists of the throttle, then hold onto the brake reservoir or any part of the handlebar other than the throttle so you don't give it any more gas while kicking it.

I would make sure you have a new cr8e plug and do the correct starting ritual. If that fails, then think about a new coil.

  • Travbisa

Posted March 09, 2009 - 05:56 PM


Air cleaner is clean. I checked the coil in 70 deg weather. Check connections/ resistance and still won't run. Its sparking, but SEEMS weak?

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  • yz400fsmasher

Posted March 09, 2009 - 07:43 PM


i belive the pilot screw should be 1 3/8 turns out on the 426's. i had the same problem with my 400 flooding out.

  • tjpop

Posted March 10, 2009 - 04:08 AM


Is your compression stroke still hard as a rock? If not your timing may be off one or two teeth. My 01 started and ran ok until I jumped the timing chain some additional teeth. The guy I bought my 426 from told me he thought the bike had a auto decomp cam because the compression stroke never got rock hard. He ran the bike with the timing off recreationally for a year -changing plugs & constantly messing with carb. It was the timing the whole time. Turns out we both had no clue. The price of being a newbie:doh:

  • travisn

Posted March 11, 2009 - 01:40 PM


^^ As in rock hard as its impossible to push it through, or just that you know you have hit it?

Ex: It hurts if you try to give it a kick before its ready, but if you push hard it will go around, because thats how my bike is.

Also with the weak spark, is the coil ground attached to bare metal frame? (I had the coil unbolted from my bike to set sag, I forgot to bolt it back on and was kicking it for 5 minutes before I realized it needs to be bolted back on, fired first kick. LOL)

  • Travbisa

Posted March 14, 2009 - 11:52 AM


I ended up checking all the resistance per Yamaha manual. The coil was on target, but the magneto #1 coil was .832 ohms (should be 700-1200 ohms). I belive its shot. #2 coil was 53 ohms (which is right). Ordered a new magneto and the old one was burned up, and should get it next week. Thanks guys for all your input! Keep you posted....

  • rufusz

Posted March 17, 2009 - 02:30 AM


I also believed my stator was dead, until I checked it, and found out that a previous owner mounted an E-Line stator :) :banghead: :banghead: :foul:

  • Travbisa

Posted March 19, 2009 - 03:36 AM


My bad, the magneto was good after all. I took it to work and had a EE look at it. I did check the ohms from coil to spark plug and noticed the new coil read 128 M ohms and the old 23 M ohms. I will put it together and try it....weird!

  • grayracer513

Posted March 19, 2009 - 06:31 AM


Sounds like a problem with your meter. Coil primary resistance is supposed to be .2-.3 Ω, and the secondary resistance should be 9.5 - 14.3 KΩ. even 1 MΩ is 66 times higher than it should be at the least.

Try again.

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