poor spark yz426


8 replies to this topic
  • fastback959

Posted December 29, 2007 - 09:32 PM

#1

i have a 01 426 that has been one bad bike for me, but lately it has been a mother to get started i pulled the plug and found that it was fuel fouled, so i put a new plug in it and if started up on the first kick, well 14 days or so went by and i went to start it and i had the same problem so i pulled the plug and found more fuel.... well i checked the spark and found a very weak spark, has any one else had a poor spark problem on their bike??? this is my first thumper and i would think that it should have more spark then a briggs and stratton...... :banghead:

  • Qwik Gixxer

Posted December 30, 2007 - 08:49 AM

#2

In the FAQ is a piece about pulling one of the wires from a connection. It evidently helps bump up spark on kickover. Did it to my YZ400 and the bike starts easier. May be time to do the coil upgrade too. Check the FAQ lots of good stuff on this

  • fastback959

Posted December 30, 2007 - 01:04 PM

#3

how do i find the FAQ page??

  • USED YZ426F

Posted December 30, 2007 - 01:37 PM

#4

Check at the top of the forum for a link to the "Common Threads".

I haven't had any problems with my '00 YZ426, and I have no clue as to its past (I got it last August). Although it is a little tough to get running when cold, usually takes 5-6 kicks, but is easy once warmed up only needing 1-2 kicks (normally one).

Are you using the recommended plug? What have the temps been like since it got hard to start?

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  • fastback959

Posted December 30, 2007 - 03:26 PM

#5

i went to the yamaha shop and got the plug. and it has been cold, like 35 or so. but when i checked the spark it was in a heated shop for about 24h that was the day i put the new plug in and it started right up with one kick.

  • 642MX

Posted January 01, 2008 - 08:17 AM

#6

i have a 01 426 that has been one bad bike for me, but lately it has been a mother to get started i pulled the plug and found that it was fuel fouled, so i put a new plug in it and if started up on the first kick, well 14 days or so went by and i went to start it and i had the same problem so i pulled the plug and found more fuel.... well i checked the spark and found a very weak spark, has any one else had a poor spark problem on their bike??? this is my first thumper and i would think that it should have more spark then a briggs and stratton...... :banghead:


Check your valves. A tight intake valve can help foul spark plugs. Also, you may need to adjust your fuel screw if your climate is changing.

One other thing... YZF's need to be started and completely warmed up before shutting them off.

  • fastback959

Posted January 01, 2008 - 12:44 PM

#7

i did sum more diag and fount out that it was not a flooding problem it was a lack of fuel... as of now it is about 30 degrees out side and i went to start it so i gave it 3 twists and kicked it over about 3 times and then gave it 3 more twists and she fired right up, i guess the cold made the bike lean??? and did not have enough fuel vapor to make it go boom. thanks for the help, off i go in the 30 degree ride.

  • BASSic

Posted January 02, 2008 - 12:23 PM

#8

I noticed similar behavior on the 01 YZ426 that I just got a few days ago. I was afraid of touching the throttle because I heard these bikes foul plugs easily. All it needs when cold (30 degrees outside) are two twists of the throttle and the choke pulled out, and it'll fire up on the first kick!

  • grayracer513

Posted January 02, 2008 - 01:30 PM

#9

i did sum more diag and fount out that it was not a flooding problem it was a lack of fuel... as of now it is about 30 degrees out side and i went to start it so i gave it 3 twists and kicked it over about 3 times and then gave it 3 more twists and she fired right up, i guess the cold made the bike lean??? and did not have enough fuel vapor to make it go boom.

Cold weather does indeed make the bike run lean, and on two counts, when it comes to cold starts.

First off, colder air is denser, and requires richer jetting. (roughly 1 step for each 15-20 degrees)

But worse, the very low temperatures of the metal parts within the engine won't allow the fuel to stay vaporized as it should on a cold start. The compensation for this is just what you found out; a good healthy dowsing of fuel. The extra fuel increases the amount of fuel in the chamber to the point that the raw liquid can produce enough vapor to start.





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