2001 426 Electrical or Fuel Issue


26 replies to this topic
  • Terrain Rider 4z

Posted April 06, 2007 - 08:47 PM

#1

Alright I am ready to bring on the big guns to deal with my nagging issue that I have been fighting for 4 weeks now.

About a month ago we were riding at the dunes when my bike died. Long story short, there was sand in my pilot jet (and upon closer observation a large collection of sand and dirt in my bowl). We cleaned out the jet and I rode the bike another 30 miles and it ran great, as it always has :naughty:

When I got home I took my bike apart, removing the subframe, airbox, and other necessary parts to clean out the airbox. I used a garden hose and carefully washed the whole bike, making sure to plug off the carb and header. I cleaned out the remaining sand and reassembled the bike.

When I started the bike it was popping and spitting fire when I applied the throttle, but it idled well. I cleaned out the jets again, reassembled, same thing. I then disconnect all connectors, blew them dry, and applied dielectric grease, same results.

Finally I took the bike to a Yamaha dealer and had their tech look at it. He checked the valves, timing, and went through the pilot circuit, claiming the bike seemed to run well. Took it home to find out it did not.

Returned the bike and he took another look, testing the TPS and stator. Apparently they tested fine, but when the TPS is disconnected the bike does run better, but not perfect. His next step was to order a CDI, so I picked up my bike and took it to a friend's house and tested using his CDI, then his coil, same effect. Went through the carb and cleaned everything, same effect.

Since the bike was in town we went to another Yamaha shop and described the problem. Long story short they put new gas in and told me that was the problem. I had already done this twice and knew it was not the problem. Took my bike as it seemed to be running better (it is running a little better, but FAR from great).

Rode my bike today and things started off OK, with some sputtering and popping. As the day went on things seemed to get progressively worse. More popping from just off idle to mid range, but up top it seems to run pretty well. Starting has become a little for difficult and requires the hot start much more often.

We have tried new plugs, gas, different CDI, coil, and been through two shops, still a crappy running 426. I think it is an electrical problem, but at this point am frazzled. I just ordered a wiring harness off of ebay and will try that.

Does anyone have experience with this problem? Is there something obvious I am missing? This thing shot me up everything I pointed it at, but it was a chore keeping it running. HELP :bonk:

  • Terrain Rider 4z

Posted April 07, 2007 - 06:00 PM

#2

Any ideas out there?

  • ____Kurt____

Posted April 07, 2007 - 06:23 PM

#3

you have explained that you have dis assembled it and assembled it several times so it could have out rulled my theory but maybe between the engine and carb and air box there is 4 posibillites that there could be a small gap and allowing air to enter in the motor a different way, 2 which would effect fuel/air mixture (engine-carb). the one between carb-airbox would just allow dirty air. not sure what else would cause this at the moment other then that. food for thought

  • Bikermice

Posted April 07, 2007 - 06:24 PM

#4

Are you sure the hot start valve is closing all the way and not allowing any additional air in? I know mine pops when I take off without closing the hot start valve.....Maybe some sand is getting in the way and not letting it close all the way..... That's my wild ass guess. Good luck. Lets us know what you figure out.

  • Terrain Rider 4z

Posted April 07, 2007 - 07:02 PM

#5

I thought about the hot start too, but haven't investigated that yet. I will look into the manual tonight.

The carb boot is also a possibility, but it acts different than air leaks I have had on previous bikes. I think I am going to install a new boot to make sure as the old one is 6 years old.

  • grayracer513

Posted April 07, 2007 - 08:02 PM

#6

When I started the bike it was popping and spitting fire when I applied the throttle, but it idled well.

Sounds more electrical to me than it does fuel related. Possibly a bad trigger coil, or some other fault in the stator assembly (like a broken wire within a coil, a faulty ground, etc.). Really tough to tell sometimes.

  • Terrain Rider 4z

Posted April 07, 2007 - 08:24 PM

#7

Sounds more electrical to me than it does fuel related. Possibly a bad trigger coil, or some other fault in the stator assembly (like a broken wire within a coil, a faulty ground, etc.). Really tough to tell sometimes.


One of the Yami techs tested the stator and said it was fine, but would this change at different RPMs? I get a lot of missing and popping down low, it is harder to start, and I am smelling fuel. I do not think I am getting enough spark down low, how can I test this?

  • grayracer513

Posted April 08, 2007 - 08:31 AM

#8

You should get a 1/4" spark at cranking speeds. Take an old plug and bend open the electrode to that gap and hold it against the head while you or someone else cranks the engine.

The stator can also be tested for voltage output. Sometimes, the continuity test can pass, but there can be internal problems with one or more coils that don't show up with an ohm meter.

No chance the throttle slide spring plate is upside down, I suppose?

  • Terrain Rider 4z

Posted April 08, 2007 - 10:32 AM

#9

The throttle slide had not been apart. I took the carb off today, first time I had detached throttle cables. The cables are shot, frayed all to hell, so I am ordering new ones along with the carburetor joint to the cylinder. Also, a seal on the slide body was wasted, so will order another. Also noticed a bare spot on the orange wire leading to the bottom of the coil, so taped it up.

I doubt that these are causing the problem, but they need to be replaced regardless. Once I make these repairs and test out the new wiring harness, I might have a better idea.

The stator will be the next suspect. For that the bike will be going to the shop again. I may as well go with an Electrex with lighting coil if there is a problem, right?

  • grayracer513

Posted April 08, 2007 - 11:52 AM

#10

Also noticed a bare spot on the orange wire leading to the bottom of the coil, so taped it up.

I doubt that these are causing the problem,

You never know. That's the kind of thing that causes transient misfiring.

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  • Terrain Rider 4z

Posted April 08, 2007 - 07:29 PM

#11

Could the neutral switch cause this problem???

  • grayracer513

Posted April 08, 2007 - 10:23 PM

#12

Maybe. It has two functions:

> Lower the rev limit (to about 7k)

> Retard the timing for a lower, steadier idle and to reduce the chance of kickback when starting.

The switch can be disconnected at the wiring harness to check whether it's defective. Since it's active only in neutral, its disconnection has no effect on performance in gear.

I heard of one guy who had a problem that he traced to a bare spot burned onto that wire behind the header. The "switch" itself, that is, the part that you can remove from the crankcase, has no moving parts; just a contact ring. However, there is a spring and contact pin that sit in the end of the shift cam just behind the switch, and these I have seen get dislodged. That could conceivably cause a problem.

  • Terrain Rider 4z

Posted April 15, 2007 - 04:54 PM

#13

OK, thought I had it, but I was wrong.

Replaced the throttle cables due to fraying and kill switch because it had zapped me on a few occasions in the rain. Also, replaced the wiring harness with one I picked up cheap on eBay.

Fired the bike up and it ran lean, but strong. Had to set the pilot 2.25 turns out and air about equally as far. Bikes idle hung and figured out I had put the piece on the slide on upside down....doh! Flipped the plate over and presto, back to a crappy running bike.

So: TPS tests fine, stator tests fine (but is it?), new plug, new gas, clean filter, been through carb, replaced from buddy bike: CDI, coil, wiring harness, STILL CRAP!

If I pull off the flywheel what should I look for if there is a stator problem. Will there be burnt coil, signs of arcing???

Two Yammy shops later, no answers..... :thumbsup:

  • Bikermice

Posted April 15, 2007 - 07:09 PM

#14

Maybe try replacing the TPS. I know you said it tested good but you also said it ran better when it was unplugged.....Also might want to double check that cam timing & not just the alignment of the marks relative to each other but the location of the cam lobes relative to the gear, cam may have slipped a little on a gear.....Do you have a manuel for the bike?:thumbsup:

  • Terrain Rider 4z

Posted April 15, 2007 - 07:43 PM

#15

I do have a manual and it is GREAT! Yamaha is the best in this respect.

I should mention, when the slide was in wrong the bike ran a bit lean, but ran awesome. Idled great and pulled hard all the way through, and smooth. There was no popping (except on decel), no black smoke, and sounded great. Of course the mixture was leaned out at this point.

When I resituated the slide I got the rich smell, choking and smoking sensation that was occuring previously. My idea is that the bike is not getting enough spark to ignite all of the fuel being added to the cylinder, which leads me to believe one of the coils in the stator is shot??? (Remember the bike ran well when the mixture was leaned out) One of the Yami mechanics tested the TPS, but also swapped it out with another one, same effect.

Sorry I didn't mention this earlier.

  • foreverblue

Posted April 16, 2007 - 08:26 AM

#16

My 426 did this to me. I found a large amount of dirt in the acclerator pump circuit when I cleaned the carb out.

  • grayracer513

Posted April 16, 2007 - 10:16 AM

#17

So then, you currently have the slice plate installed with the flat edge and the small hole located at the bottom, and the curved edge up, correct?

  • Terrain Rider 4z

Posted April 16, 2007 - 01:13 PM

#18

So then, you currently have the slice plate installed with the flat edge and the small hole located at the bottom, and the curved edge up, correct?



This is indeed correct, the hole is located at the bottom now. Though the bottom is not flat, it is curved and fits the bore of the throttle body. The projection part of the plate is located on top and the seal is sandwiched between the slide and plate.

I do have a AP diaphragm, carb joint, and slice plate seal on order. I will install these before going to the stator. :thumbsup:

  • grayracer513

Posted April 16, 2007 - 03:38 PM

#19

...the hole is located at the bottom now. Though the bottom is not flat, it is curved and fits the bore of the throttle body. The projection part of the plate is located on top and the seal is sandwiched between the slide and plate...

That's what throws everyone off. It looks like it should have the curved side down, but that's wrong (#11):

http://parts.yamaha-...ifx?d=33712,2,0

  • Bikermice

Posted April 16, 2007 - 08:32 PM

#20

What do they run like if the slice plate is in upside down? :thumbsup:





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