Wr426 running /jetting issue; help please


16 replies to this topic
  • Zsebi-2

Posted March 12, 2008 - 05:55 PM

#1

Hi,
I purchased a used 2001 Wr426 (US model) which I inhereted with some jetting or carb or spark problem that I need some help with (please)

The Problem: at about 1/4 throttle the bike develops a bogging like symptom. This is noticeable in every gear. After passing the ¼ throttle the jolts forward like crazy, and pulls hard. Holding the throttle at ¼ keeps this bogging problem constantly in all gear. I am not sure if this is a spark or carb jetting issue.
Since I got this bike use I don’t know much about, other than what the "not too knowledgeable" owner told me. He got the bike used and the only thing he had done to it is a new top end and fork seals.
The bike starts good; 1st or 2nd kick, hot or cold. Has really good power ( I owned a WR400 and 250 , so I have something to compare to.)

In the carb everything looks stock Except it has a “powernow “ flange installed between the carb body and the air filter boot.
Needle, needle position, seems is stock, Jetting stock - Except the pilot jet is 38 (leaner) instead if the stock 42-- , throttle stop screw cut, has an aftermarket adjustable pilot screw (has the rubber “O” ring and washer).
Spark plug is black! Rich!
Exhaust and airbox -open, Grey wire (CDI)seem to be connected.

Things I checked so far: accelerator pump works, TPS is in normal range, fuel float is set correctly, intake exhaust valves are in spec.
I am at 700 feet elevation , temp is around 70-75F right now.
Please point me in the right direction to solve this problem.
Thank you

  • byggd

Posted March 13, 2008 - 06:26 AM

#2

Are you running the stock exhaust? Insert in or out? Have you tried disconnecting the TPS to see if it has any affect?

  • matt4x4

Posted March 13, 2008 - 06:45 AM

#3

Ok, I was leaning towards really rich at 1/4 throttle even before you gave the plug color, so I think it's safe to say that it's rich at 1/4 throttle.
That can either be the latter portion of the pilot circuit or the early portion of the needle.
Try turning in the pilot screw all the way while counting how many turns it took to bottom out (lightly) and post that number.
I believe stock is 1 5/8 turns out or thereabouts, it should never be out more than 2 to 2.5 turns.
At any rate, once you checked that setting, turn it in 1/2 turn at a time and warm up the bike completely and test ride, see if it gets better.
If it doesn't change you may have too large of a pilot jet, or the problem lies in the early stages of the main needle, try dropping the needle one clip (raise clip up one slot) effectively lowering it's static position.

  • Zsebi-2

Posted March 13, 2008 - 07:39 AM

#4

Thanks for the reply guys,
Stock exhaust, baffle out, and also run it with an aluminum insert now with about 9 holes drilled( not sure who makes it), the baffle makes no difference in the bogging problem.
Yes, did try disconnecting the TPS, no difference the bogging is still there.
TPS check out good with an Ohm meter.

The pilot jet is 38 the smallest listed in the manual, 42 is stock, so I am already running the smallest.
Yes I did try to turn in the pilot screw; while the way the bike run change (idle drops a bit ) but when I run the bike like that the same 1/4 throttle problem is still there on the same spot. same as when I am turning it out 1/2 turn increments. When I got the bike it was at 3/4 turn.
Also, I can run the bike with the hot start valve open, of course it runs weird but still I can go through the gears , same problem at 1/4 throttle.
Also when the bike is cold, 60-70F, choke on- 1 twist on the throttle and the bike fires right up, I can push the choke back in right away and it will idle just fine,no warm up needed, so for sure it is running rich.
To best explain this bogging, is similar to an ATV reverse safety cut off, or when you hit a rev liter, it is like every other ignition /spark is cut. the bike runs on every other stroke; and loads up with gas as well.

What about the "power now" collar , could that have any adverse effect?
this is an anodized collar that bolts to the back of the carb/replaces a stock part. I wonder if the installation of that piece did require mod to the carb that was done or not done correctly when the owner installed it.

I will try to lower the needle and see what it does.

thanks for the help please keep it coming.

  • matt4x4

Posted March 13, 2008 - 09:36 AM

#5

Have you looked at your slide in the carb, sometimes the plate cracks/breaks and causes issues.
You sound well versed, so I'm just checking - when you're talking about the pilot screw, you ARE talking about the one out the bottom of the carb right? (just want to be sure, sometimes people just keep messing with the wrong screws...)

When was the carb last apart and completely cleaned minus removal of TPS?

How's you AP working? usually bogs are related to this but yours being a continuous bog kinda baffles me - Have you had the Diaphragm out and cleaned/inspected it all?

Lastly, maybe it's rich because it's just not able to get enough air - hows your filter, is your airbox opened up at all? Have you tried to run it with the filter off?

  • Zsebi-2

Posted March 13, 2008 - 11:25 AM

#6

"matt4x4;6068724]Have you looked at your slide in the carb, sometimes the plate cracks/breaks and causes issues."
--I will tear the carb down completely today and inspect the slide as well.

"You sound well versed, so I'm just checking - when you're talking about the pilot screw, you ARE talking about the one out the bottom of the carb right?" (just want to be sure, sometimes people just keep messing with the wrong screws...)"
---Yes pilot screw, with the spring, washer and rubber"o"ring on the bottom carb. It has a ZIp TY after market screw.

"How's you AP working? usually bogs are related to this but yours being a "continuous bog kinda baffles me - Have you had the Diaphragm out and cleaned/inspected it all?"
--the AP squirts well, have not times it yet, simply because like you said this bog is not during accell, but rather at a certain throttle spot, even coming from a decelerate.

"Lastly, maybe it's rich because it's just not able to get enough air - hows your filter, is your airbox opened up at all? Have you tried to run it with the filter off?"
--I know you just checking off stuff, but it is not the air filter, or the box , the air box is fully open on the top, filter is clean and oiled properly ( been riding bikes/ATVs for 20 years, done a quite few)... :-)

As I said I remove and give it a good cleaning, drop the needle one clip.

PS: I know where you coming from , lots of people do crazy adjustment to the carb not knowing what they are doing, what I found over the years on Yamahas, is that when people get the bike they instantly want to richen it thinking that the factory made it lean. On most of my previous bikes it was the opposite, it needed leaning, - afterwards always had a nice light brown spark plug electrode. Usually ran the bike on the same spark plug for a year or two. IMO, On a four stroke there is no need to change it every year.

  • byggd

Posted March 13, 2008 - 11:55 AM

#7

With the pilot jet @ 38 that shouldn't be the problem unless it has been drilled out. The power now does limit the amount of air up to just under 1/2 throttle so droping the needle one notch might do the trick.

  • Zsebi-2

Posted March 13, 2008 - 05:49 PM

#8

Thanks,

Being a used bike who knows what was done to it, what was drilled or not. When I got the bike the pilot screw did not have the "o"ring and the washer, did have a spring.
also the pilot screw being after market ( ZIP TY) who knows if it is even the right one for this bike.
will see...what happens after the carb is cleaned and needle is dropped one notch.

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  • maxtherat

Posted March 13, 2008 - 06:31 PM

#9

Thanks,

Being a used bike who knows what was done to it, what was drilled or not. When I got the bike the pilot screw did not have the "o"ring and the washer, did have a spring.
also the pilot screw being after market ( ZIP TY) who knows if it is even the right one for this bike.
will see...what happens after the carb is cleaned and needle is dropped one notch.

when removing the fuel screw, most of the time the o ring and washer will stick in the carb. Also, I would remove the power now thing and make sure that it is not blocking some of the air passages on the intake side of the carb. they go through the plastic ring that goes between the carb and the intake boot. This may be the reason that there is a 38 PJ. Most, but not all of us are running 42-45. I would check this before you mess with the needle. If it is stock it is probably close to being on the lean side.

  • Zsebi-2

Posted March 13, 2008 - 06:47 PM

#10

Thanks Max ,
I looked.... the "O" ring was not in the carb, it was absent, so is the washer.
the power now thing can not be removed because it is not an insert, it is anodized aluminum piece that replaced the stock collar that was between the carb and intake boot, the only thing I can do is remove the horizontal plate that is in the power now valve.

  • maxtherat

Posted March 13, 2008 - 07:10 PM

#11

Thanks Max ,
I looked.... the "O" ring was not in the carb, it was absent, so is the washer.
the power now thing can not be removed because it is not an insert, it is anodized aluminum piece that replaced the stock collar that was between the carb and intake boot, the only thing I can do is remove the horizontal plate that is in the power now valve.

Sorry, I thought it was a flat piece that sandwiched between the carb and the plastic collar. Another thought, you said that you thought the grey wire was cut. Have you checked this? Maybe the wrong wire was cut. On your bike, under the tank, kick start side, the grey wire is in a two wire connector w/, I believe, a black w/ white stripe.Just a shot in the dark.

  • matt4x4

Posted March 14, 2008 - 07:24 AM

#12

there are only 2 zip-ty screws - depending on the year of the carb, but if it fits it's the right one - actually there's no difference on the tip at all.

Just thinking out loud here, could your problem be spark related? Have you tried a new spark plug? I've also seen it (On cars) where under load at lower RPM's a faulty ignition wire and/or coil will act up at certain lower rpms but once you get up in the rpms the problem "goes away", you'll find the problem to be less noticeable without any load on the motor - ie - neutral.

  • Zsebi-2

Posted March 14, 2008 - 08:52 AM

#13

Thank you guys for sticking with this tread and trying to help me resolve this problem; I appreciate it. Any, and all of the issues you mentioned could be the source or cause.

I completed a thorough carb cleaning, compared all the jet sizes with the yamaha manual, checked AP membrane , carb slides, neddles everything looks good, all passages were clean. The only thing that is not stock is the Zipty pilot screw an the air boot collar- see picture. That aftermarket collar worries me bacause it block the air jets - see where the arrow point. It does not blocks it completely but sure is different than the stock boot , which has 2 channel from the airbox to the air jets. If none of my fix solve this problem than I will have to buy the yamaha collar.
Posted Image

Honestly, I don't feel the need for any power enhancement on this bike, it has plenty power in its stock mode, when I twist the throttle it is either a wheelie
or wheel spin, I don't care for nay of it because I ride in tight wooded /hilly area.

Oh....I found the gray wire disconnected, it was done very cleverly, almost un- detectable, the terminal pin was pushed out of the connector folded back and taped with black tape up to the plastic terminal housing, looked very factory like. Reconnected it for now.

Throttle cable was frayed.

Cam timing is factory.

I will try a new spark plug as well.

  • matt4x4

Posted March 14, 2008 - 10:06 AM

#14

Check all the lines off the carb and make sure they're not clogged as well.

Good luck, I'm checking out for a week!

  • Zsebi-2

Posted March 17, 2008 - 06:45 AM

#15

Good news , I have found the problem with the help of some other wiseman.
Hopefully this is some info that others can use.
Here is what I was told:
with older carbs, a couple things can cause symptoms/ problems like mine.

1: the rubber plate at the end of the choke/enricher plunger wears out allowing additional fuel to leak in making the bike run rich.

2: this is the problem on mine:
the main jet needle and the tube that the needle slides into wear slightly( soft material , aluminum and brass) causing a rich condition when a transition from the pilot jet-- to a main jet operation takes place , right at 1/8-1/4 throttle.

I dropped the needle one groove, and the problem completely went away, the bike runs superb but now the plug is white / too lean.

solution , get a new needle and seat/tube, put the stock pilot back in.

thanks to all who helped.

  • byggd

Posted March 17, 2008 - 10:32 AM

#16

Thanks for the update. Glad to hear you solved it! :confused:

  • drtbk4ever

Posted March 17, 2008 - 10:39 AM

#17

Good news , I have found the problem with the help of some other wiseman.
Hopefully this is some info that others can use.
Here is what I was told:
with older carbs, a couple things can cause symptoms/ problems like mine.

1: the rubber plate at the end of the choke/enricher plunger wears out allowing additional fuel to leak in making the bike run rich.

2: this is the problem on mine:
the main jet needle and the tube that the needle slides into wear slightly( soft material , aluminum and brass) causing a rich condition when a transition from the pilot jet-- to a main jet operation takes place , right at 1/8-1/4 throttle.

I dropped the needle one groove, and the problem completely went away, the bike runs superb but now the plug is white / too lean.

solution , get a new needle and seat/tube, put the stock pilot back in.

thanks to all who helped.



I am glad you found the problem. I have a similar issue and once the snow melts, I am going to adjust my needle to see if that helps.

Cheers.




 
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