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jimmym

2011 Intermittent Miss/Bog/Sputter/Something else

23 posts in this topic

I have a strange problem that just popped up last week on my 2011 WR450.  When trying to accelerate from a low-mid RPM range, occasionally the motor will bog or sputter, and simply won't accelerate.  It kind of feels like there's no spark, just kind of, but the motor will continue running (poorly) at the same RPM instead of revving.  Quite frankly, this is a new problem I've never experienced, and I can't identify where it's coming from.  

 

Last year I put on the DrD Exhaust system, and removed the AIS and restrictive air snorkel. I didn't touch the gray wire because the power curve seemed perfect and didn't feel like it needed to be changed.  I'm running between 200-600' elevation, but the humidity and temps have been increasing. 

 

Last weekend was the first time this problem occurred, and nothing has been changed on the bike in over 6 months.  This issue seems to happen maybe once in every 10 hard accelerations, but more often when hot.  I changed the leak jet to #40 this morning, put on an adjustable fuel mixture screw, and cleaned out the carb this morning... but the problem persists.

 

Anyway, I'm at a loss here.  Any suggestions pointing me the right direction to resolving this will be greatly appreciated!

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Leak jet will not cause your symptoms, and a 40 is too small

 

I would check, in order:

 

Plug

Plug wire

Coil ground

Battery ground to frame

Stator pick up (for debris)

Pilot jet

Gas tank (for varnishing)

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Plug replaced.  Plug wire seems to be clean.  Moving on down the list to the electrical grounds.

 

Thanks for the feedback, this is precisely the list of information I was looking for!

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I replaced the plug, checked the battery ground, and cleaned out the gas tank and pilot jet. I checked the secondary coil resistance, it's spot on.  The primary coil resistance measures at 0.4 ohms, which is outside the range of 0.08-0.10.  I talked to my Yamaha dealer to place an order for a new coil, but he said he's never heard of an ignition coil going bad, especially in such a random manner.

 

The bike runs really strong most of the time, but I can reproduce the sputter in about 1 out of every 7 heavy accelerations.  Especially after a quick acceleration and gear shift, the sputter will happen more often after the RPM drops and the load increases.

 

So, what is the likelihood that my ignition coil is truly the culprit here?  Should I fork out the $100 with confidence, or spend time and/or money on other culprits?

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I have cleaned, tested, and verified each item on the list.  I have cleaned out the pilot jet, as well as the main jet.  Also, I am finding that the problem seems to happen more frequently in hot/humid weather, and I've experienced it at higher RPMs now as well.  

 

I reviewed my notes since this didn't happen before I installed the GYTR AIS Removal kit, nor did it happen in the cooler spring weather with the AIS removed. Anyway, I don't recall seeing a new needle with this kit, and I don't remember swapping out the original, nor is there is a needle with all the parts I kept from the job.  In fact, I pulled the carb again today and verified the original needle is still in there.  I'm starting to suspect this may be the problem!

 

My current plan is to get a new needle, preferably the one I should I have received (or similar), but I'm not sure which one to get or where to find it.  The following page lists 8 needles under #12, but I can't tell the difference between them: TT OEM Parts.  I have also looked at JD kits, but that seems like a lot of cash for just a needle.

 

Am I on the right track?  Any help pointing me to the right needle will be much appreciated!

 

Thanks

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No, I haven't checked the valves yet.  The bike has under 20 hours, all trails.  She starts easily in all weather, and runs great all the time... except for this odd occurrence.  I was on the trail yesterday for about 45 minutes, and experienced the 'bog' only twice in all that time.  My gut tells me that it's jetting, especially because it happened at high RPM in the high humidity, hot weather... which takes me back to the needle.  Could valves cause something sporadic like this?

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Put in a NCVS needle. Krannie suggestion. Made a good difference in the mid on my 07. You can buy it at boats.net for 10.00.

Plus change the leak jet to a 50.

Edited by RMK800

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This page shows the NCVS needle for 2003-2004 YZ450F and 2010-2011 YZ250F.  I can't find much information on this needle, is this right one for my 2011 WR450?

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This page shows the NCVS needle for 2003-2004 YZ450F and 2010-2011 YZ250F.  I can't find much information on this needle, is this right one for my 2011 WR450?

 

There is no 'right' needle......it is the closest to being right, without more information and deeper tuning

 

The igntion is the biggest source of 'sputtering' with the WR

 

 

All the carbs are essentially the same

 

You need to read the FAQ's about the ACV, TPS, slide plate seal, Ignition, etc

Edited by Kah Ran Nee

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Quick update.  Weather was beautiful yesterday, about 75 and only medium humidity.  Due to my travel schedule I haven't been able to dig in and further troubleshoot, but the 'bog' became much worse.  This time it was happening at higher RPMs again, heavy throttle like normal, but not necessarily under load.  But this time it definitely felt like a true bog.

 

Based on this ride I don't feel like this is an ignition issue, so I'm gonna spend a little more time tweaking the carb before shelling out any cash on ignitions parts.

 

After pulling out the carb today I found the main jet that came with the AIS is a 175, which seems very large for 500' elevation.  I have a 162 and 168 in my spare parts box, any suggestions on how far to drop?  

 

I purchased a new needle, and initially set the clip at 4 from the top.  I am bumping the leak jet from 40 to 50, although my local shop doesn't have one in stock so I may have to revert to the 45 until I can get one delivered.  

 

Floats are in spec, and the accelerator pump seems to be set properly as the squirting fuel just misses the slide.

 

Thanks for your patience and suggestions.  I'm looking forward to the coming weekend, and hoping for a successful outcome!  Although, making the problem worse isn't such a bad thing either, as it will help me track down the core issue with the changes I'm making. 

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Accelerator pump should be tuned for low rpm performance, as that is it's function

Changing the leak jet will merely provide more fuel / longer squirt

You are better off changing the apump linkage spring to a stiffer version (R&D, Tokyo mods ) for a 'better' /faster squirt, not a longer one.

I would go 162 main. If it's too small, WOT above 7000 rpm will exhibit a slight lag, which goes away if you close the throttle slightly.

New needle....which one?  Is your bog a 'studder / drowning / gurgle' or a 'kill button / rag in the air box' type bog?

 

The former means too rich (leaner needle like JD blue)

The later means too lean (richer needle like JD Red or NCVS)

 

Timing issues, as in the stock ignition, can cause the timing maps to not work properly, giving you a 'sluggish' performance, not to mention the dreaded WR 'studder'.

 

You should make sure your TPS is calibrated, or, unplugged (which gives you a middle advance map, not the full advanced idle map)

 

Find a hill you can ride up in a gear slightly too high.

Try it with the TPS plugged in and un plugged.

You should see slightly better throttle response with it plugged in at partial throttle (snappier)

It's hard to feel it on flat ground, although you usually feel a loss of 'jerky-ness' at slight open throttle with it un-plugged.

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Thanks Krannie, this certainly gives me the next steps for troubleshooting.

 

You are better off changing the apump linkage spring to a stiffer version (R&D, Tokyo mods) for a 'better' /faster squirt, not a longer one.

 

 

 

It looks like the R&D spring has been discontinued, but I'll order the Tokyomods spring in the morning.

 

New needle....which one?  

 

NCVS needle.  

 

Is your bog a 'studder / drowning / gurgle' or a 'kill button / rag in the air box' type bog?

 

The bog feels mostly like a rag in the airbox (great descriptions, btw).  It sounds like NCVS is the right choice.  Any starting suggestions for clip position?

 

You've given me more things to test this coming weekend, thanks for going along for the ride.

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Well, the NCVS seems to like 4th down or 3rd down, depending on 'stuff'.

 

I have never been able to get a WR to run as crisp as the CRF, with nearly the exact same carb (ACV), and I don't know why!

 

God knows I have tried......

 

I just bought a 1999 YZ426 needle, which is supposed to be 'magic' in modded motors.

 

Not holding my breath....for very long.    

 

Dang, I just had the tank off today, fixing the leak, and could have done it then.   :facepalm:

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Thanks Krannie, this certainly gives me the next steps for troubleshooting.

It looks like the R&D spring has been discontinued, but I'll order the Tokyomods spring in the morning.

NCVS needle.

The bog feels mostly like a rag in the airbox (great descriptions, btw). It sounds like NCVS is the right choice. Any starting suggestions for clip position?

You've given me more things to test this coming weekend, thanks for going along for the ride.

Don't pay for a 18.00 spring. You can find a replacement that was made for the KTM FCR carb here for 6.00.

http://www.rockymountainatvmc.com/p/1151/41156/KTM-SXS-Acceleration-Pump-Spring

I have this on my sons 2006 250x FCR carb and it's the same as the merge racing spring that I have in my WR450. One less coil to make it stiffer.

I like the NCVS In the 3rd position, but I also ride at altitude between 3500 and 9000. 50 leak jet.

Edited by RMK800

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Well, the NCVS seems to like 4th down or 3rd down, depending on 'stuff'.

I have never been able to get a WR to run as crisp as the CRF, with nearly the exact same carb (ACV), and I don't know why!

God knows I have tried......

I just bought a 1999 YZ426 needle, which is supposed to be 'magic' in modded motors.

Not holding my breath....for very long.

Dang, I just had the tank off today, fixing the leak, and could have done it then. :facepalm:

Not to derail this topic, but do you recommend the accelerator pump kit made for CRF for WR's?

http://crfsonly.com/howto/keihin-fcr-carb/honda-crf-fcr-carb-update-how-to-install/how-to-install-honda-accelerator-pump-update-crf450r.php

Edited by RMK800

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That link you posted is to the 2008 CRF450R stock pump and parts.....which will retro fit on to all the late FCR carbs

If you have a fully uncorked motor, then the stock WR pump system cannot keep up with the demands of your right hand.

The new system is all Keihin, uses a better leak system, a longer through diaphragm, and a longer rod for the new diaphragm. 

It works GREAT.  It is the final evolution of the FCR carb, before going to more radical non-Kiehin mods.

It works so well, it actually helped me find a lean portion on my needle:

 

If I rolled on the throttle, there was a 'flat' spot in the power, until the rpms rose up high....but if you 'snapped' the throttle, and shot a nice splash of Jager into the motor, no flat spot what so ever.

 

So I tried a thinner and shorter needle  (ELN) to great success.

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Nice, I'm going to do this mod over the winter on my 2007 WR450. I'm assuming you also went and did the check valve part of the mod?

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I have cleaned, tested, and verified each item on the list.  I have cleaned out the pilot jet, as well as the main jet.  Also, I am finding that the problem seems to happen more frequently in hot/humid weather, and I've experienced it at higher RPMs now as well.  

 

I reviewed my notes since this didn't happen before I installed the GYTR AIS Removal kit, nor did it happen in the cooler spring weather with the AIS removed. Anyway, I don't recall seeing a new needle with this kit, and I don't remember swapping out the original, nor is there is a needle with all the parts I kept from the job.  In fact, I pulled the carb again today and verified the original needle is still in there.  I'm starting to suspect this may be the problem!

 

My current plan is to get a new needle, preferably the one I should I have received (or similar), but I'm not sure which one to get or where to find it.  The following page lists 8 needles under #12, but I can't tell the difference between them: TT OEM Parts.  I have also looked at JD kits, but that seems like a lot of cash for just a needle.

 

Am I on the right track?  Any help pointing me to the right needle will be much appreciated!

 

Thanks

 

Yes you must replace the stock needle. It should have come with the GYTR kit. So replace it with some of the suggestions posted or your JD needle just not stock.

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Nice, I'm going to do this mod over the winter on my 2007 WR450. I'm assuming you also went and did the check valve part of the mod?

 

Yes, you have to do that

I also use the R&D racing full floatbowl upgrade too on some bikes

I don't know why, but it absolutly smooths out the power deliver on roll on and snapped throttle, with more 'precision'

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