Major stutter/hesitation

12 replies to this topic
  • drtbk4ever

Posted May 28, 2006 - 03:19 PM


Hi gang,

I have searched and read countless threads on this topic and have questions specific to my situation.

I bought an 04 wr450 a few months ago so am bit of a newbie. I am not sure what mods were done.
My first ride was a month ago where half way through the ride, the stock exhaust insert broke off. So we took it out and I learned what an uncorked bike ran like. No stutter or hesitations that day at all - with or without insert.

Last weekend got to ride the bike for a few hours, without insert. My last ride was a medium high speed gravel road where part way into it I noticed a bit of a stutter at constant speed. It was fine under acceleration. The stutter got worse as the ride went on. Then today after cleaning the air filter I took a couple runs up the street and the stutter was very noticeable even on acceleration. (note: the oil on the filter wasn't dry yet so maybe the increased stutter and hesitation was from that?).

So my questions: :applause: :D

If the stutter was due to jetting without the insert, wouldn't I have noticed the stutter immediately after taking out the insert?

Am I missing something else as the cause like clogged carb, bad gas?

I am going to get a new aftermarket insert (to quiet it down) so do I wait until I have that installed to fiddle with the jetting?

Last question, can I do damage to the engine riding the bike with a major stutter/hesitation?


  • Numskull

Posted May 28, 2006 - 04:27 PM


Kinda of strange how it seems to be behaving differently with out any changes, that is something to keep in mind as a mechanical failure of some sort.

But it really sounds like a carberation issue. I would pull the plug and check it visually to see what it will tell you then stick a new one in to eliminate that as a cause. I have read where burned said that your jetting will make your bike run so bad that it would be hard to damage it :applause:

A constant speed on my bike only requires about 1/16 throttle. I believe the pilot circuit/jet is responsible up to 1/4, then the main jet, and needle jet as you go farther on the twist.

One other note is that the temperature changed significantly in the last week, and will cause noticeable performance difference from your jets.

I haven't got the JD kit yet, but am really tempted, It seems like I lost a few ponies with the mercury reading 94

  • odonnks

Posted May 28, 2006 - 04:34 PM


Sounds like a lean condition. The removed insert should have leaned it out. But why it didn't studder right off is the question.
A clogged jet could also be a problem and lean it out.

Do you know what jetting is in it?

  • drtbk4ever

Posted May 28, 2006 - 04:40 PM


Sounds like a lean condition. The removed insert should have leaned it out. But why it didn't studder right off is the question.
A clogged jet could also be a problem and lean it out.

Do you know what jetting is in it?

Odonnks, I don't know what the jetting is. I was hoping to have a few ideas before I got into the carb. I am more than a little afraid of that.

Thanks for the input guys, anybody else?

  • drtbk4ever

Posted May 29, 2006 - 03:37 PM


Anybody else with some words of wisdom?

  • Matty05

Posted May 30, 2006 - 09:01 PM


Anybody else with some words of wisdom?

Stutter is rich. No doubt.

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  • OneToGo

Posted May 31, 2006 - 06:20 PM


Stumble or stutter is RICH.
Depending on the jetting you have - you need to find out the numbers :D then I would initially suspect the needle especially if the temps have recently risen.
Set the MJ first at WOT, then Pilot circuit for low throttle then Needle and clip for mid throttle. Remember its the throttle setting not engine speed that dials in the jet being used. If the stutter is on slow twist and go throttle then you can discount the AP circuit. If its in the 1/8 to 1/4 range I would drop/lower the needle, raise by one clip if nothing if its on 5th from top (blunt end) put it on the 4th etc...

  • odonnks

Posted June 01, 2006 - 02:01 AM


d b 4ever

After re reading your issue I believe that Matty and One are on the right track. I saw hesitation and thought of another prob.
A stuttering or blubbering would be rich, especially if at a constant speed. Here is a FAQ that has helpful info and a graph that tells you what part of the throttle each jet effects.
You mentioned possible bad gas. If you suspect it, change it. What you did should have leaned it out, not richened it.

  • drtbk4ever

Posted June 01, 2006 - 06:57 AM


Great info guys. It helps take some of the mystery out of this jetting thing which scares the crap outta me. :applause:

  • Matty05

Posted June 02, 2006 - 05:14 AM


Great info guys. It helps take some of the mystery out of this jetting thing which scares the crap outta me. :applause:

All I can say is really pay attention to your bike, and only change one thing at a time. After a while, jetting is easy, but still a pain in the ass.

  • Moto5

Posted June 02, 2006 - 05:43 AM


I would start with the basics because I don't think it's the jetting. Get a new plug, fresh gas and clean the fuel filter. If you can fix the baffle and put it back in that would be the first thing to do. If it still hesitates that would eliminate the jetting right away. Great advice from Matty about trying to change multiple things at once.

  • drtbk4ever

Posted June 02, 2006 - 08:52 AM


Hi gang,

OK, I did a search to learn the bike doesn't come with a fuel filter. It seems some of you are installing in-line filters. Where would you install one, attached to the petcock or further down?

I have a ride planned on Sunday so will pay close attention to the throttle position when the stutter occurs. After that it will be time for an oil change so I will dig into it then. I want to get a new insert (or fix and reinstall the old one) before I start fiddling with the jetting. Because it was running fine before the insert was removed.

Thanks for all your help guys.

  • Matty05

Posted June 02, 2006 - 07:27 PM


I cut the fuel line 1/2 way between the petcock and carby. Put in an inline filter there.

I have never got crap in there yet, but sometimes get crap still in the fuel bowl.

Just clean out your carby regularly, as crap in there causes all sorts of problems.


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