Help with jeting?



8 replies to this topic
  • jj

Posted December 24, 2000 - 08:51 AM

#1

Hey.

I recently took of the carb for the first time to clean the accelerator pump and switch the needle to a EKN in the 3rd position (on the recommendation of James). My bike already ran fine, but I was looking for better response and possibly more power.

Rode it for the first time yesterday. It was extremely wet, large amounts of water. Here are my impressions.
1. Incredible power!...for the first 15-20 minutes. Seriously it felt like I just took out the baffle for the first time.
2. However...it would back fire on deceleration. About half of the time when I would start it and give it gas it would die. It seemed much more sensitive to the Hot Start switch than normal. A few times it would even shoot flames when I would rev it while stationary. Lastly when I would wick it open in any gearing it would sputter badly.

Interestingly my stock set up was a DTM in the 3rd position (I was under the impression that most WR's came with DTM in the 4th position.)

Anyway, I'm running stock timing, stock exhaust, no baffle, no air box cover.

What do you think?

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JJ - 99 WR; WR timed, stock jetting, Scotts stabalizer, Scotts triple clamps, Pro-Tapers, Terry Cable Hot start, MSR Raptor clutch lever, Moose skid plate, Works frame guards, Acerbis Pro Rally guards, Renthal MD-soft grips, Russel speed bleeders, Factory Effect graphics, YZ rear fender

  • Boit

Posted December 24, 2000 - 06:44 PM

#2

Sounds like a prime case of an air leak. It's very easy to develop an air leak after R&R'ing the carb. No amount of jetting changes will rectify an air leak. I experienced the same thing and after cursing me mum for giving birth to me, I found and cured the leak. All my carb problems vanished completely.

  • James_Dean

Posted December 25, 2000 - 08:15 PM

#3

JJ,
Air leaks?, as Boit said or:

What was the pilot screw setting?? Sounds lean.
-I would suggest trying to back out the pilot screw to richen it a little at idle and just off idle. Set at about 2 1/4 turns using a #45 pilot jet.
-Did the idle speed change? Make sure it is not too low.
-Next step would be to try 1 clip richer on the needle, EKN#4.

What Main jet? Probably not a factor for your adjustments at this point.
-Anywhere in the range of 165-172 is close.

James

  • jj

Posted December 27, 2000 - 07:32 AM

#4

Thanks guys, I'll check for air leaks. I'm pretty sure that everything is sealed. Anywhere in peticular to look?

At first I also thought that it sounded like a lean condition because of the back firing. Could it be a rich condition? I thought I remember hearing that if a bike shoots flames that it was an indication of of a rich condition. That would also seem to explain the degridation of power over the course of the day i.e. plug fowling.

Thoughts?

Oh, everything is comletely stock on the carb except for the EKN needle.

I just thought of one other thing, the bike only seemed to sputter and cut out above half throttle. It did back fire periodically over the whole power band though.
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JJ - 99 WR; WR timed, stock jetting, Scotts stabalizer, Scotts triple clamps, Pro-Tapers, Terry Cable Hot start, MSR Raptor clutch lever, Moose skid plate, Works frame guards, Acerbis Pro Rally guards, Renthal MD-soft grips, Russel speed bleeders, Factory Effect graphics, YZ rear fender

[This message has been edited by JJ (edited 12-27-2000).]

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  • James_Dean

Posted December 27, 2000 - 05:30 PM

#5

How did the plug look?

You said is was extremely wet, some other problem possible??

How did the hot start change in the way it worked?

James

  • Boit

Posted December 27, 2000 - 07:41 PM

#6

Loud exhaust popping upon decel is an indication of a lean condition. That's why I suspect an air leak. My 426 did this terribly and I wanted to pull my hair out(what's left of it) trying to correct this problem. My leak was at the juncture of the adaptor and the carb...the one that the airbox slides onto. In my earlier posts about this adapto, I mistakenly described this as the intake manifold that bolts to the cylinder head. I apologize for this error....brain burp I guess. Anyway, if you think about it, as you close the throttle when the engine is revving, there is a tremendous vacuum created between the carb slide and the combustion chamber so the intake manifold must have a good seal. Once the throttle is opened, the vacuum is expanded all the way out through the airbox so you must have a good seal in all those junction points. Any small leaks will give a lean conditions and throw jetting attempts out the window. I can't stress how important it is to have the intake tract sealed completely before moving into jetting changes.

  • jj

Posted December 27, 2000 - 08:40 PM

#7

Well it looks like it may have been a soaked air filter. I started it today, when it was dry, and did sputter alittle for the first few minutes but ran fine after that...

If this really is the cause wouldn't that indicate a rich condition? i.e. too little air.

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JJ - 99 WR; WR timed, stock jetting, Scotts stabalizer, Scotts triple clamps, Pro-Tapers, Terry Cable Hot start, MSR Raptor clutch lever, Moose skid plate, Works frame guards, Acerbis Pro Rally guards, Renthal MD-soft grips, Russel speed bleeders, Factory Effect graphics, YZ rear fender

  • James_Dean

Posted December 28, 2000 - 09:22 AM

#8

Probably, yes.

The popping can occur both ways, lean or rich. Usually it will just sputter first when rich.

  • jj

Posted December 29, 2000 - 09:23 AM

#9

I'll know for sure soon, I'm going to service everything today and am going riding Sunday. Oh, I did realize that I have not been using that thin black piece of plastic that goes between the tank and seat. It says in the manual that piece of plastic is designed to keep water out of the air box.

Anyway! Thank you for the EKN recommendation James! I was very impressed with the performance. Unless I am just imagining it, it seems like it pulls harder from the bottom thought the mid. It almost felt like I took of another baffle...

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JJ - 99 WR; WR timed, stock jetting, Scotts stabalizer, Scotts triple clamps, Pro-Tapers, Terry Cable Hot start, MSR Raptor clutch lever, Moose skid plate, Works frame guards, Acerbis Pro Rally guards, Renthal MD-soft grips, Russel speed bleeders, Factory Effect graphics, YZ rear fender




 
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