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Wow that little jet did it

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After doing a lot of reading on this site I finally bought a #40 leak jet for my 04 WR250FS. No more bog and it only cost me $12.00 Cdn. It was simple to install and made a huge difference. The stock leak jet was a #90. Thanks for all the previous posts on this subject and to those that answered my questions. :)

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I am glad it works for the 250s. :) I have been preaching it for the 450s for a while now. I even have my home made 0 leak jet for winter riding! :)

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So is that a blocked off leak jet? Also will the bike run OK like that, meaning will it hurt it? I know that I read in the thumperfact somehwere to do that but I was not really sure if it worked.

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Some bikes take a smaller leak jet like the #40, and others need their leak jet to be blocked off completely. To try it out, simply solder shut an extra leak jet, and see how it works. The only way to find out which leak jet YOUR bike needs is to experiment. Either measure the squirt and change jets accordingly, or just buy an assortment of leak jets and test them out.

Soldering a leak jet shut will NOT hurt your bike (just don't solder the jet while it is still installed). The leak jet us used only and specifically to meter the amount of fuel delivered when a quick twist of the throttle activates the accelerator pump. It has NO effect during the course of "normal" riding. A large leak jet delivers less fuel to the AP squirt, and a smaller leak jet delivers more fuel to the AP squirt.

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Hi cdn_wr250

I have the same bike and setup as you,Have you changed main jet or needle clip postion? :)

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Darcy,

Do you know how long your AP squirt lasts when you flick the throttle open?

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Darcy,

Do you know how long your AP squirt lasts when you flick the throttle open?

The motor run when you check the squirt? :)

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No, that would involve running the motor with the air filter un-attached, which I don't think anyone recommends.

Just move the air inlet boot aside, or remove the sub-frame like I did. Then look down the carb throat at that little off-center brass nozzle. When you whack the throttle open, you should see a strong, solid stream of gas squirt towards the engine's intake.

Leave the gas tank on, and turn on the petcock to make sure that the AP reservour is full so you get an accurate measurement. If you do several squirts to measure the duration, you may want wait several seconds on later trials to give the reservour time to re-fill.

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YAMAHA_EH

I didn't make any changes to the needle jet or clip position as the #40 leak jet solved 98 percent of the problem. I checked the squirt duration and noticed that it was very short (I didn't time with a stop watch as you can tell if it is short or not just by looking at it). Once the new leak jet was in I could tell immediately that the squirt duration was a lot longer. I'm glad that I tried the leak jet first as it worked great. I'm sure that I could fix the other 2 percent by experimenting with changes but for now I am very happy with the bike. Good luck.

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I am glad it works for the 250s. :) I have been preaching it for the 450s for a while now. I even have my home made 0 leak jet for winter riding! :)

What year 450 for the leak jet? As far as I knew only the 05's have a leak circuit.

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Just wanted to let you guys know that plugging the leak jet fixed the bog on my 03 WR250F also. But i went ahead and bought the #40 leak jet from the Yamaha dealer anyway. My dealer did not even have the part numbers in his computor for any of the smaller leak jets so i had to get them for him first. :)

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Didn't the thumperfaq say you can use a BB to plug off the leak jet? Can this be a permanent fix or just temporary? I tried the 40 leak jet on my 03 250f and it did help some but the bog is still there.

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I think Rick Keinle (thumperfaq author) has the P-38 and it partially solved his bog issue. It took a different leak jet in conjunction with the P-38 to fully cure it. Rick also did a lot of testing on different AP diaphragms as well. It seems that they come with different length rivets that limit the travel of the AP actuator rod. I believe that this is how the P-38 works as well.

Be aware that all carbs seem to be slightly different enough that there is no "one size fits all" fix for the bog. The P-38 might just be the whole solution for some folks. In other cases, a little more tweaking is needed.

That's one of the major benefits of using the leak jet fix. You can try different things pretty cheaply.

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