2006 40 Leak Jet?

My friend and I jut picked up our 06 250F's today, noticed they have pretty bad partial throttle response. I noticed the posts on here about people all switching to the 40 Leak Jet to cure some of the bog issues, I believe the stock LJ on the 2006 is a #80 and that seems like a massive jump to go that lean considering they do not even list it in the manual (only down to a 55). The bike seems to run well otherwise through the gears, right off idle and very small partial throttle opening while riding feels sluggish.

Would like to hear what other people are running jetting wise in these temps at sea level.

Thanks,

Mike.

I'm using a 60 leak jet in my 2006, it seemed to make everything OK, but the test ride was too short (it didn't bog ALL the time on me before, only sometimes). Then it snowed, and it's been way cold ever since, and she's just been beautiful garage scenery.

As I'm sure people will point out, search for accelerator pump (AP) timing. You can experiment with different leak jets, it's pretty cheap to do so.

My friend and I jut picked up our 06 250F's today, noticed they have pretty bad partial throttle response. I noticed the posts on here about people all switching to the 40 Leak Jet to cure some of the bog issues, I believe the stock LJ on the 2006 is a #80 and that seems like a massive jump to go that lean considering they do not even list it in the manual (only down to a 55). The bike seems to run well otherwise through the gears, right off idle and very small partial throttle opening while riding feels sluggish.

Would like to hear what other people are running jetting wise in these temps at sea level.

Thanks,

Mike.

Mike, I can't really comment on your particular machine. The 40 soes seem to be the hot ticket. I have an 06 CRF250 and just ordered a 45 and 40 leak. We'll see what it does.

To clarify any confusion you may have on what the leak jet does...It is actually a jet in the bottom of the float bowl that allows fuel to 'leak' back into the bowl when the Accelerator Pump is activated. This jet actually works opposite from other jets in the carb. A larger leak jet will allow more fuel to leak back into the bowl, delivering LESS fuel to the engine. Just the opposite with a smaller leak jet, MORE fuel. The AP is necessary on 4strokes because at low engine speeds there is not sufficient vacuum to draw fuel through the pilot circuit, so when you initially turn the throttle the AP gives a squirt of fuel to compensate for this until engine speeds increase and creates enough vacuum to overcome this. Hope this helped. :applause:

You can search AP tuning on this forum and learn everything you could want to know.

I was not sure about the leak jet and cold weather - seemed kind of strange to technically go that lean all the time. So I guess unlike the main and needle most people are running the 40 year round? I have to put an order in for the leak jets (friend purchased the same bike) and a couple different pilots.

Thanks again,

Mike.

Again, a 40 leak jet is richer than an 80. It allows LESS fuel to be "leaked" away from the AP squirt.

Also, the leak jet only affects the AP squirt, which is only seen when flicking the throttle open rapidly.

On the 06s, the AP squirt nozzle is right next to the slide and is pointing straight up, so you'll have to time the squirt duration correctly instead of the "hitting the slide method" correct? :bonk:

06 Venturi

Is the AP squirt nozzle on the older bikes set back from the plate and is pointed at the slide - I seem to vaguely remember that it does on my 02 WR... :applause:

On the 06s, the AP squirt nozzle is right next to the slide and is pointing straight up, so you'll have to time the squirt duration correctly instead of the "hitting the slide method" correct? :cry:

06 Venturi

Is the AP squirt nozzle on the older bikes set back from the plate and is pointed at the slide - I seem to vaguely remember that it does on my 02 WR... :applause:

Good question av...Never really thought about it until you mentioned it...Anyone else have input on this? :bonk:

On the 06s, the AP squirt nozzle is right next to the slide and is pointing straight up, so you'll have to time the squirt duration correctly instead of the "hitting the slide method" correct? :bonk:

06 Venturi

Is the AP squirt nozzle on the older bikes set back from the plate and is pointed at the slide - I seem to vaguely remember that it does on my 02 WR... :applause:

Hey av, just went out and looked at my carb. Yes, the nozzle is pointed straight up, but if you slide the slide up and look in your carb from the intake side you will see the outlet is actually on the side of the nozzle pointed into the venturi. I would post a pic if I was' nt computer stupid! :cry:

Hey av, just went out and looked at my carb. Yes, the nozzle is pointed straight up, but if you slide the slide up and look in your carb from the intake side you will see the outlet is actually on the side of the nozzle pointed into the venturi. I would post a pic if I was' nt computer stupid! :applause:

Is your bike also an 06 YZF? If it is, at that distance, it doesn't take much of a squirt to hit the slide, it's only 2 or 3mm away from the slide...

Here is the bigger version of that picture, I can see that the top of the nozzle is sealed off like you've stated.

I have an 04 wr250f and am running 40 leak jet .Help out alot,also have you done the other mods?

Av you're confusing me. The way I understand it, squirt duration and squirt timing are two different things.

Squirt timing relates to how soon after you hit the throttle does the squirt begin. If the AP squirts too early, some of the squirt hits the slide. Too late, and the fuel doesn't reach the cylinder soon enough to overcome the vacuum induced bog. You want the squirt to begin just as soon as the slide begins to rise. Getting the fuel as close to the slide as possible, without hitting it, should give your bike the best chance of overcoming the bog.

Squirt duration relates to how long the AP squirts once it begins squirting.

The nozzle sticks up into the carb throat, but it directs the fuel squirt towards the engine's intake, rather than straight up.

The way I understand it, squirt duration and squirt timing are two different things.

Squirt timing relates to how soon after you hit the throttle does the squirt begin. If the AP squirts too early, some of the squirt hits the slide. Too late, and the fuel doesn't reach the cylinder soon enough to overcome the vacuum induced bog. You want the squirt to begin just as soon as the slide begins to rise. Getting the fuel as close to the slide as possible, without hitting it, should give your bike the best chance of overcoming the bog.

Squirt duration relates to how long the AP squirts once it begins squirting.

The nozzle sticks up into the carb throat, but it directs the fuel squirt towards the engine's intake, rather than straight up.

this is entirely correct. :applause:

Is your bike also an 06 YZF? If it is, at that distance, it doesn't take much of a squirt to hit the slide, it's only 2 or 3mm away from the slide...

Here is the bigger version of that picture, I can see that the top of the nozzle is sealed off like you've stated.

Av, it does'nt matter which bike it is. An FCR carb is an FCR carb. Maybe I was'nt clear in my description, but barton states it correctly above. the nozzle is pointed up but the squirt exits pointing into the venturi. No there is not much room between the slide and the nozzle, htis is why it is critical to get the timing correct

I set my squirt to just BARELY miss the slide by adjust the AP screw on the carb and put a 40 LJ and no bogs (unless I'm in to high of a gear). When I 1st set the AP it was WAY off, the slide was 1/4 to 1/2 up before the squirt started. I adjusted my AP screw between 3/4 to 1 turn now it's :applause:

696

Av you're confusing me. The way I understand it, squirt duration and squirt timing are two different things.

Squirt timing relates to how soon after you hit the throttle does the squirt begin. If the AP squirts too early, some of the squirt hits the slide. Too late, and the fuel doesn't reach the cylinder soon enough to overcome the vacuum induced bog. You want the squirt to begin just as soon as the slide begins to rise. Getting the fuel as close to the slide as possible, without hitting it, should give your bike the best chance of overcoming the bog.

Squirt duration relates to how long the AP squirts once it begins squirting.

The nozzle sticks up into the carb throat, but it directs the fuel squirt towards the engine's intake, rather than straight up.

I got it now, thanks... :applause:

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