Rejetted the 09 WR450F today...WithOUT taking off the carb...

Thats right....without taking out the carb. A couple of others here

told me it was possible. I sure didnt see how. But with a couple

of small, modified tools, the job wasnt TOO bad.

Removed the access cap from the bottom of the carb using a 17mm wrench.

Used a short common (flat head) bit from a 6 in 1 screwdriver for the pilot jet, then turned with a 1/4" wrench.

Used a deep socket, without the ratchet, on the main jet, then turned

with a small set of pliers.

Had a little help from a small mechanics mirror and a small LED pen light to

help locate the jets when still in the carb. Also, when reinstalling the pilot

jet I used a small piece of shrink wrap around the bit and jet, then very lightly

heated around the jet. This helped hold it in place until I began to screw it in.

Then I just pulled the bit with shrink wrap off the jet. No problem.

Took about 30 minutes, but that was my first try. Still faster than removing

the carb. I figure next time I should be able to do it in about 15 minutes.

BTW.....

Was running the GYTR AIS removal kit jets. 50 pilot and 175 main.

Stock was 45 pilot and 162 main. New jets installed today were

48 pilot and 168 main. Ill let you know how they are, although Im

fairly confident these will be sufficient to get the job done.:p

Bloody hell!! Sounds like a fair bit of fiddling! I think I would prefer to pull the back of the bike off!

Have fun....:)

I would just rather be able to ride and test the bike, then

come back to the trailer and make some adjustments without

having to pull the rear tire, shock, seat, tank, subframe, etc etc.

I would think messing with a bit of a tight spot for 15 minutes

would be better than removing all of that.

JMHO

Bloody hell!! Sounds like a fair bit of fiddling! I think I would prefer to pull the back of the bike off!

That's funny, Aussie's type like they talk!

Taking 1/2 the bike apart to change jets sucks.

Adjustable leak jets and fuel screws make life even easier.

The pilot, main and needle changes are all very easy to do on bike. Pilot and main take barely two minutes to do, esp. with the Motion Pro 90 degree tool. The needle takes a little longer as the tank must come off. Then with a good set of ball end Allen drivers, the needle is in and out in a flash. On the alloy bikes, it is the leak jet that is a bear. Hence many like me, going to and adjustable leak jet.

The pilot, main and needle changes are all very easy to do on bike. Pilot and main take barely two minutes to do, esp. with the Motion Pro 90 degree tool. The needle takes a little longer as the tank must come off. Then with a good set of ball end Allen drivers, the needle is in and out in a flash. On the alloy bikes, it is the leak jet that is a bear. Hence many like me, going to and adjustable leak jet.

Thanks for this! I was just about to pull the subframe, etc., out when I saw this thread. 2 minutes later the main was out. Will get the motion pro set tomorrow to pull the pilot. 175 main--sheesh!

Also saw the adjustable leak jet screw head and will have to get a tool to access that puppy. Coming from a triumph, things are a bit tighter in the yam. I'm not exactly sure how the leak jet adjustment affects the throttle response--more turns out does...what? If there's a well-known link out there I haven't found I'd appreciate a pointer. thanks..J

i just opened up my new to me 07 wr450. it had a 178 mj! the bike was run in the hi dez here in calif. i put in a 168 ( cuz i didnt have a 165) went to a 45 pj from a 50. and put in a zip ty fuel screw. runs much better.

it was stumbling all over itself above 3000'. i took it up to 8k on monday.

these tin can bike are a pain in the arse to work on.....

Thanks for this! I was just about to pull the subframe, etc., out when I saw this thread. 2 minutes later the main was out. Will get the motion pro set tomorrow to pull the pilot. 175 main--sheesh!

Also saw the adjustable leak jet screw head and will have to get a tool to access that puppy. Coming from a triumph, things are a bit tighter in the yam. I'm not exactly sure how the leak jet adjustment affects the throttle response--more turns out does...what? If there's a well-known link out there I haven't found I'd appreciate a pointer. thanks..J

Want to make sure you understand, the alj (adjustable leak jet) is on the bottom of the carb, on the AP cover. It is not stock, it is an aftermarket part. If you did not put it on, how/whty do you think it is there? I just want to be sure you do not try to tweak the wrong thing.

The ALJ is used to replace a fixed jet. This fixed jet is inside the float bowl. To change it, the bowl must be removed. This can be a lot of work to do, so the expense of the ALJ is justified by the labor savings. The leak jet is part of of the AP system. It 'leaks' fuel back into the float bowl. Accordingly, a smaller leak jet 'leaks' less fuel. The leak jet controls the duration of the AP squirt, response (whether a squirt occurs in relation to the throttle opening speed) and total volume of the squirt. The jet, in conjunction with the AP timing screw is responsible for dealing with the dreaded bog that can happen when you nail the gas.

Want to make sure you understand, the alj (adjustable leak jet) is on the bottom of the carb, on the AP cover. It is not stock, it is an aftermarket part. If you did not put it on, how/whty do you think it is there? I just want to be sure you do not try to tweak the wrong thing.

The ALJ is used to replace a fixed jet. This fixed jet is inside the float bowl. To change it, the bowl must be removed. This can be a lot of work to do, so the expense of the ALJ is justified by the labor savings. The leak jet is part of of the AP system. It 'leaks' fuel back into the float bowl. Accordingly, a smaller leak jet 'leaks' less fuel. The leak jet controls the duration of the AP squirt, response (whether a squirt occurs in relation to the throttle opening speed) and total volume of the squirt. The jet, in conjunction with the AP timing screw is responsible for dealing with the dreaded bog that can happen when you nail the gas.

Good explanation, I actually understand it now! And yes, it does have the r&d powerbowl, which I verified with a quick look. Need to find an angled screwdriver to get at the pilot screw--eating me up that I can't ride the bike and just got it. I picked up a pro motion tool set yesterday and thought the driver would work but need the 90 degree angled tool. Search this a.m....

thanks again..Jack

Update:

1. changed pilot from 48 to 42

2. changed main from 175 to 172 (just to get a clean one in there)

3. drained all gas and replaced (prob sitting in the bowl/tank for 3+ mos.)

4. 1.5 turns out on the a/f screw

5. left the adj. leak jet alone as it was crisp before

6. didn't get to the needle

Test drive:

1. sputtering less at steady throttle but still there--probably appropriate

2. got the bike warm then did the a/f screw--all the way in--still no stalling or stuttering. It is possible that the screw could have turned more but my experience with carbs felt like it was at the stops.

Suggestions? It had a jd jetting kit on it so I can assume that the PO had it running right. Would I really need to go down another 2 sizes on the pilot, you think? Took me forever to get that emmereffer in there...Or...could the a/f screw be defective? Not sure the brand, it has a little cross-bar through the bottom which doesn't slide. If you think I need to monkey with it and know of the link to pull the carb, I'd appreciate a pointer. I got the subframe off then backed out when looking at the service manual for removing the rear shock...

Thanks for any hints..Jack

42 PJ is in the ballpark.

I would never assume that a previous owner tuned the bike properly. Unlees it was Alessi or CR, or JS, or ... :excuseme:

If you're at a low idle and you turn the fuel screw in, the bike should stall. That will tell you if the pilot circuit is working.

If it is, then put it at a slightly high idle and adjust the fuelscrew. If you can turn it all the way in, there's a problem.

The idle can be too high and you're pulling fuel through the emulsion tube and bypassing the pilot circuit, the float level can be too high (same problem), the pilot jet can be loose, or the fuelscrew taper can be wrong. (I had a problem with a White Bros FS taper being too wide and not changing the mixture lean enough. Go figure...)

So, if nothing else works, try a stock fuelscrew. If that solves the problem, then your aftermarket FS is bad. I exclusively use GYTR fuelscrews for that reason, although ZipTy's are supposed to be fine as are the brass t-handle ones (I forget who makes those).

I forgot if you did the ACV mod yet. If the ACV is still in working condition, it can be a real drag to tune the pilot circuit on these bikes.

So just to make sure I understand you right, if I lower the idle and the bike stalls when the a/f screw is in all the way, that's good. But if I raise the idle to high idle and it doesn't stall then there's a problem other than the pilot ckt.

I ordered a zipty regardless b/c the t-handle one is a pain to turn. I do have the stock screw and will try that tomorrow.

thanks, Jack

if I lower the idle and the bike stalls when the a/f screw is in all the way, that's good.

Yes. That means the needle is able to control the pilot circuit and no fuel is being pulled through other circuits.

But if I raise the idle to high idle and it doesn't stall then there's a problem other than the pilot ckt.

Yes. That would indicate that the bike is pulling fuel through the emulsion tube too early. It could be a float level problem, could be other things. At some point, the idle can be high enough that the emulsion tube (needle and MJ) come in to play, and that's ok. It might come down to a judgement call. At around 1800 RPM, (a high idle) you should still be on the pilot circuit only and not the needle/MJ.

Just a suggestion: As much as I think you'll get good help in this forum, if you get to the point that you want an expert's advice, hit up Eddie in the Jetting forum. The guy's amazingly good.

Thanks. I'll try lowering the idle and changing out the fuel screw today. Maybe I'll get motivated and pull the needle and also chk the float level.

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