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xlenttx

Leak jet

16 posts in this topic

Alright I'm new to the wr450 world just picked this 2003 wr450 up a few weeks ago and I'm fighting the bog. I pulled the carburetor and verified the jetting 45 pilot 165 main ncvq needle on the middle clip. I have an adjustable fuel screw set at 2 1/2 turns. Starts first kick and idles great. I get a bog 1/2 throttle at around 5-6 thousand rpm then it screams and pulls hard. Revs quick in neutral. The one thing that is puzzling me, and I've searched everywhere and can't answer my questions, is there is no leak jet. The bowl looks like it was never drilled and tapped for the jet looks made that way not like someone plugged it. Makes me think I'm getter too much fuel from the accelerator pump causing the bog. Should I buy a different fuel bowl so I can have a leak jet? Or can I fix the bog with what I have? Thanks so much for he help. I've learned a lot from this page already.

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Veryify your squit quality and duration first.

Use mirror or tilt up the subframe.

You probably have corrosion in the apump system and a shot diapragm

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I'll check it on the bike but when I pulled the carb first time I shot myself in the mouth with fuel. Lol. Thought it was squirting pretty good. Is that not surprising that I don't have a leak jet. Did an 03 not have them?

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I'll check it on the bike but when I pulled the carb first time I shot myself in the mouth with fuel. Lol. Thought it was squirting pretty good. Is that not surprising that I don't have a leak jet. Did an 03 not have them?

 

Some do some don't.

The squirt should be immediate upon wot, and held should be no more than 1 second at full force.

It has to miss the slide every time as well

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Looks to me like I got a good strong squirt misses the slide and continues to squirt for about 1 second after I hit full throttle and hold it open.

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So I have been talking to some friends who ride dirt bikes and they tell me the carb doesn't look like the original one that came on the wr since there is no acv. I thought acv only came on the 05 and up wr's. Parts diagrams show the acv on the 2003 though. Is this off of a yz possibly since it has a yz throttle stop and needle maybe the whole carb is from a yz......

Edited by xlenttx

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It probably is a YZ carb, but it doesn't matter.

The only difference is the ACV, and the jetting.

 

Or, it's a Canadian or South American market bike.

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Ok I took the bike to a shop and he thinks it's off a Ktm because it has a port for a hot start cable that is plugged and wr's never had those. We are thinking that since it's missing the hot start cable that it's pulling extra fuel from that circuit or something. Does any one have experience with the hot start cables and plugging them off?

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Ok I took the bike to a shop and he thinks it's off a Ktm because it has a port for a hot start cable that is plugged and wr's never had those. We are thinking that since it's missing the hot start cable that it's pulling extra fuel from that circuit or something. Does any one have experience with the hot start cables and plugging them off?

 

Sure they did. You have to remember that there were at least 4 different versions of every model back then. Aus, Canada, USA, and World. All has slight differences.

 

Use a Choke assembly for the simplest way to block off the hot start and eliminate the cable.

 

The other way is to replace the plastic cable nut with an aluminum one, and jb weld in a plug at the top, so the spring still has full tension on the plunger.

 

A leaking hot start plunger due to corrison in the cavity or a cracked cable nut reducing spring pressure is/are extremely common on all FCR carb'd bikes.

The hot start issue has no relation ship with the bog issue

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So what kind of problems does that create if there is no plunger in the cavity. It has the plastic nut and a rubber vacuum cap over it. That's it. Nothing inside the carb.

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So what kind of problems does that create if there is no plunger in the cavity. It has the plastic nut and a rubber vacuum cap over it. That's it. Nothing inside the carb.

 

It will run extremely lean if there is no plunger.

Obviously there is a reason the plunger is there, to open or close off a passage.

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So does it sound like this is causing my symptoms or not?? You said it had nothing to do with a bog so I'm confused. Also this hot start plunger location is coming out of the top of the carb and there isn't enough room to put a choke knob. I'd have to use the epoxy method you mentioned and that is more evidence that this carb came from a different bike correct?

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So does it sound like this is causing my symptoms or not?? You said it had nothing to do with a bog so I'm confused. Also this hot start plunger location is coming out of the top of the carb and there isn't enough room to put a choke knob. I'd have to use the epoxy method you mentioned and that is more evidence that this carb came from a different bike correct?

 

Not sure how much more clear to make it.

 

Hot start CANNOT CAUSE BOG.

If the hot start is leaking, you will have high idle or hanging idle.

 

Quick throttle bog is in the accelerator pump.

 

You must upgrade and service the pump system.

 

Billions of posts on the subject.

 

  http://tokyomods.com...arburetion.html

  http://www.crfsonly....roducts_id/3932

 

http://www.thumpertalk.com/topic/1053317-06-crf450r-still-bogs/?hl=%2Baccelerator+%2Bpump#entry11143305

 

If you are going to get impatient for answers when you are providing such limited info, then good luck.

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I don't mean to sound impatient I know it's frustrating to talk to someone who doesn't know what they are doing. Accelerator pump seems to be working just fine. I don't think that is the problem anymore. The bogging missing bucking what ever you want to call it. Happens for several seconds until the engine builds rpm and gets past 6-7k then clears up and hauls ass. Even when it's on the highway in 5th gear at about 50mph and 5k and you roll on slow to about half throttle and hold it you can kinda feel the engine struggling to rev and when it gets past 6k you can feel the power coming on with no change in throttle input. And if you roll on smooth and slow and go all the way to full throttle it bucks and surges and misses like it's running out of fuel and then takes off once you get above 6-7k. It's not just a quick bog and goes away.

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I don't mean to sound impatient I know it's frustrating to talk to someone who doesn't know what they are doing. Accelerator pump seems to be working just fine. I don't think that is the problem anymore. The bogging missing bucking what ever you want to call it. Happens for several seconds until the engine builds rpm and gets past 6-7k then clears up and hauls ass. Even when it's on the highway in 5th gear at about 50mph and 5k and you roll on slow to about half throttle and hold it you can kinda feel the engine struggling to rev and when it gets past 6k you can feel the power coming on with no change in throttle input. And if you roll on smooth and slow and go all the way to full throttle it bucks and surges and misses like it's running out of fuel and then takes off once you get above 6-7k. It's not just a quick bog and goes away.

 

That is not apump bog.

 

If you have a jetting problems, that is described by how far the throttle is turned and at what rpm.

You need to be very specific as to what/when/how your symptoms are occur, and exactly what  they are.

 

EG: at 1/2 throttle the motor feels like it is drowning, at any rpm above 5k it clears up =  too rich on the main jet

EG: at 1/2 throttle the motor feels like it is running out of power, but running smooth and dull, and if I back of the throttle a bit it gets better =  too lean on the main jet

EG: if I roll on the throttle slowly, the motor runs perfectly. If I speed up the throttle opening before the rpms can keep up, it studders/bucks under load = a stator or electrical ground/harness corrosion issue

 

If you do not have full uncorking of the intake and exhaust , a 165 main jet it too big. You should be at 150.

You have provided only partial details on the exact state of tune of your bike.

 

You need to do a stator test ( for bad coils) a harness inspection at the stator, and all ground points and connections (there are about 6 of them) inspect the battery terminals for corrosion, and inspect the plug and cap for wear/cracks/broken solder joints.

 

It is common for the WR stator harness to corrode and cause poor current flow.

It is common for the WR grounds to corrode and cause poor current flow.

 

 

Another possibility is cam timing. 

If the PO has done the 'EX cam advance' mod incorrectly (to mimick the YZ) it can cause peaky power as you describe.

Same with changing the cams to HotCams YZ spec, which makes the power all peak power.

Both were common mods back then.

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