04 wr450 surging

I'm speaking of WR450f 2006 and newer. They do not have adjustable stock needles. There is a chance your bike has an aftermarket needle. I have experienced your symptoms tuning 2006-2009 bikes. The Dynojet needle and jet system is hard to get dialed in. We ran 150 main with the needle one down from the top. Sea level Balls Hot Summertime Florida. If you faise the needle more, the surge happens sooner in the RPM band. Your jetting is not far off, I'd try leaner main jet ant try diff positions.

Not sure what the symptoms are however if the slide vacuum plate is in backwards the bike will run like crap and drive you nuts.

Check the plastic nut that holds the hot start cable into the carb body

I bet it's broken

Check the plastic nut that holds the hot start cable into the carb body

I bet it's broken

Wow. Did not think that could cause that issue. It is broken, cracked a bit. Previous owner had blocked it off with a tube but I put it back. It is broken enough to let air in if it's designed that way for sure.

Check the plastic nut that holds the hot start cable into the carb body

I bet it's broken

I think it's this part (but it's plastic) that's broken.

ImageUploadedByThumper Talk1402639941.354113.jpg

I can double check in the morning though. The old owner had a rubber plug shoved in it to block it off. I guess I'll put that back for my ride this Saturday..

Look at that. MaxPower knew.

I'm a little surprised no one mentioned that before me.

Even if it isn't all your problem, it's a good part of it

They sell them in aluminum to replace it. You probably know that because you showed me a picture of one.

The plastic cable holder nut breaks when you twist your carb in the manifold to get at the float bowl

The carb sucks to get at. They say the aluminum frame is worse. I wouldn't want to working that bike

Look at that. MaxPower knew.

I'm a little surprised no one mentioned that before me.

Even if it isn't all your problem, it's a good part of it

They sell them in aluminum to replace it. You probably know that because you showed me a picture of one.

The plastic cable holder nut breaks when you twist your carb in the manifold to get at the float bowl

The carb sucks to get at. They say the aluminum frame is worse. I wouldn't want to working that bike

I am riding tomorrow so I just got a oem one from my yamaha store. I'll update once I get it all together. With how the carb was when I got it the hotstart wouldn't even fit in, I had to fix clamps on the carb because the previous owner had them on backwards getting in the way of everything.

I went ahead and replaced the seal on the hotstart plunger while I was at it.

Sounds better, can't ride it yet till I get this new tube in so I'll update tomorrow. could this be a aftermarket needle? I hear the stocks aren't adjustable but this is and is on 2 from the top at the moment.

Are you asking about the needle as in the needle that sticks out the bottom of the slide?

Mine had slots for aadjustment stock.

Are you asking about the needle as in the needle that sticks out the bottom of the slide?

Mine had slots for aadjustment stock.

Yes I was, and I was just making sure. I've heard of bikes with non adjustable needles stock.

I just got back from my ride. Problem seems to be gone. Little touchier throttle in some spots than the 03 I ride with but it seems good. Might play with needle positions a little. I can say, it's very nice having a bike with the power to gas it and bring the front rock over a tire instead of having to hit it.

Here she isImageUploadedByThumper Talk1402790264.126286.jpg

Wouldn't you know it, the plastic is starting to melt where it's closest to the pipe, and it has a heat shield on it. Oh well. Already have spares sitting around. I am really loving it though. No longer smells like a 2 stroke like it was last weekend,

On another note, it's still idling best with the air screw all the way in. Does not seem right. The 03 and 07 I was riding with are at about 2.

Make sure you have the little oring and washer and spring on the air screw. They get lost easy

Make sure you have the little oring and washer and spring on the air screw. They get lost easy

I do. It goes oring washer spring screw right?

I do. It goes oring washer spring screw right?

 

Yes

 

If you have to bottom the fuel screw, you have a rich condition.....usually cause by a leaky choke plunger, a needle that is too high, a needle jet that is ovaled (worn out) or a over-oiled or over-dirty air filter......or a pilot that is too big.

Yes

If you have to bottom the fuel screw, you have a rich condition.....usually cause by a leaky choke plunger, a needle that is too high, a needle jet that is ovaled (worn out) or a over-oiled or over-dirty air filter......or a pilot that is too big.

Thank you. I will check these out. The choke works great so I doubt that would be it, air filter is brand new and freshly oiled. But I'll update the thread if I find anything out that's messed up.

Random question, Why would my 04 not overheat but a 03 that was right behind me boil over coolant? (Was a very tight slow trail, and that bike just all around feels hotter even on open trails)

Like the 03 you can feel heat coming from the rads but my 04 you can't. Only difference is a fmf pipe on the 03.

It can be a million things

Having a slightly more restrictive exahust, a different pilot, a dirty air filter, un-packed silencer, header crush washer leaking, corroded radiator.... etc etc.,

 

Unless you tear a bike down every year and go through it all, you accumulate problems (corrosion, wear, etc) they develop into big problems down the road.

 

A 10 year old bike, even an unridden one, still corrodes and gets old, just sitting....

It can be a million things

Having a slightly more restrictive exahust, a different pilot, a dirty air filter, un-packed silencer, header crush washer leaking, corroded radiator.... etc etc.,

 

Unless you tear a bike down every year and go through it all, you accumulate problems (corrosion, wear, etc) they develop into big problems down the road.

 

A 10 year old bike, even an unridden one, still corrodes and gets old, just sitting....

And add in the variable of a different rider, and it could be anything! He might be slipping the clutch a little bit more, which would add tons more heat to an engine. And that's just one variable!!

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