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Surging DRZ400S

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I ride a 3x3 jet kitted stock 2001 400S with 15,000 miles on it. When riding at steady speeds on the highway, my bike has always surged when ridden in blustery or windy conditions. I always attributed it to wind pressure and the CV carb... But the other day on the freeway, it wasn't windy and my bike was surging a lot(slowing down and then speeding back up when I compensate by opening the throttle more). It is only noticeable at 55 mph and above. Does anyone know what's going on and how to repair it?

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What octane fuel are you running? My SM did that until I ran a bottle of sea foam through it started using Premium. No problems since.

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mine does the same thing, mostly under hard accel but also on the freeway holding a steady speed. I'm almost through a while bottle of seafoam in it.

Hopefully when I do the 3x3 mod it fixes this

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mine does the same thing, mostly under hard accel but also on the freeway holding a steady speed. I'm almost through a while bottle of seafoam in it.

Hopefully when I do the 3x3 mod it fixes this

:bonk: I don't see the use of seafoam...CLEAN the carb the right way.

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What jet kit, needle, clip position, and main jet?

+1 :bonk: need more info...but to me it sounds like your lean.

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I've always used Premium gas on and off the road... and then at home, it gets treated with a little bit of Sta-bil.

The Jets from Thumper Racing are JD-Jet kit

Pilot 27.5 (stock 22.5)

Main 152.0 (stock 142.5)

The Uni-Filter is a little less restrictive than stock.

Every thing else is stock...

Is there an adjustable, "Closed Course, Racing Only"

Jet Needle out there for the Mikuni BSR36 #29FC :bonk:

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What clip position is on the needle?

Did you try a 25 pilot?

That information I don't have... Maybe I don't know, because I assumed that this carb needle is not an adjustable type... If it is adjustable, I'll raise the needle a position.... The service manual shows the European equipped BSR36 has an adjustable Jet Needle.

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Surging on the freeway is usually a lean condition cause by a lean needle setting. Just put a plastic washer under your needle clip to raise the needle for a simple cure.

The JD carb kit and a 3x3 is a great mod but I would make sure you fix the surging problem before doing any mods. Don't compound your problems.

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I've always used Premium gas on and off the road... and then at home, it gets treated with a little bit of Sta-bil.

The Jets from Thumper Racing are JD-Jet kit

Pilot 27.5 (stock 22.5)

Main 152.0 (stock 142.5)

The Uni-Filter is a little less restrictive than stock.

Every thing else is stock...

Is there an adjustable, "Closed Course, Racing Only"

Jet Needle out there for the Mikuni BSR36 #29FC :bonk:

Are you sure you have a JD ket installed?

If so, a 152 main jet is lean if you are near sea level.

If it is a JD ket the needle is adjustable.

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Surging on the freeway is usually a lean condition cause by a lean needle setting. Just put a plastic washer under your needle clip to raise the needle for a simple cure.

The JD carb kit and a 3x3 is a great mod but I would make sure you fix the surging problem before doing any mods. Don't compound your problems.

+1

if you're careful, you don't even have to pull the carb to shim the needle. just pop the cap off and pull the slide/diaphram. :bonk:

the 3x3 and jetting will wake up your drz in a hurry. fix the lean condition before you do damage to the engine.

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Are you sure you have a JD ket installed?

If so, a 152 main jet is lean if you are near sea level.

If it is a JD ket the needle is adjustable.

No, not sure, my notes say it came from Thumper Racing, but my mind says it was in JD-Jet Kit packaging, but no needle... it's been about 10 years since I changed the jets... I'm going to look into that JD needle.

Thank you

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+1

if you're careful, you don't even have to pull the carb to shim the needle. just pop the cap off and pull the slide/diaphram. :bonk:

the 3x3 and jetting will wake up your drz in a hurry. fix the lean condition before you do damage to the engine.

Ok is a simple washer set available at just about any motorcycle shop? And I'm guessing this is for the main needle?

Sorry carbs are totally new to me but I am not afraid to learn. Thanks

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Ok is a simple washer set available at just about any motorcycle shop? And I'm guessing this is for the main needle?

Sorry carbs are totally new to me but I am not afraid to learn. Thanks

you could use a tiny o-ring if you have one laying around that fits the needle snug. prolly richen it way too much, but will give you an idea how it all works together.

be careful taking the slide out, and popping the assembling off the needle. springs and tiny parts !

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You need a 4mm washer should be around 2mm thick....any hardware store should carry them.

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I had the same problem on my 01, and found that the plastic plug that holds the needle in the slide had came completely out. I believe this would have caused the needle to "float" due to airflow and vibration, causing the mid-range mixture to constantly change, even at steady throttle. The surging was the worst at 45 to 50 or so, but idled fine and was good at full throttle. I reassembled it, making sure the plug was firmly seated, and making no further changes or adjustments, have not had a problem since.

I wonder if the plug was just not fully seated if it would also allow the needle to have too much movement in the slide, causing the same problem to some degree.

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Everything was in place, sort of.... the little gold washer is below the spacer (pictured), it should sit above the plastic spacer and below the clip (I wonder if that's why there's a wear spot on the needle?.... I made a plastic 2 mm washer out of some thick walled carburetor vent line tubing... came out good, using only a razor blade.

http://i929.photobucket.com/albums/ad132/o-ringthing/0001AA%20Scan/2012%2001%2001/DSCN0755.jpg[/img]"]http://DSCN0755.jpg

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That the stock needle, not JD needle. Do your self a favor & get a JD ket, you wont regreat it!

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