DRZ400S Stalls when Snapping Throttle

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DRZ400S Stalls when Snapping Throttle

Postby 4Strokes » Sat May 14, 2016 5:19 pm

Topic: Snapping the throttle stalls the bike (DRZ400S)
Author: HDog
Posted: 10/13/2006 8:50:55 PM

Hello All,

I recently purchased a 2005 Suzuki DRZs 400 dual sport. It had been modified with an FMF pipe and the carburator was re-jetted. Lately, I have been having a problem. From idle, if I snap the throttle open too fast it stalls the motor. Anybody else having this problem?

Thanks,
HDog

Reply by tomass on 10/14/2006 12:51:45 PM
Welcome to 4Strokes.com. The first thing I would check is the spark plug. Replace it if it's not new. It's like it's getting drowned by gasoline. Beyond that, it could be the carb. But I don't know what you would do with the carb to fix that problem. Carbs aren't my specialty. The icat device would probably help your problem as well.
Was it giving you a problem since you first got it or did it start after you had it for a while? Also, did you open up your air box? The stock air box is designed to handle the air flow for the stock exhaust, but now you have an exhaust that allows a lot more air out of the engine, so you need to cut a couple of holes in the top of it to allow more air in. This is accomplished with a hole saw. Please let us know if any of this works.

Reply by HDog on 10/14/2006 2:02:23 PM
Tomass, thank you for your help. I will do the things you suggested an get back to you.

Reply by RobotMachines on 10/21/2006 7:22:19 PM
I just bought a 2001 DRZ400s (have had it for about 3 weeks now) and it would stall when I hit the gas. I turned up the idle and it seems fine so far. I'll be rejetting, cutting open the air box, and modifying the OEM muffler next weekend. I also have a 400E which has the "pump" carb and it would not stall. I think the S carb is just not as good. I agree though that giving it a little more air may help but check your idle as well.
Also, make sure your vacuum line to the gas tank hasn't fallen off or is pinched. From what I've seen so far with the S; it looks as though the fuel pump is on the tank petcock where the E has it on the carb. I learned the hard way. I took the tank off to run wiring for heated hand grips (Oxford) and didn't know about the vacuum line and it fell off while I couldn't see it happen. Since the E doesn't have it, I didn't know that it should have been reconnected; it was a bad ride until I figured that out; wouldn't even idle or hardly idle.
Summary:
  • DRZ400e - gas line to the fuel petcock
  • DRZ400s - gas line and vacuum line to the fuel petcock
If the vacuum line is pinched, it won't kick as well when you first hit it. Once revving, throttle is open, and you have a pinched line or no vacuum line, gravity and the carb vacuum will keep gas flowing.

For what it's worth, the E and S both have a 150 watt stator... just thought I'd mension that

Reply by b_king on 10/21/2006 7:38:34 PM
I have the same problem on my XR400R. The jetting is as close to perfect as I can get it, no bogs flat spots anywhere except if I really crack the throttle off of idle, it does a "thud" sound and bogs right out. If I let off it stays running, but if I keep at it, it'll stall and die. I figure it is being drowned with fuel, but I don't understand how a pumper carb would help because a fuel pump would simply inject the raw fuel right into the intake manifold to help when you really crack it.

Reply by RobotMachines on 10/21/2006 7:45:08 PM
Originally posted by b_king

I have the same problem on my XR400R. The jetting is as close to perfect as I can get it, no bogs flat spots anywhere except if I really crack the throttle off of idle, it does a "thud" sound and bogs right out. If I let off it stays running, but if I keep at it, it'll stall and die. I figure it is being drowned with fuel, but I don't understand how a pumper carb would help because a fuel pump would simply inject the raw fuel right into the intake manifold to help when you really crack it.

Interesting. I haven't driven my E enough yet to know if it ever would die on a hard start from idle, it just hasn't yet.
I wonder if your idle is too low or you're are not getting enough air. I'm not an expert. These bikes are new to me but I have been riding hard since I got them (mostly the S).
One big difference from the E and S (S dies on hard start from idle) is that the E has a large 3"x3" air box opening and the S has a tiny little opening (which I'll be cutting open this weekend). E also has the expensive "pump" carb to give it that initial bit a gas.

Reply by RobotMachines on 10/21/2006 7:58:06 PM

Originally posted by b_king

I have the same problem on my XR400R. The jetting is as close to perfect as I can get it, no bogs flat spots anywhere except if I really crack the throttle off of idle, it does a "thud" sound and bogs right out. If I let off it stays running, but if I keep at it, it'll stall and die. I figure it is being drowned with fuel, but I don't understand how a pumper carb would help because a fuel pump would simply inject the raw fuel right into the intake manifold to help when you really crack it.

I tried to find some info on your carb. If it's a CV carb like my 400S then I don't think there's all that much we can do but make sure it revs a tad before hitting it.

I guess if my modifications fix it on my S, then that's one solution and I'll post how it feels and the specifications... upping my idle fixed it for now. I didn't increase it all that much.

Reply by b_king on 10/22/2006 09:00:54 AM
It isn't a CV carb. But I do have the idle at around 1400rpm, give or take 100. That is what I use for road riding, but when offroad because I need to crack it sometimes, I set it to around 1600-1700rpm. That way if I gun it, it won't bog out. I am very interested to try a pumper version on my carb, as the TR-X400EX has my carb + pumper. I figure to keep it as stock as possible without trying to fiddle with a Mikuni or Edelbrock.

Reply by poohduck on 11/09/2006 02:26:43 AM
I have just had this same problem on my drz400e. And after reading what you guys said, you may have answered how I fixed mine. I undid the drain plug and drained the bowl. Then I opened the fuel tap to see if fuel was coming through OK, it was. So if the problem can be caused by flooding, I suspect I must have flushed something out when I opened the fuel tap with the drain plug out (lot of fuel running through unrestricted, enough to flush something out from between the needle and seat). It is all good now. Perhaps you could try this.

Reply by sparta4188 on 11/15/2006 8:21:49 PM
did you like the bike idle before you went for a ride? I don't do that and it always stalls

Reply by b_king on 11/16/2006 06:27:15 AM
I've found a solution to my problem. Just to remind everyone the problem was when I snapped the throttle on my bike, it would bog and choke. I went through everything in the fuel system, carb, intake, and exhaust. I sealed up everything, there was a large leak in the joint from the header pipes to the muffler. Sealed that up nice, did some fine tuning of the carb jetting and we're off to the races! It runs like a champ now.

So, in saying that, I'm not sure if that is the solution the DR-Z400S problem, it might be, or it might be something with the style of carb as Robotmachines mentioned.

Good luck guys!

Reply by Jlutty650L on 06/25/2008 10:52:07 AM
It was probably running lean with the leak and stumbling from a lack of fuel, not flooding.

Reply by Jeff_in_rc on 06/25/2008 12:15:42 PM
On any bike without an accelerator pump if you are sitting still and wack the throttle you will more than likely stall the motor. It does it on my DRZ (with the CV carb) which is jetted perfectly and it did it on my perfectly jetted XR400. Now if your riding along and wack it, it will usually not stall. This is not a problem per say, just the way the carb works.

On bikes with an accelerator pump type carb when you wack it they will usually respond and not bog and/or die.

Reply by tomass on 06/25/2008 8:17:21 PM
Unless my bike is cold, it never does that. It's an 02 400-S. Big gun exhaust, Icat, Dynojet spring and needle, stock jet, and KnN air filter.

Reply by theestate on 06/29/2008 3:50:48 PM
After spending hundreds and a year of tinkering, I solved my DRZ 400 S bogging troubles on throttle burst by replacing the Mukuni carburetor with a Keihin FCR carburetor attached to a KTM 530 EXC. Even stock (california emmissions and exhaust restrictor removed), the KTM has never! bogged or hesitated on throttle bursts. My riding is 4,500 feet to 10,000 feet.

The folks riding near sea level seem to be satisfied with the Mukuni carburetor, but I had no success at my altitude. For me, the upgrade was well worth the cost -- all smiles.

Reply by Jeff_in_rc on 06/30/2008 4:43:23 PM
Originally posted by theestate

After spending hundreds and a year of tinkering, I solved my DRZ 400 S bogging troubles on throttle burst by replacing the Mukuni carburetor with a Keihin FCR carburetor attached to a KTM 530 EXC. Even stock (california emmissions and exhaust restrictor removed), the KTM has never! bogged or hesitated on throttle bursts. My riding is 4,500 feet to 10,000 feet.

The folks riding near sea level seem to be satisfied with the Mukuni carburetor, but I had no success at my altitude. For me, the upgrade was well worth the cost -- all smiles.

THAT has to be the funniest reply I've read in a long time there theestate!

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