My new DRZ400S is lurching ?????

[amitysanimal]

I have a 2000 DRZ400S with a little over 500 miles on it. When I am riding at 25 to 30 mph, holding the throttle at a constant speed, my bike lurches/hitches.

It feels like when you have a bent brake rotor, when you hit the brakes, it lurches.

I thought maybe my back brake might have been sticking but I disengaged the clutch while I was moving and the lurching stops.

It is completly stock besides DOT approved knobbies.

Any suggestions?

amitysanimal

[pine rider]

Is your engine surging? Sorry I cannot help, I have never heard of this complaint before.

[10guy]

A 2000 with 500 miles???? Might want to check the jets

[Neil Claydon]

What 10guy said,

The fuel in the tank is not 5 years old is it ??

Or try a new plug.

Neil.

[amitysanimal]

Yes, it had 414 miles on it when I bought it.

It has fresh fuel. I only need to burn 87 octane gas right??

Suppose the carb could have gotten gummed up? I will try a new plug first and if it still does it I will clean the carb. It also seems to stall quite easy, maybe the jets are gummed up a bit.

Thanks,

amitysanimal

[flip18436572]

If it surges at a constant throttle, it is still lean from the factory. Rejet it and it will work fine. I had the same problem and fixed it with a jet kit when I did the 3 X 3 mod.

[fish1102]

Sounds like a jetting issue. But I would do the simple stuff first. Plug change. Then pull carb and check and clean jets and also take note of jet sizes in carb when you have it off, so you can report back if you are still having trouble. Probably a good cleaning will take care of it though. Has the bike been sitting for a while to not have that many miles on it? If so, the carb might for sure need a cleaning.

[Noble]

What gear are you in at 25 to 30 mph? Stock 15/44 final drive gearing? You need to be at least 35 to run 5th gear. Plus carb clean and rejet will help too.

[Spud786]

if your like less than1/4 throttle turn full screw counter clockwise 1/4 turn

[AKJeeper]

I purchased my '06 S new back in June, and I've noticed this very same problem when just cruising at constant low speeds like 25-35. Downshifting doesn't fix the problem (dealer claimed I was lugging it). I've tried 87 and 91 octane...no difference. Also, the surging is worse on warm or hot days. Not really too noticable on cold days (50* and colder). The bike has about 900 miles on it now, with no change in the surging.

Any suggestions?

[norm22]

I have a 2000 DRZ400S with a little over 500 miles on it. When I am riding at 25 to 30 mph, holding the throttle at a constant speed, my bike lurches/hitches.

It feels like when you have a bent brake rotor, when you hit the brakes, it lurches.

I thought maybe my back brake might have been sticking but I disengaged the clutch while I was moving and the lurching stops.

It is completly stock besides DOT approved knobbies.

Any suggestions?

amitysanimal

You haven't messed around with air box?

[BobNY]

I purchased my '06 S new back in June, and I've noticed this very same problem when just cruising at constant low speeds like 25-35. Downshifting doesn't fix the problem (dealer claimed I was lugging it). I've tried 87 and 91 octane...no difference. Also, the surging is worse on warm or hot days. Not really too noticable on cold days (50* and colder). The bike has about 900 miles on it now, with no change in the surging.

Any suggestions?

First thing to do is adjust the fuel screw, it is likely way too lean.

It may be helpful to know the pilot fuel screw, on the bottom of the carb, is factory sealed with a plug. This screw controls the fine adjustment of mixture from idle to about 1/4 throttle (but actually has an effect all the way to full throttle, it is never "out of the circuit"). You can remove the plug, it is detailed in the 400S service manual. With the plug out, you can adjust the fuel screw using small screwdriver or screw bit. Most people buy the extended fuel screw for 15., it makes it a LOT easier to adjust on the fly.

You need to remove the carb to remove the plug, BTW.

And beware, you need to be REALLY CAREFUL removing the plug, that you don't drill too deep, or otherwise damage the threads on the side of the hole.

I have a 2001 400S and had the same problem with the stock carb. For street use, this adjustment is one the most important areas to get "right". Unless you just drive around at full throttle everywhere, you'll spend 95% of the time at less than 1/4 throttle.

You probably should also fully clean and re-oil the air cleaner first as well before getting anal on the final adjustment. I did the rejetting and 3X3 mod, it's worth it, but still playing with adjustments. I'm not crazy about the increase in noise you get from the 3X3 hole, which is substantial under certain conditions. I'm a loudspeaker designer, and am playing around with the box resonance tuning, have all the electronics to do that. More later.

[PfM]

I purchased my '06 S new back in June, and I've noticed this very same problem when just cruising at constant low speeds like 25-35. Downshifting doesn't fix the problem (dealer claimed I was lugging it). I've tried 87 and 91 octane...no difference. Also, the surging is worse on warm or hot days. Not really too noticable on cold days (50* and colder). The bike has about 900 miles on it now, with no change in the surging.

Any suggestions?

Yep, my SM did it from new. It was a combination of clogged pilot jet, crap stock needle and jetting.

I cleaned the pilot jet and installed the DJ kit. Much better, but still some hesitation. Moved the needle clip down to position 3 from top (2 is recommended for the SM kit), which lifts needle. Pretty much gone.

Cheers