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Brand Spanking New DR-Z400 makes weird knock

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I just bought me a brand-spanking-new DR-Z400 last week. I test drove one at my local dealer, and discovered rather quickly a loud, single, KNOCK when I blip the throttle when the bike is idling. I tossed them the keys and made a deal on another one they had in stock. This one, the one I dropped serious coinage on, acts exactly the same. I'll try to describe it as best I can. 

First off, this thing is hard to start, and won't start if I choke it. It's been in the 90's around here, so when it cranked for 3-4 seconds without starting, I choked it. No worky. Anyway, once it starts it idles just fine. While warming up, if you roll the throttle on, everything's good. If I blip the throttle hard (in idle), the bike will die. About half the time, or even more so when the bike is up to temp, there is a single KNOCK coming from the engine. Sometimes the bike will die after the knock. Almost sounds like a detonation, but it only does it under no load. When the bike is in gear, clutch engaged, rolling down the road, all's well. 

I've search the internet high and low for a solution, all to no avail. There are TONS of reports of this engine making all sorts of continuous racket, but nothing about this single knock when blipping the throttle at idle.

I took it back to the dealership, and got puzzled looks and an opinion that it's probably the decompression mech in the engine. When I balked at that and pretty much demanded they  look into it, I was told that, according to Suzuki, if they tore it down and found nothing wrong, I would be stuck footing the bill. I declined and got the bike back today.

The bike is still on it's first tank of ethanol free gas, 60 miles. The fact that two bikes from the same shop are doing the same thing makes me think this is just how these bikes sound. But, it's definitely a WTH moment when you hear it. And the dying. I dunno. I'll take a any suggestions. 

I parked an '87 XL600 that was giving me fits so I could ride a new, problem free bike. I'm getting pissed.

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Why blip the throttle hard ? Dont blip the throttle hard & there wont be s noise ! As for starting, dont touch the throttle just the starter

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That knock is normal. Both mine and a friends 2012 models have done it since day one. Think its piston slap. It will also do the same knock if you lug it to the point it stalls.

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Your going to have to jet that thing. It's carbureted, get it jetted correctly and it will start easily run correctly and provide you hours of smiles.

There are mods for the carb to get it to quit stalling with the quick throttle twist. Put a little time in and you'll have hrs of smiles.

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+1 piston slap it's a thumper thing. Turn the idle up, don't be so aggressive with the throttle at really low rpm's and it will never be an issue. I'm surprised the guys at the shop couldn't tell you that.

If you have a tach ~1800 rpm's is a good idle, most have theirs set way to low.

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my friend has 2014 sm..and if his bike sits in the hot sun 90-110degrees..

it wont start for upto 30seconds trying to crank over

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As said above, idle speed is too low

Turn it up, and the knock will not happen

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I just bought me a brand-spanking-new DR-Z400 last week. I test drove one at my local dealer, and discovered rather quickly a loud, single, KNOCK when I blip the throttle when the bike is idling. I tossed them the keys and made a deal on another one they had in stock. This one, the one I dropped serious coinage on, acts exactly the same. I'll try to describe it as best I can. 

First off, this thing is hard to start, and won't start if I choke it. It's been in the 90's around here, so when it cranked for 3-4 seconds without starting, I choked it. No worky. Anyway, once it starts it idles just fine. While warming up, if you roll the throttle on, everything's good. If I blip the throttle hard (in idle), the bike will die. About half the time, or even more so when the bike is up to temp, there is a single KNOCK coming from the engine. Sometimes the bike will die after the knock. Almost sounds like a detonation, but it only does it under no load. When the bike is in gear, clutch engaged, rolling down the road, all's well. 

I've search the internet high and low for a solution, all to no avail. There are TONS of reports of this engine making all sorts of continuous racket, but nothing about this single knock when blipping the throttle at idle.

I took it back to the dealership, and got puzzled looks and an opinion that it's probably the decompression mech in the engine. When I balked at that and pretty much demanded they  look into it, I was told that, according to Suzuki, if they tore it down and found nothing wrong, I would be stuck footing the bill. I declined and got the bike back today.

The bike is still on it's first tank of ethanol free gas, 60 miles. The fact that two bikes from the same shop are doing the same thing makes me think this is just how these bikes sound. But, it's definitely a WTH moment when you hear it. And the dying. I dunno. I'll take a any suggestions. 

I parked an '87 XL600 that was giving me fits so I could ride a new, problem free bike. I'm getting pissed.

 

the drz was designed in 1999-ish, nothing is 'new' about the drz besides the papers accompanying  it.

 

now that that's out of the way - it sounds like your idle is set too low. it would make starting difficult if it's below 1200rpm, contributes to piston slap (that one KNOCK you hear) and almost impossible to start without some throttle input. the bike needs rejetting, like yesterday. might as well do the 3x3 mod, free power mod, and all the loctite fixes, MCCT, etc while you're at it.

 

the drz IS a NOISY engine. you won't hear the valves, they get tighter as they wear. 

 

but you will hear everything else from the clutch basket, ACCT, decomp mech, countershaft springs, piston slapping (idle too low), cam chain slapping, and a few other rattles. if you fix the known issues, it will happily keep making those noises and transport you for many years/miles. 

 

 

 

sounds like the warrantee is about as good as the paper it's printed on for wiping asses. get some tools, get to reading the FAQ section, and very soon, get to riding. 

 

:) good luck ! 

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Its brand new, simple answer take the f**kin thing back to the dealer, yesterday, don't put a spanner anywhere near it.

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Set idle at 1800 rpm like posted above and ride it. My bike is very quiet since I switched from synthetic to cheap old Rottella 15/40 and increased my idle to 1800. The dealers don't know/care how to set the bikes up when they assemble them. Also check your tire pressure mine were way too high and I didn't find out until I low sided from just barely tapping the rear brake in a 45mph wheelie. They had put my Dunlop 606's at 30psi :eek:

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Set idle at 1800 rpm like posted above and ride it. My bike is very quiet since I switched from synthetic to cheap old Rottella 15/40 and increased my idle to 1800. The dealers don't know/care how to set the bikes up when they assemble them. Also check your tire pressure mine were way too high and I didn't find out until I low sided from just barely tapping the rear brake in a 45mph wheelie. They had put my Dunlop 606's at 30psi :eek:

Am I reading this wrong or did you actually manage to low side on one wheel?

I have a buddy that looped out his brand new gsxr750 a week or two after he bought it. We all made fun of him like every day for it. He swears he hit the brake and the tire just locked up, not a single person believes him :lol:

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Am I reading this wrong or did you actually manage to low side on one wheel?

I have a buddy that looped out his brand new gsxr750 a week or two after he bought it. We all made fun of him like every day for it. He swears he hit the brake and the tire just locked up, not a single person believes him :lol:

sort of. Barely tapped the brake to bring the front down and the wheel locked up and went sideways. My rear brake is very sensitive as it is but 30psi in the rear wheel made it like riding on marbles. It happened first ride after I had the dealer mount the new tires. Oh well live and learn no problems with the tires at 15psi.

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Well, I only had a few minutes this morning before we took off for the day, but I jacked the idle up a bit. Seemed to do the trick. 1800 rpm seems a little high, but if that's what it takes. I'll have a little time tomorrow to play with it more. Thanks guys!

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I like mine at 1600, but everybody else seems to set it at 1800. 1500 and I get slap.

Edited by blakestree

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I don't have a tach, so I guess I'll just fiddle with it until the slap goes away. And then sell the info to the dealership.:-D

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Well, now. Jacking the idle beyond sane levels certainly has made the difference. We are now knock free. I'm having a little trouble finding the sweet spot, as twisting the idle knob just a micro-mip doubles the idle speed from "kinda sounds okay but still get a wee bit of a knock", to "sounds like I'm running down the highway but the knock went bye-bye". Just ran out the first tank of gas. Think I'm gonna try some 92 octane with Star Tron and see if that makes a difference. Kinda weird that a high compression motor only requires 87 octane.

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I don't have a tach, so I guess I'll just fiddle with it until the slap goes away. And then sell the info to the dealership.:-D

Sounds like the dealership already knew it wasn't a problem.

Doctor, It hurts when I do this,  Well quit doing that. :lol:

 

And quit running 87.

Edited by james509
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