Slap on throttle (video)

[rollandburn]

Hi, can anyone help me determine if this slapping noise is normal for the DRZ, or if it's a symptom of some problem I can diagnose and fix.

 

 

Not a noisy engine thing, but a definite metal on metal knock that happens once or twice when torque is high (ie. at the beginning of a throttle blip, but not necessarily low rpm... I believe I can reproduce the slap at speed if I give it enough goose).

 

I've had the bike for a couple of years and although it has groaned if I lugged the engine, being able to reproduce it with I quick twist is new after pulling it out of storage this season.

 

I just did a full oil change with filter, air filter, and pulled/cleaned the carb (because it wouldn't start after the winter) so she's running pretty good now except for this very unpleasant noise.

 

I suppose even if this is normal I'd like to know what it is and why it's getting worse. Any feedback appreciated!

[sbmon]

Piston slap? Raising idle can alleviate some of it or don't twitch off idle so fast.

[Yanka]

I have that thing much more distinctive when trying to accel from too low rpms (it happens when offroading). Don't like it but hope it will not brake my engine. Just trying to avoid such modes ? 

Usually by slipping clutch for a moment.

[mousie]

My 09 S does the same thing. Only had 400 miles on it when I noticed it. Now has 6000 and no problems. I just don't blip the throttle anymore. I have heard of guys with brand new DRZs making the same noise, I think its just the nature of the beast. 

[ohiodrz400sm]

Videos are misleading. I recorded mine as an experiment and the audio exaggerated a lot of subtle sounds.

Having said that, your video sounds like the bike is going lean and detonating when you open the throttle quickly. I assumed you have the stock carb?

[Gary in NJ]

Idle speed sounds too low. It's supposed to be 1,500 rpm.

[cowpie]

put some good gas in it ..

[rollandburn]

Yep... good gas is the next step. Poor fuel quality is at the top of a few lists on the causes of piston slap. However, If idle is supposed to be at 1500 rpm then raising it (from what is likely lower than that) sounds like a wise move regardless.

Thanks for the feedback everyone. Very helpful. I'll report back with findings after a fuel swap and idle adjustment!

[rollandburn]

Welp, didn't touch the idle but did top up with a few litres of 91 to raise the overall octane in the tank annnnnd presto. All good now. I was sure 6 month old stabilized fuel would still be good, it seems I underestimated how sensitive a motorcycle is to fuel quality (ie. vs. a car).

Gracias amigos!

[bumtarder]

At the start of riding season I always start out with fresh,treated fuel and at least 89 octane.

[rollandburn]

Sounds like a good habit. By "treated fuel" are you referring to adding a small amount of fuel system / carb de-gunker additive?

[bumtarder]

Yes,Amsoil Quickshot SE,Gumout multi-system,Seafoam,Startron,Techron etc.

Gasoline doesn't store well and with today's reformulated e10 it tends to go stale very quickly,leaves more deposits and clogs small jets and gums up carburetors found in small engines more easily than in a car or truck from my experience.

[Halfmt1]

I swear by Seafoam, if i store it for awhile, it comes out and runs like it never sat at all. I also add it to the gas periodically through the riding season. Bike always runs flawless!

[74jimbo]

how much seafoam are people putting? I run a Clarke 3.9 plastic tank, and don't want to destroy the tank, or my bike

I don't have that noise, but I might splurge and put in 89, instead of 97 if it is worth it?

[yamyamsx]

Hi rollandburn, I'm trying to solve my friend drz problem. I have exactly the same symptom as your video. Your drz still doing it? Did you resolve your knocking problem? Thanks Eric

[yamyamsx]

Hi,  I tried many things to get rid of my detonation problem... I opened the engine, change rings, clean and lapped valves, changed timing chain, did the valves clearance. The base gaskets are the original S/SM model.  I swaped the stator /pick up coil assy  with an other one serviceable without any chance...  I checked the timing and seems to be good also. I swaped the carb also.  When I put higher octane, the problem is almost disapeared... Now I suspect maybe a valve problem. It can't be cause by carbon because I cleaned it! I kow couple of drz suffer of this problem. I really want to find what is the cause... Thanks Eric