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Loud cackle/popping on hard acceleration.

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Hi! I'm new to the forum. I have used this site a lot through the years just from my Google searches but I'm having trouble with this one. I don't really know how to search for it so I figured it was time to become a member.

I just bought a 2007 DRZ 400s. It snowed here in iowa right after I got it but I got it out to putter around a bit today. I took it out on the pavement to open it up a bit and was startled by a pretty loud popping or cracking noise. It only happens if I pull hard from lower in the revs. If I take it easy on the throttle it does not do it. Even when I wind it way up. I stopped and revved it in neutral and it does not do it. I thought it was maybe the drive chain. It is not loose though. Back at the house I noticed that the fmf slip on did not have a clamp where it joins the stock header. Is it building to much pressure and popping there? I rode it in the yard somemore. And did some short pulls from down low but it doesn't do it, I'm guessing due to wheel spin. Back on the pavement it still does it. So it basically does it in high torque situations. The bike also has the 3x3 mod. Any help is appreciated. I don't really know how to diagnose this since I can't get it to do it when it's not driving. Thanks!

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The DRZ makes reasonable low end power, but it is often lugged by new owners. My will also 'clack' if I don't have a few more revs built before asking for full throttle.

That said, maybe up the rpms before asking for full throttle. A large metal skid plate also makes this sound pretty loud..

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It sounds like an exhaust leak, your stock muffler had a clamp on it, I'm sure. I'd start there and clamp it

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The chain is in spec.

For some reason I have 3 identical posts (I posted with the mobile app) and on one of the other posts some one suggested lean jetting due to colder weather. I started to take the carb off to change the clip position and then found out that the boot clamp was loose. I tightened it and rode it and it reduced it greatly. So i guess it is pinging?

It doesn't do it when I lug it. It happens as it pulls to the mid range. Also the skid plate is not on it. It sounds kinda like a machine gun or fire crackers and goes with the rmps. It goes away once out of the mid rpms. So if it's revved a bit and I hit it pretty hard it doesn't do it.

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The chain is in spec.

For some reason I have 3 identical posts (I posted with the mobile app) and on one of the other posts some one suggested lean jetting due to colder weather. I started to take the carb off to change the clip position and then found out that the boot clamp was loose. I tightened it and rode it and it reduced it greatly. So i guess it is pinging?

It doesn't do it when I lug it. It happens as it pulls to the mid range. Also the skid plate is not on it. It sounds kinda like a machine gun or fire crackers and goes with the rmps. It goes away once out of the mid rpms. So if it's revved a bit and I hit it pretty hard it doesn't do it.

 

So did you raise the needle one clip position? It still may be a lean condition.  You could test by duct taping off 2/3rd's to 3/4 of the  3x3 mod. If it smooths out and runs better, you've found a lean condition.

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I haven't had time yet. Short week at work so I've been busy catching up for my thanksgiving time off. I don't have a lot if experience with bigger 4 stokes. Last bike was a ktm 300 that got stolen :( does lean really make the motor pop like that? I've done jetting on 2 smokes and small 4 stokes and never had that before. Thanks for all the replies. I'm finding great info in the DRZ forums.

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I haven't had time yet. Short week at work so I've been busy catching up for my thanksgiving time off. I don't have a lot if experience with bigger 4 stokes. Last bike was a ktm 300 that got stolen :( does lean really make the motor pop like that? I've done jetting on 2 smokes and small 4 stokes and never had that before. Thanks for all the replies. I'm finding great info in the DRZ forums.

 

Thought you might be a 2 stroke guy with that "is it pinging comment"  I don't think your hearing a ping. I just ran into this with mine, thats why the "crackle and poppng" comment rang a bell with me. I believe whats happening when it's too lean, it's just starting to go into a bit of lean misfiring, which is dumping more unburnt fuel into the exhaust and then getting ignited in the exhaust, causing the popping, much like the deceleration popping, only more rapid firing.

It seems 4 strokes ping easier when the fuels octane is not high enough for the dynamic compression of the engine, were as a 2 stroke seems to ping more if there jetted too lean. Just my finding any why. Let us know how you make out with yours.

Edited by bucket list
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That sounds very similar. Thanks for the explanation. There may have been some older gas in the tank. I should have flushed it, hind sight is 20/20. I'll pick up some fresh 91 tomorrow after work and drain the tank. I'll start with that and then try taping the air box. Probably won't get to it till Sunday. My wife and I have some traveling to do for Thanksgiving. I'll report back with my findings.

I don't plan on riding it much this winter but it's good to know it's not the engine eating itself :)

Thanks again!

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Update: I was able to drain the carb and the tank this evening. The gas that was in there didn't smell great. Previous owner said he put fresh gas in but I'm guessing there was old in there with new. The bike started much easier and ran smoother while warming up. I road around the yard a bit and then hit the street. The first pull though the gears to 60 was smooth. I didn't go wide open but it didn't pop or crack. Back to the house and it popped only a couple times. I rode for a while in the yard (which includes a 30 acre timber) to get it good and warm and back to the street. Full open throttle this time and it crackled pretty bad. It was getting dark and I don't have the tail light on at the moment so I didn't do any more road riding. It never seems to have issues in the timber. I still think that's due to no traction and therefore less load on the motor.

It has fresh oil and fresh coolant. I didn't tape the air box but will tomorrow to test for a lean condition. I think a carb clean is in order aswell.

I have a question about the photo attached. Is the white knob the idle set? Or is it the fuel screw extention that I saw on the common drz parts in the thumpertalk shop?

The bike sat for 3 yrs before I bought it according to the previous owner. It only has 1600 miles on the odometer and it looks like its barely been ridden. From close inspection it looks like the head bolts have been wrenched on. I get nervous when things have been opened up. This noise scares me as it sound like something rattling or the piston smacking the head (which isn't a 4 stroke thing). I'm nearly certian that can't be it cuz the bike lugs great and if revved in neutral it sounds fine. If something we actually loose I think it would do it even if it were not under load. I'll report with more info after my tests tomorrow.

I want to get a service manual. Is the clymer one on the thumpertalk shop good enough or should I drop the coin on an oem service manual?

Thanks for the input so far!

Nick

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Idle speed screw. Sitting for 3 years with fuel in the carb is a recipe for fueling issues. Time spent cleaning and being certain it is clean won't be wasted time.

Edited by shuswap1

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Update... a very frustrating one... I cleaned the carb. Actually surprising that it ran as well as it did considering the gunk that was in there.

Jetting: main 150 pilot 22.5

Got it back together starts up and seems a bit rich. Backfires a bit on decel. The popping problem seems worse now.

The frustrating part...

I'm pretty sure the popping is a bad head gasket. I can see a bit of oily residue on the front of the cylinder. And the popping sounds like it coming from the motor not the exhaust. I rode with out a helmet and it was earshattering loud. Drained the oil and it looks milky. I had some old oil in the pan of a different weight but I'm still pretty sure there is coolant in the oil. See pics below.

So any input. Am I on the right track? The bike had noticeably more power with the carb clean and more popping due to better combustion. I'm pretty pissed about this. The guy said he had the bike gone through and all this crap and now this. I'm pretty sure he snugged the head bolts down to cover the problem when I looked at it. Thanks for the help so far I covet your advice.

Nick

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When does it pop? On decel is very normal with an open style exhaust. If there was ANY other contamination in your catch basin the oil would look like crap, mine always does anyway.

Catch some coming out of the drain, harder to tell once it's in the pan!

How does the coolant look?

Take the cam cover off and wipe around with a clean cloth, do you see coolant?

I'd hate to see you change the head gasket for no sound reason

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I'm not going to change it yet but it's my current hypothesis. It does a normal backfire on decel. Not to loud just normal rumble. It's under acceleration that this machine gun/fire crackers type of sound happens. And i dont think its frome the exhaust. It sounds like its coming dorectly from the motor. Particularly on the left side. Its only when I open it up and put torque on the motor. If I gently accelerate I can get up in the rpms with no cracking or popping. Only when the bike is under load and I'm asking for lots of power does it do it (probably past half throttle). It does not making any noise when I just rev the bike with the clutch in or the bike in neutral. I'll try to have my wife record me riding by and see of we can get the sound. I don't think I can drive and record.

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I had another thought. Could this be the chain bunching up? I have checked the tension but seeing how long it sat it could have stiff spots. Could this make a really loud clacking with out destroying something?

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So did you raise the needle one clip position? It still may be a lean condition.  You could test by duct taping off 2/3rd's to 3/4 of the  3x3 mod. If it smooths out and runs better, you've found a lean condition.

 

I still plan to try taping the air box but do you still think this is a lean condition? Seeing that it got worse after a carb clean. 

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I have heard bikes with chains too tight OR chains that were worn OR had rollers falling apart make bad, bad noises when under load. You said the chain was "in spec", but you do make other comments that could describe a chain/sprocket problem, as suggested again above.

I'd sure give every external bit a solid look (or replacement, if questionable) before I dove into a head gasket replacement.

Keep us posted.

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I'm glad to hear no one thinks it's a head gasket. I pulled the counter sprocket cover off yesterday after work. The sprocket looks good. The rear looks fine to me also. I'll take some pics to verify. I think my chain is to stiff. It's an o-ring chain but the links don't move very well. Some worse then others. There is a bit of surface corrosion so maybe internal corrosion as well. I will take it off and look it over. If I hose it down with some WD-40 or something similar will that hurt the o-rings? I use white lithium grease on my chains but I think I need something thinner to loosen it up first.

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Got a new chain to put on it?

Chains are always wearing out. Pop a new one on and see how things go. If it is the solution, you are all set. If not, stow it for when current chain is shot. One way or another, you will get your use from the new chain.

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