Decel popping and dead spot in low end accel

Hey there, just bought a 2007 400SM, seems to be a solid bike but it pops like a sumbitch on decel, and seems to have a dead spot in the lower RPMS, it has died once when disengaging the clutch and cutting throttle. Its clearly running QUITE lean, but it was allegedly rejetted for the exhaust, which is a White Brothers setup. Looks like a slip on, but not sure how to tell the difference since this is my first DRZ. Seems to have the core in place. Nobody seems to have posted much about white brothers pipes and jetting, so I'm here asking you guys. I'll continue to search in the mean time but hopefully one of you fine people can steer me in the right direction. 

My next step is to do the requisite airbox 3x3 mod, and thusly, rejet again, but I'm curious if theres something I can do in the mean time to rectify this? Previous owner doesn't know anything about it since it was all done before he got it. My best guess is it wasn't rejetted, but it seems to otherwise run pretty good, aside from the dead zone I sometimes encounter - something I'm sure will be fixed with the rejet.

While I'm on the subject, I was told by a buddy that the JD jet kit is supposed to have a cross reference sheet for the various exhausts (both with and without the airbox mod) so you can figure out which jet to run. Now, admittedly I know NOTHING about carbs, prior to this I had a fuel injected bike and have long since believed that carbs run on voodoo magic - I'd like to change that. I've searched around but didn't find anything like he described - is he high on exhaust fumes here or is it real? It sure would make the rejet process a whole lot easier than playing guess the smell with jets!

Thanks! 

If the airbox does not have a 3 X 3 opening, the carb is probably not re jetted or not re jetted correctly.  JD jet kit is the way to go.  I do not believe the jet kit has a cross reference to various replacement exhausts.  But you can always call JD Jetting for info.  The instructions are also available on line.  You probably will not cure the popping in the exhaust.  Aftermarket muffler you just hear it more

If the airbox does not have a 3 X 3 opening, the carb is probably not re jetted or not re jetted correctly.  JD jet kit is the way to go.  I do not believe the jet kit has a cross reference to various replacement exhausts.  But you can always call JD Jetting for info.  The instructions are also available on line.  You probably will not cure the popping in the exhaust.  Aftermarket muffler you just hear it more

Okay so odds are it was rejetted too lean, if anything then. I know a little popping is normal, but it reminds me of my old bike where, prior to tuning to rectify the lean condition, the aftermarket jardine pipe made it decel pop like machine gun fire once it got warmed up. This isn't quite as rapid but its still popping quite a bit when I let off the throttle - mayhaps its normal, but gut tells me too lean. I suppose I would need to take apart the carb to know differently but I suppose from looking around most everyone is running near the same jet settings anyways for most setups, so I probably wouldn't go wrong by following them as a start once I get the kit. Good call on giving JDs a holler though, hadn't occurred to me to do so! 

Also, the thing he was referring to, he sent me a link. Not exactly how he described it but a little more descriptive. Seems most setups, regardless of exhaust, are pretty much spot on. (said it was written up by JDs for their kit, but this is clearly a list of people's setups) 

https://docs.google.com/spreadsheet/ccc?key=0AorcpqswS8hkdFI4V3dCSjgzbnVUTm1IQXlNam5nUXc&hl=en#gid=7

 

I had a fuel injected bike and have long since believed that carbs run on voodoo magic

 

Silly Billy..... EVERYBODY KNOWS fuel injection is Voodoo Magic !! Old fashioned carburation (is that an actual word ?) is simple mechanical trial and error   :ride:

Hey there, just bought a 2007 400SM, seems to be a solid bike but it pops like a sumbitch on decel, and seems to have a dead spot in the lower RPMS, it has died once when disengaging the clutch and cutting throttle. Its clearly running QUITE lean, but it was allegedly rejetted for the exhaust, which is a White Brothers setup. Looks like a slip on, but not sure how to tell the difference since this is my first DRZ. Seems to have the core in place. Nobody seems to have posted much about white brothers pipes and jetting, so I'm here asking you guys. I'll continue to search in the mean time but hopefully one of you fine people can steer me in the right direction. 

My next step is to do the requisite airbox 3x3 mod, and thusly, rejet again, but I'm curious if theres something I can do in the mean time to rectify this? Previous owner doesn't know anything about it since it was all done before he got it. My best guess is it wasn't rejetted, but it seems to otherwise run pretty good, aside from the dead zone I sometimes encounter - something I'm sure will be fixed with the rejet.

While I'm on the subject, I was told by a buddy that the JD jet kit is supposed to have a cross reference sheet for the various exhausts (both with and without the airbox mod) so you can figure out which jet to run. Now, admittedly I know NOTHING about carbs, prior to this I had a fuel injected bike and have long since believed that carbs run on voodoo magic - I'd like to change that. I've searched around but didn't find anything like he described - is he high on exhaust fumes here or is it real? It sure would make the rejet process a whole lot easier than playing guess the smell with jets!

Thanks!

 

Okay so odds are it was rejetted too lean, if anything then. I know a little popping is normal, but it reminds me of my old bike where, prior to tuning to rectify the lean condition, the aftermarket jardine pipe made it decel pop like machine gun fire once it got warmed up. This isn't quite as rapid but its still popping quite a bit when I let off the throttle - mayhaps its normal, but gut tells me too lean. I suppose I would need to take apart the carb to know differently but I suppose from looking around most everyone is running near the same jet settings anyways for most setups, so I probably wouldn't go wrong by following them as a start once I get the kit. Good call on giving JDs a holler though, hadn't occurred to me to do so! 

Also, the thing he was referring to, he sent me a link. Not exactly how he described it but a little more descriptive. Seems most setups, regardless of exhaust, are pretty much spot on. (said it was written up by JDs for their kit, but this is clearly a list of people's setups) 

https://docs.google.com/spreadsheet/ccc?key=0AorcpqswS8hkdFI4V3dCSjgzbnVUTm1IQXlNam5nUXc&hl=en#gid=7

 

Hey

Congrats on your bike! :thumbsup:

 

I had similar issues, although not as severe:

http://www.thumpertalk.com/topic/1045273-what-kind-of-jet-kit-is-this-and-how-do-i-adjust-it/

 

I would pull the carb out, just in case previous owner did jet it, just didn't do 3x3 mod. You never know... might save you $80...

Although it does sound like it's running way lean....

 

Anyway, to remove the carb off bike and then reinstall it, is quite a pain!

I just loosen it and spin it to access top or bottom of carb. Much faster and easier, I find :D

 

Since you say you know nothing about carbs, it might be helpful to get the carb on a table so you can dismantle it and not loose any tiny parts the first time ;)  also you could clean it if need be...

 

Here's my quick method:

Loosen the boot clamps on both sides of carb, remove throttle wires off carb, also remove vacuum and fuel hoses off carb

(leave petcock in ON position if you got stock tank/petcock, since it's vacuum operated only little bit of fuel will leak out of tank, have some container to catch it)

Then remove the seat (2 bolts) and tank (easy, only 4 bolts, 2 under seat + 2 on bottom of shroud connecting to the rads on both sides).

Then I just spin the carb ~90 degrees to access top of carb where the needle is to adjust clip positions.

 

To access the jets, just drain fuel from carbs drain screw on bottom bowl. Then spin the whole carb towards you and remove the 4 screws holding bottom bowl.

 

To see if it's jetted or not, just access the top to see what kind of needle is in there.

Be careful when you remove the top, as there is a tiny Oring under it, that you do not wanna loose! See the manual pg. 4-4 #13

http://www.dwulet.com/bikes/docs/Fuel_and_Lubrication_DRZ400S.PDF

 

You can take some photos and post them here, if you're not sure.

I believe the stock needle will have only one slot to hold the clip in (on top) vs JDJetting will have 5 slots.

 

This is JDJetting needle, notice the slots on top:

IMG_1275_zpseccb0d71.jpg

 

That google docs link you posted, I believe, it was set up by one of the members here...

 

Good luck!

PS

This helped me quite a bit:

http://www.iwt.com.au/mikunicarb.htm

This is quite informative as well:

http://www.off-road.com/atv/tech/atv-tech-basic-carburetor-cleanup-52101.html

Edited by no1_cdn

Ha just put in my order for the jet kit, case covers and extended fuel screw. To late to stop it now! Previous owner rode it a whole 300 miles in the six months he had it. It's unlikely it has anything besides whatever the pipe might've come with. Once I get the kit I'll do the box mod and dig into the carb at that point in time.

If it turns out I don't need the jet kit because it has the proper jets installed incorrectly, I'll just sell it to my buddy for his zed. No harm done!

Thanks for the write up and advice though, it'll come in handy when I do tackle it this week! Much appreciated d, my good sir!

Edit: sorry for double post, using my phone and this app is giving me hell... heh

Edited by JLev

Ha just put in my order for the jet kit, case covers and extended fuel screw. To late to stop it now! Previous owner rode it a whole 300 miles in the six months he had it. It's unlikely it has anything besides whatever the pipe might've come with. Once I get the kit I'll do the box mod and dig into the carb at that point in time.

If it turns out I don't need the jet kit because it has the proper jets installed incorrectly, I'll just sell it to my buddy for his zed. No harm done!

 

 

Thanks for the write up and advice though, it'll come in handy when I do tackle it this week! Much appreciated d, my good sir! Edit: sorry for double post, using my phone and this app is giving me hell... heh

 

No worries

Good luck and let us know how it turns out.

No 1 - are you sure that is a JD needle?  I cant tell for sure from a picture but it looks like a DynoJet needle to me.  Is the needle copper/brass color and red or blue on the top?  If stainless steel and no color code, it is DynoJet.

No 1 - are you sure that is a JD needle?  I cant tell for sure from a picture but it looks like a DynoJet needle to me.  Is the needle copper/brass color and red or blue on the top?  If stainless steel and no color code, it is DynoJet.

Hi Noble

I'm pretty sure it's JDJetting (yes, the picture I posted is not that good)

The bike was jetted when I got it, so I had to figure out what's in there. However, from looking on the web I'm pretty sure Dynojet needle has 6 slots like this one:

http://www.suzukicentral.com/forums/17-maintenance-repairs-tuning/87137-need-hand-jetting.html

 

Mine (JDJetting) has only 5 slots, plus it has a very slight blue smudge (worn out) on top...

Scroll down to see JDJetting needles (red, blue) as well as stock one:

http://bamarides.com/ride/dual-sport/suzuki-drz-400-thread/585/

ride it at night and see if the popping produces a blue flame out of the exhaust,if so then its running rich IMO

ride it at night and see if the popping produces a blue flame out of the exhaust,if so then its running rich IMO

Good call, hadn't thought of that. I`ll give that a shot and see what happens!

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