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Drz400 big bore, mid range bog and surging?

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2000 DRZ 400e, Athena 440 kit, stage 2 hot cams, full MRD exhaust, FCR 39mm, 160 main, 45 pilot. ( The needle is 3 notches up from the bottom, it is a needle that came with a stage 2 dynojet kit which i got when it was factory bore and had on a fmf)

Right now she starts, idles, putters around just fine, but when i start to open it up into the mid range and accelerate it bogs then surges really badly, if i keep rolling on the throttle it clears up a little then does it again but much worse at 3/4 throttle. Then if i snap it open all the way to WOT it pushes through the surging and goes like she should. 

So i'm thinking it could be the needle needing adjusted? Any advice i would really appreciate, it's been far too long since this bike has been in top shape and i really want to get her straightened out finally. 

Thanks! 

Edited by eric_stoll5

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Yes, I have a drz400 with the same kit buddy! Did the same thing, was very dangerous when in a wheelie

Anyways it would backfire and whatnot at idle and had the same symptoms at gutless power at bottom end

SOLUTION, any 5$ to 100$ "jet kit" just look it up. After the carburetor jetting kit it had insane amounts of adjustments and power level options and on 91 octane it would backfire every time I let off the gas after a couple hours of riding

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3 minutes ago, durafummins said:

Yes, I have a drz400 with the same kit buddy! Did the same thing, was very dangerous when in a wheelie

Anyways it would backfire and whatnot at idle and had the same symptoms at gutless power at bottom end

SOLUTION, any 5$ to 100$ "jet kit" just look it up. After the carburetor jetting kit it had insane amounts of adjustments and power level options and on 91 octane it would backfire every time I let off the gas after a couple hours of riding

It is jetted for the big bore already, it is idling and has bottom end just fine.

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It is jetted for the big bore already, it is idling and has bottom end just fine.

I meant to say mid range but word didn't come to mind lol, but lemme ask. Was it surging as in fuel cutting out for a split second every now and then?

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16 minutes ago, durafummins said:


I meant to say mid range but word didn't come to mind lol, but lemme ask. Was it surging as in fuel cutting out for a split second every now and then?

surging as in it feels like it's hitting a rev limit, so yeah it feels like it hits a fuel cut off and falls on its face but far from now and then and not for a split second. I have almost no useable mid range, but above and below it's fine. I don't have much to work with but i can put together a video i think to help wrap everyone's heads around what it's doing exactly, because i have yet to find a post describing the exact same thing. 

Edited by eric_stoll5

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See mine for a brief example would feel like I m pulling in the clutch more and more as climb towards 4300rpms but would sound like it's bogging (which it was bogging because it usually spat blue flames?) then I crank the throttle, cuts out again for a second then back to full ludacris mode.

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I changed the spark plug with an 50$ ngk racing" plug, you upgrade these drz's to gotta upgrade every square inch. And the main thing I changed was the riding style. I didn't baby it around and Cruze or let it idle in my driveway for 3 minutes. If I was at a light I'd rev the shit out of it or else it would bog and fuel cut leaving the intersection.

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I didn't have enough room to let it rev past the bs it's doing but here's a video of what it does, I opened it up to about 3/4 throttle let it do its thing then let out. 

 

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1 minute ago, durafummins said:

I changed the spark plug with an 50$ ngk racing" plug, you upgrade these drz's to gotta upgrade every square inch. And the main thing I changed was the riding style. I didn't baby it around and Cruze or let it idle in my driveway for 3 minutes. If I was at a light I'd rev the shit out of it or else it would bog and fuel cut leaving the intersection.

I'm aware of that, it has the best parts on it and in it. 

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Just now, durafummins said:

It sounds like the bike is activating its rev limiter because it thinks it's at that point.

that's what it sounds like but that's not what it's doing, it keeps reving past that when i open it up all the way.

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Location? That's a rich sputter.

160 main is too rich for a bigbore. If you're near sea level you could run 158, otherwise I'd start with a 155. Smaller if you're at higher elevation.

Same with the needle. All aftermarket jet kits are intended for a relatively stock bike. Big bores need smaller jets as they pull more fuel thru the jets compared to a stock bore. Order a EMP needle from Jets-R-Us .
If your bike doesn't have FI like response than you may have another issue beyond jetting. The float level on an FCR also has a affect on overall jetting. It needs to be set around 9mm.



Sent from my XT1650 using ThumperTalk mobile app

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29 minutes ago, ohiodrz400sm said:

Location? That's a rich sputter.

160 main is too rich for a bigbore. If you're near sea level you could run 158, otherwise I'd start with a 155. Smaller if you're at higher elevation.

Same with the needle. All aftermarket jet kits are intended for a relatively stock bike. Big bores need smaller jets as they pull more fuel thru the jets compared to a stock bore. Order a EMP needle from Jets-R-Us .
If your bike doesn't have FI like response than you may have another issue beyond jetting. The float level on an FCR also has a affect on overall jetting. It needs to be set around 9mm.



Sent from my XT1650 using ThumperTalk mobile app
 

That's what I needed to hear, I was fairly sure it was something like that because what else could it be. I'm in southwestern Pa, near the northern panhandle of Wv. So I'll drop the jetting down so it's leaner and see what it does. 155 main,  I think the pilot can probably be left alone, and second notch on the needle sound about right? 

Edited by eric_stoll5

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I'll add, are all the modifications something you just did or was the bike worked a while back and this problem suddenly arose? I ask because you have a 17 year old bike and a wear part is the needle jet emulsion tube as well as the needle. As they wear, the bike runs richer.

As Ohio says, with the big bore and the cams, you need leaner jetting because the bike is sucking harder on the carb as well. What size opening do you have in the air box? Just the snorkel removed I hope.

Leave the pilot alone. Mostly, you need to deal with the needle,  an EMP needle probably would be best along with a new needle jet emulsion tube. Once midrange is sorted, then you can test at wot for extended runs for main jet questions.

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18 minutes ago, William1 said:

I'll add, are all the modifications something you just did or was the bike worked a while back and this problem suddenly arose? I ask because you have a 17 year old bike and a wear part is the needle jet emulsion tube as well as the needle. As they wear, the bike runs richer.

As Ohio says, with the big bore and the cams, you need leaner jetting because the bike is sucking harder on the carb as well. What size opening do you have in the air box? Just the snorkel removed I hope.

Leave the pilot alone. Mostly, you need to deal with the needle,  an EMP needle probably would be best along with a new needle jet emulsion tube. Once midrange is sorted, then you can test at wot for extended runs for main jet questions.

These are all fresh, I have maybe 6 hours on it since I did all this. That's the answer I thought I'd get, I just was tired of constantly taking things apart and putting them back together with not progress being made so I wanted to ask before I started playing with jetting and the needle. I appreciate it!

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In the mean time while I'm waiting for those two things to show up, just for the hell of it, I'm gonna adjust my current needle and see what difference it makes. Any suggestions for that?

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Just now, eric_stoll5 said:

In the mean time while I'm waiting for those two things to show up, just for the hell of it, I'm gonna adjust my current needle and see what difference it makes. Any suggestions for that?

Sure. Put the clip at the top (next to the flat) of the needle. See if it makes any noticeable change. It is a micro adjustment so you may not feel any difference. It will affect operation above  1/4 throttle about 2%.

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Ordered parts and adjusted my current needle and put in a 155 main, seems to have made a noticible difference but I'll put on my gear and go down the road and let you know. Also where should I have the emp needle set at when it shows up?

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