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Discussion Starter #1
#1) Ok this is weird.. You can see me mods at the bottom nothing out of the norm but when i'm in Therd gear and mid RPM range the bike starts to sputter like I let off the gas and then back on it real quick. Then in Forth it's the same thing.... when i hold a RPM in one spot for any period of time.

#2) When I start my bike up in the morning I now have to pull out my choke all the way. After i had the bike jetted I didn't need the choke at all just start button and go...

I don't know what the problem is. :headscrat HELP
 

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Just had the same problem with my xr, the aftermarket header retaining collars were bending on the studs, causing the headers to be loose, causing it to run extremely lean.
I spent a lot of time messing with the carb, trying different fuel, etc. because I missed the simple exhaust leak.
 

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old fuel?
 

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Just put gas in yesterday, I always use super
They weren't filling the tanks at the station when you filled up by any chance? I work as a mechanic at a dealership, and you would be surprised how many times we get cars in that have a gallon or so of water in the fuel b/c they filled up when the tanker truck was filling the storage pumps at the station. All of the fuel in the storage tanks will float on top of any moisture in the tanks. When they fill 'em up, everything mixes together and will get pumped out with the fuel until it has had time to separate. An easy way to check is to drain a sample from the tank (from the carb supply hose) into a clear container. Then just let it sit for an hour or so. Any water in the fuel and it will separate into to distinct layers.
 

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Is it backfiring a lot? I had a similar issue last year at around this time. It just got so cold and dry so quickly that the bike started running really lean because of the change in air. I went quite a bit richer and problem was cured. I had to go a bit leaner in the spring and then go even leaner again in the middle of summer, this year. A couple of weeks ago I went a bit richer with no issues. Even now, I'm finding that I will have to go richer again in a couple of weeks once I start riding in sub 45 degree weather. I've ridden in temps above 100 and then been riding down the same street 4 months later when it's like 10 degrees outside. Sport tires don't work well on ice.
 

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Discussion Starter #10
They weren't filling the tanks at the station when you filled up by any chance? I work as a mechanic at a dealership, and you would be surprised how many times we get cars in that have a gallon or so of water in the fuel b/c they filled up when the tanker truck was filling the storage pumps at the station. All of the fuel in the storage tanks will float on top of any moisture in the tanks. When they fill 'em up, everything mixes together and will get pumped out with the fuel until it has had time to separate. An easy way to check is to drain a sample from the tank (from the carb supply hose) into a clear container. Then just let it sit for an hour or so. Any water in the fuel and it will separate into to distinct layers.
I'll try that tonight :thumbup:
 

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Discussion Starter #11
Is it backfiring a lot? I had a similar issue last year at around this time. It just got so cold and dry so quickly that the bike started running really lean because of the change in air. I went quite a bit richer and problem was cured. I had to go a bit leaner in the spring and then go even leaner again in the middle of summer, this year. A couple of weeks ago I went a bit richer with no issues. Even now, I'm finding that I will have to go richer again in a couple of weeks once I start riding in sub 45 degree weather. I've ridden in temps above 100 and then been riding down the same street 4 months later when it's like 10 degrees outside. Sport tires don't work well on ice.
Nice I'll give that a try. Is the ajuster for that is located on the TB where they drilled out and inserted a flat head screw? When i picked the bike up they didn't show me shit :hmmm:

If theirs ice out I'm in the truck on 35's
 

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If the above doesn't work... do you have an inline plastic fuel filter? I had a similar problem last year and turns out I had a small hairline crack in the base of my filter. Under throttle it would pull in too much air and create the same lean mixture problem.
 

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Possibility for que # 1. When you say it sputters does the engine actually stumble or does the bike just lunge back and forth or kind of flutter a little bit. I ask this because maybe it is chain slack or that what you are feeling is the rigidness of the chain drive. Such as on sportbikes they run a cush drive where there are little rubber cushins behind the rear sproket carrier that helps dampen the driveline. But with the dirtbikes the rear sproket is mounted directly to the hub. I feel this a little when I ride around town. You wouldn't notice it in the dirt but a smooth road...
que # 2. If when they or you did the jetting did you happen the adjust the throttle cable to have very little slack and maybe now the cable play is more loose and now it takes a little more to start the bike? I like my throttle to have tention almost right at the twist of the throttle. Maybe 1 to 2mm of free play.

Next....

Kevin
 

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Discussion Starter #15
Possibility for que # 1. When you say it sputters does the engine actually stumble or does the bike just lunge back and forth or kind of flutter a little bit. I ask this because maybe it is chain slack or that what you are feeling is the rigidness of the chain drive. Such as on sportbikes they run a cush drive where there are little rubber cushins behind the rear sproket carrier that helps dampen the driveline. But with the dirtbikes the rear sproket is mounted directly to the hub. I feel this a little when I ride around town. You wouldn't notice it in the dirt but a smooth road...
que # 2. If when they or you did the jetting did you happen the adjust the throttle cable to have very little slack and maybe now the cable play is more loose and now it takes a little more to start the bike? I like my throttle to have tention almost right at the twist of the throttle. Maybe 1 to 2mm of free play.

Next....

Kevin
#1) The chain is tight, a little sag but the normal amount
#2) It was loose but i tightened it when i got it home so its like yours
 

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I feel like mine is doing something similar. At constant, Mid-throttle im getting a little surging. I just moved to a new house up a few 100ft and temps have gone from 55-60 to 45 in about a 2 week period. Do you adjust this with the mixture screw? From my understanding the pilot circuit shouldn't be effecting surging at mid to open throttle correct? Does this mean I need to change out a jet instead of messing with the A/F screw? Thanks for the input, just trying to get it running smoothly for the winter months since its my commuter rain or shine...
 

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I did all the mods, 3x3 air box, dynojet kit, N&N air filter and a Yoshi Pipe slip-on, I got the surge at 65mph and poping on decel, I was told by my dealer 2nd clip and 46 main jet- stock was 42.5, and the neddle has but one setting. Like I said it did not work!, So I spent some time on TT and came up with this, Read the Directions for the dyno kit, Well it told me 3rd clip on the needle jet and a 55 with stock exhaust and a 60 with a slip-on.
Surge went away but still have pop on decel. 09 DRZ-SM 400, all the smog removed!
 

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I did all the mods, 3x3 air box, dynojet kit, N&N air filter and a Yoshi Pipe slip-on, I got the surge at 65mph and poping on decel, I was told by my dealer 2nd clip and 46 main jet- stock was 42.5, and the neddle has but one setting. Like I said it did not work!, So I spent some time on TT and came up with this, Read the Directions for the dyno kit, Well it told me 3rd clip on the needle jet and a 55 with stock exhaust and a 60 with a slip-on.
Surge went away but still have pop on decel. 09 DRZ-SM 400, all the smog removed!
from my experience, popping on decel with after market pipes is normal... its a minor backfire. it has literally happened to me on everyone of my bikes that had any kind of exhaust system on them, but the stock ones never had the problem. i wouldnt sweat over it man.
 

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I feel like mine is doing something similar. At constant, Mid-throttle im getting a little surging. I just moved to a new house up a few 100ft and temps have gone from 55-60 to 45 in about a 2 week period. Do you adjust this with the mixture screw? From my understanding the pilot circuit shouldn't be effecting surging at mid to open throttle correct? Does this mean I need to change out a jet instead of messing with the A/F screw? Thanks for the input, just trying to get it running smoothly for the winter months since its my commuter rain or shine...
Here is a good article on tuning CV carbs. It's pretty straightforward.
http://home.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

Also if you haven't already over on Thumpertalk there is baseline settings for altitudes ind the DRZ FAQ section.
 

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drz 400sm jettting

Thanks guys, My first mistake is a 165 main jet, needs to be a 160. I'll try that tomorrow. I;m at 1500 ft above sea level. now I see alot guys going to a 75 leak jet, should I do this?
 
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