2006 DRZ400S w/ Stock Mikuni - Idles But Dies w/ 1/8th Throttle

   Sorry for yet another bogging/engine dies post but have done a ton of searching/troubleshooting and still can't figure this out. 2006 with stock Mikuni carb, no mods to the engine or exhaust. Gas tank is a Clark with a non-vacuum petcock. Bike sat for a long time and wouldn't start, took carb out and cleaned it up. Took out all of the jets and sprayed with carb cleaner and used used a wire to get through all of the holes. Cleaned the rest of the carb body and all orifices. Replaced float needle and seat, along with main jet o-ring. Drilled out fuel mixture screw and set it at 2 3/4 turns out. Now it starts and idles fine and will rev up until about 1/8th of throttle then it dies. 

  Here is what I have also done to try to troubleshoot: replaced spark plug and confirmed that I am getting spark. Drained fuel and refilled with fresh supply. Checked rubber housing on both sides of the carb, no holes/tears. Verified that carb diaphragm had no holes/tears. Rubber o-ring on top of carb next to diaphragm was intact. Capped off vacuum hole from carb (petcock does not use vacuum system). Took carb out again and cleaned it a 2nd time. I even bought another used stock Mikuni carb off of Craigslist (cleaned also) and was able to duplicate the problem.   

  So, if I am able to duplicate the issue with 2 different carbs , where do I go from here? Am I getting too much or too little fuel? I tried applying the throttle while simultaneously opening the choke halfway to see if the engine would run but it had no effect. So again, starts fine but once I go past about 1/8th throttle it dies. Happens if I twist it slow/med/fast. Just seems like there is no fuel going through the carb when I open the throttle. I have drained the float bowl several times in the course of taking the carb out so there is fuel in the bowl. I guess it's possible that I could still have a clogged fuel circuit but I was very thorough and as stated before I was able to duplicate the problem by swapping in another identical Mikuni carb.   

  One issue with the bike that is not carb related is that there is a slight leak between where the header and muffler come together. The leak is coming from the clamp and gasket that joins the 2 sections. The gasket has small gaps and I will replace it if needed. When I say leak, I mean exhaust gases (not a lot) after the motor is warmed up. Don't know if this leak would cause the problem that I am having, just thought I'd point it out. 

  Thanks in advance.

Edited by sfong33
more details

What is your idle at? Try less on the screw, like 2 turns

74jimbo,  I am at sea level in San Francisco so I thought 2 1/2 to 2 3/4 turns out was about right but I will try 2 turns out. I don't know how to tell what speed it is idling at but not idling high. Doesn't need choke when cold (but bike is garaged and it hasn't been cold) so maybe I do have it out too far. Thanks.

Edited by sfong33

I am just across the bridge and run at 1.5

15 minutes ago, 74jimbo said:

I am just across the bridge and run at 1.5

   Thanks for your input. That was my next question. With my all stock setup is 1.5 or 2 turns out better? 

   The other carb I picked up was also set at 2 3/4 turns out by me so I definitely think this will take care of my problem. I used to own a Yamaha TW200 and I think the suggested setting was 2 1/2 turns out, just assumed it was OK for this carb. Will make the adjustment tomorrow.

   

Edited by sfong33

Every carb is different, mine had a off idle bog/hesitation some times stall at 2 turns out, I now run 1/2 to 1 turn out. Vancouver , Canada

  Adjusted the fuel idle mixture screw to 1 1/2 turns out but problem is still there, dies when given about 1/8 throttle. Seems like nothing changed after the adjustment, started with choke halfway out (but needed to twist the throttle so maybe the choke is not really helping?) and idled fine. Will adjust to 1 turn out later when I get home.

10 hours ago, ohiodrz400sm said:

Did you mix up the main jet and starter like the guy did last week?

Sounds very similar.

 

https://thumpertalk.com/index.php?/topic/1237014-Bike-bogs-down-1/2-full-throttle

Sent from my XT1650 using ThumperTalk mobile app

 

 

 

 

  Saw that thread before I posted. Almost positive I did not mix them up. As stated previously I was able to duplicate the problem with 2 different carbs (same stock Mikuni). Will double check tomorrow though. Thanks for the suggestion 🙂.

Edited by sfong33

Screenshot_20170808-121542.png

Did you remove the fuel screw and pilot and then blow the passage out with compressed air? If not, try that.

Sent from my XT1650 using ThumperTalk mobile app

2 hours ago, ohiodrz400sm said:

Screenshot_20170808-121542.png

Did you remove the fuel screw and pilot and then blow the passage out with compressed air? If not, try that.

Sent from my XT1650 using ThumperTalk mobile app
 

  Yes, cleaned both throughly. Thanks.

Update: problem solved, thanks ohiodrz400sm! Turns out I did have the main and starter jets reversed. DOH! After unscrewing them for cleaning a while back I put them in a bowl so I wouldn't lose them, that is where the mixup occurred. I had a 50/50 chance of getting it right but the motorcycle gods conspired against me that day. I just assumed that the first one I picked up was the correct jet because it screwed right in. Anyway, made the swap and all is well. No dead spots and full throttle response has been restored. 

Thanks again to all who responded.

Edited by sfong33

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