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DRZ400e Mid Throttle Stumble

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Hey guys and gals, I've been trying to pin down a problem for a few weeks now with no success. I've read countless forum posts to no avail so here I am. This post will be a bit long but I want to provide as much info as possible as this has me stumped. 

I have a 2005 DRZ400e. Mostly stock besides the 'free power' mod and the previous owner opening up the airbox and drilling some holes in the stock exhaust to open it up (and make it way too loud). 

When I bought this bike last year it ran flawlessly. The day after I bought it I left on a two week adventure through far north Australia. Unfortunately the stator was toast, but I luckily had a starter pack that got me through the trip. Other than that it was mechanically solid. 

After arriving home I let it sit for a few weeks and after that the damn thing just wouldn't start. I got the stator professionally rewound and had them check compression for me. Low and behold the compression was terrible, so I pulled the top end apart and found that the piston rings were absolutely  embedded in their grooves. I assume this could be the result of overheating, as without a working stator I was leaving the bike running as much possible. It took a lot of persuading and hot water to get them unstuck before replacing them, but the piston and cylinder looked absolutely fine. 

So after this the bike started up straight away but wasn't holding idle. Knowing that I'd need to clean the carb I decided to purchase a carb rebuild kit along with a JD Jetting kit. Unfortunately my compressor has broken, but I was as through as possible trying to clean out all the circuits and replacing the clogged jets with the new ones in the kit as well as replacing all the O-rings and gaskets. 

Currently my carb settings are as follows:

Float hight 9mm

Main Jet 155 (142 is stock)

Pilot jet 45 (stock)

Pilot air jet 60 (stock)

Mixture screw at 2.5 turns

And I'm using the JD blue needle on the 4th notch as suggested by the instructions. 

Now after doing all of this the bike starts up perfectly and runs great at low speed but has a very weird problem. When I accelerate in any gear through around 1/2 to 3/4 throttle the bike falls flat on its face. It doesn't backfire, but it feels like it is starved for fuel and misses considerably until it gets to a higher Rpm and then it takes off like a rocket again. Never experienced anything like it before and the bike is unfortunately unridable because of it. 

Here is a list of things that I have tested:

Petcock flows fuel fine

Replaced fuel with a fresh tank

Checked for air leaks - no change

Rode with choke on - no change/ worse

Rode with airbox cover off - no change

Disconnected RR - no change

Disconnected TPS - no change

I'm really running out of ideas here. I need to test if putting the original needle back in changes anything, but that will probably have to wait until next week. 

A few other notes:

My battery is pretty much shot. It has enough juice to start the bike a few times but that's it. Is it possible for a dodgy battery to cause these sort of problems? I was under the impression that the bike gets its juice from the stator once running. 

The mixture screw does not seem to do a whole lot. The bike will idle with the mixture screw all the way in, and will still idle with it out 3 turns. This doesn't seem right. I have an extended mixture screw on the way so that I can test it a bit easier. 

I would appreciate any input as I am grasping at straws here. 

Thanks in advance, 

Jet

 

20170807_144603.jpg

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There's a lot going on here. As mentioned above, it could be the battery. The ECU needs 12vdc to function.

 The mixture screw will not effect any throttle setting much beyond idle. You've done a lot of things, but nothing that actually effects the 1/2 to WOT setting. Raise the needle and see if that helps. If there is still a lean bog after 3/4 throttle, go to the next larger main jet. 

Edited by Gary in NJ

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Assuming it's not a weird electrical glitch caused by the dead battery you have a rich condition. You proved this by the situation being made worse with the choke. The needle can be easily replaced by only removing the fuel tank and seat. I would put the previous needle in and see how it responds. It's possible the needle jet( tube the needle rides in) is worn and contributing to the situation.
Also, doesn't JD recommended to replace the pilot with a 42?

Sent from my XT1650 using ThumperTalk mobile app

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13 hours ago, Gary in NJ said:

There's a lot going on here. As mentioned above, it could be the battery. The ECU needs 12vdc to function.

 The mixture screw will not effect any throttle setting much beyond idle. You've done a lot of things, but nothing that actually effects the 1/2 to WOT setting. Raise the needle and see if that helps. If there is still a lean bog after 3/4 throttle, go to the next larger main jet. 

Thanks for the input, mate. Sounds like a new battery is step no. 1.

After that I'll raise the needle and then try the stock one if nothing changes. 

I understand that the mixture screw is mostly to do with idle, but is it unusual that I can seat the screw and still have the bike idle okay? I checked that all the components are there and in the correct order. 

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11 hours ago, ohiodrz400sm said:

Assuming it's not a weird electrical glitch caused by the dead battery you have a rich condition. You proved this by the situation being made worse with the choke. The needle can be easily replaced by only removing the fuel tank and seat. I would put the previous needle in and see how it responds. It's possible the needle jet( tube the needle rides in) is worn and contributing to the situation.
Also, doesn't JD recommended to replace the pilot with a 42?

Sent from my XT1650 using ThumperTalk mobile app
 

Thanks for your input mate, appreciate it. 

When I rode with the choke on, it was only marginally worse. I'm not even sure it made a difference to be honest. 

I also took it around the block with the airbox cover off and the filter removed (after cleaning the airbox) and that didn't seem to make any change. If it was in fact rich, wouldn't it be noticeably better without the obstructions? 

I don't have the instructions with me at the moment, but I definitely changed the pilot to the one in the kit. I might have written down the wrong number so I'll double check when I can. 

I'll take your advice and try the other needle, as well as a new battery since it needs to be replaced anyway. 

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The bike seems to be fairly tolerant of lean settings but will stumble and get pissed off if set too rich.

Bogging out ( making the BWAAAH sound, like you just hit the kill switch) and dying is lean.

Running roughly, sputtering, missing, burbling, and running good cold, but poorly at operating temperature are the signs for a rich condition.

I had the JD kit in my bike, I had an issue with the blue needle being too rich at 1/8 throttle. I switched to red. It helped but wasn't perfect.

Sent from my XT1650 using ThumperTalk mobile app

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