2001 DRZ400 E Carb Question

I searched and could not find exactly what I am looking for and I need some help.  The bike runs amazing at mid to high rpm's but there is a nasty flat spot at the bottom of the throttle and if you snap it the bike will sometimes shut off.  I don't know much about the these carbs other than taking it in and out of the bike is a pain.  I check all the jets and they were clean. Someone told me it might be the accelerator pump? If so any suggestions on how to clean? I live in NYC (basically sea level) and it currently has a slip on but that is the only mod.  The pilot seems kind of large to me as well as it is a 65.  Thanks for any tips, it is my fathers bike and I am trying to get it running right for him. 

Pilot jet will be 45.  The 65 jet is the starter jet.  A non-functioning AP will affect running when you snap the throttle but not at a steady throttle setting.

 

Assuming at stock parts (carb and the rest of the motorcycle except slip on), set the fuel screw 2.5 turns, set the needle clip at -5 (from the top).  Main jet 158. clean the pilot jet.  Check the float level. (9-10mm) Air box snorkel removed. Test the AP to see if it is working.  Remove the Coast Enrichener (CE), connect the 2 nipples on the carb with a hose.  Remove and seal the port on the head with a 8mm bolt.

Pilot jet will be 45.  The 65 jet is the starter jet.  A non-functioning AP will affect running when you snap the throttle but not at a steady throttle setting.

 

Assuming at stock parts (carb and the rest of the motorcycle except slip on), set the fuel screw 2.5 turns, set the needle clip at -5 (from the top).  Main jet 158. clean the pilot jet.  Check the float level. (9-10mm) Air box snorkel removed. Test the AP to see if it is working.  Remove the Coast Enrichener (CE), connect the 2 nipples on the carb with a hose.  Remove and seal the port on the head with a 8mm bolt.

 

I'll jump onto this because I just bought a 2000 and have carb questions too. I'm a total newb, haven't owned a moto since the 1973 Yamaha 360 Enduro I bought in 1982 when I was a teenaged man-child.

 

I live in Colorado. My town is 7,000 feet elevation, and often we ride to 11,000 or higher. I bought my DRZ from a friend, and he's got inlaws who are full-on mountain moto freaks. So I'm guessing the carb has been jetted for high elevation. He sold it to me stupid cheap by the way, so I don't mind that it might need a little service.

 

My key thing with it right now is it knocks when idling. One little twist on the throttle and it stops. The guy who sold it to me thinks it's a carb adjust, needing to get it a little richer. This makes some sense to me since I have found that it sometimes doesn't do it when I'm up in the mountains a couple thousand feet higher. It also is super flat at low RPM. I assume that it's because there truly is no power down there, and I just shouldn't lug it at all, but since there are possibly other carb problems it's worth mentioning.

 

So I'm totally clue-less, haven't even touched it with a wrench yet. Am I going to be able to get this thing running a little more rich without taking the carb off? Adjustment screw on the outside of it I could turn a little to try to make it more rich? Somebody I was talking to said pull the plug and see if it's white, that would suggest lean mixture.

 

I want to try doing the easiest thing to see if I can make this noise go away. My concern is that it's a valve or other thing knocking at low RPM, not just fuel detonation. But if I could quiet that knocking by doing a simple carb adjust I would feel better about just riding it.

 

I still need to get the owner's manual from the guy I bought it from.

Edited by ColoradoTom

This is one confusing carb! Do you think it is the AP?  Can I check that without pulling the whole thing apart again?  I have never worked on such a complicated carb. 

 

Pilot jet will be 45.  The 65 jet is the starter jet.  A non-functioning AP will affect running when you snap the throttle but not at a steady throttle setting.

 

Assuming at stock parts (carb and the rest of the motorcycle except slip on), set the fuel screw 2.5 turns, set the needle clip at -5 (from the top).  Main jet 158. clean the pilot jet.  Check the float level. (9-10mm) Air box snorkel removed. Test the AP to see if it is working.  Remove the Coast Enrichener (CE), connect the 2 nipples on the carb with a hose.  Remove and seal the port on the head with a 8mm bolt.

You can adjust the idle mixture with a screw pretty much inaccessible just above the starter.  I doubt it will affect a knock.  You can adjust the idle speed with the white knob.  Needs to idle about 1800 RPM. pretty high, this may cure  knock.  Can't imagine it needs to me more rich.  Knock is not from mixture strength.  Not detonation. Plug check is meaningless..

Jolly - yes it has AP.  You have to remove the carb or at least the intake boot to look in the carb to check AP.

I know it has an AP, is there directions on cleaning anywhere? Thanks

Jolly - on a 12 year old carb you need to disassemble and inspect the AP diaphragm and the check valves.  I do not know of a written procedure other than a service manual.

You can adjust the idle mixture with a screw pretty much inaccessible just above the starter.  I doubt it will affect a knock.  You can adjust the idle speed with the white knob.  Needs to idle about 1800 RPM. pretty high, this may cure  knock.  Can't imagine it needs to me more rich.  Knock is not from mixture strength.  Not detonation. Plug check is meaningless..

Thanks. Good to know that it's probably not a problem with fuel mixture. I had considered that it may be idle rpm is too low, just seemed like too simple an answer. But all you have to do is give it the tiniest bit of throttle and it quiets down, so that should at least solve the immedate problem.

 

I don't know what you mean by the white knob, but don't tell me. I'll look around and see if I can use my brain to find it.

Maybe white, maybe black.  But is clearly an adjustment knob just under the carb.

Maybe white, maybe black.  But is clearly an adjustment knob just under the carb.

 

It's under? Sounds like it's a thumb knob? Just to be clear, my bike is specifically a 2000 DRZ 400 EY. I see those white knobs on the Mikuni carbs I see in pictures, but from what I read in your post here: http://www.thumpertalk.com/topic/657246-drz-400-models/?p=6578146

 

You say that the S had a Mikuni Carb, but in your description of models you didn't say that about the DRZ 400 and 400E had Mikuni...

 

Anyway, I just went out to the garage and took pictures. Think maybe I found it? Doesn't really look like it's connected to anything, but it's a knob.

 

drzCarb1.jpg

 

drzCarb2.jpg

Yes, that's it.  Connected with a flex cabe to a throttle stop screw.

 

In the US all S/SM have Mikuni.  All Kick start only had Keihin. Early year E had Keihin. (your pictures are Keihin).  Then CA E came with Mikuni, then all E came with Mikuni, then the E was discontinued.

This is a very dumb question. Are you using premium gas? If not, then try it. That is what is recommended for an "E". (dumb happens to all of us, now and then.)

Edited by underbike

This is a very dumb question. Are you using premium gas? If not, then try it. That is what is recommended for an "E". (dumb happens to all of us, now and then.)

 

Yep, I'm using premium. That was made pretty clear. But yeah, I'm definitely newb. Pointing out that I should skip mixing oil in my gas wouldn't be too insulting even (I'm not by the way).

 

Last night I took it out and got it warmed up, then tried the adjustment knob. Pretty hard to turn, partially because it's in an awkward spot behind that hose. But I was able to turn it and it didn't seem to be doing much. I assume it's clockwise (righty-tighty) to increase idle speed? It maybe made a little change in idle speed with approximately one full turn, but not a huge amount. Didn't feel like it was working, and definitely wasn't turning easily, so I left it at that.

 

However, the knocking seemed a little better. I've been riding it quite a bit and have run at least 4 gallons of fresh fuel through it. Not sure how much time it spent stationary in the last year, but seems like stale gas could have been contributing to the problem.

 

From what I've been reading here lately, seems like a carb rebuild is on the horizon for me. Once I get through hunting season I will probably tear into the thing a little.

Edited by ColoradoTom

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