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Drz400s carb help

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2003 klx400/Drz400s... rebuilt carb with new kit and all went smoothly. Got it all back together and best way to describe it is the bike idles real high then dies. Start it back up and it's idling real high and as soon as you touch the throttle it sounds like it is missing. I've got the mixture screw 2.5 turns out with a #25 pilot but this doesn't seem to make a difference, over all bike is running very rough. Checked and no air leaks from the intake boot to carb. Bike is jetted with slip on pipe. 

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After letting it sit for two hours just went out and fired it up, was idleing perfect then started to rev up on its own and miss? 

Pilot still plugged? Float level too high? Something else wrong with carb?

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its not the float .. i would guess something got missed on the rebuild but check to be sure its not something external like a hose off or cables screwy .. if thats good i'd look at a parts blow-up diagram and go back through it ..

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Well I hate to give up but I'm taking it to the shop tomorrow. I've disassembled the carb 3 times over the weekend. I did find that my #25 pilot was partially clogged so I replaced it with the 22.5 brand new pilot that came in the kit and now the bike idles fine but I have a horrible stumble/backfire from 1/4 to 1/2 throttle. Checked the main jet twice and even replaced it with a new one to be safe but don't know what's causing it. 

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I had similar problems. There was an old o -ring jammed in the cavity below the mixture screw seat. I read an old post where another member found an old broken off mixture screw pin in the same area. Good luck.

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I did lower the idle, after swapping pilot jet it idles perfect, but stumbles and misses from 1/4 to 1/2 throttle. Double checked the jets and main 145 starter 62.5. 

I did find that old o-ring under the mixture screw and pulled it out. 

Dropped it off at the shop an hour ago, we will see what they find. 

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Let us know. This may help to dial in tuning.  Right now my carb is kicking my butt.

image.png

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Set my floats to 15mm per attachment above, bikes running great. Pilot adjust screw now works per specs, bike ran with pilot screw fully closed before.  JD red needle clip 3, 150 main, 25 pilot. 5000 ft. Full disclosure, I also flipped needle jet had it in upside down. 

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On 8/14/2017 at 7:12 PM, moparmotel said:

Dropped it off at the shop an hour ago, we will see what they find.

hope this works out, i have a very low confidence level in most bike shops, they see a bunch of varying bikes and rarely have the expertise needed to repair a specific bike (like the DRZ).  I think they mostly guess and trouble shoot w generalities and replace parts in hopes that fixes it.  Seems they commonly misdiagnose stator and compression issues w the ZED simply because theyre not familiar w the bike.

If your bike ran good before your carb work i would limit them to carb work the FCR is pretty common they should be able to get that straightened out, although when i went to my local shop for jets for the FCR one day i had to spend 20 minutes telling the guy what i was doing w an FCR on a dual sport and then convincing him it does work and to just sell me the jets (in the end they didnt even have any jets in stock) ...

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35 minutes ago, RetroRanger said:

hope this works out, i have a very low confidence level in most bike shops, they see a bunch of varying bikes and rarely have the expertise needed to repair a specific bike (like the DRZ).  I think they mostly guess and trouble shoot w generalities and replace parts in hopes that fixes it.  Seems they commonly misdiagnose stator and compression issues w the ZED simply because theyre not familiar w the bike.

If your bike ran good before your carb work i would limit them to carb work the FCR is pretty common they should be able to get that straightened out, although when i went to my local shop for jets for the FCR one day i had to spend 20 minutes telling the guy what i was doing w an FCR on a dual sport and then convincing him it does work and to just sell me the jets (in the end they didnt even have any jets in stock) ...

I don't have the fcr, I have the stock Mikuni. The shop called me last night and said it was ready, I just went and picked it up and got it home and it's doing the same dam thing! Pretty pissed... shop said it ran perfect when they test rode it but it's missing and popping/back firing... pretty hard to miss that! 

 

I dont get it... it idles perfect and as soon as you touch the throttle it starts missing/popping... 

anyone want to sell me their stock carb? I'm done messing with this one. 

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ok that sucks but no surprise re the shop...hopefully they didnt charge you to much

 

re the BSR carb did you check to make sure you have the small o ring that goes between the top cover and the carb body its commonly missed and causes running issues

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Damn that sucks. I didn't do a good job of the screen shot of the atachment I posted a couple of posts back. The title was CV carb tuning from the Mikuni Manual. It is specifically for your Mikuni BSR 36 and similar models. Will bike idle with mixture screw closed? If so your float system is not working. I rebuilt mine with a balls out kit, the needle dragged and hung up in the float valve, trash. I cleaned old brass valve and transferred o ring and filter screen now it works. As I previously posted I also set float height at 15 mm had it set before in middle of spec at 13.5mm, it was leaking and causing bike to run rich at that setting.  Also you should be adjusting the floats with the carb at about a 15 degree angle - just when the tab begins to touch needle. Have you pulled the  spark plug and checked its condition? Is it sooty I.e. Running to rich. Hope this helps. Good luck!

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9 hours ago, RetroRanger said:

ok that sucks but no surprise re the shop...hopefully they didnt charge you to much

 

re the BSR carb did you check to make sure you have the small o ring that goes between the top cover and the carb body its commonly missed and causes running issues

 

8 hours ago, Kurt58 said:

Damn that sucks. I didn't do a good job of the screen shot of the atachment I posted a couple of posts back. The title was CV carb tuning from the Mikuni Manual. It is specifically for your Mikuni BSR 36 and similar models. Will bike idle with mixture screw closed? If so your float system is not working. I rebuilt mine with a balls out kit, the needle dragged and hung up in the float valve, trash. I cleaned old brass valve and transferred o ring and filter screen now it works. As I previously posted I also set float height at 15 mm had it set before in middle of spec at 13.5mm, it was leaking and causing bike to run rich at that setting.  Also you should be adjusting the floats with the carb at about a 15 degree angle - just when the tab begins to touch needle. Have you pulled the  spark plug and checked its condition? Is it sooty I.e. Running to rich. Hope this helps. Good luck!

O-ring is in the top cover of carb. Needle doesn't seem to be dragging but not 100% sure. Float is set correctly. 

Another member contacted me with a stock carb he took off his drz a few months ago to swap for an fcr, I am purchasing that carb and will put it on whenever it arrives and hopefully that will tell me if it's carb problems or something else. Thanks for the replies! 

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Is the vacuum hose hooked up?  If you set the fuel petcock to prime does it run any differently?  Sounds like it's going very lean.

 

Doc

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2 hours ago, Doc_d said:

Is the vacuum hose hooked up?  If you set the fuel petcock to prime does it run any differently?  Sounds like it's going very lean.

 

Doc

I was going to ask the same.  The one time I left mine unhooked it ran like the OP is describing.

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4 hours ago, Doc_d said:

Is the vacuum hose hooked up?  If you set the fuel petcock to prime does it run any differently?  Sounds like it's going very lean.

 

Doc

No Vacuum line, it's capped off because I installed the raptor on/off petcock. 

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Couple of easy things to check to narrow it down.  Disconnect fuel line from petcock check for good flow. Drain float bowl using drain screw. I drained and measured mine got 33 ml or a little over an ounce. If you have a lot more or less you have a problem with your float setting or needle and valve. Too little will result in a lean mixture too much rich. I'm too new to this carb to know how far outofspec causes problems. Consensus seems to be your running too lean in pilot system. If float system is good seems to me all that all that is left is a large vacuum leak or a badly clogged pilot system. Somebody please correct me if I'm off target. You've said the needles are clean, that leaves internall passages. My carb has two capped vacuumed lines, I replaced both. Once again I am new to carb so have noidea how bad a leak has to be.  Help anyone? Everything I read says pilot system controls low end acceleration.  An intermittent sticking float needle results in all sorts of symptoms both rich and lean, drove me nuts for a week.

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5 hours ago, Kurt58 said:

Couple of easy things to check to narrow it down.  Disconnect fuel line from petcock check for good flow. Drain float bowl using drain screw. I drained and measured mine got 33 ml or a little over an ounce. If you have a lot more or less you have a problem with your float setting or needle and valve. Too little will result in a lean mixture too much rich. I'm too new to this carb to know how far outofspec causes problems. Consensus seems to be your running too lean in pilot system. If float system is good seems to me all that all that is left is a large vacuum leak or a badly clogged pilot system. Somebody please correct me if I'm off target. You've said the needles are clean, that leaves internall passages. My carb has two capped vacuumed lines, I replaced both. Once again I am new to carb so have noidea how bad a leak has to be.  Help anyone? Everything I read says pilot system controls low end acceleration.  An intermittent sticking float needle results in all sorts of symptoms both rich and lean, drove me nuts for a week.

Thanks Kurt but I actually bought another carb off another member today, it will be here Wednesday. At least that will let me know if it was my carb that was the problem or if it's something else such as a bad stator/coil. 

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