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FCR MX 39, need help

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Howdy,

 

hopefully someone can drop some knowledge on me.

Please try to follow as im not much of a writer, im probably going to be all over the place....bear with me. 

 

I installed a custom "FLOWPRO" fcr mx 39 on a drz400sm :"3x3 & full GPR exhaus, no tps connected"

WOT it runs and pulls perfectly, as expected. 

1/8th-1/4 its sputtering like crazy or if im just cruising at a constant speed after a second or two it spudders until i crack it open.

I had the A/f mixture screw and 2-3 turns out and it was sputtering like crazy anywhere from 1/8th throttle to 1/4th or just cruising at a constant speed. So i turned it all the way in and it ran much better, but its still happening, which leads me to believe it is too rich?

I ran it without the airbox and it ran better that with it on there but not a significant difference.

It has a new air filter and sparkplug looks good. It was running perfectly this morning with the mikuni on. 

Jetting spec:
Idle jet #40
Main jet #155
Main air jet #200
Idle air jet #75
Choke jet #75
Needle ELQ 4th clip from top, "was on third but ran much worse, the guy that built it said to drop it one more clip to see if that helps, It did help a good bit but still not perfect"

 

other than the spudder at 1/8 throttle and having to have the AF all the way in it runs great. WTF. 

 

I tried to give as much info as possible, let me know if theres anything i missed. 

fcr 1.jpg

fcr 2.jpg

fcr 3.jpg

fcr 4.jpg

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Howdy,
 
hopefully someone can drop some knowledge on me.
Please try to follow as im not much of a writer, im probably going to be all over the place....bear with me. 
 
I installed a custom "FLOWPRO" fcr mx 39 on a drz400sm :"3x3 & full GPR exhaus, no tps connected"
WOT it runs and pulls perfectly, as expected. 
1/8th-1/4 its sputtering like crazy or if im just cruising at a constant speed after a second or two it spudders until i crack it open.
I had the A/f mixture screw and 2-3 turns out and it was sputtering like crazy anywhere from 1/8th throttle to 1/4th or just cruising at a constant speed. So i turned it all the way in and it ran much better, but its still happening, which leads me to believe it is too rich?
I ran it without the airbox and it ran better that with it on there but not a significant difference.
It has a new air filter and sparkplug looks good. It was running perfectly this morning with the mikuni on. 
Jetting spec:
Idle jet #40
Main jet #155
Main air jet #200
Idle air jet #75
Choke jet #75
Needle ELQ 4th clip from top, "was on third but ran much worse, the guy that built it said to drop it one more clip to see if that helps, It did help a good bit but still not perfect"
 
other than the spudder at 1/8 throttle and having to have the AF all the way in it runs great. WTF. 
 
I tried to give as much info as possible, let me know if theres anything i missed. 
5a0f736c7246e_fcr1.jpg.ad554eb9737fa1d6ddbd88b9173d77c4.jpg
5a0f736d712ba_fcr2.jpg.e484083a10437ac82c91afa66ff3a96b.jpg
5a0f736e637f8_fcr3.jpg.21bfc9fc0f0a1d3cb5984006690fd982.jpg
5a0f736f4c6d6_fcr4.jpg.c8929d4dcbc2525abd6eb5647704a84b.jpg

What's your location, elevation and average temperature?

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Im in florida, US, sea level. Its typically pretty hot and humid but Its been cold for a few weeks. 

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Im in florida, US, sea level. Its typically pretty hot and humid but Its been cold for a few weeks. 

Personally I would replace the drilled needle and rifled main for new genuine units. The typical recommendation is EMN needle , 45 pilot with 100 air jet and 160 main. It may not be perfect but it should carburate cleanly. Jets R US .com is a good place to order the parts. Just make sure you order genuine pilot and mains and not equivalents just for tuning consistency.
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On 11/17/2017 at 6:37 PM, ohiodrz400sm said:


Personally I would replace the drilled needle and rifled main for new genuine units. The typical recommendation is EMN needle , 45 pilot with 100 air jet and 160 main. It may not be perfect but it should carburate cleanly. Jets R US .com is a good place to order the parts. Just make sure you order genuine pilot and mains and not equivalents just for tuning consistency.

Thanks, ok so you think i should change jetting to this? 

 

Idle jet #40 **45
Main jet #155 **160
Main air jet #200 **100
Idle air jet #75
Choke jet #75

 

 

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or this?

 

 

Idle jet #40 **45
Main jet #155 **160
Main air jet #200 
Idle air jet #75 **100
Choke jet #75

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If your carb has all those 'plates' in it, it is going to run richer than normal and have abrupt transitions as the slide is blocked by a plate the next plate is able to flow. Those plates are designed for a MX bike that is being slowly trail ridden to improve low end response. Personally, I've never seen a need for teh gimmick as a well jetted bike with an intelligent rider finds them more of a hindrance rather than a help.

I second, going to a stock EMN or possibly a EMP needle.

Main air jet 200

Slow Air Jet 100

Pilot 45

Main 155

3X3

75 starter jet or smaller (not at all critical-most FCR's have a 62.)

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*fixed 

 

Dropped the needle down one more time, cleared up everything, it was just running a bit rich I reckon. This thing screams now.

 

Thanks anyways. 

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