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04 LTZ400, Athena 435 Big Bore, Kibblewhite HD Valves, HotCams Stage 1, FCR39MX, Yoshimura Full
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Discussion Starter · #1 ·
I’ve Searched Guys! I can’t seem to find anyone with my set up and everyone seems to have a different version of the FCR39 than me. So I figured I’d post my set up and pics so hopefully you guys can help me out.
04 LTZ400
Athena 435 BBK w/ Titanium Valves + HD springs.
Port & Polish
Hot Cams Stage 1 (New Style) HD chain
DRZ extra thin gasket .08”
I think I’m running around 12.6:1 compression with that.
Trail Tech FlyWheel
Full Stainless Steel Yoshimura Exhaust
400ex Boot w/ K&N Air Filter
ProCom 8 Map +2000RPM
FCR 39 MX
Main jet 168
Pilot jet 35
Needle position ???
Slow jet ???
Elevation: California 200-500ft
I feel like it’s never been set right and has always popped on deceleration.
I just rebuilt the engine and gonna do the whole break in process again with new rings and shiny polished piston so my goal is to get the Carb close to set up so I can dial it in from there, so I don’t Fry My Piston from it being so outta wack lol
Thanks guys I appreciate any help!
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Well, if it pops with a 35, throw a bigger pilot in, lots of 48's being used around here. Exhaust leak will make it pop as well..
 

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04 LTZ400, Athena 435 Big Bore, Kibblewhite HD Valves, HotCams Stage 1, FCR39MX, Yoshimura Full
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7 Posts
Discussion Starter · #3 ·
Well, if it pops with a 35, throw a bigger pilot in, lots of 48's being used around here. Exhaust leak will make it pop as well..
What about the other jet numbers and positions?
and I hear people talking about closing off the air jet? And adjusting the accelerator pump I hear people do too but what difference in effect I’m not sure?
I wanna take care of everything I can while it’s off the bike
 

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What needle do you have? Not sure about the air jet. My leak jet broke trying to remove it, so I plugged it, resulting in more fuel on the pump squirt, seems to work fine though. Some wire the ac pump to the throttle so there is no delay for the squirt. Very popular mod.
Here are some settings from a buddy with the old slant style, looks like yours..
Carb Type: ---> Old Style Slant FCR 39
Main Jet: ---> 165
Pilot Jet: ---> 45
Fuel Screw: ---> 2 turns out
Needle: ---> NCVQ 3rd clip
Airbox: ---> None
Intake:---> Fuel Custom Intake from TRX450 (older)
Pipe: ---> Yoshimura RS-3
Engine Displacement: ---> 434cc
Cams: ---> NSHC
CDI: ---> Dyna FS Non Programmable
Altitude: ---> 0-1500 feet
 

· Registered
04 LTZ400, Athena 435 Big Bore, Kibblewhite HD Valves, HotCams Stage 1, FCR39MX, Yoshimura Full
Joined
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7 Posts
Discussion Starter · #5 ·
What needle do you have? Not sure about the air jet. My leak jet broke trying to remove it, so I plugged it, resulting in more fuel on the pump squirt, seems to work fine though. Some wire the ac pump to the throttle so there is no delay for the squirt. Very popular mod.
Here are some settings from a buddy with the old slant style, looks like yours..
Carb Type: ---> Old Style Slant FCR 39
Main Jet: ---> 165
Pilot Jet: ---> 45
Fuel Screw: ---> 2 turns out
Needle: ---> NCVQ 3rd clip
Airbox: ---> None
Intake:---> Fuel Custom Intake from TRX450 (older)
Pipe: ---> Yoshimura RS-3
Engine Displacement: ---> 434cc
Cams: ---> NSHC
CDI: ---> Dyna FS Non Programmable
Altitude: ---> 0-1500 feet
Awesome! I was looking for a guideline like that.
I just removed my needle and it’s OCEMP 5th clip from the tip. Or is it measured from the butt of it?
I don’t see any OCEMP needles listed anywhere.
I keep seeing people talk about the NMN needle being the “good all arounder”
 

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You could try lowering the clip to richen up the low/mid range, but I would start with the pilot.
 
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