tuning a 39mm FCR Carb

[duneracerweston]

80% finished, ive got the majority of the bog fixed and its runs like a champ, just the normal jetting now, i need to bump the pilot up a size and it will be perfect, then ride it and plug chop it and im done tuning it!

set up as it sets
52 pilot
185 main
bottom notch of the moose racing needle
3.5 rounds out on the a/f screw.

here is how it runs now.

(tinny bog due to the under sized pilot.)

http://www.youtube.com/watch?v=qhD1JUIcMWI&feature=g-upl

 

[88WarriorBoy]

dang sounds like the 39mm FCR could be in my future

 

[Gen1Pat]

dang sounds like the 39mm FCR could be in my future

Dude you have NO IDEA! And I couldn't get the bog out, and it was a rocket! Sounds like a q-jet with all the air it sucks in

 

[DeadLastRacing]

I'm pricing one out now.

 

[duneracerweston]

dang its off on jetting.. the pilot is lean but the main may be close, it doesnt have a rev limit, thats jetting related, ive got most of that out by jetting up to the 185 main but its there still, im gonna try the e3 plug from walle in it next and see if it smooths it out any, thats gonna be my next step, i got a dd course tomorrow in town and ill get the jets i need then.

 

[duneracerweston]

swapped it to the e3 plug and its not as far as i thought, the main is reading spot on with the 185 and e3 plug, the pilot is a minimum of one size to small, im running by yamaha tomorow and will grad the next 3 sized up pilot jets to be sure then ill have it finished jetted and then im done.

 

[duneracerweston]

the last pass is the only WOT part of the vid

http://www.youtube.com/watch?v=cpBQ6WPlGLk&feature=g-upl

 

[88WarriorBoy]

dude nice vid of you burnin the tires off with blackie and the fcr

 

[duneracerweston]

this one? i just did that tonight!!


http://www.youtube.com/watch?v=dETMpSJXf-M

 

[88WarriorBoy]

Yeah lol I saw it about a half an hour ago

 

[DeadLastRacing]

that dog is not to happy about it all.

 

[duneracerweston]

It didn't like it when I grabbed6th, it would wind out in 5th but not enough in the head to hold 6th

 

['00 WO-YA!]

I still wanna see a real deal balls to the wall pass man, quit ****** around on us bro!!

 

[duneracerweston]

I still wanna see a real deal balls to the wall pass man, quit ****** around on us bro!!

Ight, I got a couple jets today, ill swap em out and run it, should be able to get a video tomorrow

 

['00 WO-YA!]

Cool deal, Weston, glad that carb is coming around for ya!

 

[duneracerweston]

well it decided it was going to poor down rain all night last night, so no video today.

on a side note did some tuning last night, and found out that a 58 pilot is tomuch and a 52 is to small so a 55 should be dead on!

 

[duneracerweston]

CONCLUSION:

a good base line for jetting a 39mm FCR is,

52-55 pilot
3rd from the bottom slot on the needle
180-182 main.

variences in jet sizing is do to the variation of mods on each persons macine but thats roughly what you need to get it close.

the bog nevver fully left, but it feels like its to much carb and not enough cam to let it breath. or use a aftermarket accl pump ( have yet to try one and i think i will with walle if it does not perform like it should) the bog was only there till around 1700 rpm and then it would vanish and you could stab it, so its really not that bad. my mikuni bogs till around 2000-2500 so this is a leap forward! DO NOT let the bog i mentoned scare you! i only got to fiddle with it a little hear, a little there, i got it close and called it quits due to the fact that i am behind in my work and collage so if you tune with it some more im sure it can be solved! you can also just roll into the throttle and there is no hesitation or bog, it is only when you stab the throttle to WOT that it will bog at those low rpms.

i would recommend this carb to anyone looking for a power gain and a decent priced carb.

over all i give it a solid A- do to the pain it is to pork with if you have a raptor clutch conversion on the machine.

 

[warriorgirl09]

maybe a 37mm fcr would be more practical for a warrior? could always get a K&N Air/Fuel Monitor to help in the tuning till you get it set up and running right

 

[bones]

yeah i was thinking about the 37mm fcr as well

 

[duneracerweston]

The37 would be good for a stock motor, the 39 would be best with a built motor