FCR MODS

mat46 · Nov 18, 2005

Hello Guys,
My name is christos and i come from Greece.
To tell you the truth i am not riding a Berg although i would love to. I the Berg 650sm at a test ride in the Motorbike show here in Greece last year and i lost my mind. The bike pulls like a bull!
I ride an Lc4 620 sm with some mods on.
The reason for my post here is the FCR. I placed an FCR39 to my bike (the bike was a 400cc in the beginning) and since i took a 620 motor i am trying to jet this thing properly. Looking over the net i found your site and the posts made by Taffy and cookeye regarding the bore of their FCR from 37/39 to 41mm.
At the moment i ended having the FCR jetted as follows:
OCEMR#4 - main:185 - Pilot:48 - PAS: 1 1/2 - MAJ:200 - PS: 2. 1/4
THe bike runs good although it has some exchaust backfiring at closed throttle and a bit missing top end.
I saw a post at the net where a guy went to the dyno with a 450 smr and made two dyno runs 1.with fcr39 and 2.with fcr41
The power curve goes up almost the same from lows to mids BUT on the top end the difference is around 5hp.
I believe that this carbs have plenty of room to modify. The problem is that those who know don't like to share information.
Anyway i want to welcome myself to this forum - if i am welcomed from you - and i am looking forward to hear from you.

Thank You
mat46

Taffy · Nov 19, 2005

Mat 46

i would think that the MJ could go from 185 down to 160-165 no problem.

the PJ could come down from 48 to 40 no problem either. if you get a flat spot off idle and you have tried turning the PS out and out and out again and still you have it-you must change the needle to an EKP. PAS would come down with that 40PJ to 1/2 turn out.

infact 1.5 turns on the PAS was way over anyway!!!

WE SHARE information at UHE but your post doesn't recognise this. that's a shame? maybe you think that of others?

it would be nice to hear back from you. most short-term-members don't even bother letting us know how they got on.

you won't find 5 BHP at the top end of a husaberg because we have the 'sock' or 'boot' behind the carb which is very restrictive!

there Mat! is that help?

regards

Taffy

mat46 · Nov 19, 2005

Hey Taffy,
Thanks for your reply.
I will try to answer to some of your statements:
1. I use a 185 main cause i ride sm and i use the keihin air velocity bellmouth - no airbox connected)
2. My carb came stock with an 48 pilot and i read at a "FCR Jetting Guide" that the 48 = to 110-125 Air Jet = 1 1/4 - 1 1/2 turns on air screw.
3. Is is possible to place at FCR generation 1 a choke?

I dont know what to do. I am thinking of selling it and go for the FCR 41MX, but it is a bit expensive

mat46 · Nov 19, 2005

ohhh,
i also have another question taffy. Can i place the mount adapter from the 41? Not the one from the airbox side. The Front one? The one which is connected with the head gasket of the bike.

Taffy · Nov 19, 2005

the PAS to PAJ ratios are set by keihin at the following:

1/4 turn -= #45PAJ
3/8 turn out = #55 PAJ
1/2 turn out = #65 PAJ
5/8 out = #75 PAJ
3/4 turn out = #85
7/8 turn out = #95
1 turn out = #100 PAJ
1&1/8 = #110
1&1/4 = #120
1&1/2 = #125

these are keihins figures and therefore indisputable.

however the PA to PJ ratio was designed by me on thumpertalk back in 2001. so in the end i picked where the right ratio should be as;

1/4 turn -= #45PAJ 35PJ
3/8 turn out = #55 PAJ 38PJ
1/2 turn out = #65 PAJ 40PJ
5/8 out = #75 PAJ 42PJ
3/4 turn out = #85 42PJ
7/8 turn out = #95 45PJ
1 turn out = #100 PAJ 45/48PJ
1&1/8 = #110 45/48PJ
1&1/4 = #120 48PJ
1&1/2 = #125 48PJ

as you can tell it becomes less important the bigger the PA gets and the PJ get. i won't argue with my own testing!

but that 48 can run from 1-turn out onwards and up. your bike will need to be 170+5?MJ with an open velocity stack. the PJ i can't say for sure because i've never run an open engine.

the choke hole is blocked off, i haven't checked whether the circuit is still there if you were to drill down the hole (situated next to the PJ and the MJ under the carb) even though scoots carb was completely (broken) dismantled by me.

use your APJ to start the bike with dozens of tiny squirts on the minimum setting recommended. remember to always set your PS with a few snap-wheelie tests when it's warm.

regards

Taffy

mat46 · Nov 19, 2005

You dont know taffy if the mount adapted of the 41 will fit in the 39?

Taffy · Nov 19, 2005

i don't really follow you?

the stub of the carb will fit in the rubber still? indeed it is better suited to being a 41 than a 39.

regards

Taffy

mat46 · Nov 19, 2005

sorry i will try to explain

the back side of the carb connects to the airbox and the front to the engine. The generation 1 fcr have screw adaptors for the front side of the carb. Long and short ones. Can i use a 41mm instead of the 39mm that i have on?

mat46 · Nov 19, 2005

This is what i mean

http://www.taunus-biker.de/~mdvp/Vergaser/Keihin.gif

part number 125

The fcr39 has ones sized around 40mm
The fcr41 has one sized 41.5mm
Can i place this one on the 39?

Regards

LINEAWEAVER · Nov 19, 2005

mat46 said:
sorry i will try to explain

the back side of the carb connects to the airbox and the front to the engine. The generation 1 fcr have screw adaptors for the front side of the carb. Long and short ones. "Can i use a 41mm instead of the 39mm that i have on?"

Yes.

Dale

mat46 · Nov 19, 2005

I went to my keihin dealer on friday to pick one and he gave me a 41.5mm (the short one). He also had a 42.5mm but it was the long one and he suggested the short one for more rapid fuel delivery. I unscrew mine this morning in order to fit the new one and unfortunately it doesnt fit. It seems to be big and it doesnt fit in order to screw it.
So i suppose that he gave me a wrong part or it doesnt fit at all

LINEAWEAVER · Nov 19, 2005

To the very best of my knowledge Keihin does not offer a 41.5 or 42 carburetor.

http://www.sudco.com/keihin.html

If you are refereing to "spigots" from earlier model FCR then the 39 and 41 are indeed different.

Dale

Taffy · Nov 19, 2005

ok mat

i've got you now!

first of all i consider the bit facing the airbox to be the front and the bit that goes against the head to be the back.

secondly, the carb is only actually 39mm directly under the slide. both infront and behind the slide it is slightly larger.

indeed i put this question a few months ago dale?

there is no point in buying the screw in stub unless you bore the carb out and keep the ratio the same. the bore of the stub has to be off centre as well just to make it a real bitch!

unmless you have an engineer mate it isn't worth boring at an engineers and pauing full retail.

your 39mm carb will be as much as 40 infront and 40 behind and when you go to 41mm those figures whould go = 2.0000mm as well.

go for the shorter stub so that the stack can be the right length and "line up the air".

regards

Taffy

mat46 · Nov 20, 2005

Just a minute guys cause i think that we went really confused. i will post pictures as an attachment in order to make things clear.
I will post my carb and the two mount adaptors that i have.
1. The long one is the stock one from my carb (a bit destroyed - i will replace it)
2. The short one is the one from the fcr41 with an opening of 41.5mm
3. My carb

Regards

Taffy · Nov 20, 2005

but i'm no longer confused?

what i've said in the above post is still valid.

you still have to bore off centre, you still go 39.5-39-39.5 on your carb and you'll still need to go up exactrly 2mm everywhere when you machine it!

41.5-41-41.5.

ok?

regards

Taffy

LINEAWEAVER · Nov 20, 2005

Taffy said:
but i'm no longer confused?

My dear friend,
You are very confused, as am I, simply not regarding this particular subject.

Not confused, Indeed! :lol:

Best Regards,
Dale

Taffy · Nov 20, 2005

:lol: :lol: :lol:

Taffy

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