jetting a fcr 43mm carb

M

matt69

Joined Apr 2007

66 Posts | 0+

Perth West Australia

Discussion Starter
• Jan 13, 2009

• #1

Hi all
as you may or may not know i have bored out my 41mm fcr to a 43 mm and the problem I'm having is that at a constant throttle opening i am experiencing a slight miss
siting at 3800-4000rpm at about 1/8-1/4 throttle and the miss seems to happen every 10 seconds or so
any idea ? . to rich or to lean ? :?:

 

husabutt

Joined Feb 2003

3K Posts | 384+

Escondido, Ca. USA

• Jan 13, 2009

• #2

As you decreased the venturi signal by going big I would say that all circuits should probably need to be richened up a bit.

I would start by raising the needle.

 

M

matt69

Joined Apr 2007

66 Posts | 0+

Perth West Australia

Discussion Starter
• Jan 14, 2009

• #3

I have richened all circuits considerably and it goes very well how ever ther is that small glitch in the fueling at a consonant throttle that is what i was asking about. to rich or to lean see first post

 

husabutt

Joined Feb 2003

3K Posts | 384+

Escondido, Ca. USA

• Jan 14, 2009

• #4

At 1/8 to 1/4 throttle you are on the straight part of the needle. Was the needle changed to a richer one when you richened all of the circuits?

 

Taffy

Joined Nov 2001

17K Posts | 774+

Ely, England

• Jan 14, 2009

• #5

drop the needle twice.

regards

Taffy

 

S

sparks

Joined Sep 2006

989 Posts | 23+

Hayle Cornwall

• Jan 15, 2009

• #6

matt69 said:

I have richened all circuits considerably and it goes very well how ever ther is that small glitch in the fueling at a consonant throttle that is what i was asking about. to rich or to lean see first post

Click to expand...

Hi Matt,

Start with the basics my man, what colour is the plug running?.

Regards

Sparks.

 

spanner

Joined Sep 2007

782 Posts | 291+

???

• Jan 15, 2009

• #7

I have my carb bored to 43mm
My latest setup is as follows
Lineraweaver jetting kit
needle 3 from bottom,
148 MJ,
180 air jet,
38 pilot jet,
1 1/4 pilot screw,
7/16 turns adjustable air acrew,

This is very close on my 05 650.
If you can screw the mixture screw right in and the bike still runs
try a smaller pilot jet.
I went from a 48 down to 38 before the mixture screw had any affect.

Not sure if this will be my final setup but is closest so far.

 

Taffy

Joined Nov 2001

17K Posts | 774+

Ely, England

• Jan 15, 2009

• #8

spanner said:

I have my carb bored to 43mm
My latest setup is as follows
Lineraweaver jetting kit
needle 3 from bottom,
148 MJ,
180 air jet,
38 pilot jet,
1 1/4 pilot screw,
7/16 turns adjustable air acrew,

This is very close on my 05 650.
If you can screw the mixture screw right in and the bike still runs
try a smaller pilot jet.
I went from a 48 down to 38 before the mixture screw had any affect.

Not sure if this will be my final setup but is closest so far.

Click to expand...

.....and all your own work right?

:twisted: :twisted: :twisted:

regards

Taffy

 

M

matt69

Joined Apr 2007

66 Posts | 0+

Perth West Australia

Discussion Starter
• Jan 16, 2009

• #9

Ok the plug is black around the edge and white in the middle as for the needle i have a richer one cant remember what it is, i will try dropping it 2 clips as Taffy suggested . Spanner what you have is leaner than i started with accept the main air jet .
I will just have to keep on keeping on until its right. oh Taffy the starter works a treat :?

 

Taffy

Joined Nov 2001

17K Posts | 774+

Ely, England

• Jan 16, 2009

• #10

just go straight to bushie's numbers. the lineaweaver needle will be hard to source now but the EMS is the next best thing. if you'd like me to sort it just let me know as i have everything here.

regards

Taffy

 

spanner

Joined Sep 2007

782 Posts | 291+

???

• Jan 16, 2009

• #11

Matt not sure reading plugs is valid these days as the fuel has changed.
However I have noticed less soot on my number plate and around exhaust outlet with a 38 pilot jet.
I remember the days when a nice light gray colour at the end of the exhaust pipe was a good indication of correct mixture.
Haven`t seen that for awhile.
Are you still running the acc pump?
I am not.

Cheers spanner.

 

M

matt69

Joined Apr 2007

66 Posts | 0+

Perth West Australia

Discussion Starter
• Jun 2, 2009

• #12

HI all
have just changed my jetting it is now MJ 155 needle EMT on middle clip position and 48 pilot , and it doesn't appear to go as well as it did with the EMS. it doesn't pull as strong through the mid range as it did I'm guessing it a bit on the lean dose any one concur with this hypothesis

 

Taffy

Joined Nov 2001

17K Posts | 774+

Ely, England

• Jun 2, 2009

• #13

that has GOT to be a change in the temperature etc because if you measured 100cm from your front wheel, that change of needle can't affect the bike beyond it. i suggest that given a broad area of correct jetting that you were on the extreme edge and din't know it. the change in season etc has tipped it over.

i would have said that the needle needs lifting one. to me, and my views are well known, that PJ is way too high.

regards

Taffy

 

M

matt69

Joined Apr 2007

66 Posts | 0+

Perth West Australia

Discussion Starter
• Jun 2, 2009

• #14

Thanks Taffy it has gotten a lot colder over here, you would be right on raising the neddle but what i will do is go back to the EMS. also Perth is at sea level so have to concider that as well . EMT might have to be a sumer set up ween tep is 30c +
thanks again