yes
but you can install a merge racing adjustable leak jey
and a scary fast power now
and different size volicity stackx
and on the sudco fcr it comes with ever so cool adjustable slow air jet
now you have enough stuff that it will take days to get it in tune

 

All very exciting I suppose-the adjustability saving some time over removing the Mikuni to replace AP nozzles or pilot jets. Mostly non-WOT tuning.

For someone without an a/f meter all those adjustments could just give them a headache (on either carb I suppose). I do often read about how hard it is to jet the FCR properly.

Are you going to do the O-ring mod to the AP? Do you have a choke?

That adjustable leak jet (now discontinued) cost almost as much as your carb doesn't it? People on TT say just buy the correct pilot jet and then you're done with it once the bog is gone-saving money btw.


All things considered, the Mikuni seems to come out on top IMHO; size for size I'll bet the two carbs are equal at WOT.

But do carry on and let us know how it all ends up !


You're almost there and it's good to see new how-to info.

 

first of all the fcr is a very hard carb to jet
second the o ring mod is for winnies they make a spring for that
third you can still get the adjustable leak jet through boisen
the carb new is almost 700.00 the alj is 125 like they say speed cost how fast do you want to go
the correct pilot has nothing to do with the leak jet, the leak jet controls the squirt
I did not know that we were having a mikuni keihin shoot out that was not my intent this is some info for the ones that might want to run a keihin carb
to show it is doable there is a reason that all major manufactures of race bikes with carbs run the keihin fcr
wot is a very small part in the whole performance thing any body with a wide band air fuel ratio gauge can get the air fuel ratio right at wot that is a no brainier getting it right through all operating phases is a different story and you need totaly adjustable to pull that off
I will carry on that is what I do when the carb is set up proper then the whole unit will be removed and port matched to the head and tuned again
I would say for sure that if you want a plug and play smooth bore flat slide pumper the mikuni is your best bet but if you want to tune you need a carburetor that offers all the options you can get your hands on to compensate for the infinite variations that will come up when you start doing engine work.

 

Right! No shootout intended. I thought my last post might have come across as too negative and was going to lighten it up, but you beat me to it.

Keep us tuned in then.

 

Day one of tuning
box full of jets and needles and at the end of the day
have to get more needles and jets
Starting out with a blank sheet of paper.

 

Here is some good info for U fcr freaks out there
A Must Read
If you are going to dink with these carbs
Don't try this at home kids
carbkie.html, Keihin FCR Carb Tuning Procedures

 

Wow that page is a tough read; the author should have invested in more paragraphs and black fonts. I'll paste it into a Word doc and redo it a bit.




I was able to make out the "If you find that the engine runs perfectly at WOT near the torque peak, but becomes lean toward redline - select smaller main air jet" and vice versa part in the Main Air Jet: section.

I've noticed a change in a/f readings now and then (maybe every time?) at upper rpms past the torque peak. Maybe I'll pay more attention to which way the a/f ratio is changing and try to compensate. Though the 36mm comes with no air jet IIRC.


I caught a mention the other day that FCR carbs measure out 1mm different than their advertised size, but forget which way it goes-is yours an actual 34 or 36mm?

 

Here's the graph that wasn't showing up for me on that linked page about how the air jets and fuel jets interact, but I did find it after an image search



This graph is 100% a figment of my fevered imagination, and is only to be used as a general guide, not an absolute definitive end all be all word of truth. That said..

1. air jet way too small
2. air jet a little bit too small
3. air jet just right
4. air jet a little bit too big
5. air jet way too big

 

Richard what air fuel ratio are you running at wot with a load on the motor
Bill.
Yes the fcr runs a little bigger my carb is a 35 but it measures out at 35.7

 

Well I aim for 12.2 with the 10% ethanol that's sold over here, but don't always hit it or fret over it as long as the a/f is at least in the mid 12s or high 11s, because I am always changing carbs etc anyway.