FCR Woes

Alright, so, I installed the FCR a few weeks ago but it had I suppose what would be described as a hanging idle (as I have read a number of people experienced as well). It wasn't much of a big deal, but enough to irk me at every fluctuation of RPM at idle that I decided to buy some carb cleaner, pull the carb, spray it's innards, and adjust the position of the flexjet fuel screw as it seemed to be difficult to turn.

 

While I had the carb off the bike and after draining the float bowl, I was curious to see the AP squirt in action. So, holding the carb in my left hand, I turned the throttle wheel and to my surprise, a stream of gasoline hit me dead in the forehead... :facepalm: . This brings me to my first question, how much squirt should the AP squirt squirt, if an AP squirt could squirt? Seriously though, how much squirt should this thing be squirting? :rolleyes:

 

Anyway, in the process of cleaning the jets and the float bowl, some cleanser came in contact with the float bowl gasket, thereby causing it to distort ever so slightly (caused expansion of the rubber). I still was able to seat it properly when closing the float bowl (with no signs of leakage when refilled with gas). After some more sprays with the carb cleaner and adjusting the fuel screw (and moving the clip back to position 3 on the needle from position 4) i reinstalled and started the bike. I got the idle to to rest nicely, or so it seemed, at about 2.75 turns out on the fuel screw and my problems had seemed solved. Nope. Still have a hanging idle. Turned off bike and went to bed. Started it up again this morning and it seems the problem only worsened overnight somehow. Crappy idle, stalls when i crack throttle open. Starting to get pissed.

 

I ordered a new float bowl gasket and a Merge Racing Fuel Screw to replace the FlexJet and I also plan on removing the pilot/slow jet and main jet and giving them another round of cleaning/inspection.

 

Can anyone offer some insight as to wtf i need to do to fix this problem? If replacing the fuel screw doesnt to it then I don't know what will....I'm about to sell this thing and go back to Mr. Mikuni, a.k.a Ol' Reliable if I can't solve this issue soon...especially with ideal riding weather being just about in full effect.

What is the history of the FCR?  New? Used?  Slant body?  MX type?  If your carb leaner swelled the bowl gasket it likely swelled the the inaccessible body seals as well.

 

How is the carb set up?  Fuel jets, air jets, CE status, etc

 

Normally the AP squirts right in the right eye. Volume and duration depend on the carb style and modifications to the linkage.

Right, but the idle circuit shouldn't be affected by clip position.

In theory you are correct.....however when you rev the bike your off idle is changed when the needle was changed.

As far as idle goes it sounds to me as its too lean...fuel screw kinda loses effect after 2.5 turns as you know.  

What are your jet and bike specs?

Was it new or used. Curious.

What is the history of the FCR?  New? Used?  Slant body?  MX type?  If your carb leaner swelled the bowl gasket it likely swelled the the inaccessible body seals as well.

 

How is the carb set up?  Fuel jets, air jets, CE status, etc

 

Normally the AP squirts right in the right eye. Volume and duration depend on the carb style and modifications to the linkage.

 

At least its squirt is properly squirting...I was an inch away from being blinded lol.

 

FCR MX purchased new with all necessary adapters from the TT store about 8 months or so ago. Jetted per TT recommendations for sea level with open pipe w/o-ring mod

Edited by KnowUrEnemy

I would put the 100 pilot air jet in and try that with a 45 pilot fuel jet assuming the hanging idle is not a cable problem.

 

Squirt is adjusted with linkage and leak jet if you decide to fool wit that.  Should not have any affect on idle.

In theory you are correct.....however when you rev the bike your off idle is changed when the needle was changed.

As far as idle goes it sounds to me as its too lean...fuel screw kinda loses effect after 2.5 turns as you know.

What are your jet and bike specs?

160 main

200 main air

Emn clip 3

45 pilot

Removed pilot air

Flexjet fuel screw

K&n filter

MRD ssw

I agree with noble, put in a 100 PAJ..If you don't have...then try a 48 pilot jet.  I have my PAJ removed and have been between a 48 and 50 PJ and I live a 8K....

I think your K and N might like the 48 pilot also.  Heck that 160 even sounds lean with the pipe ...did you say Cams and BB?  

I agree with noble, put in a 100 PAJ..If you don't have...then try a 48 pilot jet. I have my PAJ removed and have been between a 48 and 50 PJ and I live a 8K....

I think your K and N might like the 48 pilot also. Heck that 160 even sounds lean with the pipe ...did you say Cams and BB?

I'm gonna try with the 100 paj first then maybe a 48 pilot jet. I was actually going to order a 48 pj and 162 or 165 main along with the new gasket too but removed them from my cart before ordering because I didn't want to spend the extra 15 bucks lol. Ugh.

Seemingly silly question, but the pilot air jet would only affect the air flow in the pilot circuit, right? I mean the name seems self explanatory but I'd rather ask and sound silly than not and do something silly.

Edited by KnowUrEnemy

Be careful with the carb clean. there is an oring between the upper float bowl and the carb body that cannot be replaced. After spraying carb clean thru there, I would flush out with wd40 to make sure you don't damage the oring. I would try the 48 pilot and check for air leaks.

Edited by james509

Yep, The air jet mixes air with the fuel after it comes thru the pilot jet and before it sucked into the carb bore. The bigger the air jet, the leaner the mixture.

 

    Somehow I messed up your quote below..  Should be on top.


Seemingly silly question, but the pilot air jet would only affect the air flow in the pilot circuit, right? I mean the name seems self explanatory but I'd rather ask and sound silly than not and do something silly.

Edited by james509

OP...Your initial issue could have been an air leak, On a new carb, feel the carb cleaner is somewhat over reacting.......

You want the squirt to just miss the slide and duration of around 1 to 1.5 seconds...o ring should have that sorted...

Be careful with the carb clean. there is an oring between the upper float bowl and the carb body that cannot be replaced.

Wow! So if that ring fails, time to bin the carb?

 

What are the symptoms of its failure?

 

Is it sensitive to ethanol?

OP...Your initial issue could have been an air leak, On a new carb, feel the carb cleaner is somewhat over reacting.......

You want the squirt to just miss the slide and duration of around 1 to 1.5 seconds...o ring should have that sorted...

 

Like Craigo said, your bog is caused by the AP.  It is usually spraying too long and too soon.  I also bought my FCR from the TT store and fought throttle response problems when I first installed it in the bike.  Take it back out, fill the bowl with fuel, turn the throttle wheel quickly (with a screw driver or something) and watch when the AP squirt happen.  It needs to miss the throttle plate.  The screw that you wrap the o-ring around for the o-ring mod is the timing adjustment.  I had to move this quite a bit to get the squirt to not hit the throttle plate.  

 

Also, while you have it out, I highly recommend the Merge Racing AP spring.  Its a bit of a pain to installed (removing the AP pushrod from the cam takes a bit of finesse) but then you don't ever have to worry about o-rings snapping again.  Those two things 'fixed' my throttle response.  It runs so well in fact I can, when the engine is warm, free rev without any hint of a bog.

 

As for your hanging idle, check your throttle cables.  I know, I know, I'm sure you have.  But try this experiment just for fun:

 

-remove 'return' cable from carb

-remove 'return' cable from throttle assembly on the handlebar

 

I'm willing to bet the return cable is binding just a bit, not allowing the throttle wheel on the carb to return to its rest position fully.  I found it quite difficult to get this adjustment done properly because of how the cable brackets are designed on the FCR.  My solution was to just run the one cable, but I'm more than a little OCD when it comes to throttle feel.  

 

Also, I'm fairly certain that the Merge Racing fuel screw will not fit on your bike, not enough clearance between the carb and the starter motor.  The flexjet you have is where its at.

Edited by Nightwraith

OP...Your initial issue could have been an air leak, On a new carb, feel the carb cleaner is somewhat over reacting.......

You want the squirt to just miss the slide and duration of around 1 to 1.5 seconds...o ring should have that sorted...

So With throttle wheel/slide completely open, the squirt should cut itself of at 1-1.5 sec and just miss the slide... If this needs adjustment, is the screw upon which the orings are attached for the "oring mod" the way to do that?

So With throttle wheel/slide completely open, the squirt should cut itself of at 1-1.5 sec and just miss the slide... If this needs adjustment, is the screw upon which the orings are attached for the "oring mod" the way to do that?

 

Yes.

Edited by Nightwraith

I'm in a similar situation. I bought this freakin $600 carb and it ran better with CV. Very disappointed in this mod.

Squirt is adjusted with linkage and leak jet

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now