Idle issue with FCR

I've been having an idle issue with my Bigbore/FCR install since I installed it.

It will start up fine in the garage no choke most of the time unless extremely cold. I let it run with the choke on for a few minutes, it will shoot up to 3-4k, then I let off the choke and it drops down to about 1800-2000 rpms.

When it gets warmed up more it will drop down to 1200-1300rpms and want to die, I adjust the idle adjustment to get around 1800 rpms where it's most happy, then it warms up more and will shoot to 3k+, so I adjust it back down and then it will want to go even lower. It does this ALOT. Once the bike is fully warmed up and ridden for awhile there isn't any issues. Only for the first 10-15 minutes.

tl;dr idle doesn't stay in place.


155 main jet

200 main air jt

EMP needle

clip 3

45 pilot jet

no pilot air jet

2.25 turns fuel screw

ap link wired

delayed 1/2 turn

SSW sent it with a 160, I just put in a 155. It did this when I had a 160 in there.

did you pull out the slide and put the plate on upside down?

did you pull out the slide and put the plate on upside down?

huh? (five characters)

main jet has nothing to do with idle.

did you at any point have the slide out of the carb?

main jet has nothing to do with idle.

did you at any point have the slide out of the carb?

Yes, main jet deals with high throttle, but I thought I would mention it.

Slide, do you mean throttle valve? The only thing I've done internally is change the main jet.

changed the oil recently?

changed the oil recently?

I've changed it 2-3 times since I did the big bore. It has about 1k miles on it now.

did this behavior suddenly start?

did this behavior suddenly start?

Only after I did my big bore and installed the FCR at the same time.

have you done the fuel screw setting procedure?

have you done the fuel screw setting procedure?


I just went out for the first time in a week or so to pay close attention to it in traffic. I set it to about 2200-2500rpm since it will die if I go lower when it decides to low idle. It goes down to 1200 rpm, up to 2700-2800 every other stop light.

sounds like it has a vacuum leak to me.

How do I go about testing it?

Is carb connected to intake rubber 100% correctly.?...double check..

Is carb connected to intake rubber 100% correctly.?...double check..

I'll double check, I just know the carb was a PITA to get on.

I'll double check, I just know the carb was a PITA to get on.

Agreed, it is that. And, knowing that, it's quite possible you didn't get the rubber boots entirely in place. The back one is especially difficult for me to see if it's in place properly. Might check that.

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