Keihin fcr carberator tuning tips

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PineyPower

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Getting myself a keihin fcr 39mm carb to support upcoming engine mods, just putting a little feeler out for tuning tips, upgrades, tricks, etc. from anyone else running one.
 
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Looked it up, that's a nice peice. Got any recommendations for jets? Not necessarily size because i know everyones got a different set up but even just a decent brand to trust?
 
+1 for the power bowl. It makes tuning the power jet very easy.

Stick with Keihin brand jets. Others vary and aren't consistent in size.

For parts
https://www.keihin-fcr.com

I met the owner once. He sells genuine Keihin parts for every part he can.

Couple tuning write-ups I found very helpful. Two are other forums, so don't know if it will stay posted.

https://www.braigasen.com/fcr_tuning.htm

https://www.yfzcentral.com/threads/the-mother-fcr-tuning-info-thread.129065/

This one has alot of knowledgeable members on the FCR. You can search the forum and find alot of info.
https://www.thumpertalk.com/
 
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Some damn useful info!
Any jet sizing guestimations for where to start? It's probably safe to assume the stock jetting for a 450 is gonna be miles off. I was thinking of getting a variety pack kinda kit for jets but holy hell there's over 100 for just the mains on that fcr site.
Ultimately I'm gonna use a wideband o2 to help me dial it in but a little extra help where to start is super appreciated!
 
Some damn useful info!
Any jet sizing guestimations for where to start? It's probably safe to assume the stock jetting for a 450 is gonna be miles off. I was thinking of getting a variety pack kinda kit for jets but holy hell there's over 100 for just the mains on that fcr site.
Ultimately I'm gonna use a wideband o2 to help me dial it in but a little extra help where to start is super appreciated!
Where you at in jersey ? I was just thinking about getting yhe dynojet stage 1 , 2 kit there like 90$ look it up cause I'm getting ready too tune my 39mm fcr on my warrior kayden komraus friend me on fb we can bounce jetting off each other
 
I'm actually not on social media, but if you PM me here I check I often enough
Edit: oh **** you are right down the road from me
 
Some damn useful info!
Any jet sizing guestimations for where to start? It's probably safe to assume the stock jetting for a 450 is gonna be miles off. I was thinking of getting a variety pack kinda kit for jets but holy hell there's over 100 for just the mains on that fcr site.
Ultimately I'm gonna use a wideband o2 to help me dial it in but a little extra help where to start is super appreciated!
48 /175
 
Got it in the mail, it's nice and clean and even came with some extra jets to play around with, im quite happy about that. I do have a few things, firstly there's a bit up near the choke looks like it's missing a piece20240710_201420.jpg
I've seen in pictures it has a plastic cap but otherwise it's a big ol shoulder shrug.
Secondly this didn't come with any of the many many hoses and even if it did, I don't know what's supposed to go where. Is it prettymuch all vents or do some have to go to vacuum?

20240710_201623.jpg
20240710_201725.jpg
 
I think one of the articles I posted show the vacuum tube orientation. But all 5 of those are vents. You run 5 seperate vent tubes.

On mine from a YZ450F, that pic you have is the hot start, and choke is on the side of it in the other port. Hot start looks like a cylinder with a o-ring. Your plunger is broke off in it. Try to let it soak in a penetrant oil, and see if you can get it to wiggle out.

This is what was in there
1000003952.jpg

If your going to soak it to clean it, try soaking it in whatever method your cleaning it before taking it out. Personally, I've been nothing but happy with boiling or using a ultrasonic cleaner. Chem-tool carb dip is what I used years ago.
 
Oh alright I see the bit that broke there. It came with the metal elbow and the rubber boot too I figured it was something for the throttle cable. Weird the pictured I've seen have that capped off, I guess it was optional depending on what the carb came off. The nice thing about this carb is they used it in a **** ton of completely different machines
 

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