Ok, I feel like I noob (FCR Carb)

[flyboy1294]

It's embarrassing that I have to ask this. I had my old 400ex's carb down to a science before I got rid of it.

Anyway, I have this FCR carb on it now from a CRF450R. This thing doesn't make sense. I need a 48 or 50 pilot with 180 or 185 main for my setup. So I figure you know, no big deal and went to order them

Well anyway, there are adjustable accelerator pumps, needles, pilot jets, main jets, and something called an 'air jet.' for these things.

Can someone please translate this? When I need a low end jet, do I get the pilot jet? And wtf is an air jet? :huh

Thanks guys

[eastside 400]

you pretty much answered it yourself, its still a pilot jet like any normal carb, same with the main jet. The air jet is probably the leak jet that screws into the fuel bowl, it controls the amount of fuel that goes into the accelerator pump circuit

[flyboy1294]

Originally posted by eastside 400
you pretty much answered it yourself, its still a pilot jet like any normal carb, same with the main jet. The air jet is probably the leak jet that screws into the fuel bowl, it controls the amount of fuel that goes into the accelerator pump circuit

Ah, I see.

So is the 'air-jet' a major contributer in getting this thing dialed in? Like, and I going to get dead spots in the throttle that I won't be able to resolve without trying random air-jet sizes?

[lasher45]

The air jet is not a huge part of the jetting, unless your critical about dialing in your jetting I'm pretty sure that it does not make a huge difference. I'm pretty sure too that it has an effect on 0-1/2 throttle.

[OutlawBill]

air jet and pilot jet are on the same circuit 0 to 1/4 tthottle you can make 99% of your adjustment with the pilot jet. now the adjusting the accelerator pumps too much to cover check out the how to section of http://www.thumpertalk.com (http://www.thumpertalk.com/forum/showthread.php?t=309069)

[flyboy1294]

Alright thanks guys.

One last thing,
is adjusting the accelerator pump a necessity when it comes to jetting a FCR carb? I have no experience with such a thing

[eastside 400]

if you have a bad bog off idle then yes it is. the off idle bog is the hardest things to get rid of with the FCR's but with some research its pretty easy