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keihin fcr (non-mx) 39mm carb setup and tuning question

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I recently ordered and installed a fcr 39mm carb on my 06 DRZ. I noticed while installing it that it was different from the fcr MX carb thats in the write up here on thumpertalk. I believe mine to be the non MX version.

First off what are the main differences between the two carbs? Second off I started setting my carb up similar to the thumpertalk write up by pulling the pilot air jet completely out of the carb and I'm having issues with idle (unchoked). It dies off. Chocked it runs but at a very high rpm. Was I correct in removing the pilot air jet completely? Also I can't seam to locate any air/fuel adjustment screws. Where are they located and where should I start to dial this carb in? I can only find the idle screw.

I'm fairly mechanically inclined however ill also admit my only knowledge of carbs and tuning carbs is from nitro RC cars so this is fairly new to me.

Any input is greatly appreciated.

My carb kit that I purchased and installed: http://www.motostrano.com/Keihin-39MM-FCR-Carburetor-Kit-Suzuki-DRZ400-p/016-864.htm?gclid=CKuw6r-ytrkCFY1FMgodyk8AKw

Thumpertalk write up I started following: http://www.thumpertalk.com/topic/562280-fcr-39mx-install-using-the-tt-kit/

I'll try posting pictures of my bike/carb later today.

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Right, not FCRmx.  Called a slant body. There are 2 options for pilot air jet.  100 jet or an adjustable air screw set 1 turn.  You do not remove the air jet in that carb,  Mixture screw willl be underside near where the carb plugs into the boot to the head.

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Right, not FCRmx. Called a slant body. There are 2 options for pilot air jet. 100 jet or an adjustable air screw set 1 turn. You do not remove the air jet in that carb, Mixture screw willl be underside near where the carb plugs into the boot to the head.

What is the differences in the two carbs other then the appearance?

When I reinstall the pilot air jet how many turns does it need to go in? How should the pilot air jet be properly adjusted?

Edited by sumosquid

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That's the suduco kit, I bought the same thing (different vendor though, as ouch on the price on that motostrano kit!)

 

Put the pilot jet back in, it will help your idle. I also tried to remove it on mine, and the bike basically wouldnt idle. It should have an adjustable pilot air jet which works great to help prevent the decel pops / idle mixture once you get it dialed in. 

 

It should have the EMM needle in it, middle clip which works fine for me. Should have come with a 160 main jet and 45 pilot, both were way too rich for me.  I ended up at 150 MJ 38 PJ. 

 

I prefer the slant body, easier to get in and out, and doesn't have all the vacuum hoses everywhere. I only ended up hooking up a single throttle cable from there kit and made a spacer to fill the spot where the other cable should have been.

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A pilot air jet is just a brass jet.  Screw it all the way in.  A pilot air screw is a tapered screw and spring.  Lightly seat and unscrew 1 turn.  SUDCO web sight should have details.

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When I reinstall the pilot air jet how many turns does it need to go in? How should the pilot air jet be properly adjusted?

 

Gently turn the pilot in till it bottoms out, do not force it. How many turns out will depend on what size pilot jet you are running.  

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Pilot mixture screw (or fuel screw) all FCR have one.  Pilot air screw is an option to the pilot air jet only available on the Slant body carb as far as I know.  I would assume your carb came with a pilot air jet not a pilot air screw.

 

Mixture screw in under side of the carb exposed for external adjustment.  Air jet (or air screw) is in the carb air intake. The air bell (adapter) has to be removed for access.

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Yes it has and came with a pilot air jet. I removed it during the install following the only write up I could find here on thumpertalk. How do I go about putting the pilot air jet (w/spring) back in and properly adjust it?

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Gently turn the pilot in till it bottoms out, do not force it. How many turns out will depend on what size pilot jet you are running.

I believe the pilot air jet size is 100. How many turns out would the 100 pilot air jet need?

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A pilot air jet is just a brass jet. Screw it all the way in. A pilot air screw is a tapered screw and spring. Lightly seat and unscrew 1 turn. SUDCO web sight should have details.

awesome. Thank you!

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Go back and read what I wrote.  Pilot air jet - brass jet.  Pilot air screw - tapered screw with a spring on the screw.  There is no spring with a pilot air jet, no adjustment with a pilot air jet.  You have a 100 pilot air jet, just reinstall it.  Do not confuse pilot air with the adjustable mixture screw underside the carb,

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Ok thanks.

When I pulled it out it had a spring underneath it. Its made of brass and it is tapered at the end. Even though it has a spring underneath it, its still a jet correct?

(Sorry for the noob questions. Just trying to be sure I've got it down)

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I screw the pilot air jet back in until it lightly bottoms out correct?

Also are there any performance advantages to one carb over the other? (Slant body fcr vs fcr-mx)

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I think we are confused and possibly not talking about the same thing.  Find the main air jet.  It is a 200. The pilot air jet is next to it on the left. The 100 pilot air jet looks more or less the same as the main air jet.  No springs, no adjustment.  As with any jet, it is tightened securely.

 

Still confused?  Post a picture.

 

Slant body vs MX - no advantages one way or the other that I know of.  There is the theory that an aftermarket FCR fitted to the larger S air boot may have a slight advantage over the E model all original set up.

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Here is a picture of the jet and the spring that was underneath it. The 2nd picture is from the thread I was following. The jet on the left marked pilot jet is the one I removed.

1379990224579.jpg

1379990238422.jpg

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If I may stick my nose in here..lol........ :)

 

You have the adjustable air SCREW in lieu of a fixed jet.......Turn it fully in and out 1 turn....

 

The FcrMX  is an upgrade of the slant body Fcr ,so as you would expect from an upgrade , it is a little better overall

 

EMM will be a tad richer at small throttle openings, see how it runs with it, if it's a bit fat you may need to go with an EMN

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Oh, way cool.  Your carb did come with an adjustable pilot air jet,  Install the screw thing with the spring, seat lightly and back it out 1 turn.  That will equal approximately a 100 fixed air jet.

 

A some point in this thread I thought you said you had a pilot air jet marled 100.  Yes/no??

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I just want to say thank you to everyone who had an input and catered to my noobness. It was very helpful especially for someone like myself with little knowledge about carburetors. I did exactly as you guys said and the bike fires up immediately and holds a smooth idle.

While I had everything apart again I installed a R&D remote fuel screw. So tomorrow I'm onto tunning.

Would anyone have any good tips/input or know of any good threads to read on carb tunning that would relate to my fcr carb?

Edited by sumosquid

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