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Need base jetting for Big bore, stock carb

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Hi all, been looking for hours, and still don't have a clue what to use as a base setting 

 

The bike is used for commuting, so smooth, cool running in light traffic and highway is the goal, with no excess fuel consumption

 

So I'm looking some settings to start with

 

Please do not start the "get a fcr39 or cv40", I know they are better, but not an option at the moment, so no discussion on that please

 

Specs:

 

- Cylinder works 434cc kit

- Stock carb

  - Stock needle (5DH36), 3rd groove from the top

  - 27.5 pilot jet

  - 142.5 (stock) jet

  - 62.5 air jet

- seal level

- yoshi exhaust with a wire mesh restrictor

- stock airbox without the snorkel

- everything else stock

 

The manual says 165 air jet.. 

 

Here is a pic of the actual jet

 

air jet.jpg

 

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That would be your starter jet(62.5) you say the needle is on the 3rd clip. Stock needle does not have clip positions.are you installing a jet kit?

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140 mj, 22.5 pj, needle on the sec clip, around 3 turns out on the fuel screw

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140 mj, 22.5 pj, needle on the sec clip, around 3 turns out on the fuel screw

 

Hmmm I had 22.5 before, and it started a bit difficult, and there was some poping, and after going 27.5, no popping on decel, and it starts very very easy, so I think I will stick to that

 

Judging from the spark plug, its slighlty on the lean side, and I think this setup will make it even leaner

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Do yourself a favor....To set it up better,install the JD Jetting Jet Kit - DR-Z400S/SM and do the 3x3 mod....

The stock needle is borderline lean..Going richer on the pilot circuit is helping to cover a lean needle circuit..

A 22.5pj with extended fuel screw will be fine in the majority of cases when a jet kit needle is used..

A bigger main jet will also be needed here

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Well I checked JD earlier, but it comes out at $105 including shipping, and it feels kind of steep when I only need a needle and a couple of main jets to play with

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Well I checked JD earlier, but it comes out at $105 including shipping, and it feels kind of steep when I only need a needle and a couple of main jets to play with

 

Unfortunately the adjustable needles can't be purchased separately for these Mikuni carbs , so the jet kit companies kinda have you "by the balls" in this respect 

Edited by Craig-o

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You would want the Blue needle from the JD jet kit....

Maybe someone that lives and rides at higher altitude (which would be using the red needle from the kit) could donate or sell to you the blue.?

 mikuni main jets can be purchased separately 

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Hmmm I had 22.5 before, and it started a bit difficult, and there was some poping, and after going 27.5, no popping on decel, and it starts very very easy, so I think I will stick to that

Judging from the spark plug, its slighlty on the lean side, and I think this setup will make it even leaner

big bores want to run leaner. Some popping on decel is normal. Getting a jet kit takes all the guessing out of the jetting.. Well at least most of it :)

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Well I checked JD earlier, but it comes out at $105 including shipping, and it feels kind of steep when I only need a needle and a couple of main jets to play with

In my case(the DJ kit) I used only the needle and spring. My bike, stock cylinder/valves/cams, full jardine (LOUD) exhaust, runs like jack-the-bear with great throttle response(25pj). My only complaint is that I can't loft the front end easily but I'm not spending the $660+coins for a FCR just to do that.

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Yeah, you need an acceleration pump carb, with mechanical activation slide for that

 

But I think thats the beauty of the stock carb in the DRZ, its so easy to ride, the vacuum carb helps in the street

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Judging from the spark plug, its slighlty on the lean side, and I think this setup will make it even leaner

 

Good luck reading a spark plug while using modern fuels.

 

 

A bigger displacement sucks in a bigger gulp of air.  The extra velocity through the venturi creates a greater pressure drop than the stock 400cc.  The greater pressure drop in the venturi will allow more fuel to be pushed from the float bowl into the air stream making it richer.  So to get the correct amount of fuel the jet has to be smaller than what was correct without the big bore.

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Its running lean at steady throttle (like 70 mph), you reckon I should move the needle clip, or go 1 up in main?

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Its running lean at steady throttle (like 70 mph), you reckon I should move the needle clip, or go 1 up in main?

 

You said you have the stock needle...?...No clip adjustment...

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Ok...,I see, ...you are in Greece... your EU model does have an adjustable needle(5DH36)..USA needle code is 5DH37 which has no clip adjustment ....

 

Your stock needle clip position is clip 2,... clip 3 is one position richer than stock...this is where you are set now.?

 

Try going another clip lower to P4, 

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