Hello,

First off, I hate to post yet another question regarding jetting an FCR but I've been reading some conflicting information...

To start, some basic info...

Bike: 2005 DRZ400sm (Full Yoshi TRC Ti, 3x3 mod), riding at sea level (Indiana).
Carb: FCR39 mx with choke and hot start

I'm using a JD jetting kit specifically made for a DRZ with an FCR39mx. The instructions that came with the kit tells me to jet the carb as follows...

For sea level to 4k feet and an aftermarket free flowing exhaust:

- Red Needle 4th clip from top
- 165 Main jet
- 42 Pilot jet
- O-Ring mod

It says nothing about the MAJ or PAJ. The carb came with a 200 MAJ and NO PAJ.

Now, after reading through multiple posts here, I have found most are reccomending the following for my setup...

- Blue needle 4th clip
- 165 Main jet
- 45 Pilot jet
- 200 Main air jet
- Remove pilot air jet
- O-Ring mod

Which is correct, if either? I have also read multiple things regarding the PAJ. As it sits now, there is NO PAJ in the carb. When I intially installed  the carb, I ran into troubles with a hanging idle. I couldn't figure it out at the time, so I removed it and put the stock carb back on. I just recently ran across a thread where someone had the same problem (hanging idle) and fixed it by installing a 100 PAJ. When should you NOT use a PAJ and when SHOULD you use a PAJ? I bougt the carb used so I do not know where it orginally came from, however the previous owner stated he had it installed on his DRZ. The carb looks to be in good working condition as I completely took it apart to clean it and check all seals, ect.

Also, the carb came with a boot to join the motor and the carb, but not an air intake boot. Can I get away with using the stock SM boot or must I get an E model one?

I hope I did an alright job explainging things and sorry to beat a dead horse. Thanks for any help ahead of time!

Pm craigo or Eddie or noble, there are others but those names come to mind

First question is - Is it FCR MX or FCR slant body.  Makes a difference for several reasons.

Is the JD jet kit actually for the FCR MX?  If you ordered it for a DRZ400E, it is for the slant body.  You can al sways call or email JD jetting.

You remove the air jet only on "some" FCR MX.   If it works without, fine.  If it works with a 100, fine. That is how you know.

The E air cleaner boot is smaller than the S boot and used with the stock E FCR carb.  So once again it is necessary to know what carb you have but probably you use the stock S/SM boot.

Thanks for your reply Noble.

I stated in my original post that it is indeed a FCR MX and that the JD jetting kit is specifically for a DRZ (S/SM) using a FCR MX...

So there simply is no rule for when you remove the PAJ? It just works on some and doesn't work on others? That is very odd!

What jetting would you then recommend? Red or Blue needle, what clip and which pilot jet (42 or 45)?

Thanks.

It is indeed very odd and I don't understand it.  But a 100 air jet and 45 pilot jet is a pretty standard place to start.  If too rich on idle, then take the air jet out as an option to smaller pilot fuel jets.

JD jetting must have expanded their product line to include the aftermarket FCR mx applications.

Best advise you are going to get is to call James Dean at JD Jetting.  Jetting is more than just putting in the right parts 1 time.  There is some trial and error to it.  Have you installed this carb and run it?

I have installed the carb once. Like I said though, I had a hanging idle issue so ended up removing it for the time being. When I installed it the jetting was as follows per the JD instructions...

- Red Needle 4th clip from top
- 165 Main jet
- 42 Pilot jet
- O-Ring mod

The instructions said nothing about the MAJ and PAJ but it was setup as follows...

- 200 MAJ
- NO PAJ

The bike seemed to run well, except for the bad hanging idle. I essentially had ZERO engine braking. I'm now thinking the hanging idle issue may be due to the PAJ being removed. The carb did not come with one, where can I find a 100 PAJ?

Thanks again!

Edited by cj_desmit, 27 March 2012 - 01:45 PM.

Pretty sure James assumes you will have a 100 pilot air jet when using his jet kit, but once again, ask him.  He may have an air jet for you. 100 air jets can be ordered from many motorcycle stores or on line.  Try Yamaha and KTM stores.  I believe 100 PAJ is used OEM in many Yamaha and KTM applications.

The lack of compression braking is because the slide is up so far to keep the engine running, it is like not closing the throttle all the way.  The true idle speed is the high idle.  As it leans out the idle speed dies off.

Ok, so I should keep the jetting as is and simply add a 100 PAJ?

Also, what was essentially the issue I was having then since I had to have the idle turned up so high to keep the bike running?

Thanks.

Essentially lean idle circuit.  When you turn the slide stop screw way up to maintain idle, the motor starts to idle off the main circuit.

I can't really advise you on anything other than try 100 air jet with a 45 pilot jet.  Other questions should go to James Dean of JD Jetting.

100 air with your 42 pilot might be OK, but I would rather see you start with 100 and 45.  I like plenty of fuel from the idle circuit and you have some adjustment with the fuel screw.

Ok, thanks Noble. I will swap the 42 PJ out for a 45 and try and find a 100 PAJ. I'll report back with the results after I get it installed, as I'm sure some other question will arise...

Edited by cj_desmit, 27 March 2012 - 05:48 PM.