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have been searching up and down the TT [font=inherit][size=1]

forum

[/size][/font] on how to fix this jetting problem and have yet to find the right answer. I have contacted XR's only and they just say the same thing over and over (NO HELP from them).[/size][size=4]
Just some background info on the problem.i recently purchased a 99 california xr400. The bike had the top end rebuilt with the 430 kit from xr's only along with a mikuni pumper carb. After cleaning the carb and reinstalling it, the bike runs like crap. It pops and coughs and at night you can see the pipes glow at an idle.  The carb originally has a 130 main and 15 pilot which i cleaned and reinstalled. XR's only states that this is the only jetting they recommend. I finally got a hold of a 20 pilot and after installing that it still runs like shit at idle. Also i have been trying to do some research about the 430 kits installed by xr's only and would like to know if there is any special service schedules that are required for them because the bike has almost no hours on the new top end and there is a definite tick in the engine, not loud but noticeable, I have readjusted the valves and everything is in spec. My only concern is that after the previous owner rebuilt the top end the bike sat for about 2 years, if that makes any difference.[/size][size=4]
My questions are:[/size][size=4]
what pilot is [font=inherit][size=1]

safe

[/size][/font] to put on 17.5 20, 25 etc? (i have downloaded the manual for tuning the mikuni carb) [/size][size=4]
Where should the needle sit and how to find out what position it is in? Do i need a new needle?[/size][size=4]
what is up with this ticking noise? or do the 430 kits just have a subtle tick to them.
I live in ontario california elevation 0-1000 ft and will be using the bike as a pure dual sport, street and dirt/fire roads.
FYI
I have performed all the gordon's mods (Snorkle taken off, header welds grounded, crankshaft exhaust etc)[/size][size=4]
The bike also came with a super trap ids2 race series exhuast[/size][size=4]

If there is anyway anyone can help or point me in the right direction it will be greatly appreciated.

JOE[/size]

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After a proper valve spec adjustment it is normal to hear a slight ticking. It,s when you hear nothing at all from the valves that you need to be concerned, as that could mean they,re too tight. Too loose is better than too tight.

Did you verify correct fuel screw assembly and installation?

If a 20 pilot made no difference, I,d be looking for air leaks. Xrs Only doesn,t  make the carb boot adapters quite long enough to fit into the boots as far they they should, so it can be tricky to get good clamping and good seal.

Also check for air leak at the intake manifold oring, head cover, cylinder base gasket and header flange.

Has the spark plug been checked?  What plug is in it?  Should be an NGK-DPR8 or 9 Z. Gapped at .023-.028".

The needle is accessed from the top of the carb. If I recall, stock clip position is 2nd from top. Shouldn,t need a different needle. The needle won,t be the cause of the idling issue.

The tank doesn,t still have 2 year old gas in it does it?

Have you had the valve cover off to verify proper cam timing?

How many discs in the Supertrapp?

After sitting for 2 years, check for corroded connectors in the wiring, frame ground points. No frayed, knawed on, or shorts with the frame of any of the ignition system harness.

We,re looking for anything that can mimic a fuel/carb related problem.

17.5 pilot at the most. 15 should be just fine. Agree with TR42, check for air leaks, bad wires, bad gas etc. Also, if your using the "generic" Mikuni tuning instructions, ignore the part about having the pump come on right away. For the XR, you want the pump to kick on as late as possible. Bottom out the adjustment screw for it and if your pilot screw has all the correct bits and pcs. in place, set that at about 2 turns out to start with.

thanks everyone for the insight... the 20 pilot did make a difference however it still is idling on the lean side.  I am going to try a 25 pilot and if that doesn't work i will rule out that  its the pilot and will look for air leaks. The pilot screw currently is at about four turns out in order to compensate for the lean idle, ( I know this is too far out but its what i have to do until i get the 25 pilot. Yes the carb does not sit perfectly but i think i have it sealed rather well on the exhaust and intake.  Is there a proper way to look for air leaks? Cause everything looks good.  I will take a look at the exhaust and find out how many disks there is,  is there a bare minimum amount of disks i could use that could richen up the exhaust?

Appreciate the help
joe

You're trying to put a band-aid on the problem. That pilot seems way too rich, and I agree with all the above posters and I would check for an air leak.  I would start by checking the carb boot ( air box side and motor side ).  Warm up the bike and let it idle, spray carb cleaner around suspect areas and see if the idle changes.

Hi,

I think I just got my 1999 XR400 with a Mikuni pumper carb "in the ball park".
I am 99% certain the tip of the fuel screw broke off.  I noticed the hole from the fuel screw into the carb body was plugged.
Pull the fuel screw and see what it looks like.  Post up a photo of it.   I used "canned air" to test the fuel passage into the air tract of the carb.

Edited by Kev_XR, 29 June 2012 - 03:15 PM.