CR jetting issues

[scotty dog]

Im not happy with the way my 05CR 250 is running at the moment.

It fouls up easily if im just riding slow even for a short distance and it never has been very crisp.
On the weekend even just sitting on the start gate for 2 minutes it would choke up even though i had just cleared it out. Although i have issues with it pinging. I dropped the needle one clip position but then it pinged worse so i lifted the needle 2 positions and it stopped it pinging and seemed to run ok on the track.
Its doing my head in not really knowing what to do and i know it will perform a whole lot better once its sorted.
I checked out the FMF jetting guide and they reccomended,
Pilot-35
Main-410
Needle-12-82 second clip position
Air screw- 1.5

At the moment it has
Pilot-40
Main-430
Needle-26-65.......(im guessing you go by the last four numbers on it)
Clip- 4th position....(down from the top)
Air screw- 1.5

I dont know what the standard jets are but have been told that it is one bigger than stock on the main and they go up in tens.
I think its stock apart from the FMF Pipe and shorty and i run 98 octane.

Any help or suggestions would be greatly appreciated if i haven't confused you all

Cheers Scotty

[eprovenzano]

I'm not familiar with the CR jetting specs, but, in my experience, the correct needle can really make a big difference.  I have a KTM for which jetting can be difficult, but after some trail and error, I got her where I want it.  

How worn is the top end? I ask as many times I've seen a worn top end wreck havoc on jetting.  What worked before now doesn't, why...  the top end is over due for a rebuild...Sorry I can't help you with the specs, but I'm sure someone will post something that will get you headed in the right direction.    One piece of advice, change one thing at a time Keep notes as to the changes made and how the bike runs.  It helps knowing what changed when trying to evaluate how the bike is performing.

[scotty dog]

Oh yeah the top end is 2 rides old and the cylinder is near perfect.
Pipe is not much older with zero dings or anything.
Thanks Eric :-)

[SachsGS]

Could you post a picture of the plug?

Silencer/filter o.k?

[scotty dog]

The the silencer is new and have only ridden the bike about 4/5 times with it on there.
Filter is clean everytime i ride the bike, i checked it yesterday after the weekend and it was spotless because it was so muddy.
Pplug is black n wet.

[TMKIWI]

Check your needle and seat. It may be flooding.

[scotty dog]

I thought about that kiwi and the float level seemed a bit high, the needle n seat looked good though so i set that.
Goin out again sunday so will see how it goes then.
Thanks for the input  

And can anyone tell me what a JD jetting kit is? Is it just a box full of jets n needles n stuff?

[oldermxr]

Scotty
  What spark plug are you useing in your CR? If you are useing a #9 plug try dropping to a # 8 plug that will be a little hotter plug and that will help burn off the excess pre-mix that is put into the engine on start up. You could also drop 1 number on your pilot jet that will cut back on the pre-mix that is put into the engine on start up also. Find out what the stock jetting should be first and go from there but dropping 1 number on the pilot and going to a # 8 plug would be the first two things I would do then adjust the air screw according to get the correct reading on the spark plug. You say you are useing a FMF exhaust so FMF is probably saying to go 1 to 2 main jets leaner I'm just guessing though if thats the case then start with the next leaner main from stock main jet and try  adjusting the air screw 1/8 turn in from what your manual says for that leaner main jet and do the WOT test and see what your plug looks like. I have a 2002 Honda CR125 I'm useing a pro circuit works exhaust with mine and I did the things to my bike that I suggested to you and my 125 is running great I'm going to go 1 more main jet leaner #380 to get rid of a little more spooge nothing is running out the end of the exhaust but you can see just a little yet just around the inside edge of the silencer.   

[oldermxr]

Scotty
  The stock jetting spec for your 2005 CR 250 are main jet #420
                                                                   pilot jet #40
                                                                   neddle 6DGy26-65 clip 3rd position from top
                                                                   air screw 2 turns out
                                                                   

[oldermxr]

Scotty
  One thing a motocross bike shouldn't have is a idle couple of reason's for that 1 being if your racing or just play riding and you go down your bike will shut itself off and not lay there running wide open and possibly blow the engine. Reason 2 is fairly simple when you start the engine your putting pre-mix into the engine and if your bike is sitting there idleing your engine is actually loading itself up.Because the engine isn't running at high enough RPM to keep the eccess pre-mix burnt off. If you get rid of the idle you have to keep blipping the throttle to keep it running and your keeping it cleared out. But I would still try going 1 size smaller on the pilot jet and 1 number hotter on the spark plug both of these will help also.

[scotty dog]

Hey Oldermxr
Im pretty sure im runnung an 8, and obviously my jetting is stock apart from the richer main jet,
i think i'll take your advice and go one leaner on the pilot coz thats were i thought
the problem was.
I know what ya mean bout the idling thing, ive never really liked my bike to idle for those reasons you stated. When im sittin on the line just givin it small blips to keep it goin while puttin me goggles on she got choked up bigtime.
Will try the smaller pilot and check the plug heat range and see how it goes.

Thanks for the info, appreciate it
Scotty 

[SachsGS]

What type of mix are you running?

[scotty dog]

Im running 32:1 bel ray SL-2

[oldermxr]

Scotty
    No problem hope I was some help I'm useing a NGK iridium plug in my CR125 and I think they are much better than the regular NGK plugs they take less spark to fire and throttle responce is some better also.

[SachsGS]

What type (octane) of gas are you using?