Jetting

[paulxr]

Hi guys this site has been a awesome amount of information for me and my new toy:worthy: but i just have a little jetting question,i am very happy with my 08 CRF450X in stock trim the only thing that has been done to it was de-restriction at the shop when i bought it which i think was a carby block taken out and exhaust mods done the airbox etc is standard which i like because the bike has heaps of grunt and the aircleaner stays nice and clean the only mod i might do there is remove the snorkel under the seat.The mechanic at the shop said it doesn't need re-jetting but after reading here i believe he didn't no what he was talking about:bonk: As a rule i ride from sea level up to around 1000 metres and the temperature is anything between 10 degrees up to around 30 degrees in the summertime,so what do you guys think leave it standard jetting or upgrade the main jet?if i remove the snorkel i assume i will have to re-jet anyway?The reason i ask this is because i seem to get unreal fuel economy out of it which to me means it might be lean but on the same token it has never boiled on me yet so it must be ok.I have never had the carby apart on this bike and being new i wasnt planning on doing it but if the jetting needs to be changed is it a hard job on the CRF?Thanks in advance Paul

[MarkF3x]

JD Jets:

Red Needle clipped on 4th notch (I'm assuming 10-30 degrees was celsius)

165 Main Jet for what you described, 170 if you decide to put a new pipe on it. Leave the rest of the carb stock.

It will run much better after rejetting.

[paulxr]

JD Jets:

Red Needle clipped on 4th notch (I'm assuming 10-30 degrees was celsius)

165 Main Jet for what you described, 170 if you decide to put a new pipe on it. Leave the rest of the carb stock.

It will run much better after rejetting.

Thanks mate i will do that,i was looking in my owners manual and standard is only a 145 main jet a 45 pilot jet and a NKJU needle 2nd groove from the top.Instead of buying a JD jetting kit can i buy a genuine Honda needle which will do the same job?Thanks again Paul

[MarkF3x]

I have an 2008 450x that I installed the JD Jets in (with the setup I listed). The bike is configured almost exactly like yours (Smog blocked, airbox opened, stock exhaust). Sorry, It's the only bike I've jetted.

Maybe someone else can pipe in with alternative needles, etc.

[paulxr]

I have an 2008 450x that I installed the JD Jets in (with the setup I listed). The bike is configured almost exactly like yours (Smog blocked, airbox opened, stock exhaust). Sorry, It's the only bike I've jetted.

Maybe someone else can pipe in with alternative needles, etc.

Thanks Mark i have left the smog pump on it at the moment due to the bike still being under warranty all i really want to do is open up the top of the airbox(not the sides) so the way i read it all i have to do is put the 165 main jet in and replace the needle which is the problem:banghead: not sure which one to buy and i dont want to buy a complete JD jetting kit when all i need is a main jet and a needle can anyone point me in the right direction for what needle to buy?

[paulxr]

I went for a good ride on the weekend and due to my bike being stock as a rock i decided to richen up the standard main from a 145 to a 150 when i done this the bike seemed harder to start when cold and was hard to get it to idle properly it seemed to hang for a few seconds on a higher idle speed and then drop down to normal idle speed.I just put the standard 145 back in and it has gone back to normal easy to start and idles properly any suggestions of what i did wrong much appreciated.

[FORMA MOTO]

I went for a good ride on the weekend and due to my bike being stock as a rock i decided to richen up the standard main from a 145 to a 150 when i done this the bike seemed harder to start when cold and was hard to get it to idle properly it seemed to hang for a few seconds on a higher idle speed and then drop down to normal idle speed.I just put the standard 145 back in and it has gone back to normal easy to start and idles properly any suggestions of what i did wrong much appreciated.

Jetting is a system. You can't just change one jet an hope for an improvement. If you change the Main you should change the needle too.

You need to change the main, needle, pilot, leak, and adjust the Accelerator pump.

www.jdjetting.com

[detox]

Clearly the problem is your name,"paulXR". You're on a CRF, you can't be XR any more. Once that's fixed your bike will love you and work like a champ. Other than that, I used the JD on my 06. I followed the instructions, including cutting holes in my air box. I can't believe the difference, and I only had to open the carb once. The time savings was well worth the cost of the JD kit.

If you have more time then money, there is a honda needle and instructions that can be found by using the search feature on the TT 450x forum. I'd search for you and post a link, but that's beyond my technical abilities.

[agermaney]

I went for a good ride on the weekend and due to my bike being stock as a rock i decided to richen up the standard main from a 145 to a 150 when i done this the bike seemed harder to start when cold and was hard to get it to idle properly it seemed to hang for a few seconds on a higher idle speed and then drop down to normal idle speed.I just put the standard 145 back in and it has gone back to normal easy to start and idles properly any suggestions of what i did wrong much appreciated.

This is strange.

Going up from a 145 to a 150 should make no difference to starting and low to mid throttle running.

Are you sure the 150 wasn't blocked.

I'd check that the hole is visibly larger than your 145 and re-try.

Andy.

[FORMA MOTO]

This is strange.

Going up from a 145 to a 150 should make no difference to starting and low to mid throttle running.

Are you sure the 150 wasn't blocked.

I'd check that the hole is visibly larger than your 145 and re-try.

Andy.

Sure it would, depending on how he uses the throttle to start it.

[agermaney]

I didn't think anyone used any throttle to start crf450's. I know I dont.

[detox]

Mine won't start if the throttle is even crack a smidgen.

[davegod]

jd it and forget it! they did the work for you and they did it right.pay the money, install the kit and go ride.i would recommend an adjustable air screw though.r&d make one that has the adjuster screw mounting out where it's easy to mess with.5 stars in mxa and i love mine for those high altitude rides on a cold morning in the sierras.?

[paulxr]

Thanks for the replys guys i am just going to bite the bullet and buy a JD jet kit:ride: i have been reading the posts on them and they seem great,what i have read about them for use in Australia they say run them one jet below the recommended setting due to our fuel here not being as good as what you have in America:bonk: and i am still going to stick to cutting the top of the airbox not the sides.I wonder if that is why the CRF can have valve problems?my mates WR 450 is stock standard and it comes out with a 165 main jet maybe alot of the problems stem from running to lean stock and as we all no the WR has a pretty good valve life record.

[ratter]

Hi guys another aussie here

This is my first post here.

I purchased a new 2008 450x in nov, I have had a good relationship with the service manager at the dealership so he derestricted it for me and adjusted the carby.

I have been getting more interested in fine tuning the bike (I do dyno tuning for cars as a living) so thought I'd try to find out what was done to my bike.

The manager has sinced moved, but they keep a record of what was changed on the carby.

My air box has had the top cut open to the battery. sides still in place

Back fire screen still in place

I'm still using the (ugly) honda deflector in the tail pipe.

carb mods were

48 pilot jet

155 main jet

Needle clip to middle position

2.5 turns out on the air screw.

I'm assuming the throttle stop was removed???

Now this is my first dirt bike for possibly 15 or more years so I don't have much to compare to, I don't know whether to expect more power or not, but these are my opinions based on just over 350 klms of riding.

The bike starts first time every time when cold, just by pulling the choke and giving the throttle a pump and then hitting the start button.

Idles straight away whan started, but takes maybe 3 or 4 seconds to pick up to normal fast choke idle speed

Can push choke in after possibly 15-20 seconds and bike will idle

Have only had to use the hot start lever once when stopped on a steep hill and possibly a very hot motor

As opposed to some of the stories I have read on hereThe bike has never flat spotted, stalled or even bogged while I have been riding, (although it has fallen over a few time, must be a balnce problem with the bike ? )

The tuning appears to be spot on for what my riding level is.

Like most people I would like more low down and mid range power, but don't know whether what I have is good or average.

Does my carb set up sound good?

Does my aussie bike have a smog pump?, I have looked at where the block off kits go and it appears it is not needed on my bike, but read the one of the aussies above talking about that his is still connected.

I spoke to my dealer today about the R&D adjustable fuel screw, and he did not have a high opinion of them, have others used them and is the adjustment position the same as the factory item, ie the carb setting at 2 turns out is still the same at 2 turns out with the R&D

Is there much to be had with adjusting the leak jet , don't know what size my bike has or what the stock size is?

Is there anything else I can/should do?

Sorry abut go of topic, I started out just to give my carb specs and got carried away with my questions.

Thanks

Mick

[paulxr]

Hi guys another aussie here

This is my first post here.

I purchased a new 2008 450x in nov, I have had a good relationship with the service manager at the dealership so he derestricted it for me and adjusted the carby.

I have been getting more interested in fine tuning the bike (I do dyno tuning for cars as a living) so thought I'd try to find out what was done to my bike.

The manager has sinced moved, but they keep a record of what was changed on the carby.

My air box has had the top cut open to the battery. sides still in place

Back fire screen still in place

I'm still using the (ugly) honda deflector in the tail pipe.

carb mods were

48 pilot jet

155 main jet

Needle clip to middle position

2.5 turns out on the air screw.

I'm assuming the throttle stop was removed???

Now this is my first dirt bike for possibly 15 or more years so I don't have much to compare to, I don't know whether to expect more power or not, but these are my opinions based on just over 350 klms of riding.

The bike starts first time every time when cold, just by pulling the choke and giving the throttle a pump and then hitting the start button.

Idles straight away whan started, but takes maybe 3 or 4 seconds to pick up to normal fast choke idle speed

Can push choke in after possibly 15-20 seconds and bike will idle

Have only had to use the hot start lever once when stopped on a steep hill and possibly a very hot motor

As opposed to some of the stories I have read on hereThe bike has never flat spotted, stalled or even bogged while I have been riding, (although it has fallen over a few time, must be a balnce problem with the bike ? )

The tuning appears to be spot on for what my riding level is.

Like most people I would like more low down and mid range power, but don't know whether what I have is good or average.

Does my carb set up sound good?

Does my aussie bike have a smog pump?, I have looked at where the block off kits go and it appears it is not needed on my bike, but read the one of the aussies above talking about that his is still connected.

I spoke to my dealer today about the R&D adjustable fuel screw, and he did not have a high opinion of them, have others used them and is the adjustment position the same as the factory item, ie the carb setting at 2 turns out is still the same at 2 turns out with the R&D

Is there much to be had with adjusting the leak jet , don't know what size my bike has or what the stock size is?

Is there anything else I can/should do?

Sorry abut go of topic, I started out just to give my carb specs and got carried away with my questions.

Thanks

Mick

Hi Mick i have the 08 aswell and i am not sure if it has the smog pump i have seen pics on here of what it looks like and i cant find it on my bike so maybe our Aussie models arent fitted with it.Interesting on what you have written about your jetting the more i read about it the more i get a head swell:lol: thats why i think i will go for the JD kit the bloke who makes them sounds like he has done lots of research and in the long run i think it might be the better option.You havent got a pic of the toip of your airbox have you?when i re jet it i will do the same mod as what u have and leave the sides as is.Paul

[lubeking]

Hi To You Aussie Blokes!

I have a 2007 X and being a European model, it doesn't have the smog kit.

I have only just re-jetted my bike and went with the JD jetting kit. It takes away the headache and is very simple to install. I also went for an after market fuel screw (CRF's Only). The fuel screw looks to be of equal quality to the OEM part just easier to adjust.

The re-jetting made a massive difference. I ride from sea level up to 1500 metres in altitude. I went with the 165 main jet and the red need le jety on the 4th clip (all as recommended by JD's guide).

I only cut the airbox out at the top. I really don't believe that cutting the sides will make any difference (I did a load of 'Post searching' on this).

I also cut the two disks of the baffle and left the spark screen In place. The 'baffle-ectomy' made only a small difference.

I would really recommend the JD kit and would rant forever about the difference the whole process makes to the performance of the bike.

As I ride from sea level up, I cannot see the point in fitting a main jet less than 165.

Good luck!!!

P.S. I am coming to Adelaide and Melbourne for 6 weeks over Xmas. Do you guys know if you can rent enduro bikes anywhere near????

[gc8steve]

hi guys , my 07 is running with a 162 main and the standard needle moved up 1 position and the accelerator pump mod has been done. The top off my air box is cut out but i"ll be cutting the sides out tomorrow while it's apart for repair, the dirt seems to build up on top of the filter and not on the rest of it .

i'm running a stage 1 hot cam and white bros xcr pipe and it rips with no bogs from closed throttle . If your anywhere near newcastle take it to axis motorsport they'll get it sorted for you:ride:

[ChrisLuce]

Here are my current jetting settings:

Year: 2006

Elevation: 100-4000'

Temperature Range: 4-F to 105F

Smog (AIS): Disabled (JB Weld)

Airbox Modified Top: Yes

Airbox Modified Sides: Yes

Backfire Screen: No

Air Filter: Stock

Pilot Jet: 48

Main Jet: 165

Needle: JD Red

Needle Clip Position: 4th

Fuel Screw Type: CRF's only "T" screw

Fuel Screw Setting: 2 Turns

AP Modified: Yes O-Ring

Leak Jet: Stock

AP Cover: Stock

Exhaust Type: DrD Full System

Exhaust Modified: Yes

Pink Wire Modified: Yes