[Runt777]

So to help clue you in as much as I can. I have a 2006 450r and I just installed a new fmf powerbomb header as well as a powercore 4 muffler. I also got a fmf jet kit. I just followed what fmf said to do. Installed their adapter to the emulsion tube and their jet which is number 160, as well as their needle with c clip on the 4th slot down from the top. And now it runs fine and everything escept while decelerating in gear it back fires not like really bad but it pops allot. It kinda bugs me. Never did that before and it had a white brothers aluminum pro with header and the stock jetting. Is this normal or what could be the issue?

[der_berger]

just gonna have to do a little more fine tuning. i put the fmf powerbomb and fmf ti powercore on my 2005 crf 450. i used the jetting recomendations on fmfs website and my bike was doing the same thing where is was real popy and would back fire when decelerating. i just fine tuned my jetting.

[ERICHSHONDA]

Popping on deacell usually indicates a lean condition. Try opening your fuel mixture screw a 1/4 turn out. This richens the mixture

[Runt777]

Will give that a try today. m a little confused with the fmf jet kit as the stock jet was numbered 168 and this says 160 but it does seem to get more fuel just from looking at the little black cloud it chuffs when you whack the throttle. Ill let you all know what happens with the fuel screw adjustment later today.

[Runt777]

Well i think that 1/4 turn might have done the trick. Its pretty icy out right now but i took it for a little spin and its seems like the pop is gone. Ill keep you guys posted. Thankx for the advice.

[Leardriver]

Decel popping means that you have a good running modern four stroke. The main jet has nothing to do with it.

If you have a 45 pilot at about 2.0 turns out on the fuel screw, you are close enough.

[crfsonly]

excessive decel popping is a sign of the pilot circuit being lean. if it's marginal you can adjust out your fuel screw to eliminate (up to 2 1/2 turns). more than this indicates you need to go up one on the pilot jet size.

also, CRF's with the emissions equipment will exhibit more decel popping.

ken

[saefabri]

My 2010 450X pops on decel. This started after installing Two Brothers performace exhuast and K&N high flow filter.

I can't see fuel screw to adjust the mixture. There is nothing in the factory manual about mixture adjustment.

[crfsonly]

a lean main and pilot will increase decel popping. the fuel screw fine tunes the fuel metering from the pilot circuit. here's a photo of the fuel screw (CRF's Only T-Handle fuel screw which is brass):



the stock fuel screw will not be visable like our t-handle version but will be in the same location.

ken

[saefabri]

Thanks Ken.

I will install the JD kit once it arrives. The only that I am not sure of is how to remove the Honda fuel screw.

Other than the exhaust and air filter, the bike is stock. It just loses power at about 2/3 of full thruttle, like it is starving for fuel.
Exhaust glows red when idling.

[gripnrip]

Easiest way to remove the fuel screw is to take the bowl off. Or buy the D shaped tool. Or make ones yourself using a flux brush. A flux brush is a thin walled aluminum brush that plumbers use. You can flatten one side of it to match the D shape of the screw. Dont forget to look up inside to make sure the spring,washer,and Oring come out.

[crfsonly]

in a pinch you can use an electrical butt connector, heat up one end and slide it on the d-shape fuel screw and let it cool. once cooled instand d-shape tool.

ken

[saefabri]

Received the kit from Ken. It took 5 days to reach me here in Oman, which is quick.
This is how I installed it:
My bike is 450X 2010 stock.
1- Cleaned my bike to remove dirt from the bike and anything that may get into the carb after I open it
2- Removed seat and fuel tank - strait forward. You will need 8mm and 10 mm sockets. I disconned the negative battery terminal.
3- Removed top cover of carb. You will need Allen key size 3 mm. They are 2 screws to remove. Lift the cover
4- Removed the needle. You will need 8 mm socket. The stock needle will come with retainer. So I removed the clip from the needle to pull needle out of retainer
5- I dropped the JD needle in position in carb and screw in the needle retainer. The kit comes with 2 needles. One is marked red and the other blue. The blue is for cold weather. The JD needle comes with clip installed in 4th position from top, so I did not change it. Do not over torque retainer, as you may strip thread.
7- Install the carb cover.
8- Loosen air boot clamp and rotate carb clockwise to gain access to bowl nut.
9- Loosen bowl nut with 17 mm ring spanner. Be prepared to catch fuel that will spill out of bowl.
10- Remove main jet with 6 mm socket. I installed JD jet size 170. The pilot jet is further inside and I did not bother to change it since I had no issue with zero to 1/4 throttle response
11- Installed the bowl nut and rotated carb back to its original position.

Results:
Popping stopped
More top end power. I test this climbing dunes
Better throttle response.
But still on 1st to 3 gears, kind of starve for fuel beyond 80% of full throttle. Maybe I should have move need clip up one notch to third position.

[crfsonly]

try first to go up one size on the main jet.

[saefabri]

The largest main jet in the JD kit is 170.
I moved the needle position to 5th and kept the main jet 170, fuel screw at 1 1/4" turns out. Now I have other problem:
Bike starts, and idle fine and pulls fast on acceleration. But when it comes to a cruising speed (constant throttle) the bike hesitates / sputters.