Well Ive been working on doing the jets on my bike and I a JD kit on order now, but I did put in a DynoJet kit about a week ago, had new air filter and plug as well. On Decel (ie going down hill in lower gear ) im poping, yet when at 50%-75% throttle I bog, Bike idels great and starts no problem at all regardless of temp. Here is more info on the bike

type: 2007 CRF450x
Mods: air box mod, and stock pipe baffle out ( came like that dont have the baffle )
Location: Comox BC Canada
Elevation: Sea Level to a 1000 ft ( typical riding areas )
current temp: 18*C ( 65*F )


Items on order
-JD jet kit
-DG Performance Keihin Pilot Jets - 22 Series, Size 48
-DG Performance Keihin Pilot Jets - 22 Series, Size 45
-JET, LEAK (#50)
-R & D Racing Products Flex-Jet Remote Fuel Screw

and I wont lie I understand most of whats going on in th FCR, but abit baffled on the Leak Jet and how to determin if thats even a issue, just picked it up on a earily post repy. ( sorry for the massive photos )

From the plug, looks like your fairly rich, but I wouldn't worry about that for the moment.

The JD Kit has very specific recommendations based on altitude and temp; put in this main jet, use this needle, place the clip in this position, use a xx pilot, and bang, your dead on.

beyond that, popping on decel is caused  by two things:

1. Your lean (which judging by your plug your clearly not).
2. The PAIR air valve, which injects fresh air into the exhaust and burns up anything leftover from combustion.  By a block off kit or use JB Weld on the tubes.

As for the leak Jet, what it does is determines the amount of fuel that gets squirted when you wack the throttle open suddenly.  When I got my '09, it was a 50/50 proposition if it would stall or not.  Put in a 55 leak jet and that fixed it good (stock was 60).

And yes that's right; smaller gives you MORE gas for the AP to squirt.  The leak jet determines the amount of fuel that leaks back into the main bowl, so the smaller the jet, the less that leaks back and the more gas you have to squirt.

Some have gone to 50 and I might still do that as I get a slight hesitation on occasion.  Some even pinch it shut, but I think that's too much and a waste of gas.

Beyond that, the screw adjustment on the AP arm controls the timing of the squirt; you want it to just miss the slide (the squirt) as it's going up.   Some also buy a new diaphragm or grind down the rivet on the diaphragm so that the squirt is longer in duration.  There is also an "O" ring mod where you place an o-ring over the adjustment screw and the linkage arm so that they stay together (the stock spring on the arm is not strong enough to hold it against the screw).  An alternative to that is to buy a new spring from Merge Racing.

I didn't bother with the last two as the leak jet change and the timing adjustment were enough, and the '09 carb had a redesign which eliminated the need for the O-ring or new spring.

Jim.

Edited by JimDettman, 26 June 2012 - 11:06 AM.

Thanks Jim ! maybe im worring too much about this poping, id just hate to have to spend alot of $$$ because I did not change a $4 jet when I take the bike apart ill take a look to make sure that im getting fuel as soon as the flap is out of the way slightly. I find it funny that the Leak Jet is coming into the convo because when i bought the dynojet kit and called the rep for it and told him the issues I was having ie - bike is popping on decel and when I go from idle to 3/4 pretty fast the bike just stalls... he told me this was normal and thats the way the carb works that i have to ease on to the throttle to full to get the power i need or want.....

Brad5638, on 26 June 2012 - 11:40 AM, said:

I don't know who you talked to but my bike is not like that. The plug looks like your too fat on fuel.  On these 4 strokes to fat on the AP can cause a bog too. I found that out the hard way.  My 09 the air valve failed and it sounded like I was shooting ducks on decel. I just pluged it off and the pop is gone.  I don't know if your 07 came with that cra& or not but any air leak or a lean condition at decel will cause popping. Good Luck.

Im leaning more towards the pilot jet due to the fact that the popping only happens when off the throttle, that or the Fuel/Air screw ( at 2 turns out atm ) waiting for R&D Flex-Jet Remote Fuel Screw.

Attempt nothing, if you don't do everything.

The carb is a system, so you need to change airbox intake, exhaust restriction, jetting, apump linkage upgrade, apump tuning (leak jet size), apump timing, fuel screw adjustment.

The color of you plug means nothing, unless it's brand new, you ride only at WOT, and use race gas.

Gas additives mask burn quality to the point that plug reading with pump gas is usually meaningless.

Having said that, I find the Chevron station in my neighborhood to be extremelely consistent in fuel quality, and I get a burn like this:




Do the JD kit, uncork the intake and exhaust, add the 50 leak, adjust your leak squirt timing (which is usually way to early, causing a 'rich' condition at idle range), and adjust your fuel screw. Fuel screw adjustment takes some practice, as it's not about turns, it's about quick idle recovery and smooth running.

yeah , with pump fuel you cannot get a plug reading due to additives

I can't say you should totally ignore a plug read.  What is your current jetting setup(pilot,main,needle,clip position,leak,a.p. mods,etc.)?

When you "Read" your plug also has impact on the reading.

Did you read this after it sat and idled ?  ....or after a mid-range full "on/off" throttle ?

It looks slightly rich, but again, when you took the "Read" makes a difference.

No mention of the main jet.  Size ?

My plug looks perfect, but may pop on decel (depending on what I was doing just before the throttle "Off" condition).

The mid-upper bogging isn't correct.  Sounds like the pilot jet may be too small.   Size ?

Believe it or not, the temp and humidity will also change the "Read" characteristics.  

...and Krannie's looks about right to me.  

The following isn't a direct correlation to your bike/plug, but it's a data point.

Edited by X-Racer, 27 June 2012 - 09:48 PM.

X-Racer, on 27 June 2012 - 09:46 PM, said:

Yah im waiting for my JD kit to get in to Jet the way krannie has said, I have rejeted already but with a dynojet kit im runnin with 45 pilot needle 3rd down from the top and main jet is a 136 as per what the kit has said, i did try a 132 but it was popping on acel too so i went back to the 136 heres a link to the instructrionshttp://api.viglink.c..._13408631801261 and it helped that, I feel im getting closer, just not 100% yet. I may even video tape me downshifting and post to see if its normal. Ive been riding for 15 years now but always sport bikes with fuel injection so this is quite a learning curve.

mods i have done are air box mod opened sides and top, its stock pipe with baffle out ( came like that when i bought it , so i dont have it ), and i just did he smog mod were i blocked all the holes with JB weld, and im getting about a 1sec squrit when i open the throttle and seems to be working as it should ( squirting fast, yet not hitting the slide)

Edited by Brad5638, 27 June 2012 - 10:07 PM.

The dynojet jet size/numbers are different from Kehien jet numbers.
You will remove 90% of your decel pop after blocking the exhaust gas re circulation plumbing.
Pilot jet is for IDLE ONLY.
Fuel screw is for adjusting pilot circuit, and off-idle throttle response.
Needle is for adjusting the transition from idle to main (taper and length) and Air Fuel mixture (diameter).
The JD Red needle works good, and the Kehien NCVS needle works better.

Krannie, on 28 June 2012 - 04:59 AM, said:

What does this all entail for the gas exhasut re circulation plumbing, could you send me a link of  some info on how to do this , Im guessing in not typing in the key words into the search

Edited by Brad5638, 28 June 2012 - 08:33 AM.

Brad5638, on 28 June 2012 - 08:08 AM, said:

http://www.thumperta...h&fromMainBar=1

Pilot jet is not for "IDLE ONLY". It will certainly change throttle response from 0-1/8 throttle, and actually does affect jetting throughout the range.

Krannie, on 28 June 2012 - 08:10 AM, said:

I know were the search is, I could not find anything using it explaning how to do this

Brad5638, on 29 June 2012 - 09:25 AM, said:

That was supposed to be the link to the threads.

Search 'smog block'.

I had a great diagram at one time, but here's another link to about the same info.

http://www.zrxoa.org...jetting-diagram

it doesn't show the pilot jet functionality in this "Contribution to fuel flow" diagram, however, the pilot's contribution is about from one-eighth (1/8) to about five-eighths (5/8) throttle.  Basically where the top of the "air"  adjust functions end and the main jet functions begin.



In this view the pilot would essentially bridge the space between the "Air screw slow jet" and "Main Air Jet / Main Jet"

<<it doesn't show the pilot jet functionality in this "Contribution to fuel flow" diagram, however,>>

Actually, I believe that is labeled "Fuel Screw, Slow Jet".  And it is 0 - 1/8 throttle.   There's hardly any impact from it beyond that.  By 1/4 throttle, it's almost next to nothing.  The Screw, Slow Jet, and Slow Air Jet combined are only 5% effectiveness at 1/4 throttle (shown in the last chart).

Jim.

Krannie, on 29 June 2012 - 10:12 AM, said:

Yep did this mod already, still waiting on pats to come in , when they do ill finish up the jetting with a proper kit, if it still decel pops ill just video tape it and see if im just being anal ( for all i know this could be "normal")

Krannie, on 29 June 2012 - 10:12 AM, said:

Well got all my parts in and did what you said to do ( also same as instructions ) , WOW ! the bike is not even the same, the power is there! Decel pop is now gone ! Life is Good ! only thing I noticed now is bike is abit harder to start but I can live with that, thanks !

*** dont buy dynojet kits they suck !, stick to what  people recommend on this site ! ***

Edited by Brad5638, 11 July 2012 - 02:20 PM.