Changes to stop flame out.

I have an 05 these early models were know for abrupt power and flame out. When I first got it flameout was an issue even backfire the whole jetting and AP was way off. Now its pretty good. The reason I ask is all the later tests say how smooth the bike is and from what I can glean the only changes were the AP circuit in 08. Does anyone know if there were ignition timing changes to the later models and if a later CDI unit will smooth the older x even more off the bottom.


Thanks to the help on here my bike is 95% it does flame out occasionally if I'm not quick on the clutch in tight stuff but there is no bog at all anymore. I'm not sure if its me as traditionally I'm not a bike bore rider, spent most of my time on 250 2bangers and 250f's with many 125's and 200's thrown in :) :)  I do ride a fair bit of single track with plenty of large logs.With suspension valving respirnging including the ICS springs its a pretty damn nice bike just getting caught out every now and again with this is a pain. Just feel like I'm missing something. 



1. All years are exactly the same, accept for the pump changes and jetting change in 2008 (re: carb/motor response)

2. If you have not visually confirmed you pump squirt by lifting up the subframe (NOT by linkage gap) and watching it squirt, you are not done with it's tuning

3. If you used an oring or safety wire to 'fix' the apump, you are not done. Change the linkage spring to a tokyo mods spring, and use a 50 leak jet.

4. CRF450X are not nor have ever been know for 'abrupt' power. Not in the least. Very smooth power delivery, unless jetted wrong, or has stock intake and exhaust plugs

5. All CDI's are the same

6. Valve adjustment and fresh top end contribute strongly to throttle response quality, as does proper fuel screw adjustment

7. If you are going to compare a bike with a 11lb torque peak at 6k to a bike with a 35lb torque peak at 3k, you will be unhappy for some reason or another. Don't compare.


Until you tell us EXACTLY how you bike is set up with intake, exhaust, jetting, valve clearances and results, you will not get any definitive help.

Top of the air box cut,

Uni filter backfire screen still on,

full pc system with 496 muffler about to be DRD next week as I feel the 496 hurts bottom end. 

Jetting 165 main,

NCVS needle 3rd clip,

stock pilot,

1 3/4 turns on the fuel screw,

#50 leak jet, squirt confirmed ok it was really poor, R&D AC spring, ground rivet so arm is in contact the whole way, stretched AP spring,

BIke has done 120hrs just had a fresh genuine top end, new kibblewhite inlet kit seats cut to suit, clearances spot on.

It is smooth I just want it perfect :) Its a nice bike far far better than it was, rode a mates 2013 YZ450 and mine is every bit as good without the wheel spin in the top end. He was shocked at the X. 


I was thinking of getting a R&D fuel screw to mess with it on the hop, I had one on all my YZ250f's for this reason.


I think I maybe comparing apples to oranges :) :) 




Sounds like you have covered most of the bases very well.


Pink wire?

Remove back fire screen and use No toil

Get that R&D fuel screw!


I'd also get a *new* accelerator pump diaphragm (2008 crf450r)...and double check that the squirt never hits the slide, no matter how you hit the throttle, and that it shoots all the way into the left side of the head.

Installing the R&D fuel screw was an easy way for me to dial in my fuel screw mixture. I ride my bike hard for a minimum of 10 min. Then, peak the idle speed by adjusting the mixture. It was easier for me by using the tach on my Vapor. I had a more difficult time doing it precisely by ear. The idle speed will be a little high after tuning so lower idle with idle screw. Seems like 1700-1800 rpm works best for me. I no longer get unexpected flameouts. I have an 05 with original head. Looking forward to having the head done.

To add further to this I rode a 2010 on the weekend it was way smoother same jetting full yoshi system mine  has a PC system. My bike pulls much harder into the mid and top his is heaps smoother especially the lower part of the powerband made it easier to loft the front over logs etc. Has anyone tried a later cdi on and older model to me it feels like a more mellow ignition map smoother and slower yes but faster and easier to ride. 



Every year CDI is the same, with the same part number.


The differences are in jetting, Apump tuning, a fresh slide plate seal, etc etc.


Same bike.

Are you sure all passages (particularly those above the slow jet and pilot jet) are 100% clear?

Intake vales are smaller from 07 on. higher flow rate in cylinder at lower rpm?

Intake vales are smaller from 07 on. higher flow rate in cylinder at lower rpm?


On the R yes, not on the X.

Intake valves have stayed the same on both the X (35mm) and the R (36mm).


The R changed it's exhaust valves to match that of the X in 2007 to give better throttle response.

Intake valves have stayed the same on both the X (35mm) and the R (36mm).


The R changed it's exhaust valves to match that of the X in 2007 to give better throttle response.


That's what I said.


:smashpc:  :facepalm:

So which valves does the X have again.....................................



















Just kidding :) 

Still messing about here :) I just checked my pump timing again. If I whack the throttle it misses the slide, if I turn it slowly it hits ! Should adjust it to miss the slide on a slow application ? This means the slide would have to be higher than the nozzle before it squirts I'm worried I'll get a flat spot due to the slide moving with no squirt. I know I could always check this but trying to save time :) 




Turning really slow so the squirt is about long enough to hit the slide is not a problem

But if a full stream hits the slide, you will notice it.

Moderate opening it hits so I think its a bit early will adjust it anyway. I feel like a kid in a lolly shop my mousses and tyre levers just arrived also a video of the 2013 6 day :) :) 

Moderate opening it hits so I think its a bit early will adjust it anyway. I feel like a kid in a lolly shop my mousses and tyre levers just arrived also a video of the 2013 6 day :) :)

It's all about a full throttle turn, at less than 1 second.

Misses at full throttle less than a second but was hitting with what I would call normal throttle opening. Changed it 3 and a 1/4 turns cw it now missed at moderate and whacking the throttle. Will report back the effect after a ride tomorrow. 

Just got home from my ride only one flame out or stall. Its much improved. While I get the WOT test with the acell pump I think to fine tune it it must never hit the slide even with small to moderate openings. 3 and a 1/4 turns cw on the timing screw is a major change the difference is pretty impressive. Worth checking if your bike passed the WOT snap test. 



Don't know if it'll help you or not, but I developed a flame out problem on my 02 R Cam'd bike.  Changing to a bigger pilot cured it for good (45 pilot to 48).  If it takes more than 2+ turns out on the fuel screw, you probably need a bigger pilot.  The bike also starts SO much better cold when you get the right pilot in it.

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