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09 450f revving issues. Backfires and popping.

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I'm having a strange issue that has now consumed 3 weekend days of headaches to get nowhere but worse and back. 

I'm getting some small backfires and popping while revving. The issue started the last time riding when I noticed the bike would stall if it was hot and I blipped the throttle off idle coming out of a turn or any situation snapping the throttle quickly off idle. Slowly revving hot or cold it has popping when trying to hold a higher RPM with the trottle, and certainly will backfire when snapping the throttle if it doesn't stall first. Now its parked in the garage while I try and get things right before riding again.

For those "jetting is your issue here" people, please let me know where I'm going wrong then. Here's what I've tried the past couple weeks:

Current jetting; Main 165, Pilot 75, Needle 4th clip. Tried 2-6 needle clip positions with no noticeable change.

New CR8E plug
Borrowed another working coil, CDI unit, and even the harness from the CDI. Original coil metered out fine anyway.
Unplugged the neutral wire, and unplugged the throttle position sensor.
pulled out the carb and cleaned it twice. all jets in great shape. changed the o-rings and whatnot in the carb. 
Accelerator pump shouldn't have much to do with this but I did try and advance it a little.
Valves all checked and dead center of "in-spec" 
checked resistance of the stator coils and pickup magneto, all center of the "in-spec" range
Visually inspected the coils and all look good to me. bolts are tight.
Timing is good
finally, new fuel. 93 with ethanol treatment which has always worked for me.

Anybody have any insight to this? I cant seem to get any good direction from searching here or google. Thanks!

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If it ever ran well the jetting you had, there is no reason to suspect jetting.

It sounds like an arcing problem or a jumped timing chain problem .

If it idles, it's not the latter.

If it gets worse with heat/time or load, it's the former.

Plug, plug cap, wire, ground corrosion, stator harness plug corrosion, dying stator.

Get a factory service manual and do a stator test.

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75 pilot? That can't be right. Either way, very your pilot is clean and clear of obstruction. I just cured this exact issue on a crf (same carb), blockage in the pilot jet.

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Thanks Kran. It definitely ran well before so I agree that I should be able to eliminate changing jets. I did the manuals stator test across 3 sets of wire pairs for coil 1, coil 2, and pickup coil and all resistance values were well in check. I suppose I could maybe check ground resistances references between all 6 wires (3 different coils) there really shouldn't be any ground continuity should there be? 

In my head I've been leaning toward a dying stator or pickup on the stator. Timing is good and it's a new cam chain so I know it didn't (or shouldn't have) jump timing. But a new stator is pricy and wanted to cover all bases first. 

Woodweapon, EDIT: 45 pilot is correct, not 75. Smh. 

I've checked the pilot multiple times trying to figure this out. And blew out the pilot passages as well when I had the carb out. 

Edited by leadfoot100

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Woodsweapon, disregard. I was meaning to say 45 pilot. Don't ask, I don't know what I was thinking. Good catch. 

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One last thing,

The manual shows this wiring diagram for the magneto coils. 2 sets of coils; one on the brown and green wires, and one on the pink and black wires. The testing process in the manual is clear but what is not clear to me is they show the BLACK wire part of the pink/black coil is also tied to chassis ground. 
I pulled the cover back off and tested it at the plug and at the coil itself and nowhere can I get a ground reference through the back wire. According to this diagram I should also get a ground reference on the pink wire through the resistance of the coil, but I get nothing but an open circuit as if it's not grounded at all. 

Is this SUPPOSED to be grounded, or is this diagram false?

yz450f wiring.JPG

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leadfoot100, did you find the cause of your problems re 09 450f backfiring and popping reason I ask is I have the same type of problem with an 08 450f. I am waiting on a new ECU to see if it cures my issues.

Cheers

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On 9/14/2017 at 7:56 AM, vayama said:

leadfoot100, did you find the cause of your problems re 09 450f backfiring and popping reason I ask is I have the same type of problem with an 08 450f. I am waiting on a new ECU to see if it cures my issues.

Cheers

Yes actually. I ended up changing everything on the electrical side, even though the original equipment was metering out as OK. Bad call on my part because it didn't change a thing.  

Ended up pulling the carb AGAIN, putting in a new slide seal, new needle and needle jet, and most importantly new AP diaphragm AND a Boyesen quickshot 3, as well as accompanying o-rings and seals. Set up the AP spacing per Boyesen instructions to .10" 

fires right up, revs well, doesn't stall out when hot, starts up one easy kick when hot, all things seem even better than before  

 

 

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Thanks for returning my call leadfoot100, you have now more or less confirmed what my first thoughts were, I always had this gut feeling that it was a carb issue but for the life of me I could not find it I guess (as you have done) we go thru the process of elimination.

I have replaced the ECU with no change and also I have tested coil and stator and they are in spec, replaced cam chain also valves are in spec.

As I have a very similar issue as what presented itself on your 09 I have taken the opportunity to follow your lead and will now put a full kit thru the carb and also replace the  AP diaphragm with o-rings.

 

Thanks again for your reply, I will let you know what transpires.

 

Cheers.

 

 

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On 9/18/2017 at 10:07 AM, vayama said:

Thanks for returning my call leadfoot100, you have now more or less confirmed what my first thoughts were, I always had this gut feeling that it was a carb issue but for the life of me I could not find it I guess (as you have done) we go thru the process of elimination.

I have replaced the ECU with no change and also I have tested coil and stator and they are in spec, replaced cam chain also valves are in spec.

As I have a very similar issue as what presented itself on your 09 I have taken the opportunity to follow your lead and will now put a full kit thru the carb and also replace the  AP diaphragm with o-rings.

 

Thanks again for your reply, I will let you know what transpires.

 

Cheers.

 

Vayama, that should hopefully do it for you too. This issue is such a headache isn't it? I originally had that same hunch it was carb related but just couldn't understand why it was acting up still after a basic rebuild and jetting. I thought for sure it had to be something else at that point. Oh well i guess. I would Definitely get a thumb screw for your slow needle (fuel screw). I really like the JD flexible fuel screw. once you get it all set up you'll want to re-set the fuel screw and adjustable AP together. You could possibly get away with not getting a Quickshot 3 and just do a smaller AP leak jet and new diaphragm, or maybe even the quickshot 2, but I'm glad I ended up with what I did. It hammers.

Order a new diaphram and bowl O-ring and D-ring because the QS3 doesn't come with them.

Edited by leadfoot100
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leadfoot100,
                   Well the saga is ongoing, what has happened up to date..........Replaced all seals in carb including vacuum release plate seal also accel pump O-rings and diaphragm, new NCVS needle new mixture screw with O-ring.

The issue is still a consistent, I paid a great deal of attention to the carb making sure everything was as it should be looking for wear on the slide wheels and their contact points on the guides, vacuum release plate was checked for cracks or excessive wear I did all this under the opinion that i did not want to look at the carb again.

 

The positive is that the lean issue has become very prominent now more so than previously. Taking the bike for a run it idles clean.... above the 3000 rpm it revs up to the limiter with no hesitation.

 

What now.... I am thinking a new stator or alternatively generic mid body carb gasket as a last resort.
I will fix this bike it is only a matter of time.

 

Thanks for your time and thoughts "appreciated".

Cheers.

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On 9/23/2017 at 6:02 AM, vayama said:

leadfoot100,
                   Well the saga is ongoing, what has happened up to date..........Replaced all seals in carb including vacuum release plate seal also accel pump O-rings and diaphragm, new NCVS needle new mixture screw with O-ring.

The issue is still a consistent, I paid a great deal of attention to the carb making sure everything was as it should be looking for wear on the slide wheels and their contact points on the guides, vacuum release plate was checked for cracks or excessive wear I did all this under the opinion that i did not want to look at the carb again.

 

The positive is that the lean issue has become very prominent now more so than previously. Taking the bike for a run it idles clean.... above the 3000 rpm it revs up to the limiter with no hesitation.

 

What now.... I am thinking a new stator or alternatively generic mid body carb gasket as a last resort.
I will fix this bike it is only a matter of time.

 

Thanks for your time and thoughts "appreciated".

Cheers.

 

Well that's interesting. Assuming you're working with a new plug, does the coil "bite" the threads on the plug for good contact? Is the rubber coil boot in good shape? I ended up putting plug sealer on the boot to hopefully eliminate any stray voltage leaks which I have no idea if it helped but I know it doesn't hurt. 

Check your ground screw too on the frame. Make sure it's corrosion free and solid.

Electrical aside, since your bike idles good try a couple things. Make sure your pilot Air jet is in good shape not enough air boosting the pilot jet would jack up its flow rate. Make sure the tiny little o-ring and washer are in the correct place on the fuel screw. Then go ahead and check for air leaks. Get it warm and while idling, spray some carb cleaner on the outside of the carb housing and around the inlet and outlet and see if you get any idle change. 

All that is just either how I would or did go through my issues too. Not being a bike mechanic there's probably better methods for diagnosing these issues but for me it's just ideas more than anything. 

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Hey leadfoot100,

                          Cheers for your add on, to answer some questions you posed.....

"Assuming you're working with a new plug" yes new plug - trying a CR8EIX to see if any improvement.

"does the coil "bite" the threads on the plug for good contact?" yes good contact.

"Is the rubber coil boot in good shape?" yes no cracks or wear.

"Check your ground screw too on the frame' Done.....contact points sanded and cleaned.

"Make sure your pilot Air jet is in good shape" Jet is new.

"Make sure the tiny little o-ring and washer are in the correct place on the fuel screw" New o-ring with gasket kit.

"Then go ahead and check for air leaks. Get it warm and while idling, spray some carb cleaner on the outside of the carb housing and around the inlet and outlet and see if you get any idle change." Did something a little differently pulled sub frame off used a atomized spray of fuel, when raising revs to where it leans out sprayed raw fuel into carb throat ......no change problem still persists.

 

Disconnected neutral position switch.......no change

Disconnected TPS......no change.

Has to be either/ither Coil or stator.......... I have punted on stator new 09 (4 bolt) stator should be here early next week.

 

Same Same not a bike mechanic but enjoy the process even tho it can be frustrating when these types of issues present.

But hey thanks for contributing.

Let you know what transpires......

 

Cheers vayama

 

 

 

 

 

 

 

 

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At this point in time.......stator has been replaced (New 2009 fitted) replaced hot start seal.

The Issue is "still present" no change sooo I guess unless a reader has a check this thought I will toss a coin... either a Mid Gasket (Carb) or an Ignition coil next.

 

Frustrating....

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Purchased the bike with the issue Red800rider apparently the issue just presented with no warning. Running the bike in motion - 2nd gear or 3rd build the revs to around 3000 rpm (lean issue is very prominent at these revs) pull the choke out and there is a slight drop in revs otherwise no change. Waiting on a ignition coil assembly to see if this cures the issue.

 

Head scratcher indeed. 

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I got a great deal on mine cause of similar issue. Here was the cause of mine. Some previous owner broke off the very tip of a pilot screw tip (red anodized) then just ran flex screw in behind it. I could only find this by looking at pilot holes, in throat, through slide area (with slide removed) while shining light up from bowl. Front hole was dark. Removed mid-body and red tip was easy to see. Had to tap out (toward bowl). Ran like a champ after slight tweaks of pilot screw!

20170211_173654.jpg20170211_175404.jpg

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****Is the idle screw turned in that far? Have you backed it out to see if idle drops?**** yes idle screw is at 2 turns out at present with a 45 pilot....screw it in and it stalls!

The mixture screw tip breaking is very interesting Red800rider if indeed a tip has broken off (This bike has a aftermarket mixture screw) it could well be jammed somewhere in the mid body....it was a toss up between ignition coil assembly and mid gasket, the reason i went with coil is the mid gasket has to come from the US as i cannot source one here in Australia.

I am not that confident that the coil will fix the problem as i don't think the coil would be breaking down at specific revs (I hope i am wrong lol).

 

That's motorsport!.

 

 

 

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