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jayninja

crf450x issues

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wondering if anyone has had similar problems or could point me in the right direction.

ive got a 2008 crf450x and its ran fine for the last month started first go ran smooth ect, now all of a suddon it kept cutting out randomly when it was ideling and low rpm like a bog/flame out, and when i would go to start it after wouldnt start with electric start only with kickstart after alot of kicking and swearing!

now thought it was a partially blocked pilot or tight valves, checked the valves they are within spec & pulled carby off cleaned top to bottom blew out jets ect put a bigger pilot jet in and it went again diddnt cut out so much but i think it was just masking the problem as half an hour later it did the same thing exept this time after playing with the carby it started bogging backfiring running spluttery when i am cruising with not much throttle, i can accelerate through the gears fine and it wont miss a beat and at full throttle still pulls smooth and hard, now dosnt matter what pilot or mixture setting  i put in it ive gone from a 45,50,55 pilot same problem occours.

not sure what i should check for next  i just cant explain how it will idle fine then randomly bogs and thats game over. until it starts again but that normally takes about 2 failed starts(idles and dies within 2 seconds) for it to sit there and idle again rides fine with varying throttle but with crusing or light throttle dosnt matter what rpm it carrys on.

any help or advice would be appreciated.

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Sounds like something is stuck in the pilot circuit.  Also, check that your hot start hasn't stuck open, and check that your float valve isn't sticking.  I'd kinda suspect grit in your fuel.

 

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If it was running great before....I wouldn't start changing pilot jet sizes.  Keep the pilot size that works for your bike....and get a new one, blowing it out might not have gotten it clean.  If the bike is running great past idle, I wouldn't think fuel or fuel filter etc. is problem.  Learned a good trick (recommendation from this site) using guitar string to clean the carb circuits...works well.  Check all your air leak spots (hot start, carb boots, etc.).  

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Stick with a 45 pilot. Up at the top of the pilot passage, and sometimes at the top of the fuel screw. chunks of goo and sludge accumulate. Nothing that a shot of compressed air and a gentle probing with a dental pick can't clear up. 

No need to pull the carb. Lay the bike down on its right side so that you can see clearly.

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So ive cleaned carb 

checked:

hot start

accelerator pump

Mixture screw

Jets 

Float level 

Blown out with air and flushed it with fresh fuel

Just seems to have gotten worse since i pulled carb off ive even went back to original settings and still the same. 

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Could be gunk/ dirt/ bad o-rings in the mid-body of the carb.  Need a security/ torx bit to take that apart.  Never done mine but I think Krannie was having similar issues before he rebuilt his carb.  Said his was really cruddy and it cured the problem.  Think he took it to AS Racing, if I remember right.

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I have an 06 crf450x with the same problem. I rebuild  the carb, the same problem. So I try to analyze the problem and come to the conclusion and it might be the valve clearance and it was. Adjust the clearance to oem spec and it working happily now.

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Mid body carb kit and your bikes will be like new again...here is a video:  

 

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Posted (edited)

Still having this problem?  With your description, it sounds like you have a too lean running condition. 

Have you done any mods to your bike?  Like a new aftermarket exhaust and aftermarket air filter while running the stock jetting? this would cause a too lean running condition. 

Another cause of running too lean is an intake leak. Check the boot that is in between the carburetor and the cylinder for cracks, rotting and loose clamps that would cause the bike to suck in extra air. If your problem as been growing worse over time, an intake leak that is getting worse could be the culprit. 

Try changing the float level and/or needle valve position to deliver more fuel to the engine. Or, stage 2 jet kit if you have the aftermarket pipe and air filter. 

 

 

Edited by bobbyloomis
wording
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Not saying it's what you got, but some stuff that drove me nuts before: floats start to sink, fix is to get a new float.  There's an o-ring/seal in the throttle plate, if someone hit it with carb cleaner before they get hard and brittle and mess things up.  Mid-body gasket goes bad.  

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I've taken apart 500 carbs from 450's. I've never seen one that needed a mid body gasket, that is the "read it on the internet" fad of the month. Use carb cleaner all you want.

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On 5/23/2020 at 4:35 PM, Leardriver said:

I've taken apart 500 carbs from 450's. I've never seen one that needed a mid body gasket, that is the "read it on the internet" fad of the month. Use carb cleaner all you want.

Maybe it's just a coincidence, but somehow replacing those items makes shitty or non running bikes run fine.

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The act of taking them apart and cleaning the carb in general while chasing a ghost gasket may help. I wouldn't say it's never needed, I am just 0 for 500 or so in not needing them.

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On 5/23/2020 at 6:35 PM, Leardriver said:

I've taken apart 500 carbs from 450's. I've never seen one that needed a mid body gasket, that is the "read it on the internet" fad of the month. Use carb cleaner all you want.

Well I can tell you mine did and it made a tremendous difference.  Fixed the problems I had been chasing since I got the bike.  My gaskets/o rings were melted and clogging or blocking the passages.   It is about a $20 kit and will at least give piece of mind that it is not the problem.  If it is the problem and not fixed the carb will never work correctly.

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so just an update , I pulled the coil lead apart and there was corrosion in the lead  that goes to the plug, replaced it with an oem coil, well it started up and I thought the problem was fixed but ended up breaking down after a 30 min ride, 

After giving up on the carby I thought it must be an ignition issue,  chasing the wiring harness I didn't find anything so I decided to have a punt and replace the stator , I only got a cheap $80 off ebay compared to $500 oem one as I didn't want to take that much of a gamble Incase it wasn't it, well I've been riding it for a few weeks now with the new stator and runs better than ever , starts straight away, no bogging or stalling. So I think it was a combination of ignition coil & stator in my case. 

 

Thanks for the input! Appreciate all the help. 

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On 5/23/2020 at 4:35 PM, Leardriver said:

I've taken apart 500 carbs from 450's. I've never seen one that needed a mid body gasket, that is the "read it on the internet" fad of the month. Use carb cleaner all you want.

gotta take issue with this...i was chasing carb issues for a couple years...did the mid body which was all melted and deformed...and now my bike runs like new, it's an 05...i can't even tell you how many times i pulled that carb to clean and fiddle with jets and all and taking careful notes on those changes and whatever...popped in the mid body and the bike run perfectly...it was like i hit the lottery, the gasket only cost less than $20 bucks, every body with old bikes needs to do it imo

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