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Thread: crf 450 bogging on the bottom :(

  1. #1
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    Default crf 450 bogging on the bottom :(

    I have already crashed 3 times because of it, as soon as I crack the throttle off idle, it boggs out, if I roll it on slow, it works, but in circle combos and sit down one handed circle wheelies I need to just bump the throttle off the idle, and the eingine dies. I took the bowl off the carb and blew everything out, hoping it was just a dirt particle in the pilot or something, but it still does it. I also took what looks like a throttle pump apart, on the bottom of the bowl, no dirt in there though. Does anyone have any other ideas, I'm not sure where to look next. Thanks for the help! My Aprilia has been down for almost 2 weeks now because the oil fill plug came out, so I can't ride anything, and its killin me!

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    Quote Originally Posted by Ryan Moore
    I have already crashed 3 times because of it, as soon as I crack the throttle off idle, it boggs out, if I roll it on slow, it works, but in circle combos and sit down one handed circle wheelies I need to just bump the throttle off the idle, and the eingine dies. I took the bowl off the carb and blew everything out, hoping it was just a dirt particle in the pilot or something, but it still does it. I also took what looks like a throttle pump apart, on the bottom of the bowl, no dirt in there though. Does anyone have any other ideas, I'm not sure where to look next. Thanks for the help! My Aprilia has been down for almost 2 weeks now because the oil fill plug came out, so I can't ride anything, and its killin me!
    I have that problem all the time! j/k Maybe you need to try adjusting the accelerator pump(I am assuming they are adjustable) so it squirts a bit more fuel. I'd say you are in virtually uncharted territory since most guys aren't operating their bikes vertically.

  3. #3
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    I just tried a spare carb I had, same exact problem. That carb came with this motor and ran cherry, so it must no be the carb. I hate these type of problems, specialy when I have shows lined up.

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    Quote Originally Posted by fizzmoto
    I'd say you are in virtually uncharted territory since most guys aren't operating their bikes vertically.
    It does it on flat ground, bike on both wheels.

  5. #5
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    Check out this mod, it might be just what you are looking for!

    http://www.thumpertalk.com/forum/sho...d.php?t=374181

  6. #6
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    Quote Originally Posted by kwoody51
    Check out this mod, it might be just what you are looking for!

    http://www.thumpertalk.com/forum/sho...d.php?t=374181
    I just want to get it back to stock running condition, it has been workin fine for me for over a year, except for one engine failer, popped another stock motor in the hole and I was good to go again, till now.

  7. #7
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    Maybe it's running a little lean due to the heat? Maybe turn the pilot screw out a bit? If that's not it then maybe your air filter is dirty.

    Another thing on the heat note - check your coolant level. A hot engine tends to run lean.

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    He has lean and rich backwards, on hot days engines run rich not lean and when hot they also run rich so you would need a smaller a pilot and or turn in the fuel screw.

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    Could also be bad timing on the acel pump the screw under the black plastic cover. You can look in the carb and watch for the squirt of fuel and make sure it just misses the slide.

  10. #10
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    I had a lot of luck with the JD jet kit for that bike. It really improved throttle response. A worthy upgrade even if it doesn't solve your problem. Its got some suggested settings that were absolutely perfect for me.

    Also, I'm just wondering what the condition of your spark plug is, as it'll run like shit around idle if needs replacement.

    Check for dirt in your fuel filter too.

    Its something along these lines though.

  11. #11
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    It should probably be noted that his bike has no air box, just the filter and a custom exhaust slipon. Was the bike ever jetted properly for the setup? Are these problems new? Maybe the heat has something to do with it like what was mentioned before.

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    How does the bike run in the higher revs once you get past the stumble?

    Make sure your fuel lines are unobstructed and your fuel filter is clean. If a line is pinched even the slightest bit your bike will run lean. I cooked a snowmobile motor once because the line had a kink in it. On a long shot, take the petcock out of the tank and make sure its working properly and theres nothing in the tank that would be plugging it.

    The heat would make the motor run richer and feel doggy but it would still run. This sounds more like a fuel starvation problem.
    04 Husky SMR 450
    85 Yamaha RZ 500

  13. #13
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    The problem is new, I have been using the same setup with air filter/jetting/exhaust for months now. no temp change, I live by the beach and the outside tem barely fluctuates.

    I took the bike apart to change the plug and check the valve clearances. the plug looked a bit black, but I was running it with the choke on to see if it helped the bog, it did. My exhaust valves were .003 and .004 to tight, so I adjusted them into spec, and the compression tappet, inatake valves were in spec. Now the bike won't run at all!!! Went from bad to worse, I gave up for today after checking everything 3 times and taking the rocker cover off 3 times. Not sure what is wrong now. Cam chain was dead on, valve clearances cherry. I'm gonna go at it again tomarow, now that I missed the stunt comp in Long Beach :( Damm bike!

  14. #14
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    Quote Originally Posted by A.R.C.
    How does the bike run in the higher revs once you get past the stumble?

    Make sure your fuel lines are unobstructed and your fuel filter is clean. If a line is pinched even the slightest bit your bike will run lean. I cooked a snowmobile motor once because the line had a kink in it. On a long shot, take the petcock out of the tank and make sure its working properly and theres nothing in the tank that would be plugging it.

    The heat would make the motor run richer and feel doggy but it would still run. This sounds more like a fuel starvation problem.

    The fuel lines are clear, and I don't know were the fuel filter is on this bike, don't see one. The petcock is flowing good, and it does rev out if I roll on it slower.

  15. #15
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    Weird.
    Try a new plug tomorrow when you go at it again. If it doesn't help then at least you can say you tried. Got me stumped.


    OT: "I live by the beach and the outside temp barely fluctuates. " -Must be nice

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    Sounds even more like a fouled plug to me now. Try a new one, at least you can cross it off the list then if nothing improves. Those iridium tipped CRF450-specific plugs cost a bit, but I was putting in about 2 or 3 a year with all the street riding/urban assualts that I was doing.

    The fuel filter screen is on the bottom of the tank. Here's the 03 manual:
    right click, save target as:

    http://www.jonmarshall.ca/crf/03crf4...cd_is_pass.pdf

    'motocd' is the password

    Good luck

  17. #17
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    [QUOTE=Kwota]Sounds even more like a fouled plug to me now. Try a new one, at least you can cross it off the list then if nothing improves. Those iridium tipped CRF450-specific plugs cost a bit, but I was putting in about 2 or 3 a year with all the street riding/urban assualts that I was doing.


    +1
    ZIPPER
    94´XR600R

  18. #18
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    Quote Originally Posted by Kwota
    Sounds even more like a fouled plug to me now. Try a new one, at least you can cross it off the list then if nothing improves. Those iridium tipped CRF450-specific plugs cost a bit, but I was putting in about 2 or 3 a year with all the street riding/urban assualts that I was doing.

    The fuel filter screen is on the bottom of the tank. Here's the 03 manual:
    right click, save target as:

    http://www.jonmarshall.ca/crf/03crf4...cd_is_pass.pdf

    'motocd' is the password

    Good luck
    I did put a new plug in there. Thanks for the manual link.

  19. #19
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    send it to tokyo mods.. they'll sort it out.

  20. #20
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    Quote Originally Posted by SWAT
    send it to tokyo mods.. they'll sort it out.
    +1
    Let someone else figure it out. You can't afford to be missing shows. Yeah, it'll cost ya some cash, but at least it will be fixed & running good. I've always worked on my own bikes, but sometimes it's gotta go to the shop.
    By the way, I got my passenger rearsets & pegs you sent. Holy crap, frickin SWEET! They look awesome, just like yours & they are so light, you couldn't even tell there was anything in the box!
    Thank bro & good luck with the bike.
    -Gross.
    Jay, funhouseDVD.com

    2002 YZ426F Stuntmoto
    www.funhouseDVD.com

  21. #21
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    Quote Originally Posted by funhouseDVD
    +1
    Let someone else figure it out. You can't afford to be missing shows. Yeah, it'll cost ya some cash, but at least it will be fixed & running good. I've always worked on my own bikes, but sometimes it's gotta go to the shop.
    By the way, I got my passenger rearsets & pegs you sent. Holy crap, frickin SWEET! They look awesome, just like yours & they are so light, you couldn't even tell there was anything in the box!
    Thank bro & good luck with the bike.
    -Gross.
    Shipping a bike to a shop is nuts, you guys must be rich or something!! I don't know who or what toyo mods are, but I'm sure its not in Gorver Beach CA. This bike won't even run now!!

  22. #22
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    Quote Originally Posted by Ryan Moore
    This bike won't even run now!!
    Do you got spark? Secondly you are riding the bike verticle most the time, do you have a full tank of gas because if you ride it a while in vert position I would figure you may not get the gas going to the carb unless the tank is full since the petcock will be at a 90 angle to the ground. Maybe every so often you are lacking gas at the carb, in the accelerator pump?... maybe a second petcock at the back so verticle will still get gas. Of course all this is coming from a non stunter so I may be full of poop.

  23. #23
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    Quote Originally Posted by antigrav
    Do you got spark? Secondly you are riding the bike verticle most the time, do you have a full tank of gas because if you ride it a while in vert position I would figure you may not get the gas going to the carb unless the tank is full since the petcock will be at a 90 angle to the ground. Maybe every so often you are lacking gas at the carb, in the accelerator pump?... maybe a second petcock at the back so verticle will still get gas. Of course all this is coming from a non stunter so I may be full of poop.
    I don't see any spark now. but yeah, I have been riding it vertical for 2 years, bone stock, no problems, so that is nothing new to this bike. I am thinking electrical now. anyone know how to check the stator? I changed the coil and still nothing.

  24. #24
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    It's got to be your stator . Sounds funny but I had the same issue w/ my kids KTM seinor pro 50. Evrything u'v been explanning until it would not start any more. I tried the coil 1st and no spark then slapped in a stator and wahla. She was alive agin and my kid was on cloud 9.. The tech at ktm told me there was no way to check it. He told me to just try it and if it dosent work bring it back..But I still think there's got to be a way to check.
    Good luck!!!

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    Quote Originally Posted by rippon
    It's got to be your stator . Sounds funny but I had the same issue w/ my kids KTM seinor pro 50. Evrything u'v been explanning until it would not start any more. I tried the coil 1st and no spark then slapped in a stator and wahla. She was alive agin and my kid was on cloud 9.. The tech at ktm told me there was no way to check it. He told me to just try it and if it dosent work bring it back..But I still think there's got to be a way to check.
    Good luck!!!
    The stator should have 3 wires (they do on all the streetbikes I've ever owned). You have to check the resistance between all of them to see whether or not the stator has failed/broken/w/e

  26. #26
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    I had baja designs add a lighting coil to my crf's stator. their rewind job blew on me and the bike was doing the weirdest things. it would fire up, run normally, and then when i gave it over about 1/3 throttle, it would start chugging, missing a bit, and then suddenly go through some death throws of massive lurching and then backfire until it was dead. quite dramatic. then you'd give it 2 mins, and it would fire up again, behave normally, and then do that again.

    is there anything that you changed or put in that you could have put in wrong or grounded? i'm thinking that in all your swapping you might have put something back in a little wrong. i just don't see how if it was running rough before it would suddenly die like that. look again at what you've done and try to repair the repairs first... nothing personal, we all make small mistakes

  27. #27
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    I just changed the coil, checked the stator ( ohm meter says its good ) and changed the cdi box and whent over the cam chain timing 4 more times, it still wont run. I pushed it down a hill and pop the clutch and the motor just tunrs over, then gives me a loud pop out the exhuast. This bike is killin me right now. I am out of things to check and try.

  28. #28
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    Quote Originally Posted by Ryan Moore
    I just changed the coil, checked the stator ( ohm meter says its good ) and changed the cdi box and whent over the cam chain timing 4 more times, it still wont run. I pushed it down a hill and pop the clutch and the motor just tunrs over, then gives me a loud pop out the exhuast. This bike is killin me right now. I am out of things to check and try.
    damn... I know how you feel. I've been stumped like this before. I don't really know what else it could be. Seems like you have checked over every possibility.
    You know what though, once you finally figure out the problem yourself you will feel absolutely estatic ....

    or feel like a total idiot because it was something ubersimple that was overlooked.

    Hopefully a solution presents itself. If not, we'll keep trying.

  29. #29
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    It runs again!!! I put the stock stator back in and it runs like a champ, now I just need to get my other stator fixed so I can hook the fans back up before I smoke another motor!

    Thanks for all the input!

  30. #30
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    Good to hear your rollin again.
    04 Husky SMR 450
    85 Yamaha RZ 500

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    I'm thinking the stator blew because of the fans...

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    I knew it had to be your stator...... Glad to hear your rollin again. I think Kwota might be on to something w/ those fans. Be carful, dont want to blow another one. What kinda of coolint are u running? I use the engine ice in all my bikes. I have a temp gauge for my oil fill cap on my 03 CRF450 and it always runns 20 to 40 degrees cooler than it used to. But I also have fluidine radiators and a boison high flow water pump. Because, I put in stainless steel valves, Heavy duty springs and a JE 12.5:1 high compression piston with a bulit high lift WEB cam. Granted it is always in the dirt. But I run the shit out of it and it never heats up at all. Good luck, and see ya in the next vid!!!!!

  33. #33
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    Quote Originally Posted by rippon
    I knew it had to be your stator...... Glad to hear your rollin again. I think Kwota might be on to something w/ those fans. Be carful, dont want to blow another one. What kinda of coolint are u running? I use the engine ice in all my bikes. I have a temp gauge for my oil fill cap on my 03 CRF450 and it always runns 20 to 40 degrees cooler than it used to. But I also have fluidine radiators and a boison high flow water pump. Because, I put in stainless steel valves, Heavy duty springs and a JE 12.5:1 high compression piston with a bulit high lift WEB cam. Granted it is always in the dirt. But I run the shit out of it and it never heats up at all. Good luck, and see ya in the next vid!!!!!

    It looks like the magnet cracked inside the flywheel, not sure how or what caused it yet, but my setup is supposed to run my fans with no problem. It worked for about 3 months. I gotta figure out what cuased the magnet to crack before it happens again. To many rev limiter coasters maybe. I use coolaid in my bike, ever since I put the fans on it has worked great, from slow circle combos to burnout combos, no more coolant blowin out all the time.

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