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crf 450 bogging on the bottom :(

21K views 32 replies 12 participants last post by  Ryan Moore 
#1 ·
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!
 
#2 ·
Ryan Moore said:
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! :laughingr 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.
 
#10 ·
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.
 
#12 ·
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.
 
#13 ·
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 ·
A.R.C. said:
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.
 
#16 ·
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/03crf450rmanual_motocd_is_pass.pdf

'motocd' is the password

Good luck
 
#18 ·
Kwota said:
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/03crf450rmanual_motocd_is_pass.pdf

'motocd' is the password

Good luck
I did put a new plug in there. Thanks for the manual link.
 
#20 ·
SWAT said:
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.
 
#21 ·
funhouseDVD said:
+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 ·
Ryan Moore said:
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 ·
antigrav said:
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 ·
It's got to be your stator:headscrat . 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!!!:thumbup:
 
#25 ·
rippon said:
It's got to be your stator:headscrat . 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!!!:thumbup:
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 ·
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
 
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