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Hi guys. Im so dissapointed on this bike. I've really taking care of it and the last problem that i had that it would idle on choke but not without and when i gave it little bit throttle it would just bog. Well i dis everything. Checked valves (they are new hasnt even gone 10h) compression really good. And. I took apart the whole freaking bike just to clean the carb hehe. And the jets were not even clogged up. The float bowl was so clean i couldnt see any dirt it looked like brand new. The acc pump does give a good stream of gas when i twisted the throttle. Well after i took 8h to put everything togheter outside the garage in like -10 i got it together and tried starting it. Well gues what? Same thing again! Now i have only 2 things that might need to check into. Can it be the airfilter? Bought a new airfilter before this happended from twenty and it was really thick for being a airfilter. And i oiled it pretty much it was all blue in strong color. Should i put on the old one and see if it works better? Thanks for every answer its almost season in sweden and i wanna drive. All tracks here sucks rear and we have to pay 200$ to drive in their bad tracks so im just driving in the woods

The air filter can be a issue , especially if it was running fine before hand , a overly oiled filter will cause a rich condition , did you try starting it with the Hot Start lever pulled ?? , if it starts or tried to start when using it , then the issue is a rich condition

A way to test if it is a lean condition is to remove the spark plug and dip the electrode part in gas , then reinstall the plug , and boot , and try to start it , if the bike starts or tries to , then its a lean condition , these quick tests will at least narrow down your issue

When you say the jets were not clogged (Pilot and main jet) , how did you actually determine this ?? , a Pilot jet can still be clogged even if you can see thru it with a light , , also , you did not mention anything about the Fuel Screw , have you tried adjusting it ?? , in the inspection of the carb when you took it all apart , did you confirm that the O-Ring , washer and spring were intact and in the correct order (from tip it should be O-Ring,Washer,Spring) , a torn or damaged O-Ring can cause a massive lean condition , did you confirm the Hot Stat is working properly and was not stuck inside the carb ? , did you confirm the Floating Slide Plate Seal is intact ??

JimDirt wrote:The air filter can be a issue , especially if it was running fine before hand , a overly oiled filter will cause a rich condition , did you try starting it with the Hot Start lever pulled ?? , if it starts or tried to start when using it , then the issue is a rich condition

A way to test if it is a lean condition is to remove the spark plug and dip the electrode part in gas , then reinstall the plug , and boot , and try to start it , if the bike starts or tries to , then its a lean condition , these quick tests will at least narrow down your issue

When you say the jets were not clogged (Pilot and main jet) , how did you actually determine this ?? , a Pilot jet can still be clogged even if you can see thru it with a light , , also , you did not mention anything about the Fuel Screw , have you tried adjusting it ?? , in the inspection of the carb when you took it all apart , did you confirm that the O-Ring , washer and spring were intact and in the correct order (from tip it should be O-Ring,Washer,Spring) , a torn or damaged O-Ring can cause a massive lean condition , did you confirm the Hot Stat is working properly and was not stuck inside the carb ? , did you confirm the Floating Slide Plate Seal is intact ??

Hello, sorry for the late answer but the pilot jet was clogged up, i cleaned it with brake cleaner and compressed air

You should still go ahead and replace the pilot jet if you get the chance , unless you get the carb cleaning tool , the pilot jet is fairly cheap (at least it is in the states , not sure what parts cost over there) , it does not take much debris to clog them , even if its slightly clogged it will cause issues , i always have a few extra lying around as well as different main jets , just in case .... but glad its running !!

JimDirt wrote:You should still go ahead and replace the pilot jet if you get the chance , unless you get the carb cleaning tool , the pilot jet is fairly cheap (at least it is in the states , not sure what parts cost over there) , it does not take much debris to clog them , even if its slightly clogged it will cause issues , i always have a few extra lying around as well as different main jets , just in case .... but glad its running !!

yeah it does run but i can't seem to find whats causing the bike to bog from idle or driving slow and give it full throttle really fast. the bike has a 40 leak jet in it I'm pretty sure about that because the ap nozzle squirts gas for 1 second when i pull the throttle wide open. so its not in the ap thats causing it to bog like this. can it be the pilot screw is not set good or maybe to small main jet?

This is a basic jetting guide , you should be within this range

Jetting Guide for Main Jet:(pilot 45) CRF450R/X

:*: Elevation is measured in "Feet" Above Sea Level , you might have to convert to your measurement system , Temp is also in "Fahrenheit " , not Celsius :*:

Sea level....165
2000 ft.......162
4000 ft.......160
6000 ft.......158
8000 ft.......155


Temperature/Elevation:
One main jet size (up/down) for every 2,000 feet or 25 degrees in temp.

Also , on the squirter , its just missing the slide correct ?? , you do not want it hitting the slide if it does you have to adjust the AP timing accordingly , usually the bog is caused by AP timing , unless your jetting is way off

Fuel Screw should be between 1-1/4 to 2-3/4 , if its less than 1 turn out (need smaller pilot) or more than 3 turns out (need larger pilot) , you will need to change your pilot jet accordingly

Also , what clip position (from the top) is your needle clip at ?? , it should be 3rd or 4th (usually 4th works best)

JimDirt wrote:This is a basic jetting guide , you should be within this range

Jetting Guide for Main Jet:(pilot 45) CRF450R/X

:*: Elevation is measured in "Feet" Above Sea Level , you might have to convert to your measurement system , Temp is also in "Fahrenheit " , not Celsius :*:

Sea level....165
2000 ft.......162
4000 ft.......160
6000 ft.......158
8000 ft.......155


Temperature/Elevation:
One main jet size (up/down) for every 2,000 feet or 25 degrees in temp.

Also , on the squirter , its just missing the slide correct ?? , you do not want it hitting the slide if it does you have to adjust the AP timing accordingly , usually the bog is caused by AP timing , unless your jetting is way off

Fuel Screw should be between 1-1/4 to 2-3/4 , if its less than 1 turn out (need smaller pilot) or more than 3 turns out (need larger pilot) , you will need to change your pilot jet accordingly

Also , what clip position (from the top) is your needle clip at ?? , it should be 3rd or 4th (usually 4th works best)

Hi. My jettings are good im pretty sure. The ap squirt does not hit the slide so i doubt that would be the problem. However i've noticed de bike has a pretty low idle and when the bike is cold it just stalls without choke but when it is warm it can idle but still pretty low. Could it be the idle being set too low that can cause this "hesitation" or bog? Or could it be that i need to set my fuel screw? I just bought this adjustable one but havent installed it. I really wanna get that bog of man...

If you have eliminated the AP circuit as a issue , then either the Fuel Screw or the Idle can cause issues , its easy to test by simply raising the idle , and riding it and see if its better or the same , the same goes for the fuel screw , 1/4 turn in , see if its better , another 1/4 turn in , see if its better , if not or worse , then go out 1/2 turn to get you back to original position , then 1/4 turn out , etc , this will give you a good feel of the changes and improvements , if any

This will either confirm or rule out the idle and/or fuel screw as the cause of the bog , if it rules them out , then you are back to either the AP system , or a float level issue , or a internal carb blockage

Also , the guide i posted is for a 450 , so the 250 will be slightly less as far as actual jets go (usually about 1 jet size less than chart) , everything else should be about the same

Also , the AP squirt , should just barely miss , if it is a major miss , then that could be a issue as well , the timing should be so it misses , but just barely , not delayed , a delayed miss will cause a bog , just as a squirt that hits the slide would , because air is overpowering the fuel mix , the squirt is what makes up the difference before the vacuum draws the gas thru the jets , if its delayed too much , you get a lean bog