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CRF250x Throttle Bog

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Have a 2013 x with about 200 miles on it.  Cleaned the air filter a short while ago, first time. Ever since doing so, the engine bogs when wrapping the throttle a quarter turn from idle.  I've read several posts regarding this issue, and note a number of potential solutions.  However, could my air filter cleaning effort have caused this, or is this just a timing coincidence?  There was no bog previously.

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Since your problem started right after cleaning your air filter, I'd start by reverse engineering your filter setup back to it's correctly running configuration.

1) Air filter oil. You could have used too much or too little (or none at all?). This can change intake air volume available to your carburetor. What type of filter oil was used? How was the filter cleaned to ensure good flow and eliminate residual oil left in the filter which may not be compatible with your new filter oil?

2) Filter installation. I find these filters somewhat tricky to install correctly. They fit tightly in the airbox which increases the chance of shifting the filter during installation leading to incomplete filter/airbox surface mating. I use a little grease on the filter mating surface for better sealing. It doesn't help things that Honda chose such a short filter winged screw( apparently the longer '04-05 CRF 250R screw can be used to make things easier) . I get mine started, then carefully run my finger around the filter mating surface to ensure full contact before tightening securely.

I'd take the filter off, use one of many proven poduct cleaning methods matched with it's compatible motorcycle air filter oil and reinstall it with the above techniques.

Oh yeah. Make sure the small diameter mating surface lip has not separated from the main filter. This can occur during even the first cleaning and cause an air gap (engine damage). I now run a Twin Air filter which does not utilize this PITA lip and seals better than stock or Uni filters which have the separation prone inner foam mating lip.

I hope this helps. Good luck

Edited by motrock93b

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Much obliged for the input.  Suffocation was my first thought, so backed the filter out, started long enough to check for bog...it still bogged.  I cleaned filter with soap & water, then re-oiled with a filter oil acquired from the Kawasaki shop just down the road.  I was a spray oil...Polaris (ATV) brand I think.  REALLY sticky. Instructions advised to remove excess.  HA!  THAT wasn't happening.  May run to the Honda shop...and get the Honda oil and recommended cleaning fluid...start over.  I will definitely check the mating strip for separation.  The 250x filter and housing are an annoyingly tight fit.  Just a few more millimeters engineered into the box opening would be quite helpful.

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Yep the filter is a tight fit. 

Next check is if the accelerator pump is delivering a proper squirt. You'll need to lift the sub frame and disconnect the air boot from the carb.  I had a similar problem and the AP discharge port was partially blocked and delivering a forked squirt, which meant a carb cleaning. I also discovered a tear in the tank filter screen which is probably how dirt got into the carb, so I added an inline filter for extra insurance.

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Thanks much.  I've read some other posts regarding the AP discharge port.  I will check that, if the "reclean" of the filter has no impact...and I doubt it will.  On the subject of an inline fuel filter, seems that would just good medicine.  Inexpensive extra insurance to keep crap out of the carb.  Good idea.

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Update:  Recleaned the filter element using mineral spirits, followed by soap & water, then retreated with a filter oil acquired from the local Honda shop.  Not Honda brand, but "...what they use in (their) shop".  That had no impact on the bog.  Flipped up the subframe to inspect the AP discharge port.  All seems fine there.  Single stream of fuel shooting beneath the gate, as it rises.  Hmmmm...still bogging. 

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Have you checked the jetting?  What size slow jet and main jet are you running, and where is the needle clip?  Sounds to me, ruling out over oiling and filter fit, that by cleaning the filter the air mixture has changed.

 

~DS

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Frankly, do not know what size slow jet or main jet or position of the needle clip I'm running...other than it's stock. Believe I'll dive into the carb and play around with it.  The bike also runs rough at midrange steady throttle.  Going to pick up a JD Jetting kit and see what results.

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I just read your other post.  I'm sure jetting needs fixed.  The X is rather sensitive and I had the same problems with my brand new 2012 250X.  I ride at high altitude and had to change the slow jet to a 45 and adjust the fuel screw.  Main was reduced to a 128.

 

Did you purchase your bike used?  A lot of people neglect the air filter.  My brother bought a 2001 CR500 that was immaculate, previous owner took good care of the bike.  Except for the air filter.  The darned thing looked like a chocolate bundt cake when I opened up the air box.  I re-jetted the bike just after replacing that nasty air filter.

 

~DS

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Bought the 2013 250x new in April '14...leftover.  Airbox/filter clean as a whistle.  The throttle bog began the first time I cleaned.  May well be only coincidence.  I'm low altitude, not far from the Texas coast.  I do believe my answer lies in some jetting experimentation. Have some Carburetor 101 to get through, though.  I am thankful for the internet and youtube!

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i had this same problem, it was bad.All i did was replace the AP and make sure the little tunnel where the squirt of gas comes out is clean

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Of course, jetting should be optimizedn but feeding the clutch on corner exit tames the drive of any evil doers.

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Of course, jetting should be optimizedn but feeding the clutch on corner exit tames the drive of any evil doers.

 

I agree. That works for the track and higher trail speeds but a lot of trail riding is on/off the throttle at relatively low engine speeds and any hickups or roughness  when rolling the throttle back on is disconcerting and can be a problem in low traction situations.   

A couple of weeks ago we got on a trail that was badly overgrown, went about a mile and hit blockage and had to turn around. The brush was so bad we had to go slow and do a lot of heads down riding to protect our faces. Throttle response in first gear made the bike difficult to control at the low speeds so I used 2nd and slipped the clutch.  My friends EFI bike just purred like a kitten.

 

On edit: I added a Stealhy Flywheel and impressions from riding around the block was not much improvement, just a smoother idle. But on the trails it made a big difference in smoothing out the off idle throttle response.

Edited by Chuck.

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Today, Installed a JD Jetting kit at JD's recommended set up for my altitude/temp.  While at it, installed a Kouba (CRFOnly) fuel screw...backed out 1 3/4 turn. Not much ride time, but it is apparent the throttle bog is gone...zip...done.  Surging at constant low to mid rpm's disappeared.  Add to this noticeable low to mid range gains, and I figure this might be the best money spent on the 250x.  Did do the complete airbox mod, as recommended by JD.  I've got a new bike!  Jumped on it late this evening.  Hit the start, no choke. It fired right up, and took gas with no bog.  That's a first!

 

The "O ring mod" for the 250x is not applicable to models later than 2008...though the kit includes O rings for this mod. 

 

Ran into an unexpected challenge with the 2013 carb.  Access to the fuel screw was blocked by an aluminum "pin" inserted across the fuel screw access port. The pin is located in the primary carb body, not the bowl.  Dug all over the net, but found no reference to it.  It is a benign part, doing nothing more apparently that keeping me from screwing with my fuel screw.  Finally, grabbed a small pair of vice grips, grabbed it and gave it a yank.  Came right out.  Hmmm...  the head of the pin looks very similar to an allen head bolt, only with a round ID, instead of hex.  That little hurdle added a couple of hours to my project.  Don't let it rob you of the time.  Go straight for the Jr. vice grips and get rid of the thing. The 2013 carb does have the "D" head stock fuel screw.  Using the "blue electrical screw cap" to remove the stock screw, works.  Had to trim some of the plastic back so I could get the wire spiral cone to the screw head, but it was a simple, effective trick.

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There are aftermarket fuel screws such as Kouba etc.  I used a R&D remote screw so I could adjust while riding.  The knob mounts right next to the idle speed knob.

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