02 CR 250 jet problems

[Weberg36]

I have a 2002 CR 250 it has a pc pipe and silencer and v force reed cage... the bike runs great at half throttle but when i give it full throttle it bogss out ... Any suggestions of wat 2 do 2 fix it ??

[JENN]

No problems starting it? No chance of water in the float bowl?

Can you easily push the kick starter down with your hand? If yes, there is lack of compression..Could be a blown gasket or a piston ring..

Clutch fully engages? Unscrew clutch filler plug and smell if it smells burnt you have fried your plates...

Have you pulled the sparky and taken a gander?


Your question is relatively vague as you don't offer what you have tried thus far... Have you ever adjusted your valves?

Top end/maintenance done recently?
You have quite a laundry list/a scheduled date with your tool box and bike ahead of ya!

[Young&Fast]

Sounds just like your main jet is too big. Try going down a few sizes with that. That should do it. But also check your air filter and box for dirt or some sort of blockage.
Sorry Jen but I don't really get what you are saying.
A lack of compression would create bottom end problems.
Water in the float bowl would run horrible all around if even at all.
Doesn't sound like a spark plug thing.
And powervales are a compression issue again so that would create mucho smokeo and lack of bottom end.
And a top end... maybe.
But I think a main jet problem is much more likely. What you said were all good maintenance suggestions but I don't think they match his symptoms. If I'm wrong please correct me. I always want to learn more about the wonderful things that we call motorcycles.

Here is the carb jetting piece from LukesRacing.com that I think is pretty good.
Carb Jetting -Each thing that you change will effect the carb jetting. It is not possible to tell you exactly what jets to run. Carb jetting is time consuming but dollar for dollar will pay off in performance more than any part you can buy.
Here's some instructions for jetting a carb:
Start with the jetting already in the carb or to be safe on a rebuilt motor or big bore kit start with about 2 sizes bigger on the main jet.. Always warm up the motor by riding it, do not warm up the motor by revving the motor excessivly in neutral. On 2-strokes use a quallity synthetic 2-stroke racing oil and jet the carb with the same oil that you will be using. On a new motor- Break the motor in for at least an hour. The only thing you need to do for breakin is not over-heat or over-rev the motor, wide open is ok for short periods, just normal riding. Start out running it easy and progressively run it harder. A new piston will run slightly hotter because it does not have any carbon to slow heat transfer into the piston, also new rings will allow some blow-by which causes the piston to run hotter. Do not add extra oil to the gas or do anything different. Extra oil changes the fuel mixture. If you are going to use race fuel, pump fuel or a mixture of the two use that fuel while jetting the carb. Most race fuels contain more oxygen than pump gas and will cause the motor to run lean. Jet the carb with the fuel and oil you will normally run. Be sure you have a clean air filter, the condition of the filter greatly effects the carb jetting. Do not over-oil the filter excess oil will cause the motor to run too rich. Try to jet the carb on a day when the weather is closest to the same weather conditions when you are doing most of your riding or racing.
Find an area where you can run the bike or quad safely on a long straightaway.
#1. Start with a warm motor and install a clean spark plug (sometimes a new plug is harder to read than a plug with some carbon on it)or just remove the plug and take note of the color (black, gray, white). Start the motor and run it at wide open throttle, run through several gears at wide open, then pull in the clutch and hit the kill button. Remove the plug and check the color, white is too lean and black is to rich, (you want a light to dark shade of gray) The plug will usually be lighter in color toward the center electrode and darker toward the outer edges. This will give you a reading of the fuel mixture at wide open throttle (main Jet). The idea is to let the motor run at wide open and avoid part throttle or idleing which will change the plug reading. If the plug is to white install a larger main jet, if its to dark install a smaller main jet. Go back to #1. If the plug color is a light shade of gray, its good. Dark at the outer edges is OK.
#2 Run the motor at part throttle (1/4 to 1/2) as much as possible, try to avoid idling or wide open. Shut the motor off and pull the plug. Check the plug color as in step #1, If the plug is to dark, lower the needle (moving the clip up, lowers the needle) If the plug is to light, raise the needle (moving the clip down, raises the needle) If you end up with the clip at the top or bottom groove and still not jetted right you might have to go to a different needle(richer-thinner or leaner-fatter). Usually the stock will work
#3 Run the motor at a normal idle speed. Turn the air mixture screw in until you can notice the RPM's going lower, back the screw out until the RPM,s are highest, if you go to far out the screw will have no effect, try to find the point where it idles the fastest but the screw is not out so far that theres no effect. When you have the right setting, a half turn in will slow the RPM but a half turn out will have little or no effect. Now shut the motor off and turn the air screw in until it stops (gently tighten so as not to damage the air screw seat) It should take about one and a half to 2 turns. If it takes less than 1 ½ turns the pilot jet (slow jet) is to small ( try a larger pilot jet). more than 2 turns and the pilot jet is to big ( try a smaller pilot jet).

[JENN]

He didnt provide too much info.. so I provided him with a nice laundry list of things to check into ...

[Weberg36]

the bike runs fine besides when its wide open... the bike has good compresstion .. float is good everything is pretty much fine .. besides when the bike is wide open ... A friend said that i might need a bigger jet because the bike doesnt get enough fuel when it is wide open thats why it bogs out

[Young&Fast]

Could be, but I think when it is too lean it tends run better and not bog until it blows. Does it smoke before it dies? If so jet is too big. If you are not to confident take it to a shop.

[Peaches]

if it bogs down try changing the needle position... if un touched it should be in the middle when the bike is stock try moving it either up or down before going and getting a new jet.

[Weberg36]

maybe im running 2 big of a jet then ... im not sure wat size it is .. but maybe i should go buy a stock 380 and try it out

[Young&Fast]

10-4 that should help