bogging at full throttle when engine is hot

I have an 03 WR 450 that started bogging only at full thottle and only after riding for at least 15 min. I have already cleaned the carbs and checked the jets, replaced the airfilter with no luck. Any suggestions?

Put in a new sparkplug and ride the bike. When you go full throttle and the bike bogs immediately shut the bike off. Pull the plug and see how it looks (white/black-smelling like fuel). That should give you an idea what to look at unless you already can tell if it's bogging from a lean or rich condition.

Another option is checking the fuel line for restrictions/kinks as well as all of the carb vent lines. Has there been a significant change in riding conditions since this problem started?

No change in conditions the spark plug looked white.

If your plug looks white, you are running lean. Start by checking for an airleak by squirting some wd40 around, then if that wasnt the problem, start upping the main jet. Once your bike runs better with the larger jet, fine tune it with the needle.

I agree you most likely have an airleak. I wouldn't ride it until you find the problem.

If your plug looks white, you are running lean. Start by checking for an airleak by squirting some wd40 around, then if that wasnt the problem, start upping the main jet. Once your bike runs better with the larger jet, fine tune it with the needle.

Hey Yamaster,

When you are talking about air leaks, do you mean on the intake side or the exhaust side? Can you explain a bit more what the testing procedure is for that, ie where exactly do we spray the WD40?

Thanks.

Intake side check for any air flow leaks at boots and make sure the vacuum vent lines are not clogged with dirt. :ride:

Sounds like your not getting sufficient fuel flow from the tank to the carby and are running out of fuel in the carby. Pull your tap out and clean the filter. Could also be crap in the line above the needle and seat (fuel inlet to carby). Check the one way valve in the tank breather is letting air in. Also, as someone else mentioned, check your breathers are clean and free to flow air.

You spray the wd40 on the intake side. Start from the airboot between the carb and the airbox and work your way down to the boot between the motor and carb. If you have an airleak your rpm's will change when sprayed with the wd. Hope this helps.

A friends WR 250 started doing this so I pulled the one way check valve out to the gas cap and now it doesn't do it anymore. The valve seems to be very sticky in the housing. WR Dave

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