Only at High RPM's engine bucks and seems fouled but

I have a 2009 DRZ400sm and all of a sudden the engine has been crapping out at 75 miles an hour, bucking, low speeds, low rpms runs great once the rpms get higher it acts like it just stops getting fuel, when I gas it, the engine sounds like its fouled a plug but still continues to run great at low rpms all of the time. Confused

FMF power bomb

Q4 Silencer

JD Jet Kit (shop installed the kit need to get the specs)

That's all that's been done

HELP

My guess is water in the gas... or a clogged main jet.

I have the same thing... not really bucking but hesitating/ gagging out when i get into the throttle... its weird though cause its only occasional not every single time... vadrzsm is going to help me pull and check the carb im hoping its just a clogged main jet...

I have a 2009 DRZ400sm and all of a sudden the engine has been crapping out at 75 miles an hour, bucking, low speeds, low rpms runs great once the rpms get higher it acts like it just stops getting fuel, when I gas it, the engine sounds like its fouled a plug but still continues to run great at low rpms all of the time. Confused

FMF power bomb

Q4 Silencer

JD Jet Kit (shop installed the kit need to get the specs)

That's all that's been done

HELP

 

 

check:

 

ignition switch continuity

stator

water in float bowl

fuel lines

spark plug connection

spark plug wire

spark plug hole (for water)

Thanks for the input. I used seafoam to try and clear it up, so there is no water in the gas. I failed to mention that I've done all of the 3x3 typical drz mods. Time to get in the carb. Thank you Rob.

I also dropped some seafoam in yesterday... if it is something gumming up the main jet (obviously depending on what it is) it shouldnt take long for the seafoam to clear it out should it?

mntryder25 I sent you a message, seafoam didn't do anything for my bike. Have a good one.

Yeh i have run the seafoam about 20 miles now... going to test it out this evening after work see if im still getting the sputter like i was... if so pulling the carb if i have time this week if not definitely this weekend... will let you know what i find...

Been easy on it back and forth to work the past couple days... dont want to foul anything major up! Cause mines same as yours its only at high rpms...

well good news and bad news my friend.... bad news first? ok then... im not sure what your problem is... i didnt have to pull my carb... good news now? the sea foam seemed to do the trick for me... must have cleared out whatever was buggering my main jet... ripped one up in second on the way home from work and she pulled right up like usual! (thats the way i noticed my problem it would hardly even pop the wheel off the ground) and yes i have gotten good enough to be able to wheelie in second gear so no it wasnt my wheelie skill there really was an issue at high rpms... and i havent had the gag/hesitation that it was doing! hope you get your problem figured man i know this was a huge relief for me i was started to get worried! how long have you run with the sea foam in there? like i said i put a fresh tank of gas and i assume the proper portion of sea foam (didnt have a measuring cup) if anything i probably poured a little more in then what it called for to treat 2 gallons or so.... 

I ran a whole bottle through it so i'm screwed. I'm pulling the carb tomorrow to see if there is anything in the main jet. I ride my bike every single day so there is no chance of the carb gumming up or water in the bowl, so i'm happy for you, that's super cool, I do wish that was my end result. Well, I'm Mike, keep it one two wheels.....................unless you rip one down the street once in awhile, later man.

Damn mike sorry to hear that! Yeh i run mine every day as well so i was suprised when it all of a sudden did this... maybe my problem wasnt quite as bad as yours... my opinion checking the carb is the best way to go.. hope you find your problem there if not im stumped youll have to get advice from an expert here... best of luck bud!

thanks!

I had that as well... Started out like you described then got worse. In the end, it was a bad crank position sensor... Hard to diagnose. I see u r in San Diego... Contact me, maybe I can help

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