650R - suddenly lost top end???

so i'm riding to poker tonight, about 5 miles from home my xr suddenly goes sluggish. i was just about out of gas so i thought it was just running out, so i quickly switched over to reserve. but then, it never picked up, just felt like a dog all the way to the gas station.

so i fill up, switch back to ON, start it up, it idles fine, wacking the throttle sounds okay...not as much bite on the top, but it doesn't stumble or anything.

sure enough i ride off and it's still a dog, i ride to poker, check out the air filter, it looks okay, not super clean, but not clogged or messed up.

so i park it and hope it changes for the ride home, but alas nothing. basically the bike lost it's juiced from like 1/2 to full throttle. off to 1/2 thottle feels pretty much the same, but it's hard to say since i usually thwack it open pretty fast, but it was good enough that it kept fooling me to think the bike was okay.

when i go from 1/2 to full it sounds like it's pulling harder, like it's opening all the way, yet it barely feels like it. basically i can go WOT and it won't redline. the bike feels like a heavily corked 400.

anyway, i haven't had a chance to look, but my first guess is clogged main, anyone have any other/better suggestions/guesses?


Clogged main, rats nest or other in your pipe or airbox etc... Although, the main jet shouldn't really pick up until ~3/4 throttle, your needle has more effect in the 1/2 throttle range. I've never heard of this problem, assuming it happened just all of a sudden, it's got to have something to do with air/fuel flow. Good luck on it.

You might want to check the tank screen...

i had similar problem after installing edelbrock cause my fuel line had a slight kink, it got way worse as i ran low on fuel

Try just taking the jet cap off (bottom of the carb bowl) and remove the main jet first only takes a couple minutes, I had a flake in my 600R jet and it acted that way, 5 minutes and I was back to normal, good luck!

Open up the carb, did the needle break? Or is the main jet loose or has it fallen out?

Check to see if the choke flap has cracked off and strated to block the intake side

Pretty common problem.

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