My bike just started doing this. It always does it when I start up the mountains here in Colorado. as the RPMs are between 8-12 my bike will start to intermitantly die out (as if running out of gas) then on the way down it will be fine. Then last night on my way home from work I noticed a very similar symptom between 8-12,000 here in the city and thats the first time it has done that. Any suggestions as to things I should check?

 

maybe it's knock. are you carb'd or fuel injected? you might rule it out by running a tank of high octane.

 

When is the last time you checked your air filters? What is your maintenance schedule?

 

Brand new K&N less than 800 miles on it, fuel filter the same,and new plugs.Yes it is carburated, and NEVER run 85 octane. No knock, and for the most part I don't have any problems in the city, my clutch is releasing really late so I know I need a new one, but if it was slipping, it would rev up real high and not go anywhere, not bog down right??

 

yup. was the loss of power in any way associated with the k&n? could the loss of power be associated with the humidity, altitude, or temperature? i'm not too familiar with carbs, but ive heard those have an effect on the performance of a carbureted engine.

 

If you've not had your carbs jetted for the altitude, that's most certainly your problem. Denver is 5K feet above sea level, not a lot of oxygen and even less once you start climbing altitude in the mountain roads. You're simply not getting sufficient oxygen/fuel mixture. That's why it boggs down when adding more thottle(fuel), it's running sorich I'm surprised it doesn't die.

 

Thats what it sounds like to me.
With new high flow air filter, jetting should be checked.

 

I appreciate all the input, but my bike has always been in Denver at this altitude, thats nothing new to it, and this problem just started. Also where I live it is alittle closer 6000 ft.How often do you need to recharge a K&N filter? I'm going to take off the tank and look at it after I get off work. Also what do you guys think about this, could be ignition related? Do you think at higher RPMs my plugs aren't firing? They are brand new so I would think they should be fine but just something I was thinking about?