low power....starving for fuel or too rich

[GRU]

so these last 2 days i went on the freeway to see what speed i can hit and everytime i get to 60mph or so the bike loses power for a second, then accelerates then loses power again.....if i twist the throttle more the bike loses power again...i also noticed that my bike is runing a little rich so would it runing rich lose power at about 60mph and 7000 rpm or is it just not geting enough fuel intothe carbs? maybe i should try running on PRI :dunno:

btw, the gas tank if full

[i3randon12]

um i was told  to fiddle with the idle screw... i think its to "high"      too much gas is getting in the carbs and flooding it temproarly

i dunno             no harm giving it a shot

[Kerry]

This probably wouldn't explain the cyclical nature of the power loss, but have you checked your valve clearances?  Richard's bike was experiencing some serious power loss on the freeway until he adjusted his clearances.  It made a huge difference.

Meanwhile, you mentioned that you're running rich.  Throw out some more clues by listing anything non-stock in your carbs / air filter / exhaust setup.

Also, I can't remember: are your float heights OK?

[GRU]

ok, 150 mains, 40 pilots, 2 washers under each needle, 3 turns on the mix screw, k&n pod filter, gsxr exhaust canister and DIY timing advance

[JohNLA]

Did you recently rejet ? If not I would check your fuel hoses and petcock. If nothing turns up it might be time for the valves like Kerry mentioned.

[GRU]

i rejetted about 5 months ago but havent riden on the freeways....the weird thing is it accelerates good and even up to 85mph, so rpms don't make a difference...only when i'm trying to keep the same speed at 60 or 70 the bike loses power and comes back up after a second or so....

everything else is good, good idle, a flat spot on low rpm but that's normal for a gs, right? if it doesn't rain tomorrow i'll try it on PRI and see what happens...then if that doesn't make a difference i will buy a inline fuel shut-off valve and get rid of the petcock....i just don't want to mess with the valves  

edit: so if i'm standing at a light and want to accelerate fast the bike has no problems even riding up to 10 000 rpm

[jcbdc]

I'm having the exact same problem with mine.  Previously the bike wouldn't start and I found that the spark plugs were not firing under compression.  Now, I'll go to give it gas and it bogs down.  It's intermitent.  It's not a particular rpm.  I put it to PRI and it seemed to help...but still feel a lack of power.  The bike died take a corner last night with cars on my butt...and it would startup until I placed in on PRI  ...no fun.   I like to see if you have a solution.   Can it be bad fuel?

[jcbdc]

I'm having the exact same problem with mine.  Previously the bike wouldn't start and I found that the spark plugs were not firing under compression.  Now, I'll go to give it gas and it bogs down.  It's intermitent.  It's not a particular rpm.  I put it to PRI and it seemed to help...but still feel a lack of power.  The bike died take a corner last night with cars on my butt...and it would startup until I placed in on PRI  ...no fun.   I like to see if you have a solution.   Can it be bad fuel?

[dgyver]

If at highway speeds you are probably at a small throttle opening, correct? Sounds like lean surging. Air mix screw, float level & pilot jet are the primary sources of this. Try turning out a 1/2 turn on the mix screws. If that does not correct it, check your float levels. Try lowering them, which actually raises the fuel level to increase richness.

[Kerry]

check your float levels. Try lowering them, which actually raises the fuel level to increase richness.

In case dgyver's instructions confused anybody, he's talking about reducing the measurement in the diagram below, which is taken while the carbs are upside-down:



EDIT: Changed link from sisna.com to bbburma.net