busa hitting an imaginary rev limiter

[chuckfina]

I need help diagnosing a problem I'm having on my '04 Busa (37k miles).  Here are the specifics:

Revs normally in first and second gear until around 6k rpm, then it climbs very slowly
Will not even go past 6k in third gear or higher, it's hitting a rev limiter that's not supposed to be there!
At 34k miles, a good mechanic did a full service (new plugs, new air filter, adjusted valves, etc.) and the bike ran like new
At 35k miles, the bike started bogging down so we added a fuel injector cleaner
This seemed to work for a couple of Saturday rides, now it's doing it again
I was told at the time that we added the fuel cleaner that my battery was on the tail end of it's life (can a weak battery cause this?)

I'm taking it to my mechanic this week, however, I don't expect him to ride it on public roads in the higher rpms so I"m hoping some of you may have suggestions on what to troubleshoot.  Thanks in advance for your help.

 

[Mr Bogus]

bet you are on the right track.. but my bet is pump or filter..

 

[pbghost]

6k...you're lucky, mine's doin it @ 5k with an occasional bubling noise in the tank a '00 w/59k miles

 

[WiLL_FLY]

How old is the battery? or check out this forum https://www.hayabusa.org/forums/?act=ST;f=47;t=30993;

 

[Professor]

Sounds like Busawhipped's when he was loosing a pump.

 

[Gunnybusa]

My 02 did that and it was the fuel pump

 

[Mr Bogus]

https://www.hayabusa.org/forums/?act=ST;f=3;t=101307;hl= smokin deal on pump... John is a stand up guy too...

 

[BA BUSA]

Sounds like your fuel pump is on it's last leg

 

[Mr Bogus]

Sounds like your fuel pump is on it's last leg

and that came straight from the "GAS GAS GAS" guy....

 

[BusaWhipped]

Sounds like Busawhipped's when he was loosing a pump.

Sure does. I was going to say the same thing. Bogus has you hooked up to R8s fuel pump for sale.

 

[chuckfina]

Thanks for the replies, everyone. Today I changed the battery and added more Suzuki Fuel Injector Cleaner. I'm almost done with the bottle (one bottle per 15 gallons of gas). One (or both) made a big difference in the engine performance; however, it still will not pull steadily past 8500 rpm. I'll finish the FI cleaner and if the engine is still lazy in the higher rpms, then the above suggestions and my bike will be dropped off at my mechanics house. I'll post the results. Thanks again!

 

[Pipefighter248]

Fuel issue.
Had the same problem and wouldn't go above 8K.
Ended up being a restriction in the fuel pump housing.

 

[321CYA]

Hey bro check your FUEL PUMP the exact same thing happened to my "03" I can guarantee it is the pump..if your not getting 40-42psi at the fuel rail the pump is toast.

 

[BIKE DUDE]

It's not the battery! If the battery was low enough to not power the ignition then it definitely wouldn't have enough power to turn the bike over.

 

[BusaWhipped]

Hey bro check your FUEL PUMP the exact same thing happened to my "03" I can guarantee it is the pump..if your not getting 40-42psi at the fuel rail the pump is toast.

You need to be able to check it at 8500 RPM under load. It might show a problem with the bike brunning on the side stand, but mine was showing 42 PSI in neutral no matter what you did. With a fuel gauge hooked up and the bike on a dyno, the PSI dropped to around 10 by the time it got to 8000 RPM or so.

 

[Fate]

Battery would not be the issue, I would bet on the fuel pump as well.

 

[chuckfina]

Ladies and Gentlemen.., we have the solution.., sort of. First, thanks to everyone that offered suggestions for troubleshooting this problem. I was all set to buy the fuel pump, but my tech wanted to just make sure everything else was checked out first as a possible cause. I just got the following response from him a little while ago:

"After adjusting the throttle position sensor, regapping the spark plugs, and removing 6 pounds of unnessessary plumbing (smog stuff), I took the mighty Busa for a test ride. I also rigged up the fuel pressure gauge so I could watch it during the test ride. It never dipped below 42 psi from idle to 9k under a load. No need for a new fuel pump, this one works fine. As a matter of fact, the bike ran awesome! Not a hesitation or stumble of any kind. I'm not sure which procedure fixed it, or a combination, but I believe I nailed it."

Prior to this I replaced the weak battery and he checked all the pertinent hoses, etc.

I'm so happy I don't have to buy a fuel pump! And let's hear it for a tech that will take a busa up to 9000 rpm on a public street (remote one, I'm sure) and eyeball a fuel pressure gauge at the same time!!
If I had a daughter, I would encourage her to marry this guy!

 

[Mr Bogus]

Glad you got someone with a gauge.... is part of the diagnosis and why are normally ahead to use a shop that has as much brains as tools...

 

[chuckfina]

Glad you got someone with a gauge.... is part of the diagnosis and why are normally ahead to use a shop that has as much brains as tools...

He actually bought one just to test my bike! Told him I would pay for half of it. This guy is gold to me.., he is old school "do it right, or don't do it at all".

 

[Mr Bogus]

He actually bought one just to test my bike! Told him I would pay for half of it. This guy is gold to me.., he is old school "do it right, or don't do it at all".

Good techs are gold, there are so many in the repair field that just start swapping out parts until things work...

About the only thing you mentioned that sounds "feasible" is the TPS adj.. cleaning plugs (not sure why? replacement is the norm) and removal of the smog equipment should not have had much to do with the problem (I would hang on to that stuff, you may wish you had it some day)..

All the same, if the bike is running correctly,