Power loss at high speed (on highway)

So on the highway today the traffic cruising speed was about 75, I got up to speed, and held it (it was fully pinned but not full rev) after a few minutes the engine started loosing power. Speed slowly started dropping down and I tried dropping down a gear but nothing, next thing I knew I was down to 55mph getting passed left and right. does anyone know what would cause this? Bike is at 1600 miles, all stock but fmf pipe. Premium gas.
Ideas?

Something sounds wrong on more than one count here.

You say 100% stock except you have replaced the stock exhaust with an FmF?
Is that right?

There's no way you should be topping out in 6th gear at 75mph with stock gearing.

Have you checked inside your airbox?

Sounds like your bike is being starved of air for some reason.

What happened when you downshifted into 5th gear? Same issues?

What happened when you got off freeway and had to slow down and shift into lower gears?

What was temperature and humidity like when this happened?

You have a pipe, but no EFI programmer right?
Did you do the AIS removal and airbox mod?

How long were you running at WOT on freeway?

Only thing I can think of is fuel starvation, or air starvation.

How did the bike run in 1st, 2nd, and 3rd gear after that freeway incident happened?

Would it pull through the rev range in 2nd or 3rd gear like normal?

You say 100% stock except you have replaced the stock exhaust with an FmF?
Is that right?

There's no way you should be topping out in 6th gear at 75mph with stock gearing.

Have you checked inside your airbox?

Sounds like your bike is being starved of air for some reason.

What happened when you downshifted into 5th gear? Same issues?

What happened when you got off freeway and had to slow down and shift into lower gears?
It almost sounded smoother as dumb as it sounds...
What was temperature and humidity like when this happened?
nothing bad at all, like 70 and not humid at all.
You have a pipe, but no EFI programmer right?
yep, and no programmer, but I dont see that as causing a problem like that
Did you do the AIS removal and airbox mod?
Not yet, was going to this weekend
How long were you running at WOT on freeway?
like 5-10 min's.
Only thing I can think of is fuel starvation, or air starvation.
How did the bike run in 1st, 2nd, and 3rd gear after that freeway incident happened?
It seemed tolerable, but I didnt want to push it...
Would it pull through the rev range in 2nd or 3rd gear like normal?
After I stopped at the exit for a min, then it seemed to work fine.

Im gona go to my friends shop and have him check it out.

My bet is your flapper door on the airbox closed. I don't remember the configuration - isn't it spring loaded and then gets pulled shut under high vacuum? Maybe the spring broke?

toast wrote:

My bet is your flapper door on the airbox closed. I don't remember the configuration - isn't it spring loaded and then gets pulled shut under high vacuum? Maybe the spring broke?

Remove airbox door....easy test - but without a fuel programmer, I wouldn't run long with that door off.

does your oil look like chocolate milk?

spacecadet wrote:

does your oil look like chocolate milk?

wow, you're jumping right to a blown head gasket?

not jumping, just trying to add to things to check, plus with an oil glass its pretty easy to check.

i thought the flapper closed off at high RPM to reduce noise, so it should be closed at high rpm right or do i have that backwards?

Naively I would assume it is closed at idle to keep the bike quiet and then opens up under load. That's why I was thinking it was spring loaded with a vacuum actuator to keep it shut. When you got on the throttle vacuum decreases and the flapper opens.

But that is totally from what I remember - my flapper was disabled in the dealer parking lot

Ok did an oil change, oil looked like new, lubed up the chain and wheels, and took it for a spin, and it seems fine. My friend (owns his own shop) said that he has no idea what would cause it.... My only idea would be that the ecu limits the engine if you hold it at WOT long enough. bike seems to be running fine now and will go up past 75 (ats as fast as I could go on that road). But Idk If I want to risk goin on the highway at 70-80 for more than like 10 mins

bren5279 wrote:

Ok did an oil change, oil looked like new, lubed up the chain and wheels, and took it for a spin, and it seems fine. My friend (owns his own shop) said that he has no idea what would cause it.... My only idea would be that the ecu limits the engine if you hold it at WOT long enough. bike seems to be running fine now and will go up past 75 (ats as fast as I could go on that road). But Idk If I want to risk goin on the highway at 70-80 for more than like 10 mins

There is no F'n way the bike has some kind of built in "regulator" for being WOT.

That's just not even remotely reasonable.

I also have some very high doubt that your oil had anything to do with it.

It doesn't. I've run mine WFO for a good 15-20 min on the highway trying to keep up with a Hayabusa. All it did was make the tires hot. I didn't have any power loss issues whatsoever.

Yeah I didnt really think thatd be the case does anyone know what would cause this?

is your's an 08 by chance?

Hmmm...fuel pump cutting out...never thought about that....

yeah, the wierd thing is that its not doing it anymore. went on the highway again and it was fine. I wonder if It might have been just some bad gas.
Im going to do the airbox flapper mod and try a long distance run to see if it does it again.

no cus it was just not letting me go any faster, not cutting out or anything.

What's happened is that the unit heats up and starts to get weak; ultimately ending in fuel pump death. My mistake, it doesn't necessarily cut out, it just runs poorly and there is significant power loss. Most noticeably when the engine is warm. Doesn't do it when it's cold...but it was definitely early 08's that this affected.

Bren, I'd still keep an eye on that fuel pump. Yours is an 08, so just be aware of it.

VERY interesting, Does Yamaha replace it free?

bren5279 wrote:

VERY interesting, Does Yamaha replace it free?

Go here: click me

Ok so I am officially stumped. I just did the AIS mod and flapper mod. Still doing it

I dont think its the fuel pump; it isnt cutting on or off, it isnt hard to start, it doesnt sputter or have any kind of throttle or responce issues at all, doesnt matter if its hot or normal.

I went on the highway right after starting it at night when it was cold, same thing, goes up to the 80's peak (hit 86 now that I did the flapper mod) and then It slows down to about 73 and wont let me go any faster. I can drop a gear into higher rpm and the engines revs fine, just wont allow me to go above about 73 and it slowly starts dropping down the limit.

Its as if the ecu has an auto remaping when at wot????????????

The only thing that could do that is a lean condition
Water in the gas, air leak?
The is no ECU function that causes that, back up through any mods and look carefully

You have the bike up for sale don't you???

Why are you modding the bike more when you have an issue, AND you are trying to sell it????

This makes no sense?

Yeah Im thinking that its got to be something simple like bad gas or a leak but I dont know where to start looking to fix it : /

Yeah I put it up for sale because I made a deal with my brother that If I didnt pay off the money I owed him in time Id put it up for sale, Im still hoping that I can get it paid off, and I did the AIS mod and Flapper mod (took all of 10 mins) hoping that it would help, which it did (increased top speed too) but Im hoping that I can figure this out because its got to be something simple since the fuel pump is good and the engine is fine.

HMMMMMMM I wonder if It could be the fuel filter