Hey guys, I've pondered this for a while now and just want to see some other responses instead of just throwin money out there. Bike is an 04 1kRR about 14k miles on it and has had a flat spot around 6 or 7k rpm while at full throttle since I've had it(9k miles). I got a yoshi slip on for it and didn't seem to change anything right away but now about a month later and after a 2400 mile trip the problem seems worse. Sometimes it will power through it and rap out strong if it's hot out, othertimes when it's cold out it won't go more than about 6500rpm at full throttle. I have a feeling it's my O2 sensor but didn't think it should be bad by this many miles plus they cost $130 so I don't want to buy one if I don't have to. Let me know what you guys think as far as possible scenarios so I can rule some out.

 

It did that with the stock end-can too, correct?

 

Correct.

 

Anybody, anything? Anyone know how to check the O2 sensor?

 

And its not flashing the light on startup showing a code? Sounds like something that would show up on a diagnostic computer. If it doesnt throw any codes on startup or when plugged in then start looking into intermittent fueling or spark problems by process of elimination.

 

Nope, not throwin any lights. I'm probably going to rip into this weekend and see what I find. Thanks for the comments.

 

Not sure if its related, but I believe 6 grand is the rpm that the flapper and the exhaust valve actuate. Your slip on should have removed the exhaust valve, but I would take a close look at the intake flapper. If its hanging up or working erratically, that may explain something.

At 6 grand, the ECU is doing quite a few different things, exhaust valve open, intake flapper open, increase fuel delivery, and timing changes. If any one of those are not working correctly, it could explain your issue.

 

Also the upper injectors start firing around then too right?
Justasquid has a good point about checking the intake flapper. I suggest checking that the flapper is open when the bike is off and then doing the flapper mod and see if that makes a difference before putting too much work into it. Maybe want to check the inside the airbox and look at the filter too. Who knows, there could be a dead squirrel in there or something.

 

If I were you I'd just remove the intake flapper because all its going to do is restrict air flow, if you take it off you will notice a little better throtle response in the lower gears and the lower end of the power band right around 3-5500rpm's.

 

Good suggestions guys. Here's what goes through my head on the intake flapper(I haven't tested it or anything) but the tract is clear and so is the air filter and I'm thinking if it just restricts the intake tube it may not get as much power as is should because of airflow but it would still run. When I say flat spot it at some points garggles and completely chokes on itself sometimes it does not. I may think ecu like squid pointed out but it doesn't throw a code, I think the only way to rule it in or out would be to buy a new one = not cheap lol.