GEN 2 dropping RPMs at 4500 - 5000??

busagirl4444

HyperActive
Donating Member
Registered
Ok I have been having a problem with my GEN 2 since changing the exhaust.

When I am riding cold or hot weather every once in awhile my GEN2 will drop RPMs from 4500 - 5000 down to about 3000 - 3500. It's like getting whip lash all of a sudden and when you are cruising and don't expect it, it is quite scary. It was only happening in 4th gear at about 75/80 mph no it is happening in 5th gear at 85/95 mph too. I've tried it in high gears to keep the RPMs low and work up to high to try to replicate and to try to see if there was a pattern. No pattern and extremely difficult to replicate. Bringing it up to MO it got worse. I know what your thinking climate and gunck in the filter right? We took the fuel filter out and found nothing(that in mind on the gen 2 this is 1 piece now, thought I could change out the mesh thingy) That piece isn't cheap although if it is the cause I will dish out the funds for it. the last time it happened was two weeks ago while on the highway in 4th gear at 80 mph in a group. Usually I can down shift and slow the bike and then continue on(this time I was able to do just that) In September when it happened I had to stop the bike, shut it off and then continue on after a 5 minute rest. I can continue for about an hour or two before it would do it again. I bought the bike in FL and took it to MO. Right now it is in FL where it will be staying as I'm moving back.

I have an M4 full System exhaust that has been powder coated. Once put on it seems that every once in awhile it will just drop RPMs for no reason at all while riding. A bit scary since the bike seems to slow, body(me)keeps going. Makes me think my bike is trying to buck me over the front of it. Make sense


Ok so far it has been dyno'd and that shop put a racing map on my bike with the assumption I suppose that I was going to race my bike. That map was replaced with the correct map from M4 for my bike.

two people have been able to replicate the issue and it has taken them forever for it to happen to them. One was the mechnic who put the correct map on it, the other way my ex-husband. Both of them got the scare of a lifetime they said. Really duh.. try it from my perspective.

The bike does have a Power Commander III on it. I have not ever tried to connect to it as I really didn't know how. (I am willing to learn with proper assistance standing next to me)

I have changed my levers to the FP levers and changed them back to stock to see if that was the issue(someones suggestion) Nope did it with the stock levers too.

I don't know if it has thrown a code, no one has ever told me. The mechanic has had it for about a month or longer right now and in his down time is trying to replicate the issue. Good Luck with that. I do have a video with the sound of what happens.

My Questions:

Throttle bodies adjustment?
New filter? AIR & FUEL?
Put stock exhaust back on to see if issue is still there?
Connect to PCIII to see what I can find out?
Stand sensor?
Mapping?
Spark plugs?

What do you suggest? What are your ideas?

Any help, any ideas, any insights are welcome at this point. I'd like to also find out myself for the satisfaction of doing it and learning.

At this point my confidence in the bike is wavering. Makes it hard to ride. My gen 1 never did this. I want it back to normal and want my confidence back without having to give up my bike like a lot of recommendations.

All else fails I could turn it into a show bike.. :rofl:


Edited:
I still have the full exhaust
I do not know how to edit the ECU
I have not been riding the clutch
 
You say it looses RPM. Does that mean it gradually slows down as if your close the throttle a little or does it slow down like the engine shuts off completely momentarily?
 
It sounds like an intermitent electrical problem to me. Maybe the connector to one of the injectors is loose and disconnects from the vibration of riding at a certain speed/rpm and causes one cylinder not to fire which in turn would cause the sudden loss of rpms. I would start by checking and cleaning all connectors on the bike...especially those involved with the ECU and fuel system. It's time consuming but it is cheap. Worse case if that doesn't fix it, at least you've eliminated that possibility.
 
You say it looses RPM. Does that mean it gradually slows down as if your close the throttle a little or does it slow down like the engine shuts off completely momentarily?

it goes from 4500/5000RPM and shuts down to 3500/3000 depending on speed. it's a big jerk that makes me move in my seat if that makes sense to you.

It sounds like an intermitent electrical problem to me. Maybe the connector to one of the injectors is loose and disconnects from the vibration of riding at a certain speed/rpm and causes one cylinder not to fire which in turn would cause the sudden loss of rpms. I would start by checking and cleaning all connectors on the bike...especially those involved with the ECU and fuel system. It's time consuming but it is cheap. Worse case if that doesn't fix it, at least you've eliminated that possibility.

thanks for the info, I'm so sorry to ask my next question all this would be in the manual to show me where all these connections are or just clean each and everyone one I find? I'm learning guys and appreciate all the help given and looking forward to more tech time with the bike...
 
You say it looses RPM. Does that mean it gradually slows down as if your close the throttle a little or does it slow down like the engine shuts off completely momentarily?

From around 4500- 5500 rpm, it would slow down dramaticly like the engine shuts off completely. It would remain off for a second then surge suddenly back up to 4500-5500 rpm, then slow down dramaticaly again. Hence the "bucking" term BusaGirl used to describe the feeling when riding. And yes it has happened to me a few times as well and it is a safety issue especially when in traffic!!

It sounds like an intermitent electrical problem to me. Maybe the connector to one of the injectors is loose and disconnects from the vibration of riding at a certain speed/rpm and causes one cylinder not to fire which in turn would cause the sudden loss of rpms. I would start by checking and cleaning all connectors on the bike...especially those involved with the ECU and fuel system. It's time consuming but it is cheap. Worse case if that doesn't fix it, at least you've eliminated that possibility.

Intermitent electrical problem is the first thing that came to my mind as well.
We have already checked just about all connections on the bike however we never fully disconnected and cleaned every single one.

I have suggested that the Power Commander come off and the factory exhaust go back on just in case one of them is making the bike faulty for whatever reason. Just dont know.


I have also suggested that she sell the bike to me as well.
We'll see how that goes......
 
From around 4500- 5500 rpm, it would slow down dramaticly like the engine shuts off completely. It would remain off for a second then surge suddenly back up to 4500-5500 rpm, then slow down dramaticaly again. Hence the "bucking" term BusaGirl used to describe the feeling when riding. And yes it has happened to me a few times as well and it is a safety issue especially when in traffic!!



Intermitent electrical problem is the first thing that came to my mind as well.
We have already checked just about all connections on the bike however we never fully disconnected and cleaned every single one.

I have suggested that the Power Commander come off and the factory exhaust go back on just in case one of them is making the bike faulty for whatever reason. Just dont know.


I have also suggested that she sell the bike to me as well.
We'll see how that goes......

You've probably already checked this but with that description, it could be a bad connection to the kickstand switch, faulty switch or even a loose spring that causes the switch to think that the kickstand is down for a second.

@ busagirl, all of the connections are in the service manual.
 
This is what you need to do.
Check for codes(very easy), leave the jumper wire in and go for a ride.
An electrical or fuel problem should momentarily throw a code(only while the problem is occuring, and the ecu does not store trouble codes).
Make sure to look at the dash(if safe)when it happens, a "C" and a 2 digit number should flash and the FI light will come on.

https://www.hayabusa.org/forum/gene...-diagnose-fi-light-obtain-ecu-fault-code.html
 
From around 4500- 5500 rpm, it would slow down dramaticly like the engine shuts off completely. It would remain off for a second then surge suddenly back up to 4500-5500 rpm, then slow down dramaticaly again. Hence the "bucking" term BusaGirl used to describe the feeling when riding. And yes it has happened to me a few times as well and it is a safety issue especially when in traffic!!



Intermitent electrical problem is the first thing that came to my mind as well.
We have already checked just about all connections on the bike however we never fully disconnected and cleaned every single one.

I have suggested that the Power Commander come off and the factory exhaust go back on just in case one of them is making the bike faulty for whatever reason. Just dont know.


I have also suggested that she sell the bike to me as well.
We'll see how that goes......


LOL you are not getting my busa yet. I won't give up on her yet. Hell maybe she is mad at me because I am calling her a her. Maybe I should change it to a he. You do crack me up, thanks for your comments too, I knew you could explain it.. :thumbsup:


thanks guys you rock as usual.. I'll keep you up to date
 
it is a bad feeling when the bike falls on its face...the drop of 1-2 k rpm is funky...only based on what I came across double check the connections of wires...battery, additional grounds, and whatever else was removed while adding the pc3...if the tune was that bad it would seem it would break up prior to just cutting out...
 
If it throws a code while she's riding, wouldn't the FI light come on and stay on until she turned the bike off ?
 
So witch injectors is the PC3 hooked up to? The Primary's or the secondaries?
 
If it throws a code while she's riding, wouldn't the FI light come on and stay on until she turned the bike off ?

No, if the problem is random the FI light(and visible code, if jumper is in) will only be on while the problem is occurring.
The ecu does not store the code, and when the problem itself temporarily goes away so does the FI light.:beerchug:
 
I think you should bring to a good Dyno shop, they can sniff it to see what is going on, if you where close to NH i would bring to my friend shop for free.
 
No, if the problem is random the FI light(and visible code, if jumper is in) will only be on while the problem is occurring.
The ecu does not store the code, and when the problem itself temporarily goes away so does the FI light.:beerchug:
I know I accidentally hit my kill switch in an emergency stop once and it stayed on until I cycles the key switch. I don't know what happens with the jumper in.
 
I know I accidentally hit my kill switch in an emergency stop once and it stayed on until I cycles the key switch. I don't know what happens with the jumper in.

With the jumper in the "C" and 2 digit code will display whenever the FI light comes on.
The FI light is telling you that something is wrong and a code is present.
 
ok update. The PC III has been taken off the bike(I got to watch and learn from Shawn thank you thank you thank you). Took it out for a ride yesterday and didn't have any issues during the ride. Seems a little smoother too, not sure if that is because it's different or not. We'll see. I'll go for a ride today to try to see what if it'll happen again or not. Going to ride it to work all week.
 
Back
Top