07 Busa With Rough Idle And Hanging Revs

[Shaun Ketterman]

Sounds really interesting, did the guy who rode the bike, offer any explanation or how your bike could have a bent shifting fork or how it could affect the bikes running so much?

I didn't even mention the rough idle to these guys again, I just wanted them to replicate the stutter I was getting. His best guess was a possible bent fork, but for sure 2nd gear was slipping big time.

I'm thinking 2nd gear is bad.
I doubt the shift fork(s)are damaged.
If they were, there should be noticeable shifting problems.

No issues shifting at all, it's perfect in every gear. That gives me a little relief. The warranty, as I confirmed, is only 50 percent parts and labor, so I'm still on the hook to shell out some cash.

These dudes at the dealer are wanting to test everything before even considering the tranny. They want to put a new gas tank on there (after I told them I JUST put a new pump and filter, Ima fight that one), and they want to put a different ECU on there just to rule it out. The dealer also has a guy who is big into Busa's, and they want him to ride it around today to get his input.

Regardless, I'll keep you guys in the loop with how things play out.

David - I haven't read all of your other threads front to back...any chance your upper RPM issue is the same as mine? I think the fact that for me, it's only 1st and 2nd gear, makes it seem obvious (in hindsight) that it's the tranny.

 

[David Offor]

Your problem is a pain in the neck for you but like mine, it's also an interesting problem, I know that I'm getting closer and really want to post a closure update and cause.
I've learnt over the years not to presume that 2 problems, with similar symptoms, will have the same cause but we do have similar symptoms, my bike has 40k on it and I'd never given it a thought, that it could be gearbox related, I will pick some peoples brains regarding this, see what they say.
I wonder if hooking the bike upto a dyno and computer, would show up a gearbox/gear selector switch fault, while riding it through the gears?
If the new stator/ckps doesn't fix mine, I'll be seriously giving it consideration.
Hope you get some good news soon.

 

[Shaun Ketterman]

Your problem is a pain in the neck for you but like mine, it's also an interesting problem, I know that I'm getting closer and really want to post a closure update and cause.
I've learnt over the years not to presume that 2 problems, with similar symptoms, will have the same cause but we do have similar symptoms, my bike has 40k on it and I'd never given it a thought, that it could be gearbox related, I will pick some peoples brains regarding this, see what they say.
I wonder if hooking the bike upto a dyno and computer, would show up a gearbox/gear selector switch fault, while riding it through the gears?
If the new stator/ckps doesn't fix mine, I'll be seriously giving it consideration.
Hope you get some good news soon.

Likewise man. When yours misfires in the upper RPMs, if you can, try to keep an eye on your tach. What gives mine away, besides the fact that it happens in only 2 gears, is that every time it slips, my RPM's increase by about 300, which is exactly what should happen if the dogs on the gears are worn out and it's losing 'grip'. It loses grip, slips, and regains traction, but since this happens to fast, the RPMs increase by only a little bit. For us, it feels like a misfire. I've already been quoted over a grand for parts + labor to replace only 1st and 2nd gear. Lots and lots of labor. I'll find out what the dealer is going to do here in a few hours

 

[David Offor]

I'm in 3rd gear and nail it, it never feels like slip or cogs jumping up until the misfire but it's totally possible that when getting to the high revs, that the gears are then letting go, giving the misfiring feeling but remember, I'm getting missfire codes, when mine starts playing up, you are not, also I have the bad running from tick over to 3000rpm in neutral, which you do not have, I also haven't noticed any rpm increase or idle hang, with the clutch pulled in but also I haven't tested for it either.
If the gearbox can be accessed and stripped without splitting the casings, it's possible you could carry out the work yourself, if you feel competent and confident.

 

[Shaun Ketterman]

No dice with the tranny. Turns out, the warranty was 2 months / 1000 miles. And, seeing as it's my DD...in San Diego...1000+ miles in 2 months is completely normal. So...no warranty for me.

Gonna start a new thread to get some input on my options for repairing / replacing transmissions, will continue this one for any updates on the rough idle

 

[Shaun Ketterman]

Also forgot to add something I noticed with my bike this morning...

While I was waiting for it to warm up a bit, I was just kinda sitting on it in the driveway. I noticed that my headlights will flicker exactly with the idle fluctuation. I should get a video. But anyways, I thought that was interesting, and would certainly point toward an electrical issue. But then again, maybe this is normal?

 

[sixpack577]

Also forgot to add something I noticed with my bike this morning...

While I was waiting for it to warm up a bit, I was just kinda sitting on it in the driveway. I noticed that my headlights will flicker exactly with the idle fluctuation. I should get a video. But anyways, I thought that was interesting, and would certainly point toward an electrical issue. But then again, maybe this is normal?

The brightness of the headlight may increase slightly as rpms rise away from idle.
The flickering may be normal with your irractic idle. I'm not saying it's normal, but I also wouldn't assume it's a problem yet.
But, at this point.
As for the trans, I wouldn't buy new gears.
As they could potentially fail in future also.
Send the gears to a machine shop and have them undercut.
I would definately let the dealer try another ecu in it too.

 

[Shaun Ketterman]

Figured a close-out post would be a decent idea here.

So for anyone who has similar issues as me (ie, the rough running in low RPM / rough idle and the misfire-type occurrences with heavy load:

1. Rough Idle/Degraded Low RPM Performance - I never did officially determine the cause of this, though I highly suspect it was electrical. I had put in a brand new fuel pump, new fuel filter, cleaned the injectors completely and fitted new o-rings and seals on all 4 injectors. These actions, I am confident, ruled out a fuel issue. The likely cause was either a faulty (NOT broken) TPS or faulty (NOT broken) Crankshaft Position Sensor, or a combination of the two starting to fail. My Busa wasn't throwing any codes, ruling out a *failed* sensor, but if one of them was faulty (as my resistance and voltage tests showed), they wouldn't throw codes, but could certainly cause the issues I was experiencing. If you have similar issues, recommend reading through this thread started by fellow member David Offor as a starting point:

https://www.hayabusa.org/forum/thre...-last-7th-thread-hope-its-my-last-lol.191371/

2. Hanging rev's while in 5th/6th/Neutral - Another issue I never determined the cause of. Probably the main culprit in trading in the 'Busa. The most bizarre issue, and even a handful of Suzuki mechanics could not pinpoint.

3. Misfire in Upper RPM's under medium to heavy throttle - This was discovered to be the transmission. The dogs on gears 1 and 2 had been worn down, likely from a previous owner beating the poop out of the bike, clutchless shifting, drag racing, or a combination thereof. With the dogs on those gears worn, there wasn't enough left for the gears to 'lock-into' the main shaft in the tranny, and they would slip.

Hope this ends up helping at least 1 person in the long run!


Shaun