Mysterious vacuum leak?

[madbrad16]

I have an 04 RSVR and have had a vacuum leak feeling for quite some time now. It will fire up and rev itself up to the normal cold-start idle speed, but once it idles down to the normal idle speed it has a weird missing phenomena (and sometimes it will die if its started from cold). If I have been riding for awhile and shut it off and then restart, it wont die when started, but still has the weird vacuum leak missing feeling going on.

I first replaced those two tiny lines on the MAF sensor on the airbox, but it didn't help anything. And then I replaced the two intake boots below the throttle bodies and then replaced the throttle bodies (because I thought one of the injector seals on the left side was bad and I had a spare set of TB's on the shelf so why not). But to no avail. I still have that weird same sputter at idle, and I still have weird small hesitations at cruising throttle range. And also it kind of sputters and hesitates when rolling back on the throttle. At full throttle it still pulls fine.

I have done a ton of forum searching and I'd like to think that I'm not an idiot as I have worked on multiples of bikes and cars all my life. But as of right now I am truly stumped. Any ideas?

[jmardy]

This is a shot in the dark and evidence of my newly-found paranoia, but check the stator's output. When they start to go, they cause all sorts of weird running problems.
People smarter than me should be along shortly.

[jfryjfry]

Funny, I have a very similar problem. The bike just started having a slight miss at idle and would occasionally die. I found a vacuum hose off, and that seemed to fix the problem. (oddly, i had to disconnect the PCIII to get it to start, but after it initially started i hooked it back up and it seemed fine).

The problem got worse and went into limp mode. When I got home I disconnected the power commander and it was better. After idling for a few minutes and riding for one, it seemed to be back to normal.

So my suggestion would be to disconnect the pc if you have one.

I'm not convinced the stator can cause this problem unless the battery is low which is easily testable. I would imagine the bike would run fine with the stator disconnected until the battery ran down, so a low-performing stator shouldn't (in my mind at least) cause a stumbling issue.

[mcjongs]

Have you checked the oneway valve for the PPM clutch?
I had a similar problem on a former RSVR (that I bought with that failure) and it gave the same behaveour.
It is black and white located on the right side between the cylinder heads. It had gone apart in the glue.

[madbrad16]

Ok, so I have an update. I decided to sync my TB's. I was able to sync them just fine, but it didn't change anything until I just randomly decided (as a last resort) to replace my airbox (and sensors) with my spare air box on the shelf. It fired it up and it ran like a champion for the first time in forever! So I think one of my sensors on my airbox was bad or something. I tuned it and it was sounding awesome. I took my TB sync tool off and I put everything back together and when I started it again it was back to idling low and missing and acting stupid. Why would it do that? Any ideas?

[Galaxian]

Sometimes a high flashpoint contact cleaner can be useful in tracking down vacuum leaks. Use with extreme caution and at your own risk of course.

Checking fuel pressure is advisable as well as general charging system health.

You also mentioned that you'd swapped TB assemblies. Did you tell the ECU to relearn the Throttle/TPS parameters? This requires access to either an Axone or Navigator.

Additionally, it would be useful to know if the bike has any 3rd party electronics such as a Power Commandant or Bazzaz unit.

[mini_me]

He mentions that he has a powercommander.

[SoulDaddy]

Is that a higher rank than a Commandant?

Brad, did you have any backfiring out of the top on decel?

[mini_me]

Brad, did you have any backfiring out of the top on decel?

You mean like this:

[SoulDaddy]

Ay carumba!!

Yeah, kinda like that.

[theknurl]

You also mentioned that you'd swapped TB assemblies. Did you tell the ECU to relearn the TPS parameters? This requires access to either an Axone or Navigator.

don't think so......the ECU looks at the TPS value every time you turn the key on and 'sees' it as zero
try holding the throttle open a bit and hit the starter button.....

new idle speed 3-4,000 right? turn the key off, restart, idle is back to normal
the Aprilia has a real ECU not a Weber-Marelli from 1980

[madbrad16]

Hahaha! That picture kinda looks like me when I was a kid! haha. It does have backfiring out of the top on decel. You can see that its coming through the rear cylinder if you hold the butterfly valve on the TB's open and look down inside it. The bike did have a power commandant (better than the commander , but I took it off a lil while ago to see if it had anything to do with it, and it stayed the same. I checked the voltage recently (doing it the right way following the sticky instructions) when I performed the brown connector mod and everything was kosher.

I haven't checked the fuel pressure, but I did change the fuel lines and clamps last time I had the tank off and took the fuel pump off.

What doesn't make sense is the airbox. When I put the other airbox on it, it ran like a champion. But then I disconnected my TB sync tool and plugged the vacuum lines back in and it ran like a butt just like with the first airbox! I've been chasing this for way too long! I just want it fixed!

[DanV990]

But then I disconnected my TB sync tool and plugged the vacuum lines back in and it ran like a butt just like with the first airbox! I've been chasing this for way too long!

Since it ran fine with your meter attached to the TB but then went back to crap when you plugged your vacuum lines back in there may be a correlation there. Have you checked the oneway valve going to the slipper clutch like mcjongs suggested and the diaphragm in the clutch for leaks?

The diaphragm is number 14 in the diagram below.

[madbrad16]

So how do you check those valves? I replaced the check valve (with my spare one) going to the ram air duct up past the radiator ya know? But those are a pain in the butt to get off and I couldn't get the clutch one off so I haven't checked it yet. Maybe I'll give that a whirl tomorrow. Any ideas on how to get that off without busting my knuckles everywhere?

Also, I'm not doubting the check valve, but why do you think it improved when I put the other airbox on? I'm gonna replace that check valve tomorrow. Is it a pain to get to that diaphragm in the clutch? It looks like just pulling the side cover off and there it is yah? Am I gonna ruin that gasket pulling that thing off or is it reusable?

[DanV990]

Simplest test would be to take the vacuum line that goes to the clutch off the TB and then cover the port on the TB. If your problem goes away then you know that there is a leak somewhere in that line, either the hose itself, the check valve, or the clutch diaphragm. A little investigation and and you should be able to tell which of the three it is. The diaphragm is easily accessible by removing the bolts on the clutch cover. I've had mine off a couple of times and haven't had any oil leaks, the diaphragm itself acts like a gasket. Just be careful you don't tear it when removing it, take the diaphragm off of the locating studs around the outside edge and rotate it a little so it can't slip back onto them and get caught and tear when you remove the nut from the middle and then lift it off.