990 engine vibration.

In terms of twin carburetors, it would sound as if one cable was tight -this being on the cylinder that wants to "take-off" at initial slight acceleration. This would cause the uneven idle. Are you sure your throttle free play at the grip is adjusted correctly, via TuneEcu? With a 990 one cylinder providing all the power down low (the needle swing) is all down to the linkage adjustment, assuming your fuel and ignition maps are more or less identical in this area. You can check the butterflies move in sync visually or by feel (maybe a third hand needed). Any slight differences here will make a big difference near idle but will virtually disappear once the throttles are opened to a midrange and above. That's simple math.
That being said, doesn't really explain your vibes all the way to redline. That sounds more mechanical in origin to me.
I have recently found my pressure plate is all over the place at idle (clear clutch cover). My Rekluse is grabbing at idle too, so I am hoping a clutch rebuild will get rid of my vibration problems.

Well this is going to be on hold the next 6 months while I move, rent out my house and build a new work shop in my new garage.

Aw, jeez, the suspense !!!

Hey, that's quite an endeavor. Hope it all goes as smoothly as it can and your shop turns out awesome.

Not totally on hold, you're endure it for two days this weekend.

So you have tried different exhaust systems, swapping the H pipe and didn't find any holes in the H shape pipe? they get to rust next to the mounts and get holes.

Yup.


Once I have my new garage built im going to do some major service and check some other things. Until then I'm going to be Uber busy.

I was thinking last night I checked the engine mounts but I never losened them all and retorqued. Maybe that's it. I did get hit by a car a while back.

Reading through this thread, I know it's a bit old, but my bike is doing exactly the same stuff as Parx400's--vibes are bad when it's hot outside or when my bike has been doing slow stuff (heating up the engine). I've recently replaced fuel filters, valve adjust, spark plugs, etc. Fuel filters had some debris stuck to them but nothing small enough to make me worried it got past the filter. I haven't checked TB sync in a bit, but it hasn't had any impact on the running in the past when I've made minor adjustments. Same with TPS adjustment (properly with TuneECU).

I've tried most of what Parx has (although not compression yet), and have even swapped my exhaust system for a 2->1 SSO, and did the power commander with the rotty tune. Got more power out of it but still super vibey. My buddy @Jking 's 990 is butter smooth by comparison. I haven't tried pulling injectors yet but I'm starting to consider that as a next step. I love this thing but want those vibes and flameouts/hiccups gone!

Parx, did you ever figure this one out?

Okay, I *finally* sorted mine out. It was dirty fuel injectors.

This thing is a totally different bike now. Far smoother and far better power. I'll need to ride it more to get MPG info, but without a doubt a massive improvement. I used the MotionPro fuel injector cleaning tool with PJ1 contact cleaner. Other than one of the screws immediately stripping (it was basically made of butter), it was super simple and quick to do (probably like 30-45 minutes of extra wrench time over tank removal). Make sure you have the tools to rebalance the throttle bodies (just in case). Mine were a tad off but I didn't check them before disassembly. Rebalancing didn't make any noticeable difference but it was good for peace of mind.

I was discouraged from cleaning my fuel injectors due to the general wisdom of the forum. I had read in several places that "nobody has ever had issues with clogged/dirty fuel injectors", and that the throttle bodies aren't meant to be disassembled in any way, so I always ruled it out as a cause or even a troubleshooting step. My gut kept pointing back to a fueling issue so I tried power commander, autotune, etc etc. I guess it was a good excuse to put all kinds of parts on the bike I wouldn't have otherwise.

I will now be including this as a step during my valve check maintenance (since I'll have the assembly off the bike anyway).

Good to know!

any chance you have pics of the disassembled injectors, or a howto to take em apart and clean?

https://advrider.com/f/threads/07-tuneecu-map-reviews-and-musings.1233761/page-24#post-37737703
Post 466

Great idea! Next time I have the bike apart, I'll try to remember to take pics and post them up.

This would have saved me thousands of dollars in parts and lots of frustrated wrench time.

Great info Zuber! Is there an easy way to remove the injectors? Did you follow the procedure described in the following thread?

https://advrider.com/f/threads/replacement-injectors-help.865408/

thanks

Not much detail on there, but unbolt the two throttle bodies so you can separate them and pull out the injectors all at the same time. Probably want to stock up on the two types of o-rings first.

Looks like I don't need to do a writeup. That one is pretty decent and covers the important parts (separating the halves).