Hi,
I have a completely stock 95 900RR which had been sitting in the garage for more than 15 years (yeah I know...) After many months of work, I had it running well... or so I thought. After sitting for a few days, it would only run on choke (I guessed that the old fuel line past the fuel filter had deteriorated and was shedding bits clogging the pilot jets).

So I pulled & separated/disassembled the carbs (again), (they had been previously ultrasonically cleaned) re-cleaned the float chamber & bowls (although spotless), polished the valve seats, tested & checked float levels, replaced all the jets & float valves with OEM new, replaced every O-ring, all fuel lines, and all the fuel & air t-fittings. (The fuel filter and pump had also been previously replaced with new.)

After reassembling, and resyncing the carbs, it ran perfect on a test ride at all RPMS.

It then sat in the garage for six to eight weeks after that test ride (poor weather/work.) I tried starting it (which it did with no issue) and idled ok after warm up without choke. However, giving it throttle, it would hesitate / lag / bog.

What could cause it to go from running well, to having poor throttle response just from sitting? Something obviously changed during that down time... but what?
Gas gone bad (was purchased 2-4 months ago)?
Electrical? (probably unlikely)
Other carburetor / fuel issues? (Keep in mind it went from running great after previous shutdown, to its current poor running just from sitting.)

Here's a video of the throttle response in case someone can recognize the symptoms from the sound:

I know the moral is, just don't let it sit (which I wish weather & my schedule would permit). I'm hoping it's just something obvious I've overlooked. Any suggestions of where to look to get this thing running well again would be great.

Thanks!

 

Have you tried putting a meter across your battery whilst she’s running as the video shows ? I had a vaguely similar issue where I did much the same as you to try and rectify my issue. Everything pointed in my case to a fuel/air issue but after spending a day inhaling fumes from constant stripping, I had one of those “l wonder” moments. Meter readings confirmed the battery was shot. Seeing as she had always fired up I didn’t even consider a battery issue.
Replaced it and my issue was gone.
Other than that, have you inspected your carb’ rubber mounts or “boots” as I call them for splits or perishing.
Best of luck mate.

 

I've not thought to check the battery (LiPo) as it turned the starter without hesitation and I have a custom built voltage monitor system (you can see the red flashes at the very beginning of the video) which is suppose to alert me to any electrical / charging issues. However, since I am currently grasping at straws, I shall leave no stone unturned, and check it.

As far as the intake boots, those were replaced last year during the resurrection with new (after a hard fought battle getting the originals to let go of the carbs.) They are soft & pliable although a leak would certainly make it behave poorly, so I shall inspect & recheck the tightness of the clamps as well.

Oddly, when I started it today to record the video, it actually ran better than it did yesterday during the first start up. I wish it would just work or fail... I hate these variable problems!

Thanks so much for the suggestions!