Carburetor question. Bowls not filling back up under hard acceleration

[ducriderinct]

Hi, I've got a carbed 96 monster that's having a small problem. Stock mikuni carbs. It starts and runs great, isles great, makes good power. Runs fine until you hit the gas hard and drain the carb bowls at which point it falls on it's face.

Ease up in the throttle and when the bowls fill back up it's has tons of power again for a few seconds of hard acceleration, then sputters again. He jetting is good, the mixture is good, the bike ran fine with the existing setup but sat for a month or so and this problem appeared.

The actual carb jets themselves seem fins as I have access the the full spectrum of throttle usage, but it seems like the carb bowls just aren't filling fast enough to keep up with demand.

I have tried changing the fuel pump out for a good known fuel pump, fuel filter does not appear to be clogged, there are no kinks in the fuel lines, the vacuum petcock has been replaced with a motion pro fuel valve.

I've pulled both of the carburetor bowl's, and the floats are not stuck at all, nor is there any varnished gasoline residue on the floats or in the bowls at all.

The only thing out of the ordinary that I noticed, was that when I drained the bowls prior to removing them, the right-hand side bowl let out less than half the amount of fuel that the left hand side bowl drained out which leads me to believe that the right-hand side bowl is not filling correctly while the left-hand side one is.

Really hoping to avoid having to pull the carbs out as it is a huge pain in the ass, but I'm not sure what to do at this point. My knowledge of carburetors is very limited. Any help would be greatly appreciated.

[ducpainter]

There is a filter in the inlet where the fuel line attaches to the carbs. Have you checked that?

[ducriderinct]

I have not. Is it just in the fuel line itself?

[greenohawk69]

It is in the part that swivels, where the fuel line attaches. Once you're there, you'll know it.

[ducriderinct]

Awesome. Thanks. I'll check it out when I get back home.

[koko64]

I always remove them when I find them and trust my in line filter. Some stale fuels act like a resin over the mesh when they go off, or its just crap build up over time.

It means any in line filters with the porous bronze elements  require more regular replacement or they will be glued up by modern fuel additives. I soaked one in carb cleaner overnight and it looked pristine, but wouldn't flow gas.
That T piece connector filter mesh is very fine.

[ducriderinct]

Awesome. Thanks for the help guys. Will check and report back!

[ducriderinct]

So, there is no filter in line on the carb inlet... any other ideas?

[ducpainter]

Are you running the vacuum petcock, or a manual unit?

[ducriderinct]

Motion pro manual unit. Same unit I have on my other m900 with fcrs. No issues with it on the other bike. I've check the lines, there's no kinks in them anywhere.

[ducpainter]

Sorry...missed that in your OP.

Are you getting strong vacuum at the pump? Vacuum line in good shape?

What are the float levels set at?

eta...Is the vent hose free of constrictions/kinks?

[Howie]

Is the hose from the fuel pump to the carb original?  If so, it might be collapsing when warm in the area around the V.  Another area to check is the float bowl venting.

[ducriderinct]

No worries as for the floats, I don't have any idea on the float levels. I don't know my way around carbs very well at all.

I know everything is exactly as it was and the bike had no issues at all prior to the bike sitting for a month or so.

[ducpainter]

With the fuel line disconnected from the carbs, crank the starter to verify that fuel spurts from the hose. The pump has way more capacity than a Monster requires.

I can't explain why this would be an all of a sudden thing, but a month shouldn't be a long enough time for problems internal to the carb/float bowl...but who knows? I'd check delivery. If you have fuel, I'd look into setting float levels. Your description of one bowl having more than the other is an indication one is wrong. I'd also verify the vent hose is free of kinks.

[ducriderinct]

Ok. I'll check those things now