VM carbs still dumping gas after rebuild--what the heck!?

[GSstiny]

I know this comes up all the time, but all the suggestions Ive found in other threads are geared towards dirty carbs or bad orings.

Since I got my bike back in november, it would occasionally dump fuel out the vent of the 1 & 2 carb. Since it sat on the sidestand for a couple months before I got it, I assumed that the needle valves were gunked up and not always closing properly.

Last week I completely disassembled them to install Robert Barrs orings and clean them out once and for all. Almost every gasket and seal in all 4 was toast, but other than that, they were spotless. :shock: I Chemdipped the metal pieces and put everything back together and it STILL dumps fuel. The float heights are within spec and I didnt see any damage or excessive wear on the needles or seats, so whats causing it?

BTW, its not a steady stream. It runs happily along then it dumps fuel for 5 seconds or so then stops. It acts like the valve doesnt close as quickly as it should or something.

[Hoomgar]

Did you replace the needle valves and seats? I know you say they look OK but those suckers will leak even when you swear they look new and are spotless clean. If you can see a ring marking on the needle valve at all it could be them. The springs in the needles could be mushed out or sticking. Also the needle seats wear out.

Next suspect is the needle seat gaskets. If they are not sealed right or cracked from over tightening it will leak.

Next thing to check is after a good dip on dirty carbs sometimes passage way clogs loosen but don't come completely out until everything it back together. Even if the passage way was dissolved open and flowing, these little suckers can still be in there allowing flow around them but still be there. Kind of like a passage way booger, they will then fall out with the fresh fuel and clog up (you guessed it) the needle valves. This also creates the intermittent problem you describe and is in my experience the most common issue with this type of problem. It will have you thinking your fuel screen on your petcock is bad and that you need an additional inline filter but in fact the problem came from within the carb passages themselves!

If your sure the float heights are spot on and that the floats themselves are good, not saturated, tweaked excessively or damaged in some other way, then those things I mentioned above are the things to check.

It could be a petcock issue but if your needle valves are doing their job that shouldn't matter UNLESS...
the diaphragm in the petcock is damaged. It can allow fuel to flow down the vacuum line and that will bypass the needle valves as it drains right into the vent tube area not into the bowls.

It's a pain I know buddy but check these things. You'll find it.

I'm putting my money on passage way boogers. The most common problem after a good dip/cleaning.

[GSstiny]

Thanks Hoom. I guess Ill yank em back off tonight and re-inspect the needles and passages. I replaced the seat gaskets on the 1 & 2 carb since they were the only ones dumping. If I dont find any gunk Ill take a long hard look at those needles. Not necessarily for close inspection, but because Im half nearsighted and half farsighted :-D

[retrex]

Sinking ship

Just a thought, have you checked your floats to make sure that they float? Put them in a container of gas, I rig a paper clip with a fishing sinker to put an even load on the float so that both potoons are beneath the surface and are level. If the float list to one side or sinks after a while in the fuel I replace it.

[GSstiny]

Ive got everything checked out, it has to be the needles themselves. The stealer wants $25 for a needle/seat assembly, which translates into YET ANOTHER benjamin that I dont really have. Z1 has a 6 pack of needles for 15 bucks, but they dont have the seats for the VM carbs. As hoom said, the seats wear too, BUT, the needle is steel and the seat is brass, so is it ok to replace the needle and not the seat?

[rkubik]

grit

from the sounds of the problem, could be there is pieces of grit or rust flakes or dead fly parts in the gas, which as they flow into the carbs intermittently jam the the needle from closing against its seat. I'd suggest swish some gas and pennies around in the tank to loosen any crap, pull the petcock and clean it thoroughly,then put in some fresh gas.

[Hoomgar]

Ive got everything checked out, it has to be the needles themselves. The stealer wants $25 for a needle/seat assembly, which translates into YET ANOTHER benjamin that I dont really have. Z1 has a 6 pack of needles for 15 bucks, but they dont have the seats for the VM carbs. As hoom said, the seats wear too, BUT, the needle is steel and the seat is brass, so is it ok to replace the needle and not the seat?

Are you 100% sure the petcock diaphragm isn't bad? Between passage way boogers and bad petcocks I have learned A LOT about this issue. And more times than not it is one of these two

Being that it is intermittent then I really still suspect particles like I explained in my first post.

Also, I said about saturated or damaged/tweaked floats, are you 100% sure they are good?

If all of this lines up then what do the springs and pins in the needles look like? Do they push in and pop right back out freely? Do they seem to have a good bit of push? If any of them seem hesitant to pop back out or stick or just feel weak then that is suspect.

The needle valve seating in the seat itself is rarely the issue when your leaking a lot of gas. That is why I re ask the same questions again. I wish I could look at it with you. This is one of the few things I am good at finding now

[chris myers]

I had the same problems and bypassed the petcock issue by putting an inline shut off valve from a Briggs and Stratton mower. Petcock issue solved then moved to needle and seat issues. Just a thought. It was only $6, so a cheap aggravation saver.
Chris

[GSstiny]

Guys, Im saving all your replies just in case I run into this again in the future. I rechecked all the floats and needles this morning, floats are not bent and they do in fact float. The seats are good, but a couple needles have that ring hoomgar was talking about. I cant feel a groove in them, but they are showing some wear. The springs dont really feel like they are as strong as they should be. I went ahead and ordered some replacements. I also gave the petcock a thorough going over, and the diaphragm seems to be good. I did get some possible boogers out of the #4 carb, but otherwise there was no crud whatsoever in the carbs and the petcock screen is clear, so I dont think theres anything coming in from the tank. Im thinking the needles will solve it.

Just to clarify, the dumping was intermittent back in the winter, its gotten pretty consistent since the rebuild.

Once again...THANKS for the help...what would I do without the GSR? \\/