Overflowing Carbs (sometimes)

Ok, so I've been trying to figure out why my carbs are leaking out of the overflow while on the side-stand. Some of you might have seen my earlier post related to the petcock.

kzrider.com/component/option,com_joomlab...w/catid,3/id,133026/

So the petcock is fixed and I wanted to see exactly how my carb/float/overflow deal was working. I set my floats to the (generally accepted but not official) 25mm above the gasket (see this post).

Then I hooked my tank up to the carbs and did some tilt testing. Below, you can see, I tilted the carbs progressively to see if the float valve would hold off the gas at an angle. Pic 1, 2 & 3 I had no gas coming out. Great

Pic 4 is where I tilted the carbs toward me. Gas dribbled out of the overflow and (what I believe is) the pilot (marked "M" on the left of the ports).



My question. Is This Normal Operation? Should I expect that under these conditions, no gas should be coming through the overflow?

One thing to note, when I held them tipped forward, the gas coming out of the overflow stopped after a bit, indicating that there was no more gas coming through the float valve, but it was just overflowing the gas that was in the float bowl. The pilot continued to flow however.

What do ya think?

Ah! 800 pixel height limit on pix. Here it is:

PS - These carbs are pretty clean and float needle and float needle seat are new on both. They're clean too so I think the mating of the two is pretty tight.

Sorry, man, I got nothin'.
I've never tested mine like that, so I don't know.
Nor have I ever done a wheelie in which I fell over to the left at just that angle.
:lol:

heheh, i figured i'd get a comment like that. i'm just more concerned with parking it on an incline. the angle in pic #3 is probably about the angle they're at when the bike's on its kickstand (which seems to lean the bike quite far).

I used to get that problem of a carb leaking when parked on the sidestand and think it was due not to the float needle valve but more likely to a float hanging up on the inside of the float bowl when tilted. Anyway. I replaced float needle valves and played around with the floats themselves to make sure they were not catching on the inside of the bowl. Problem solved....I think
I occasionally park on the sidestand but mostly use the centerstand.

float level too high?

Mm, well, my center stand was ripped off violently a while ago by the looks of it (bent metal hinge left on the bottom of the bike), so side-stand it is for now. (anyone got an extra?)

when i shake the carbs, i can hear the floats move. i guess that's not a guarantee that they're not hitching, but i would think the gas would just never stop coming out if that was the case.

what i've realized about the float level from this forum is that the float level has to do more with the fuel uptake happening at the appropriate speed more than preventing overflow (although it does that too). is that right? too low of a float level, too lean of a mix?

i've set them to 25mm. i'm going to check the level externally, make sure it's perfect, and put them back on the bike. we'll see if they overflow.

where should the overflow tubes route to, ideally?

My first guess is float height. That can be checked with a piece of clear tubing and some Teflon tape:



Then you can determine how much more to adjust your floats.

A second possibility could be a crack in the overflow tube:



It would have to be in a position that allows the crack to be in gas on the sidestand and not when the bike is upright. Trust me, a slight crack like that will spew a lot of gas. BTW, the bike that bowl is on had three tubes cracked like that. I sealed them by polishing them up with some 1600 grit sandpaper and then applying JB Weld Quick.

Post edited by: N0NB, at: 2007/05/30 23:05

Oooo, subtle crack! I'll check, just in case.

Can I ask a stupid question? What's the Teflon tape for?

Ok, I think I answered that question myself (to help the seal when stuffing the tube up the drain port.

SO, I tested my levels (clear tube/tef. tape/leveled vice/center of bowl) after measuring 25mm and both the float levels look Perfect!

BUT...

A.) when I drained carb 1, the gas in the line from the petcock drained out (this is correct, right? as I drain the bowl, the float should drop, opening the valve and letting the rest of the fuel in the line flow through.)

B.) when I drained carb 2, the gas in the line from the petcock DIDN'T drain out. Now this is WRONG, right? This would be an indicator that the float stayed stuck closed? :S

Hey guys,

Sorry for the nag post. Does anyone have a yes/no on my "B." from the last post there? It seems right but I don't wanna screw this up and hafta take them off again.

Thanks for all the help!