#4 dumping gas

[SanDiegoMike]

Okay...I tore all the carbs apart to clean them prior to taking Soccer4m up on his offer of using his sync tool. I used 4 cans of carb cleaner, went through them 1 at a time, and was super careful to put everything back in its proper place. The idle mixture screws on 2 of the 4 were out 1 1/4 turns, one was out 2 1/2 turns, and one was out 1 1/2 turns. I re-installed all of them 1 1/2 turns out, set the float levels to 23mm (most were 27), replaced 2 broken o-rings on the piece that the float needle goes into, and buttoned them all back up. I did the best bench sync I could, and re-installed all back on the bike. Re-connected fuel lines, set the choke, hit the switch, and fired it up. At first, 1 & 2 exhaust heated right up, but 3 & 4 stayed cool. They finally did fire though, and I clicked the choke back to half way. Choke fully off a few seconds later, still idling high, but I wasn't too concerned because I was expecting that they still needed to be sync'd. I shut everything down, and noticed a nice puddle of gas forming under the bike. Closer examination revealed this.
[IMG][/IMG]

Can anyone please tell me what I need to do to correct this? Do I need to get a new needle/seat assembly, or is it something worse? Are my floats set okay at 23mm? Pretty frustrated right now...at least it's only one carb doing it. As always, any help is greatly appreciated.

Mike

P.S Hey Wiz...what part of Vista are you in? I'd like to get your opinion on this if you are close by...PM me and I'll give you my address/phone #.

[XSPastor]

Hey Mike,
Nice Graphic!

That hole is the float bowl vent. Only the 80 and 81 models have it. Earlier models had a vent hose. If the fuel rises high enough and the float valve does not close, fuel will pour out of that hole. Possible causes: float sticking open, fuel leaking past the o-ring in the float seat bore, or float needle valve not sealing completely.
I had the same problem and it ended up being that I had a float that was dropping so low that it would jam open. 23mm should be good for the float level. That's what I run. Make sure the bores that contain the needle valve seats are clean and smooth so the o-rings make a good seal, gently polish the float valve seat with a q-tip and some brass polish, then look at the carbs with the bowls off in the position that they run on the bike and make sure that they all drop to about the same level. If the leaky one looks different in any way, match it to the other three. Make sure the floats move freely on thier pivots and check for any flaws where the float needle ends contact the float tangs. Any burs there could cause sticking also. Look very closely at the needle valve for that carb too. If you see any defect at all in the sealing surface, you'll need to replace the needle. You can buy them individually at mikesxs.com.
Good luck!

Tim

[skids]

Yep, if it only happens when the bike is running, you have a bad oring around the needle valve (fuel float valve). If that is the case, it will also leak when just sitting on prime.

[81xsproject]

Can also be caused by debris from the tank getting stuck on top of the needle valve and not allowing it to seat. On older models it can be attributed to a leaking float. But, I have yet to see a plastic float leak.

[79XS11F]

I bench tested my needle valves with a vac pump like for bleeding brakes. I hooked it up to the fuel supply line and made sure it would hold a vacuum between the needle and the pump. If the needle is worn, dirty or not closing completely for any reason this will show it.
Also ... are you filtering your fuel? if not do so.
Rob

[XSPastor]

A vac pump? That seems like a good idea but be careful. This is not a high pressure fuel system. With too much pressure, you can force fuel past even good float valves.

Tim

[XSPastor]

If you suck too hard with the pump, you could also damage the sealing surfaces on the float needles...

[79XS11F]

That's right .. you don't need to apply a lot of vacuum ... it's about holding the vacuum not how much vacuum it will take.
Rob

[XSPastor]

The sucking action could also force valves that normally leaked to be forced closed with much greater force and so not be an accurate leak test...

Ok - I'm done.

[prometheus578]

"Vacuum pump... registers nothing."

I mean... it's a vacuum, ain't it?
So.. it doesn't hold vacuum... is it the O-ring... or the needle?
Can't tell, can ya.
Take the bowls off, flip the carbs upside down and hook fuel to it. You will then see where the fuel is coming from and what you need to deal with, be it O ring or needles.
If there's no leakage within about 15 minutes, then you're good.
(blip the floats to clear the air from the fuel line first, then dry everything and watch fer leaks)
No leak...? Put the bowls back on, flip the carbs right side up, turn on the gas and watch again.
If it leaks, refer to what XSPastor wrote about hanging float height.

If there's "wear rings" grooved in the tips of the needles.. replace them.

[SanDiegoMike]

I forgot to mention that after I shut the engine down is when I saw the problem. With the engine off and the petcocks set to "on" (I don't have an octopus and both of my fuel lines have inline filters), fuel will leak from that hole. I pulled that bowl off, and it was completely full (no surprise to most of you, I'm sure). I moved the float assembly up and down, and there doesn't seem to be any problem with it hanging up or sticking. I guess the next step will be pulling the carbs back off and going through all of your suggestions.

Thanks for all of the input...

[TADracer]

Mike,
Not sure what the float level is supposed to be for an 80SG but if it is like my 79SF (25.7MM) then your 23MM setting may have your fuel level too high. It could be just syphoning what is in your line, etc. If all else fails, you could try raising your float adjustment a MM or so. I know that mine will drip fuel as soon as I turn on the cocks if the floats are set at 24MM but at 26MM it will not.

[thewiz]

Float level 80SG

According to the manual, the 23m (=/- .5m) is correct. That also equals .906 (+/- .020) in inches. Still though, it sounds like a lower float level (a bigger number) might be called for here ... assuming no other problem, that is.

Incidentally, I was the owner/operator of a carb shop in the '70s when it was a pertinent enterprise. We rarely ever worked on CV carbs that I recall .... I thought I knew a little about carbs and these bikes would be a snap. WRONG!! I'm better with 'em now but only after lots of R&Rs, mistakes and more mistakes, and a watchful eye from Planedick, Promster and others here on this site. Hang in there, I'll PM ya.

[SanDiegoMike]

Pilot plug

In looking at MikesXS for float needles, I noticed this
The description says: Rubber pilot jet Passage Plug (Pk./2) Fits: XS650G/H/SH/SJ/SK/SL (1980-84)
stock Mikuni BS34 CV Carbs. Used inside float bowl to seal pilot jet passage -
1 used per carb

I didn't see any of these in my carbs. Are they used? What do they do?


Sorry the picture is so big

[tarzan]

The description under the pic doesn't say SG,which is your bike.My bike is the same as yours and I dont have those plugs.