Gas Leaking When Using The Choke

[Spartanman]

So my 81 XS1100 was sitting over the winter and when I first started it, there was a little puddle of gas underneath which of course concerned me. However, since then, it hasn't leaked at all, and I ride regularly. Until this morning....when it leaked a lot, but again only when the choke is open. The choke lever itself is wet, so that's where the fuel is coming from I assume. Over the years, I've rebuilt the petcocks, relined the tank, replaced the octopus plastic lines, to eliminate previous leaks. Any suggestions or things I should know, before I start tearing this thing apart?

[Radioguylogs]

Leaking choke would be uncommon.

Maybe you should run your hand under the edge of the gas tank and make sure it is not leaking?

[Socer4m]

3 things to check,,,,whack the side of the carbs with a rubber hammer a few times in case a float hung up,,,,try running it and see if anymore gas leaks,,,,,,if so,,,look at gas lines and connections in case they are loose,,,,,next, put a stick in the crankcase oil, pull out and smell,,if any gas smell,CHANGE THE OIL ASAP,,which means it flooded the crankcase, probably the most common thing, float is hanging up and not sealing the gas.......let us know how it checks out.....Mike in S.Diego and PA....

[skids]

One of the holes in the carb inlet bell is for venting. If venting is blocked it can cause flooding.

[Spartanman]

Thanks for the replies. Upon further investigation, this is not a carb issue, which is either good news or it isn't. Fuel is leaking it appears out of the bottom of the vacuum block, or at least that's where I see it dripping from where the yellow plate separates the two aluminum sides. Anyone have any experience with this, before I pull the tank and tear that mysterious thing apart?

Also, I tried looking for info on the octupus system in the OEM service manual, and I couldn't find anything.

[Radioguylogs]

You will find the octy is simple inside- just a vacuum diapgram that opens the gas valve.

You can find rebuild kits on eBay.

[Spartanman]

You will find the octy is simple inside- just a vacuum diapgram that opens the gas valve.

You can find rebuild kits on eBay.

Thanks for the info. Went searching on ebay and when I entered fuel pump rebuild kit, it returns these petcock rebuild kits. I assume the square thing is the diaphragm? It obviously wouldn't fit in a petcock.

[DiverRay]

That one should work. The large diaphragm is for the Octy, and the two round/4 hole parts are for the actual petcocks. Just VERIFY that the small O-ring on the end of the metal valve is the correct length. K&L kits were ok, if I remember correctly.

[Spartanman]

That one should work. The large diaphragm is for the Octy, and the two round/4 hole parts are for the actual petcocks. Just VERIFY that the small O-ring on the end of the metal valve is the correct length. K&L kits were ok, if I remember correctly.

Just ordered up the K&L kit. Your feedback is very much appreciated.

[jetmechmarty]

”K&L kits were ok, if I remember correctly.“

In my experience, no they aren’t. The pin is too short. I posted a fix for that recently. If you simply put the kit in it, the vacuum valve won’t close.

18-6633 is the K&L part number for the diaphragm. Every K&L diaphragm I checked, the pin is too short.

https://www.xs650.com/threads/vacuum-petcock-rebuild-kit-fail.65527/

Post #10 has the fix.

see also:

https://www.xs650.com/threads/rebuilding-yamaha-vacuum-operated-fuel-valves-petcocks.20662/

originally posted on the XJ forum.

[DEEBS11]

Much ado about nothing. What a cluster phuck. Chuck all that crap and go manual.

[DEEBS11]

This is correct for your bike.

[DEEBS11]

A thought: It's nice to have a perfect original system on a valuable bike but in my humble opinion, our XS11's ain't exactly a KZ1000MKII. It's OK to eliminate some troublesome features that are complicated and expensive to keep stock. The Octi is a prime (haha) example of a system that you can do better with todays parts and practices. These are also (similar part) on early 80's CB750 & 900 Custom's. I always remove these annoying parts and go with a simple manual (or vac) petcock. Pingel units are top quality and are rebuildable.

[DEEBS11]

Wait,,,,is that an aftermarket petcock on a MKII??? DAMN.

[jetmechmarty]

FYI, that K&L pin that’s too short also applies to the vacuum petcocks on the standard XS11.

FWIW, I have an XS650 that I bought new. It has a vacuum petcock. I have never futzed with it. It has been working fine all these years.

I contacted K&L about the short pin issue. They did not respond.