carb #3 leaking fuel from center hose

[superawesome]

Hi,


after introducing myself in the GS Owners section, I think I qualified for posting my first technical issue here


My 1978 GS1000 is leaking fuel from carb #3 since about a week. It is coming out of the center hose at the botton of the carburetor. Maybe 10-20ml a day, so not a critical amount.
But since the GS has a vacuum petcock, shouldn't the carb's fuel chamber be empty by now? And if the petcock would be broken, shouldn't all carbs be leaking?


So where would you start looking? I guess it is a combination of issues, I am thinking about the best logical approach to tackle this issue...


Thanks
jürgen

[jlyon40]

Is your petcock on Prime. If so that's probably why its leaking.

[Big T]

Or, the petcock has failed and is filling up the float bowl

Check the vacuum line for fuel, Also, check the crankcase oil for gas

[superawesome]

Petcock is "On", not "Prime". Also no smell of gas in the crankcase. Vacuum line is dry.

[allojohn]

The fuel chamber will not empty, the "leak" will stop when the fuel level drops below the overflow tube.
More likely is the float valve on #3 is failing and just draining the fuel line. It will stop eventually, unless the petcock is failing.

The test will be to leave the bike for a day or two to see if it stops. Every time you fire the bike up the cycle will begin again....

[superawesome]

Thanks John, the bike's been standing for about 10 days now (since my rectifier died, and I am waiting for a replacement). The hose was still wet with fuel today, but it seemed like the dripping got less. Will put a different bowl underneath tomorrow to make sure.

[Big T]

One other thing

The small brass tube in the float bowl that is the overflow is prone to cracking where it goes into the bowl

So, swapping out the bowl could cure your problem

[allojohn]

One other thing

The small brass tube in the float bowl that is the overflow is prone to cracking where it goes into the bowl

So, swapping out the bowl could cure your problem

Good point.

[superawesome]

Thanks a lot so far! I ordered a used Honda R/R and will try to put that in on the weekend and then head for the carb afterwards. Will let you know about any progress.

[superawesome]

Okay, new R/R is installed and battery charging again. Back to the fuel issue:
I just checked the petcock briefly this morning and there is fuel coming out of the fuel hose even if it is "On". So it seems like Big T, jlyon40 and allojohn were sort of right, the petcock has failed.

So my next steps would be to get a petcock repair kit. Anything to look out for in particular?

[Rijko]

i have not had much luck with the yellow K&L kits - especially with the diaphragm.
They have new repair kits now, in a blue label bag. Have not tried those.
Have you tried cleaning the internals ?

The petcock is one of those parts i replace if cleaning fails because of the low success rate with repair kits.

[Big T]

Petcock rebuild kits have a bad reputation around here
I'd recommend a new petcock, but they cost about E250
I'd start with replacing the rubber disc and the O ring (available from Suzuki) and seeing if that solves the problem
Drain the fuel tank and remove the two screws holding the face plate. Work the lever out and see if the rubber disc is intact, The O ring I mentioned goes around the lever

Or, buy a 750 petcock for much less money, and modify it per Chuck Hahns Project Blue GS 1000 thread

[superawesome]

Thanks Big T,

I did order a rebuild kit from Tourmax on ebay yesterday (somewhere read that someone with a GS1000 was happy with that one).
Drained the tank this morning and removed the petcock but did not find the time to take it apart yet.

Obviously I want to try the rebuild kit (as I ordered it now). What are the critical parts that I should reuse if in good condition?

I guess the 1980 GS1000 petcocks are not compatible, right?

[Big T]

Only the metal parts are worth saving, plus the filter

I can't say for sure on European 80 models -ours got the weird leverless petcock

[superawesome]

My rebuild kit arrived today, and I replaced all the rubber parts. One question on the washer that goes in the little lever part:
Which way does the open edge go? On BassCliff's website I found a pdf(http://members.dslextreme.com/users/...ck_rebuild.pdf) that states the open edge goes to the inside of the petcock, mine was the other way round when I took it apart (luckily I took a picture, see below).

Otherwise the kit seems to be ok, when I suck on the fuel pipe (setting ON) I don't get any airflow (which was the issue before). Can't install it on the bike yet, as the two washers that go on the two main screws are still in the post (previous owner didn't take much care of that it seems).

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