Overflowing carbs, '79 GS1000 (for btgs1000)

[Guest]

Hi,

Since I'm no expert in VM carbs, I'm sharing this PM I received today so that you experts can help Bryan. He just re-joined the forum but can't post yet. (Don't worry. Frank will get around to it in a day or two.)

Hi BassCliff. Sorry to bother you in PM. My name's Bryan. I'm not new to the forum but haven't been here in awhile since I sold my old GS1000. I now have another I'm working on. It's a 79 GS1000 with the 80 style vacuum petcock with no shut off. I cleaned and rebuilt the carbs (VM26s I believe) and since my petcock is probably caked with varnish and won't flow, I ran another tank with a free flowing petcock on it just to try to get the bike started. In doing so, all the carbs overflowed immediately before I could get it started. Then I noticed I forgot to plug off the vacuum line. Would that cause them to overflow out the drain tubes on the bottom? The other suspect is that one of the brass overflow tubes in one of the carb bowls was nearly broken off. I wasn't sure if they could operate that way or am I going to need a new carb for that one?
Thanks,
Bryan

Hi,

I'm not as well-versed with the VM carbs as others on the forum. But an unplugged vacuum line would not cause all of the carbs to overflow. It would cause a big vacuum leak and run lousy.

If I were to guess, it could be that the floats are stuck, or at the wrong height, or the float valves are not working properly.

If you don't mind I'll post this in the carb section of the forum so you can get some real expert responses.

All the best,

Cliff

Thank you for your indulgence,

BassCliff

[Agemax]

the broken off overflow tube will definately leak fuel, the only remedy is a new or used float bowl. i had a broken tube as well a few months back and a GSR member came to my rescue.

[Steve]

There are a couple of issues going on here:
First, even the "dreaded '80 petcock" has a vacuum shut-off.
None of the other GS petcocks have a manual shut-off, they are ALL vacuum operated.

Second, It appears that the bike might not have been running for a while, because some of the fuel parts are "varnished over". That could also be the case with the inlet valves.
It is also possible that the floats are stuck or not adjusted properly, but the inlet valves are good candidates here.

Third, Plugging the vacuum line on the carbs will do NOTHING to prevent overflowing due to any other problem, including stuck inlet valves.

Fourth, if the overflow tubes are broken off inside the float bowl, the new "overflow" height is the height of whatever is left in there.
If the tube is short, it will basically free-flow, trying to raise the fuel level above the height of that tube.

Fifth, how sure are you that it's a '79 bike with an '80 petcock? Be aware that the '80 models were produced as early as August or September of '79,
so please do not think that the assembly date is the model year of the bike.

.

[btgs1000]

Just to follow up with results. I was referring to the wrong piece on the carbs. The piece that was broken was the choke tube on the carb base. The reason it was overflowing was because of a weak float valve spring. I replaced all the float valves and seats with new ones from Z1 Enterprises and the bike started and ran well. Thanks.

[BassCliff]

Hi,

Just to follow up with results. I was referring to the wrong piece on the carbs. The piece that was broken was the choke tube on the carb base. The reason it was overflowing was because of a weak float valve spring. I replaced all the float valves and seats with new ones from Z1 Enterprises and the bike started and ran well. Thanks.

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