Fuel leaking

[MikeS]

I've been smelling gas when I go out to use the bike for quite a while, but have never noticed any indication of fuel loss on the guage or in operation of the bike . . . until very recently.

I don't see any obvious places where fuel is leaking. I think I've read that petcocks sometimes need replacing so I'm guessing at 39K miles this could be the culprit. I've got my old '79 parts bike sitting under cover in the back yard so it's possible the petcock on it is still servicable although any seals, o-rings, gaskets would surely be toast after sitting unused for the last ten years or so. Other than this concern, the '79 petcock appears to be identical to the '82 petcock.

Anyway, question to the group . . . is the petcock the prime suspect in these situations? It seems to me it almost has to be the problem since fuel from lines or carbs couldn't possibly be leaking unless fuel is making it's way past the petcock. I'm losing quite a bit of gas so I need to get my attention on it. If I need to buy a new petcock, I'm guessing the dealer is my best option . . . any alternate sources I should know about? Thanks, Mike

[1978GS750E]

What bike are we talking about???? Is there a gas odor in the crankcase oil? Is there fuel on the bottom of the carb bowls? The easy way to test the petcock is to run 2 hoses from the petcock into separate containers. If there is a petcock leak, the container with fuel in it will let you know. As for rebuilding a petcock, most on here say they don't have much luck with rebuilding them. Myself, I've rebuilt 3 or 4 without any issues.

[Redman]

First, lets verify/confirm that you are not leaving the petcock in the PRIme position are you?
PRIme position would be with the lever handle pointed back.
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[LAB3]

The group consensus is you're best off buying either a stock Suzuki petcock or a high quality aftemarket unit. The owner of Z1 Enterprises is member of the board here and I certainly can vouch that I got a good petcock from there as well as other parts. https://www.z1enterprises.com/

[cowboyup3371]

One other option - check around your tank for any pinholes that might allow for the leaking

[MikeS]

You know, I might have only stumbled across this idiot move on my part once I had the tank off and was in the process of replacing the petcock, not even having considered that I could have been so dumb as to turn it to Prime instead of Reserve. Following your post I went out and checked and thanks to your mentioning that the lever should not be pointing backward, sure enough . . . it was pointing backward!. With my eyes getting worse with age, especially at night and even with a flashlight I need a magnifying glass to see what's stamped into the bezel so your mentioning the position of the handle saved the day.

When I unexpectedly started stalling while going through an intersection a couple days ago I had reached down and by feel, moved the lever to what I figured was Reserve. I've done it many times - moved from the vertical position to reserve but instead of the lever pointing forward, I stupidly moved it the other way - probably because the stalling was so unexpected but also probably because I'm getting unreliable in my old age (only 74, but still . . .).

So, putting it on Prime has certainly contributed to the recent increase in loss of gas, but the original problem - the source of fumes - will still be with me so I'll take the tank off and give the petcock a good inspection before ordering a new one. There could possibly be a bit of rust or crud lodged between the valve and seat and might just need to be blown out real good. Thanks to your post though, instead of a serious leak I'm back to having just something minor to take a look at when it's convenient.

If I need to order a new one I'll for sure get ahold of Z1.

Gracias Redman and all who responded!

PS: Having done that . . . leaving it on Prime for a couple days as I have . . . do you think any gas has worked its way into the crankcase?

[LAB3]

It could very well be. Give your oil a smell test keeping in mind a gallon of Shell Rotella is pretty affordable.

[cowboyup3371]

It probably did. Do an oil change and just remove that possibility from the equation

[Steve]

One other thing to keep in mind: for gas to get into the crankcase, you have to have TWO failures.

1. The petcock has to fail.
2. A float valve has to fail.

In your case, the petcock probably did not fail, but it DID point out that at least one of your float valves is not holding back the gas like it should. That might be because of a bad seal, but it's more-likely that the o-rings around the float valves are leaking.

I will have to echo what others have asked: what bike is being discussed? The fact that you have a '79 parts bike for a running '82 model sort of limits the selection a bit, but it still would be nice to know. Although the petcock looks the same, be sure to also check the tubes on the back side to make sure they are pointing the correct directions.

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