82 GS450LZ: Replacement Petcock fuel outlet not oriented correctly

[Jestercinti]

Call me crazy, but I think I have a rare petcock. Mine is going south I think. Only runs well on highway on PRI. In town, will run using ON and RES, but on highway, will only run smooth on PRI. ON and RES causes a fuel starvation situation during high speed. No kinks in line.

I have an 82 GS450LZ, and the petcock fuel outlet points to the back (not left like the replacements on Z1 that I see), so it's directly behind the ON RES PRI lever. For the life of me, I can't seem to find one where the fuel outlet is oriented correctly except the OEM Suzuki Replacement, and that's $70 from Bike Bandit.

Here's my question...Can I go to Z1, buy a petcock, then put a 90 degree fuel line elbow to orient the left side outlet line back to where it should be on the stock version? Is this recommended? If I have to, I will buy the OEM assembly.

Has anyone else had this problem?

[JEEPRUSTY]

I think if your petcock works normally at lower speeds but not at highway speeds you may have a collapsing vacuum hose.

I would replace the vaccum hose and test it because if fuel flows at what should be lower vaccum at lower RPM then it would not seem likely that the petcock is itself to blame.

[Jestercinti]

Excellent point. Let me try replacing the hose (probably original), and will let you know what happens.

[BassCliff]

Hi,

Hopefully a new vacuum line will fix it. If not, I would not recommend introducing another point of failure in your fuel delivery system, another place where it could leak. I would encourage you to buy the OEM petcock and not worry about it for another 30 years.


Thank you for your indulgence,

BassCliff

[Jestercinti]

Another problem is that I forget and leave it on PRIME in the garage. I typically remember it is set to PRIME when I open the garage door and it smells strong of gas.

Stopping by the store tonight after work and buying a vacuum line. If that does not work, then it’s time to replace the petcock. I prefer OEM stock parts anyway since they have stricter quality requirements, and you know it will fit...after all, not looking for a high-flow petcock since it's just a 450 anyway.

[BassCliff]

Hi,

If you left it on PRIME, check your oil. It is quite likely that gas has drained past the carbs, through the cylinders, and into the crankcase.


Thank you for your indulgence,

BassCliff

[Jestercinti]

Looks like the hose worked! No more starvation issues. Rode on the highway at nearly WOT at a lower gear, and the fuel kept right on flowing! Due for an oil change anyway, so that should solve the problem if any gas seeped into the crankcase.

You guys are the best!

[JEEPRUSTY]

I am happy this simple thing worked for you.
You saved a pretty hefty sum of money.

[rockford]

Noooooooo

If you've got good enough vacuum to collapse your line (very unlikely), it wouldn't close off the flow of gas through the petcock. On the contrary, it would keep it from closing, leaving gas flowing freely. That's not what's going on.

[chuckycheese]

Yep

If you've got good enough vacuum to collapse your line (very unlikely), it wouldn't close off the flow of gas through the petcock. On the contrary, it would keep it from closing, leaving gas flowing freely. That's not what's going on.

That's just right! The suction created by the vacuum port ensures that the diaphram remains open and it takes very, very little (which is good since very little is generated by the carbs). I don't think the vacuum port on my GS1100 could collapse a plastic straw, much less a rubber hose.

The problem described is often caused by a partial occlusion at the petcock filter (rust in the gas tank) or a faulty petcock (really common as many of us have sadly discovered).

[tommyp]

I'm also having trouble with replacement parts/petcock on 1982 GS450LZ. Jestercinti, did you find a replacement?

Just bought the bike and am getting it back on the road. The pet cock leaked gas from the front, so I replaces the 5 hole rubber seal and the t-seal around the lever. That stopped the front leak. But now I discovered that the inlet valve is not getting sealed off. I order the BikeBandit recommended part, which is wrong. They actuallt don't sell the internal diaphram and I can not find anyone that does sell the internal diaphram.

It seem that the problem is that the internal piston is not seating down into the res/on inlet port. So with the tank off the bike held over a bucket, On position shows a trickle and Res. shows a trickle (should be shut off). Prim of course flows freely.

I tried putting in a stronger spring, this did not work either. I'm thinking that the oring that is supposed to seal off the intled port has dried out and shrunk. But I can't find the darn part for this thing.

anyone know where to get the LZ rebuild kit or a new petcock?