Bad petcock: Big deal or manageable?

[bdub416]

Hey guys, back again with more questions regarding my 82' 450gs restoration project... and for those of you that haven't read my previous posts ... I am by no means anything close to a mechanic ... Lehmans terms appreciated :-D

I removed the gas tank to troubleshoot my electrical and found out that I was unable to stop the gas from flowing regardless of what position the petcock was set to. Is this a big deal in terms of performance? I have a long list of things to fix so I guess I am trying to get an idea of whether this has a big impact on how the bike runs.

What is the best position for the petcock to be in? If indeed the recommendation is to replace the petcock, any suggestions on OEM vs aftermarket ... and potentially where the best place would be to get one?

Appreciate the patience fellas.

His,
dubs
[-o<

[doctorgonzo]

VERY big deal. The gas will evntually make it's way into your crankcase, thin your oil and likely destroy your engine. Z1 sells petcocks for these bikes, you'll need to measure the bolt spacing, and the width of the plastic piece that goes up into the tank. The rigged up short term solution is to put a manual shutoff in the line between the petcock and the carbs and turn it off when the bike isn't running.

"Prime" is for right before you start the bike after it has sat for some time. It usually stays in the "Run" position which means gas only flows while the bike is running and providing vacuum to the petcock.

[bdub416]

hmmm, somewhat concerned reading your post ... I just picked this bike up, hadnt been run in 2+ years ... and am in the middle of trying to get her running again. When you say "likely destroy your engine" ... I am assuming this would be fairly clear if this has ALREADY happened?

I have had the bike running, albeit rough, but I've had it around the neighborhood a few times, sounds ok ... just clearly has many issues to tackle.

[doctorgonzo]

hmmm, somewhat concerned reading your post ... I just picked this bike up, hadnt been run in 2+ years ... and am in the middle of trying to get her running again. When you say "likely destroy your engine" ... I am assuming this would be fairly clear if this has ALREADY happened?

I have had the bike running, albeit rough, but I've had it around the neighborhood a few times, sounds ok ... just clearly has many issues to tackle.

Well, not gonna destroy it instantly. What happens is that gas that is constantly running into the carbs from a bad petcock has to go somewhere. It may leak out the carbs, it may go out an overflow tube, it MAY run down into the motor, fill your crankcase with gas, and turn your oil into a thinned out useless mess that doesn't lubricate your engine causing it to wear extra fast or even seize up. Before you start the bike again, take the oil cap off and see if you smell gas, check the level and make sure it's not too high (from the gas filling it up). if either of those is true, dump the oil and refill. If the oils seems good, the short term solution is a manual fuel shut off (probably can get one for a riding mower at walmart or auto parts store) Put in inline in the fuel line and shut it off when you're not running the bike. The larger point is, gas constantly running from the tank to the carbs is bad, bad, bad.

[twistedwankel]

What is the best position for the petcock to be in? If indeed the recommendation is to replace the petcock, any suggestions on OEM vs aftermarket ... and potentially where the best place would be to get one?
[-o<

For OEM quality parts I normally go to Bikebandit.com and their petcock which you will see on the exploded view for your exact bike will match your factory one totally. Also order the to tank large rectangular o-ring and new mounting bolts. I think it cost me $36+shipping for my last one?

None of the kits sell you the parts you really need waste of money when you don't get all the parts needed.

You leave it in Run (UP) position normally unless you have less than a gallon of gas then you put it in Res (left)...Prime (right) is only used when the bike has set for a week and you need to fill the carb bowls again prior to starting due to evaporation.

[bdub416]

Great, thanks for the help!

Until the next time I'm stumped ... If I were a betting man, I would bet sooner rather than later :-D

His,
dubs

[Steve]

If you are a bit adventurous (and cheap, like me), you can take the petcock apart. It sounds like the plunger is just stuck, but it's also possible that the diaphragm is torn. Either one of these situations will result in free-flow, but if it's just stuck, you might be able to clean the residue that is causing it to stick and put it back together. If that does not fix it, the general consensus is to not waste your money on a rebuild kit, just replace the entire petcock. Seems that they tend to last about 20-25 years, so let the next owner worry about it later. 8-[

,

[Roostabunny]

If you are a betting man, you could try finding a rebuild kit. They get mixed reviews, to put it mildly. My swag is about 60/40 against. Maybe even 70/30. But they're cheaper.

I commute 50 miles on my bike every day, so I didn't like those odds. I replaced mine with an OEM (from Flatout, I think). Took 10 minutes to swap it out and I haven't thought about it since.

Either way, you need to get it fixed. I doubt that it's already caused any damage by leaking gas into your oil (how was the oil when you changed it?) but it eventually will. Or, your #1 float will stick while it's on the side stand and you'll come out one morning to find all the gas from your tank is on the ground. :shock:

Besides, it's a pain when you take the tank off.