What is a petcock and what is its function?

[Anonymous]

Yup, that's right -

I've searched like crazy the last few months I've been perusing the forum. I see its talked about constantly, but I still have no idea what it does.

I've gathered that "pet" comes from petroleum, but "cock" ? Can someone explain how this integrates and operates with the carbs and fuel tank for me? Please speak on basic terms, as I'm an electrical engineer with very basic knowledge of engines.

I really appreciate your help!

[SqDancerLynn1]

petrol tap

pet?cock [ p?t k?k ] (plural pet?cocks)

noun

valve for draining: a small manually operated valve or faucet used to drain off waste material or excess fluid from the cylinder of an internal combustion engine


[Mid-19th century. From pet (of uncertain origin: perhaps from pet1 or obsolete pet ?fart,? via French from, ultimately, Latin peditus ) + cock1 in the meaning of ?spout.?]

[Anonymous]

THanks SqDancerLynn1

what excess does it "drain"? Is the petcock in between the tank and carbs? If so where does the "extra" gas come from? I thought that when the carb needs more fuel, the float lowers and lifts a valve to allow more fuel into the bowl. What's the purpose of the petcock?

Sorry - not trying to be a nag or retarded...

[Anonymous]

The petcock on a bike is mounted on the underside of the tank. It has a lever on it that will change its function from run, to reserve, to prime. In the run postition, it relies on vaccum from the engine to allow fuel to flow the the carbs. In prime it allows fuel flow without the engine runnning. And, in reserve it lets you make it to the gas station if you forget to fill up the tank in time.

Craig

[chuckycheese]

Right

Come on, Scott.....I happen to think you're "pulling our leg" :P

[robinjo]

Swingline your bike is a bit different then most other bikes in the petcock area If I remember correctly you don't have a lever that you can turn with your hand to the desired position like 'On', 'Reserve' and 'Prime' like this one.





but a sort of "outlet" with a screw slot in it which the only had on the 1980 models, I'm going by what I seem to remember reading about here on the forum, more knowledgeable people feel free to correct me .[/img]

[chuckycheese]

Yeah

You're just right, Robinjo...the 1980 petcocks are unique. :roll: There is only a plastic, slotted adjuster (no reserve) and...the 1980 petcocks are the worst of the bunch,

[Anonymous]

Swingline your bike is a bit different then most other bikes in the petcock area If I remember correctly you don't have a lever that you can turn with your hand to the desired position like 'On', 'Reserve' and 'Prime' like this one. ...[pic]... but a sort of "outlet" with a screw slot in it which the only had on the 1980 models, I'm going by what I seem to remember reading about here on the forum, more knowledgeable people feel free to correct me

robinjo, yeah... i haven't looked to be honest (only had the bike one week). The previous owner told me there is no switch/lever for reserve or on/off. I found it kind of odd at first, but he seemed very knowledgable about the bike otherwise, so I didn't question him.

You're just right, Robinjo...the 1980 petcocks are unique. There is only a plastic, slotted adjuster (no reserve) and...the 1980 petcocks are the worst of the bunch,

Well, that really sucks. What exactly is "bad" about it (other than not having a reserve and on/off??)?? Can I replace it with a newer style? Having a reserve would help put my mind at ease... but I also feel much better having the fuel gauge on this bike - THAT is cool, IMO

[chuckycheese]

Yes

Yes, Scott, you can replace it. Actually, there are about a zillion posts regarding just that. I've written a number of them (as have others) and have included stock numbers for Pingel petcocks which seems to be the one most of us have changed to. Do a search and you'll find all the information you'll need in order to do a good job of switching to a new one.

I looked for quite awhile to see what else might be available and found nothing else that would fit the 1980 models because of the very restricted clearance. The biggest drawback to the stock model is that you've got no reserve and the major "biggy" is that they're prone to leaking gas into the crankcase...which can be disastrous!!

There a few tricks involved in getting the Pingel to fit on a 1980...if you don't find them in the "searches", let me know and I'll be glad to help. It's a fairly tight squeeze and the stand pipe will have to be shortened, but once it's on properly, you'll be quite pleased! :P