Petcock rebuild or new? '80 550L

[ChicagoRob]

Hello.

This is for the boy's '80 550L. It has the simple petcock:

http://www.z1enterprises.com/detail.aspx?ID=2636

I took it out for a spring shakedown ride. It stalled and then wouldn't start. Luckily the cavalry soon arrived with tools and jumper cables. By dumb luck, I found fuel in the vacuum line and was able to limp it home.

I did a static vacuum test on it and it won't hold a vacuum. Did the same test on mine, and mine does hold a vacuum. Hmm.

I took it apart and it's a pretty simple thing. Besides the mysterious slotted, sprung plastic bit on the front marked "Pri", there is only one moving part, a rubber diaphragm. I gotta figure that it has failed. Z1 has a replacement:

http://www.z1enterprises.com/detail.aspx?ID=1900

which looks to be the correct part. BikeCliff's Mega Greeting says to buy a NEW petcock (his emphasis). I know by now that I shouldn't doubt the collective wisdom of GS'ers, but what am I missing? Why new? If this were a master cylinder, I'd rebuild, so why not the petcock?


I know that this makes me sound cheap, what's another $30 for a new one? Well, there's a bit of a back story.

Last summer, after I dumped $200 in parts and many hours of labor into his bike, I told him that I wasn't buying any more parts. I'd help him with repairs, but parts came out of his pocket. Be a man, that sort of thing.

Since then, he joined the Marines and is currently at Camp Lejeune waiting for his MOS training to start. (He's a 1371 if you're interested.) It's another 6 weeks until the next training starts so he may be able to come home and pull recruitment duty. As a surprise, I'm trying to get his bike runnable. So far I've put on new handlebars/grips, did the coil relay mod, new green Dyna coils and wires (Boy, those were a tight fit!) and have on order a stator & rectifier from ElectroSport which I hope comes very soon. (Plus the gasket from Flatout.) It could also use a o-ring chain, sprockets, tires and _alot_ of paint.

So whatcha think? Should I rob my motorcycle fund (which needs all the cash I can throw at it) for another $42 and get the new petcock or get the new diaphragm for $11?

Thanks in advance,

Rob

[cp___32]

I have an '80 550L as well. Stock Petcock but when I pulled mine apart things still seemed to work fine so I still have it on. I've had other issues so my bike hasn't been running yet, but I plan to run the stock one for at least a little while.
I was under the impression that when folks on here say 'replace the dreaded 1980' petcock, they mean with an aftermarket one by the company "Pingel". I've heard that it's a tight fit but a few guys on here have gotten them, and if I'm not mistaken Z1Enterprises has been quoted as the place they got theirs from as well. I think I also read that they have good customer service and if you call them about the 1980 petcock they're quite helpful.
But like I said, that's coming from what I read, not personal experience
Good luck with the bike!

[rphillips]

This has been thrashed around here a lot. Seems to me it's about 50/50 on the forum. Personally, I'm in the rebuild half, Like you I wonder what can go wrong with replacing parts, as long as the replacements are installed properly. If it doesn't fix it, worst case is you spend $53 instead of $42.

[Nessism]

If the internal parts look except for the diapharam, throwing a rebuild kit at it will most likely work.

[ChicagoRob]

I think that I'm going to go the safest route and order both. Z1 is cool about taking back unused non-electrical parts.

cp, I thought about a non-vacuum petcock, but having the vacuum feature is a nice convenience.

How does the prime on the front work? Am I supposed to supply suction to it? I know that twisting that slotted piece of plastic does nothing.

Thanks,

Rob

[Griffin]

I think that I'm going to go the safest route and order both. Z1 is cool about taking back unused non-electrical parts.

cp, I thought about a non-vacuum petcock, but having the vacuum feature is a nice convenience.

How does the prime on the front work? Am I supposed to supply suction to it? I know that twisting that slotted piece of plastic does nothing.

Thanks,

Rob

I just replaced the petcock on my wife's '80 550L yesterday (gas would flow down through the vacuum line into #2 cylinder, fouling the plug and smoking out the left side exhaust). While testing the new petcock, it did nothing on "prime" until a slight vacuum was applied, then it gushed out gasoline, and continued to do so under no vacuum until the tank was empty, or the slot was turned to "run".

So...in order to prime your carbs with this style of petcock, you would need to crank the engine for a second or two to get the gas initially flowing, but then all should be well.