pepcok

[ram45red]

need to replace pepcok has anyone tried the one for sale on ebay that has on off reserve and does away with vacum line the item number 260975419140 should i get this one or a replacement from cheap cycle parts .com or kawasaki dealer trying to fix up a 89 for sons first bike got to replace this and ignition switch please let me know best way to go for trouble free riding

[Jet⚡Black]

The carburetors require a vacuum, in order to operate; so I doubt a petcock without a vacuum will work out for you. You can try cleaning out and servicing the one you have first, if the internal rubber is in rough shape then there are rebuild kits for them for pretty cheap.

To do this remove the tank, the bolt is under the front part of the seat, then it lifts from the rear and just slides out when you pull back. Get a container to catch the old gas, and one for bolts etc. remove the bottom mounting bolts, slide the petcock out, you will be ble to see how dirty your tank has been by the screen part. remove the two little screws, on the front of the petcock, then pull the handle to remove that part the face plate comes off with it. Clean the passages and the screen, being especially careful to not damage the rubber diaphragm. place a small amount of lubricant on the o-ring on the handle part and reassemble.

You can do this without removing the tank, just know dealing with the gas coming out will not be as easy if you don't.

[rustbuckett]

I'll be the "dissenting voice" for this one ok guys?

First: my input to your question -- make sure your existing petcock allows fuel to flow; and then install an inline on/off aftermarket petcock right underneath it, between the tank's petcock and the carbs. Use the tank's original petcock only to switch to Reserve when needed; and when you stop the bike and shut down, turn the aftermarket valve to Off. Turn that valve back to On before you try to start the bike up again. Simple and cheap; will cost you about six bucks.

It never made sense to me why they call this valve-thingy a "petcock". Brings obscene things to mind and nobody likes to say the word around women!

So I just looked it up. Wikipedia lists 4 types of valves, including ballcock, bibcock, stopcock, and petcock; with petcock being "a small valve, primarily for draining liquid or releasing pressure from a vessel".

Ok there's the vocab lesson I guess.

The petcocks on my dirt bikes and ATVs are all turned with the handle facing inside towards the engine; presumably to prevent the accidental turning-off of the fuel while riding/racing. Imagine your knee or boots bumping the petcock to "Off" while you're in the middle of an MX race. So the dirt-machine companies seem to mount them inside, where they won't get bumped by your leg or boots.

The dirt bike ones also have an "Off' setting to completely shut off the flow of fuel from the tank. Most motorcycles that I knew before also had an Off setting. I'd use that to either run the carb bowls dry before long term storage, or to make sure the carbs wouldn't get filled up and overflow with unwanted gas if the float needle didn't seal 100% perfectly and slowly allowed gas to drizzle into the carb bowl while the bike sits in the garage or dirveway.

Our 454's (and a bunch of other bikes, from what I'm finding out) have a different kind of petcock that doesn't have an "Off" setting. My guess (smart guys, please pipe in with smarter answers -- I'm just guessing) is that people would tend to leave their petcock set in the "On" position and then park the bike, and the float valve would slowly drizzle/leak, flooding the carbs to overflow.

So i guess the companies "fixed" that problem by taking the "operator error" piece out of the equation -- and they designed a petcock that refuses to allow fuel to flow through it unless its valve is opened by the vacuum of the running engine.

That's the kind that our 454's have. No "Off" position. Just a "Run/On' and a "Reserve".

When you start your bike's engine, a vacuum hose that's connected to one of your carbs gets sucked on by the air flowing thru the carb and into the cylinder. That causes a venturi effect, causing suction inside that hose. the other end of the hose hooks to a diaphram inside your tank's petcock. Once that diaphram gets sucked on, it pulls a small piston-valve out of the way inside the petcock, which allows gas to begin flowing by gravity down the fuel hose.

When you turn your key off and the engine stops, so stops the vacuum on that diaphram -- and a little spring pushes the diaphram's attached piston back into its hole in the petcock, blocking off the fuel supply to the fuel line.

So they made it a "gas can flow out of the tank by gravity when you need it; and gas stops flowing automatically when your engine shuts off" thing.

I have a nice photo of a completely disassembled diaphram-type petcock that i just took a couple days ago, from a kawasaki Kz750 i have; but I can't seem to upload photos onto this site. If you can see a detailed view of the internal pieces & parts of the petcock you can get a better idea of how they work, and maybe of what to do about them when the don't work right anymore.

Sound good to anybody? This is just my guesswork, from looking at the parts....

[eaglerider]

Rustbucket, there are two 454 petcocks....early model with PRI, ON, RES.....and the later model with OFF, ON, RES. The PRI on the early model is gravity flow, to fill the carb bowls after they have been drained.....the later model did away with the PRI, and put an off position. I personaly would not recommend using a non- vacum operated petcock from another bike. The engineers designed everything on this bike for a reason.

[rustbuckett]

Thanks for the add -- I didn't know the model had two different petcocks.

I usually agree with logic like "an experienced team of world-class engineers, working to design products for a multibillion-dollar international corporation, are a lot more likely to know what's best for the machine than some bumpkin in central new york state"...

But when it comes to these diaphram petcocks, they seem to have mostly started in the 80's, same time as the anti-petroleum environmentalists started bribing their way to power and the new federal emissions standards and all those fail-fail emissions systems were invented in a scramble to keep up with the new laws. I don't have confidence that their vacuum controlled on/off petcock was necessary for the bike itself. Necessary as one part of an emissions-control system, maybe....

To me, it's just a valve, and it's either open or closed. Whether a suctioned diaphram opens it or a finger-turn opens it, it's still just a valve that's either open or closed depending on what you want it to be. It either lets gas flow by gravity through a line, or it stops gas from flowing by gravity through the same line. Nothing complicated about what it does or how it does it.

Augmenting that expensive petcock with a simple mechanical one makes perfect sense to me, unless money's not an object.

[ram45red]

someone before we got bike has replaced tank and petcock and rebuilt carbs carbs flood even after i had new kits installed bike is a 89 450an the petcock on it has a vacum line with a on off and res.dont think this is correct petcock thought id put a new one on to solve this mystery/problem new one from cheap cycle parts .com is about 70.00 the one from ebay that does away with vacum line and is suposed fow correctly for this bike is about 30.00 our buget is tight now but i want to fix it correct not gust save money only to have same problem come back later down the road

[Blaine]

May 22, 2012 7:39:30 GMT -6 ram45red said:

someone before we got bike has replaced tank and petcock and rebuilt carbs carbs flood even after i had new kits installed bike is a 89 450an the petcock on it has a vacum line with a on off and res.dont think this is correct petcock thought id put a new one on to solve this mystery/problem new one from cheap cycle parts .com is about 70.00 the one from ebay that does away with vacum line and is suposed fow correctly for this bike is about 30.00 our buget is tight now but i want to fix it correct not gust save money only to have same problem come back later down the road

That petcock is the right one for that year.Mine is a 90 model,with the same petcock.The older models had "pri" instead of "off".Bot all are vacuum operated.

[Rob]

vucum control acts as an automatic on/off position for that model petcock - (petroleum cock) Petro - from our UK cousins, used for sampling / venting petro tanks (thats the story I got from a British Cheif Engineer on Subs anyway)

engine not running - no fuel needed vaccum control petcock closes!!

starting - engine turns over - creates vaccum opens fuel flow!!

on - off - res : replacement will work fine, plug the vaccum line on the left carb!

vaccum on right carb will still control all the California emmisions crap on the US models.

on will be like leaving it in prime - full gravity gas flow

if your vaccum petcock works in prime and reserve- leave it be!!! unless the vaccum diaphram is leaking or floats sticking open

just use the "on" as your new "off" position!!!

clear like mud?

PS:
trouble free riding, 454 and son in same sentence ?? your new to riding old bikes arent you

[Jet⚡Black]

From your recent post, the petcock is getting fuel to the carbs. So it sounds like the actual problem: Flooding, is from the floats being set at the wrong height or something is stopping the float needle from seating properly, which keeps the Jet open and causes flooding/ overflowing. If you get no fuel to the carbs then its time to suspect the hoses/petcock.