is it bad to ride with petcock on PRI?

when i point the petcock to it to ON, the engine eventually dies like it runs out of gas. i'm assuming the petcock is bad and is getting no vacuum action. so i have been riding it on PRI. however, i've been reading that it should only be a temporary fix.

is it bad to ride on PRI?
does it affect gas mileage since the fuel is entering differently?

thanks.

 

no harm will come to your engine.....unless you forget and leave it on pri while the bike is parked, and the carbs leak gas into the oil. i have been riding mine on pri for quite some time now as well.

 

Ha, I went over to my boss' place today and he had been doing the same thing and then leaving it in that position overnight. I changed out the oil for him after his bike spit out oil and gas all over the place as he was riding. Fortunately he didn't ruin his engine, but when I drained the oil from the bike it was like a 60-40 mix of gas and oil and drained out like water. It was really really bad.

Changed out the oil with some cheap stuff, going to have him run it for a day or two and then change back out again for some good stuff with a new filter.

 

Not uncommon - you don't have to wait a day r two - 10 minutes running should be plenty. I've done that dance twice...

 

Thanks for the info Bill. Just wanted to make sure he didn't get any additional wear, but if ten minutes is all that's needed, then I'll go get that changed for him.

 

whoa...ummm...i've been leaving it in PRI the whole time. since i read some of these posts, i quick put it back to ON last night. So here's another question. I changed the oil on wednesday. when i drained the old oil it looked like regular black oil with no gas in it (how can you tell?). But since then, i've left it on PRI as always up until last night.

Should I switch the oil out again, or is the leaking (gas into the oil) problem only if you have bad float valves?

 

You will smell the gas in the oil (Strong smell - slight smell I think is normal). I also leave a small bubble at the top of the sight window so I can see if gas is filling my oil.

If your needles are working properly you won't get gas in the oil but if one sticks....

When I had bikes with true on/off petcock the advice was always turn off when parked. It it good practice to leave it the on position and just use prime to ride until you get it fixed.

 

Precisely. Rather than counting on the "bubble" I always check my oil by starting out on the sidestand (should be NOTHING in the window) and then start standing the bike back up and watching the oil come up in the window. THEN I pop it on the centerstand and check the actual level. I just don't fully trust 27-year old automatic ANYTHING so I always double-check.

 

thanks for the info bill. now to get it "fixed" what all needs to get replaced? and to get the "vacuum" action going again, should i avoid used ones on ebay?

Thanks!

 

sorry bill. what i meant is "should i replace the petcock and any other tubes?" what do i need to do to get it working properly with the vacuum action going on.

thanks

 

Depends on the problem. Chacal has rebuild kits and rebuilt petcocks. I have read of folks having problems with the rebuild kit but I'm not sure why that would be.

Your problem could be the vacuum diaphragm or a clog in the "on" tube of the petcock or both . You can inspect your vacuum line for cuts etc also. Be sure to get vacuum line if you replace it. Non vacuum line can collapse under load and you will have a devil of a time figuring out why you go 2 miles then die.

First test your petcock. With it set to on and gas line to carbs disconnected, suck on the vacuum tube gently. Gas should flow and you should not taste any gas. If you taste gas or you get no flow you probably have a bad diaphragm. If no gas taste but no flow it could just be gummed up.

At that point you should drain the tank and remove the petcock. Take it apart and inspect all the pieces. Also check the screen filter that sits inside the tank and ensure all the openings into the petcock are clear.

Alternately you can order a rebuild kit and just go ahead and rebuild it. But there is no problem with looking it over, then put it back together and use it till the parts come in. I did that just last week.

As for used ebay parts - you take chances and may have to rebuild the thing when you get it anyway...

 

I solved this problem. I installed a simple in-line on/off fuel valve between my tank and my carbs. I bought the on/off valve from chacal. That way i can turn it off when i am done riding with no fear of leaking needles or failure of the "automatic" petcock

 

uuuuugh! i smelled the old oil and it does have a strong gas smell. Thanks for the tip. but now would you suggest i rechange the oil. like mentioned before, i had it on PRI since when i changed it on wednesday night. remained on PRI all the way until thursday night. kind of a pain to have to buy more oil and do it again. but it wasn't that hard, and i don't want to do any permanent damage assuming i already haven't.
any advice for a noob, guys?

 

Your Bike is "Pushing-30" Years Old.
The Petcock needs to be replaced.
It only lasted you ... lets say ... 25 Years ... roughly.

A Brand New Petcock from doing a web search is: 80-Bucks (average)

80-Bucks ... divided by 25 Years = $3.20 @ Year
That works-out to about $0.25 @ MONTH! Twenty-five cents. A Quarter!

Now, I ask you (and everybody else) if paying 25-Cents a Month is cheap enough insurance for not having to change your oil because the Petcock leaked.

Seems like it to me!
Look at how much its going to cost you to flush the crankcase and then change the Oil and Filter!

 

You can also rebuild your existing petcock; the castings don't wear out, the rubber stuff becomes crispy and gives up, sliding parts wear, springs get weak. A rebuild kit from you-know-who is only like $53 or something like that, so that's a viable alternative, too. Bill's advice is right on, as is Rick's, I wouldn't let it go, there are alternatives to complete replacement. As far as changing the oil again, if you have been watching your oil level and it hasn't mysterioulsy INCREASED (even slightly) then you probably aren't filling the engine with fuel. Test the petcock (Bill's troubleshooting procedure is right on) and determine if you have a problem and what it is. Clean and examine the petcock, rebuild or replace as necessary. Don't leave it on PRI while it's sitting, and don't put off servicing the petcock. Change the oil again if you even SUSPECT it is being diluted with oil.