Fuel dumping from the carbs when running

[Silent]

I think I screwed the pooch the other day when I left one of my petcocks on prime. Now I have fuel pouring out of the carbs when she's running. I pulled the carb rack tonight and popped the bowls, and everything seems to be in order. The floats are free, and the needles seem to be doing what needles do. I'm in need of a direction to move in, I'm lost at the moment. She was running great last week, even took a spin over Siera road last weekend.

She's been running rough lately with the petcocks on run, and running better with the petcocks on prime. I pulled both petcocks and cleanded them up, even tho I could find no obvious fault with them. I rebuilt both petcocks a few months ago when I switched to a standard tank. With a full tank of fuel she will run ok with the petcocks on run.

'79 Special with a standard tank and petcocks.

Thanks guys

[GARTHXS]

float valves

even the littlest piece of crap will hold a float valve open, as to the running issue sounds like your octy is leaking

[motoman]

Hmmm........which petcocks do you have on the tank, standard or special?

[Silent]

I took the Octy off when I switched over to the standard tank, and I rebuilt the standard petcocks when I made the switch as well. Guess I'll just have to rip the carbs out and stuff them into the ultrasonic again.

[dbeardslee]

Is gas coming out of all the carbs or just some of them? It would be unusual for crud to get under several carbs at the same time, but I see where you had issues with rust in the tank, so maybe. Are you running line filters? The 78/79 carbs have two sets of T's - the lower for fuel and the upper for vent. If the vent lines get restricted it'll do exactly what you're describing. If the carbs are leaking in pairs (1&2 or 3&4) I'd double check the vent lines. DO NOT PUT COMPRESSED AIR ON THE GAS OR VENT LINES WITH THE BOWLS ATTACHED! The 78/79's have brass floats, and the increased air pressure will squeeze them good. Aslo, if it sat there leaking for a while the gas may have migrated into your oil. Take a stick and put it in the oil fill hole. Try to light it on fire. If it ignites easily you've probably got gas in the oil and it's time to change it. There have been a number of members that experienced bearing problems from running gas-thinned oil. Just some more stuff to think about.

[Silent]

I'll try the vent lines and see if that helps when I get home. I don't have anything more than light surface rust in the tank, and I'm running the mesh filter towers, and secondary filters in the fuel lines. From the quantity of fuel dumping, and what I've seen, it looks like all of the carbs are dumping fuel.

[randy]

Take a stick and put it in the oil fill hole. Try to light it on fire.

Remove the stick and step away from the bike before you light it

[Larrym]

No Fumar...Por Favor.

Hey Silent,

While the carbs are off the bike is the best time to check for any float needle/needle seat, float level, or petcock shenanigans. Both upside down with the bowls off and right-side up with the bowls on.









It's always unpleasant when leaks happen while the carbs or on the bike. Puddles on the shop floor along with the spills on the engine: Yuck!

I'd suggest using the tank/petcocks from the bike and remember: No Open flames or smoking allowed.

[Silent]

Funny thing about motorcycle engines. As it turns out they do not like it when there's over a gallon of fuel mixed in with the oil, from sitting with the petcock on prime for a couple days, or for other mysterious reasons. Now the old 2 strokes liked having oil in the fuel. that's how they were lubricated, but modern four stokes don't care to much for fuel in the oil. They try and spit the offending solution out of engine thru the bypass tube, right into the airbox, causing the offending solution to leak all over said four stroke and the ground beneath. This tends to make for a very messy, and dangerous situation.

Now that thats out in the open, the oil's been drained now, and the carbs are back in and ready to go. Just waiting for the fuel to evaporate out of the engine caseing a bit before putting in new Synthetic oil.

On a side note, watch your reciepts, my local auto parts store tried to charge me $7.50 a quart for oil that was listed at $5.00. They did make it right and sold it for the lower price tho, but only because I noticed the price difference on the way out the door.

[dbeardslee]

Just waiting for the fuel to evaporate out of the engine caseing a bit before putting in new Synthetic oil.

And a new filter, right? $7.50 a quart!!! That's about what I pay for a whole gallon of the stuff I use.

[Silent]

And a new filter, right?

But of course, I wouldn't have it any other way! I just happened to have one in the spare parts box with brand new O-rings

[ross]

oil change time...

hey there silent...been there, seen it, done it....nothing says XS-ive when you do a 5-7 quart oil change.....(i know there is supposed to be only 3.5 in the bike!).....the rest is gas.....thought i was gonna overflow my oil change pan the first time......that was the moment i decided to put manual shut-offs on each line coming outta the tank.....shut them off every time i stop and have not had a problem since....4 dollar each down a the lawn mower store.....$8 fix total!!...


even if you leave it on primary, when you shut these suckers off, bikey no go....(pulled outta the gas station with them off, made it 1/8 mile down the road and it died...gee, go figure!!!)....anywho that is what i did to make it right....cheaper than rebuilding the diaphragms and all....faster too!!!...ride hard, ride safe...ross