okay so i have a 96 lt 80 and i have had it since i was young and it was new. its now on its 3rd rebuild after sitting for 5 yrs, im a mechanic so i know pretty well what i am doing. i just had the cylinder honed, installed a new piston, rebuilt the carb, cleaned every part squeaky clean as it went back together and its been apart for a few months now and i cant remember what lines go where on the carb, im having a problem with it just dumping fuel uncontrollably, after 15 seconds of cranking it FILLS the cylinder with fuel and wont let the engine turn over at all, i dont know if i have the lines hooked up wrond or what but its driving me insane! if your looking at the petcock on the right side of the bike i have the line closest to you hooked to the brass nipple, the back line on the petcock on the nipple closest to the cylinder and the vaccuum hose on the front nipple, is this my problem or what? any help is greatly appreaciated. im tryin to get this thing running for my cousins to ride and its got me stumped, great site by the way! braap

 

First i would check to see if petcock lever[cut off value] is in the on or res. not pri. if in correct spot take fuel line off and see fuel in flowing! fuel shouldn,t be flowing without engine running..if fuel flows then petcock diapham is stiff and can,t cut fuel off. need to replace. ok nipple that is closest to cut off lever is fuel outlet and goes to brass nipple that is just above carb.bowl level, the farest nipple is vaccum one thats goes on the nipple closet to cylinder, the middle one is vent and goes on other one on carb..... Good Luck.....

 

Welcome to the forums.
Looking at it..left (closest to cyl) is the vac supply. Middle (brass) fuel supply, front hole is the vent.
Once the lines are connected properly,and if the problem persists, there is a problem in the float needle/seat area allowing fuel to pass and fill the motor up w/fuel.
FYI: the best way to fix a bad petcock is to get a 3 buck on/off valve at the autozone and stick it in the fuel line.

 

Sorry! Lt80 is correct on petcock plumbing I got crossed up on value..... But i have used an inline cut off value to use instead of replacing my petcock assy. and didn,t work good for me, quad would run rich from unregulated fuel[gravity fed] an would cause an hard and rich start up.... when i replaced petcock assy with new runs perfect..... just what happened to me.....ino LT80 has seen an heck of lot more than me just my experance......Good Luck..

 

Oh goody..I appreciate a good conversation..
So how is it that you consider any petcock a regulator? I see it the same as a on/off valve.
I've called this "the great petcock debate" LOL.
I see it as the float needle as the fuel regulator with that area being a problem at times.
Hydraulic weight is my theory, simply too much weight for the float needle to stop the flow.
What you think papa?

 

LT80 I understand how the float and float value and spring inside value works.... the fuel inside of carb.bowl rises and causes the float to lift up and cut fuel off by the pressure of the spring inside of float value..LT80 I am not going to get an debate with anyone it,s not important..I do this for an living also....for 38 years and not perfect. why does this unit have an vaccum fed petcock on it?? Just IMO that the engine[stock] cant run correctly with gravity fed....and Ino you and some others here also have experinace in this feild, Im not debating that.... we all are to try to help others that ask for advise... Lets just try to help others and not just see whos right or wrong... Like i stated i my post to braap this is what i have experinced with this atv... Thanks....

 

I'm sorry if you took my reply as agressive. I really was looking to discuss this in length. Basically cuz I sence and appreciate your knowledge and expieriences. That and like you mentioned, we all learn from it. I agree, it's not about being right or wrong.
With that being said, and with all due respect, let's move on....
I don't know exactly why the LT80's have a vac petcock. I suspect it was a "make it easy" for the kid thing as they (kids) didn't have to remember to shut the petcock off. Again, pure speculation.
Most every motorcycle I know of (I'm old school) has a regular on/off/res petcock. These same petcocks HAD to be shut off or the cylinder could fill w/fuel. This was just accepted till Zuki got a idea..LOL
FYI: a popular fix has been a standard petcock off a banshee/LT160/LT250. They seem to work just fine for most all that have tried. I find it peculiar that a vac petcock would work differently, or seem to for you.
So If you don't mind me asking, how do you feel a petcock regulates fuel as opposed to the on/off valve not regulating it.

 

I just feel that the vaccum type is design off the pulse of engine... which is not an stready flow like and open or gravity is an consist flow...... Also adult models have vaccum type petcocks and some motorcycles....But any way I respect you LT80! And thanks you for the help and advice you have gave people and I will ask you for some also.... So thanks an million.....

 

Now there ya go. Ya went and learned me something.
I understand how the exhaust pulse effects a motor running but I never thought of the vac petcock having a pulse....I can see a bunch of pondering from this..hehe
Thank you!